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Old 03/18/17, 08:26 PM   #1
DJs74
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EFI advice - not a Bronco and not mine

Hoping the EFI gurus can shed some light... trying to help my brother-in-law with his 1986 F250 project
► 302
► 4 speed
► EFI
► all factory electronic and fuel components
► single tank / not dual

Brother-in-law purchased an '86 F250 that ran but needed some body work and some general maintenance. He drove it a few times just beating around in it to get the feel and to evaluate things. He had a set of shorty headers from a past purchase and decided to install them... he removed the stock manifolds but removed nor unhooked any wiring except the battery cables and the starter cable bracket that was fastened to one of the manifold studs.
After the header install, it would not start... a friend of his told him to replace the module on the distributor (not sure how he knew/ why he thought that or suggested it because I hadn't gotten involved just yet), so in order to get the module off, he had to pull the distributor, replaced the module, reinstalled and still no start - that's when he called me.
We went through some trouble shooting by phone - was anything unhooked, if it had fuel, if he by any chance bumped into anything possibly tripping the inertia switch, etc. - answers revealed nothing obvious so I met him to take a look.
Problem #1 was the firing order was slightly wrong and wires were setup to fire CW (he is new to turning wrenches) so we took care of that but still no start. The coil is getting and sending fire to the distributor and plugs are getting fire.

Next, and here is where I'm not sure what is supposed to be happening and what feeds what electrically... the fuel pump makes no noise (no buzz, hum, priming noise) when the key is turned to 'on' prior to cranking. According to the literature I looked up online, it appears there are two pumps - one in the tank and one on the frame rail - not sure why or how all that works either but they are both there and neither seem to be doing anything.

Here is something that might be important but strange, at least to me anyway... after I reinstalled the distributor and rewired the plug wires, I stayed at the distributor while my BIL was at the key - I told him to try to start it while I worked the distributor and as mentioned earlier, it did not start but I kept hearing a clicking noise when I rotated the distributor (key on / not cranking the engine). When I rotated the distributor CCW, the clicking was coming from around the master cylinder area and when I rotated it back CW, I could here a clicking coming from somewhere under the intake plenum - it clicks every time, not sporadic or once in a while but with every rotation back and forth.
So, I started trying the track down the click, at the master cylinder area, I found the fuel pump replay (yellow square box with green connector). I cannot find the specific part that is clicking under the intake.

So, does anyone know if the relay clicking is normal or indicating the problem? What would the other clicking noise be coming from under the intake? Should there be an initial priming noise at the pump, humming, something / anything with the key on? How do the two pumps work / tie together? What mechanism causes the injectors to activate? Does each pump have its own relay or just one relay for both pumps? How to electrically test the relay(s)? I can only find one relay but there could be another hidden I suppose. I checked all the fuses under the driver side dash and they are all OK - not sure if there is a fuse for the pumps in addition to the relay? The inertia switch is located on the passenger side, in the cab next to the heater duct - there is a white button on top and it is down... could it be part of the problem? anyway to test it or manually trip / reset?

Sorry so long, trying to give as much information as I've learned so far and not sure what the next move should be. At the moment, I am thinking either one of the pumps are bad or maybe there is something preventing the one or both pumps from getting power. Don't understand the clicking. The truck ran prior to the header install and according to my BIL, he did nothing electrically other than the battery cables and distributor module.

Thanks for any information or things to look for and try. Let me know if you need to know anything else, I will be going back over to try again Monday evening but can get more information tomorrow if necessary.


DJs74
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Old 03/18/17, 10:41 PM   #2
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Quote:
Originally Posted by DJs74 View Post
Problem #1 was the firing order was slightly wrong and wires were setup to fire CW (he is new to turning wrenches) so we took care of that but still no start.
So it was running before with this firing order? Or did he actually remove the spark plug wires prior to it not starting?
Or was this bit about the firing order just out of sequence and this was after the removal of the distributor to change the TFI module?

Which firing order did you use finally? If this is a Speed Density 5.0, wouldn't it still be the old 302 firing order?

Quote:
Originally Posted by DJs74 View Post
The coil is getting and sending fire to the distributor and plugs are getting fire.
Then it seems like the module is good and the ECU is getting power through it's relay. At least I think you won't get a spark at the plugs unless the computer is getting power.
So at least for now that seems to be good.

Quote:
Originally Posted by DJs74 View Post
Next, and here is where I'm not sure what is supposed to be happening and what feeds what electrically... the fuel pump makes no noise (no buzz, hum, priming noise) when the key is turned to 'on' prior to cranking.
As you're thinking I think, this is not right. You are correct to assume that at least one of the pumps should be making enough noise for you to hear it priming the system for a few seconds each and every time you turn the key.
I was not aware that Ford used two pumps on one vehicle. Different locations for different years, yes, but didn't know about two for a vehicle. Interesting stuff though. Learn something every day.
Maybe double check that though, just to be sure.

Quote:
Originally Posted by DJs74 View Post
I told him to try to start it while I worked the distributor and as mentioned earlier, it did not start but I kept hearing a clicking noise when I rotated the distributor (key on / not cranking the engine). When I rotated the distributor CCW, the clicking was coming from around the master cylinder area and when I rotated it back CW, I could here a clicking coming from somewhere under the intake plenum - it clicks every time, not sporadic or once in a while but with every rotation back and forth.
Two things possible here. You're sure you're not hearing a spark jumping somewhere? If it's indeed the relay clicking, it's likely that the PIP signal (if that's the proper term) is telling the fuel pump relay to turn on.
This is the signal that lets the computer know that the engine is cranking so it's ok to let the pump run continuously instead of just the initial priming.
So that seems like a possibility at least.
Not sure about the other click, unless they decided to throw a second relay in a completely unrelated place. Seems unlikely, but you never know.
Maybe it's a fuel pump shutoff relay of some kind? So when the engine quits it forces the other relay to shut off power to the pump? No idea really, just throwing out random thoughts.

Quote:
Originally Posted by DJs74 View Post
Should there be an initial priming noise at the pump, humming, something / anything with the key on?
Yes.

Quote:
Originally Posted by DJs74 View Post
How do the two pumps work / tie together?
Not sure how they tie together, but you're correct that there is a relay that comes on with the turn of the key that the ECM/ECU/Computer tells to run for a couple of seconds.
Then the PIP tells the pumps to stay on because the engine is now spinning and is expected to start.
I think too that there is some function that tells the pumps to stop pumping after a certain amount of time and the engine does not start. But I'm not 100% sure on that.

Quote:
Originally Posted by DJs74 View Post
What mechanism causes the injectors to activate?
Here again is where the PIP signal from the distributor's TFI module comes into play. I don't think these engines had a crank or cam position sensor, so it was all done in the distributor.
And it does need to know exactly which one is cylinder #1 and when it's firing. I believe this could be part of the trouble maybe. Double check your wires and where they are and what firing order.
Maybe you've got it right, but there is room for error here, so worth a double take.

Quote:
Originally Posted by DJs74 View Post
How to electrically test the relay(s)?
What do these relays look like? There are easy ways to test them, but I'll wait for someone more in tune with those processes to give the details. The way I talk, I'll just confuse things!

Quote:
Originally Posted by DJs74 View Post
I can only find one relay but there could be another hidden I suppose.
And if you find any more that are alike, one way to test is to swap relays between like-units to see if anything changes.

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Originally Posted by DJs74 View Post
I checked all the fuses under the driver side dash and they are all OK - not sure if there is a fuse for the pumps in addition to the relay?
Usually there is. Not always, but usually yes. Did you check the under-hood box too? Usually there are at least two fuse and/or relay panels on a modern vehicle (and yes, I consider an '86 to be almost modern!). Sometimes even another one under the dash, or on the opposite side. Looks for any additional areas with fuses.

Quote:
Originally Posted by DJs74 View Post
The inertia switch is located on the passenger side, in the cab next to the heater duct - there is a white button on top and it is down... could it be part of the problem? anyway to test it or manually trip / reset?
Down does seem to be ok, but I thought there was a reset procedure you could use on these. Here again, someone with direct knowledge will have to give with the goods.

Good luck.
Always go back to what was done. Did he disconnect a body ground? Or break any wires?
Did he disconnect the battery first? Or did he do some work, then decide it would be a good idea? Maybe something got fried in the meantime.
What about sensor wires? A MAP sensor should be around somewhere, if it's a speed-density engine. And in that case would have a vacuum hose attached. A mass-air engine would have no hose.
What about the MAF wires and connectors?
Did you verify that the distributor rotor was turning when the starter was cranking the engine? I know it's working when you are turning the distributor, but what about with the starter?

Anyway, others will have some good tests for you I'm sure. Just throwing out some food for thought.

Paul

'71 Wagon, 3.5" WH, F150 disc brakes and steering, 4.11 33x11.50 Thornbirds, Kayline soft top, Hanson bumpers. "Built, not bought"

'68 LUBR, 2.5 + 1 WH, 31x10.50, 4.56, Explorer and 4R70w by EFI Guy, WH disc brakes, Hanson front bumper, Warn winch. "Bought, not built"

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Old 03/18/17, 11:38 PM   #3
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Ford's have an inertia switch. If it's not getting fuel, and the pumps are kicking in. Locate the inertia switch and make sure was accidentally tripped.


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Old 03/18/17, 11:39 PM   #4
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Oops Didn't see DJs post.


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Old 03/19/17, 04:15 AM   #5
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Quote:
Originally Posted by DirtDonk View Post
So it was running before with this firing order? Or did he actually remove the spark plug wires prior to it not starting?
Or was this bit about the firing order just out of sequence and this was after the removal of the distributor to change the TFI module?

Which firing order did you use finally? If this is a Speed Density 5.0, wouldn't it still be the old 302 firing order?



Then it seems like the module is good and the ECU is getting power through it's relay. At least I think you won't get a spark at the plugs unless the computer is getting power.
So at least for now that seems to be good.



As you're thinking I think, this is not right. You are correct to assume that at least one of the pumps should be making enough noise for you to hear it priming the system for a few seconds each and every time you turn the key.
I was not aware that Ford used two pumps on one vehicle. Different locations for different years, yes, but didn't know about two for a vehicle. Interesting stuff though. Learn something every day.
Maybe double check that though, just to be sure.



Two things possible here. You're sure you're not hearing a spark jumping somewhere? If it's indeed the relay clicking, it's likely that the PIP signal (if that's the proper term) is telling the fuel pump relay to turn on.
This is the signal that lets the computer know that the engine is cranking so it's ok to let the pump run continuously instead of just the initial priming.
So that seems like a possibility at least.
Not sure about the other click, unless they decided to throw a second relay in a completely unrelated place. Seems unlikely, but you never know.
Maybe it's a fuel pump shutoff relay of some kind? So when the engine quits it forces the other relay to shut off power to the pump? No idea really, just throwing out random thoughts.



Yes.



Not sure how they tie together, but you're correct that there is a relay that comes on with the turn of the key that the ECM/ECU/Computer tells to run for a couple of seconds.
Then the PIP tells the pumps to stay on because the engine is now spinning and is expected to start.
I think too that there is some function that tells the pumps to stop pumping after a certain amount of time and the engine does not start. But I'm not 100% sure on that.



Here again is where the PIP signal from the distributor's TFI module comes into play. I don't think these engines had a crank or cam position sensor, so it was all done in the distributor.
And it does need to know exactly which one is cylinder #1 and when it's firing. I believe this could be part of the trouble maybe. Double check your wires and where they are and what firing order.
Maybe you've got it right, but there is room for error here, so worth a double take.



What do these relays look like? There are easy ways to test them, but I'll wait for someone more in tune with those processes to give the details. The way I talk, I'll just confuse things!



And if you find any more that are alike, one way to test is to swap relays between like-units to see if anything changes.



Usually there is. Not always, but usually yes. Did you check the under-hood box too? Usually there are at least two fuse and/or relay panels on a modern vehicle (and yes, I consider an '86 to be almost modern!). Sometimes even another one under the dash, or on the opposite side. Looks for any additional areas with fuses.



Down does seem to be ok, but I thought there was a reset procedure you could use on these. Here again, someone with direct knowledge will have to give with the goods.

Good luck.
Always go back to what was done. Did he disconnect a body ground? Or break any wires?
Did he disconnect the battery first? Or did he do some work, then decide it would be a good idea? Maybe something got fried in the meantime.
What about sensor wires? A MAP sensor should be around somewhere, if it's a speed-density engine. And in that case would have a vacuum hose attached. A mass-air engine would have no hose.
What about the MAF wires and connectors?
Did you verify that the distributor rotor was turning when the starter was cranking the engine? I know it's working when you are turning the distributor, but what about with the starter?

Anyway, others will have some good tests for you I'm sure. Just throwing out some food for thought.

Paul
Firing order is standard 302 (1-5-4-2-6-3-7-8), BIL took all the wires off the cap in order to be able to pull the distributor to change the module, there wasn't enough slack in the plug wires to be able to move the cap far enough out of the way to pull the distributor when he changed the module, the firing order I found was I don't even remember?
I only mentioned that part of the story to tie it together with and lead up to the head scratcher of rotating the distributor and discovering the clicking noises in the two different areas.

I'm pretty sure the ignition system is working correctly. Something else I forgot to mention in the first post - I sprayed some starting fluid into the throttle body and it tried to fire... very briefly but nonetheless, it did fire.

I'm 100% certain the noise is clicking at the relay beside the master cylinder because I put my hand on it while I rotated the distributor (that was a little bit of a stretch). It almost has the same feel as the old turn signal blinker relay when it clicks. As for the other clicking under the intake, I cannot find or feel anything in there, it's too tight to get my hand in there and I can't really see anything except the fuel rail and tops of the injectors... so that one could very well be a spark or something???

The relay is a little plastic box, yellow in color with about 5 terminals inside (that's from memory - could be 6 but don't think 4). Has a green connector attached and was recessed up under a black cover.

Fuses: I checked all the fuses inside the cab and they are all OK. I didn't realize there were more under the hood but now that you mention it, I do remember seeing another black box on the passenger side inner fender just behind the battery that appeared to have about 4 or 5 electronic widgets all in a row - could that be fuses or related to the fuel / pump system?

I have tracked down the ground to the frame from the battery, its present and accounted for. My BIL walked me through everything he did when he installed the headers and the only thing he removed was the cable running from the solenoid to the starter - it had a cable clamp attached to one of the old manifold bolts and it is just hanging right now... starter works fine.

About the pumps: The in tank pump is pretty easy to see and get to because the fuel tank where the pump is installed is angled so its very accessible right above the driveshaft, it has a connector with 5 or 6 terminals. The pump on the frame rail is mounted on the inside right around the transfer case area, had a somewhat round shape. Then just ahead of that closer to the motor is another round object that appears to be a filter maybe?? not sure about that but thinking that's all it could be... certainly wouldn't think its a pump #3 but who knows.

Thanks for the thoughts, I will get back to it Monday and see what else we can learn.

I told my BIL that we need to get a Haynes manual for this vehicle and/or purchase or download something that will show us a diagram of the fuel system electronically as well as mechanically so we can establish what we've got. Thought maybe someone might've had a similar experience as this or know these systems well enough to narrow down the possibilities.

EFI and the electronics that go along with them are not my thing... not afraid to dig in and try to figure it out but don't understand how everything works together well enough to be able to know where to start to determine what is and what is not working correctly. Case in point is this clicking noise at the fuel pump relay when the distributor is rotated... to me, that seems abnormal but I also assume with EFI, the fuel system is tied to and becomes dependent on the ignition system to function properly.


Thanks again,

DJs74

Last edited by DJs74; 03/19/17 at 04:27 AM..
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Old 03/19/17, 11:17 AM   #6
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Stupid question, it may have been mentioned already. Did you remove the fuel filter makes it there's no clogs


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Old 03/19/17, 12:45 PM   #7
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Don't think we talked about that, so good call. Might just be a fluke that happens to have gone wonky at the same time. I hate coincidences!

One thing I'm thinking of is the ECM relay. I doubt that the '86 was the same as the '83 I worked on with a no-start condition, but you never know. Back then it was just a primitive computer under the seat controlling timing and a couple of things on the electronic carburetor. The '86 is likely more sophisticated.

On the earlier one there was one of those Ford-specific smallish rectangular relays that are apparently known for corroding inside from lack of weatherproofing. This one was just adjacent to the battery on the passenger side. Replacing it fixed the whole issue.
Well, the carb sensors had deteriorated over time too, but the only reason it wouldn't start was because it was not getting power to the ECM.

In your case, I was leaning away from that being the problem because you said you had spark. In my limited knowledge about such things, I'm pretty sure that the ignition system can't generate a spark without the computer being powered up.
If that is incorrect and there is another way the ignition gets power, dig around for the ECM relay and see what you can find.

Oh, and yes, that box you saw would indeed house at least relays, if not some fuses as well. Some of them were for the bigger "Maxi-Fuse" size dudes. Probably have a couple of relays as well. Some are just to house relays, but might have a fuse or three as well.
The designs varied greatly over the years, but you should definitely look inside to see what you see.

Paul

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'68 LUBR, 2.5 + 1 WH, 31x10.50, 4.56, Explorer and 4R70w by EFI Guy, WH disc brakes, Hanson front bumper, Warn winch. "Bought, not built"

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Old 03/19/17, 12:56 PM   #8
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...it would not start...
That's vague. Over a few decades of participating in discussions like this one, I've encountered at least 20 distinct conditions that have been described as "won't start" including everything from "key doesn't fit" and "battery too weak to spin the starter" to "runs for a minute and then dies". You need to tell us EXACTLY what is & isn't happening.
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...it appears there are two pumps - one in the tank and one on the frame rail - not sure why or how all that works either but they are both there and neither seem to be doing anything.
Because early EFI was optional on trucks, so the parts they shared had to work with both the new system, and the old carbs. That included the gas tanks, whose openings were sized for only a float. Not big enough for a high-pressure fuel pump and everything else. So Ford initially put a small "lift pump" into each tank, a tank-select valve (of some kind, on 2-tank trucks), sometimes a reservoir (sometimes integral to the select valve), and then used 1 external HP pump to supply the injectors. This shows the '87-96 systems, and yours should be vaguely similar:

Quote:
Originally Posted by DJs74 View Post
So, does anyone know if the relay clicking is normal or indicating the problem?
Normal. The EEC watches the PIP (the sensor inside the distributor) to know if the engine is spinning or stopped. If stopped, the EEC doesn't turn on the FP relay because it's not needed (and to prevent fuelling a fire after a collision). But any time the PIP sends out a pulse, the EEC thinks the engine IS spinning, and turns on the FP relay (the click) for a moment.
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What would the other clicking noise be coming from under the intake?
Possibly the spark from the coil passing through the distributor & echoing under the plenum; possibly some other actuator (like the CANP) cycling. I doubt that identifying will help you get the engine running, though, so I wouldn't worry about it.
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Should there be an initial priming noise at the pump, humming, something / anything with the key on?
Yes, for ~1 sec. each time the key turns to RUN.
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Originally Posted by DJs74 View Post
How do the two pumps work / tie together?
They should be wired in simple parallel: both controlled by the FP relay and the inertia switch. I haven't found the specific diagram for your truck, but this one references it at the top (ZZ to fuel pumps). The bottom Right shows that the FP relay trigger wire (Tan/LG on that old truck) goes to the DLC just like later trucks, so jumpering it as shown here should turn on the relay & both pumps:

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Originally Posted by DJs74 View Post
What mechanism causes the injectors to activate?
The EEC grounds them (in banks, but not the same as the engine banks) based on the PIP (for the timing) and several other sensors & internal programming (for the duration).
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How to electrically test the relay(s)?
Same as any other relay, but the short answer is: DON'T. Those early relays are known to be problematic, so the best thing is to just cut them off & replace them with the newer, more-common, MUCH-more-reliable Bosch/ISO/Tyco-style (cube) relays, as this caption & the NEXT few describe:

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Originally Posted by DJs74 View Post
...if there is a fuse for the pumps in addition to the relay?
Not a dedicated one on most Ford trucks, but the bottom Left of this PDF suggests that it's fuse 18 on that early EFI.
Quote:
Originally Posted by DJs74 View Post
anyway to test it or manually trip / reset?
Pry the white button up to open the switch; push it down to reset (close) it. This shows the guts:

Quote:
Originally Posted by DJs74 View Post
Firing order is standard 302 (1-5-4-2-6-3-7-8)...
Follow this diagram, precisely:

Quote:
Originally Posted by DJs74 View Post
...4 or 5 electronic widgets all in a row - could that be fuses or related to the fuel / pump system?
No, those are the emissions controls, and the MAP. No fuses or relays there.

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Originally Posted by DJs74 View Post
The in tank pump ... has a connector with 5 or 6 terminals.
It should have 4, like this:



But the colors on a single-tank truck are probably different. Look at the top Right corner of this diagram:

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...appears to be a filter maybe?
Yes.

.
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...we need to get a Haynes manual for this vehicle...
Agreed! For the best applicability to such an old truck, look for a red cover that stops before '92, like the one in this pic:



Read that caption & follow the link.
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...download something that will show us a diagram of the fuel system electronically as well as mechanically...
You can get some of the wiring diagrams (like the PDF I linked above) free here. But in 25 years of collecting documentation on these trucks, I've never seen a plumbing diagram for any of them. That's why I made the one I posted above.

Last edited by Steve83; 03/19/17 at 01:07 PM..

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Old 03/19/17, 05:03 PM   #9
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Stupid question, it may have been mentioned already. Did you remove the fuel filter makes it there's no clogs


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Haven't removed the filter but good thought. Actually, we've not done anything physical to the fuel system other than check for the pump working by listening and feeling to see if there was any signs of life. Wanted to get some feedback from others first on a starting point, electrical evaluation and possible tests and in what order.

thanks,

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Old 03/19/17, 05:06 PM   #10
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Don't think we talked about that, so good call. Might just be a fluke that happens to have gone wonky at the same time. I hate coincidences!

One thing I'm thinking of is the ECM relay. I doubt that the '86 was the same as the '83 I worked on with a no-start condition, but you never know. Back then it was just a primitive computer under the seat controlling timing and a couple of things on the electronic carburetor. The '86 is likely more sophisticated.

On the earlier one there was one of those Ford-specific smallish rectangular relays that are apparently known for corroding inside from lack of weatherproofing. This one was just adjacent to the battery on the passenger side. Replacing it fixed the whole issue.
Well, the carb sensors had deteriorated over time too, but the only reason it wouldn't start was because it was not getting power to the ECM.

In your case, I was leaning away from that being the problem because you said you had spark. In my limited knowledge about such things, I'm pretty sure that the ignition system can't generate a spark without the computer being powered up.
If that is incorrect and there is another way the ignition gets power, dig around for the ECM relay and see what you can find.

Oh, and yes, that box you saw would indeed house at least relays, if not some fuses as well. Some of them were for the bigger "Maxi-Fuse" size dudes. Probably have a couple of relays as well. Some are just to house relays, but might have a fuse or three as well.
The designs varied greatly over the years, but you should definitely look inside to see what you see.

Paul

Thanks Paul, honestly at this point - everything is suspect until we can deem things OK so will definitely check out anything and everything associated with the fuel system until we find the culprit. thanks for the insight.

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Old 03/19/17, 06:17 PM   #11
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That's vague. Over a few decades of participating in discussions like this one, I've encountered at least 20 distinct conditions that have been described as "won't start" including everything from "key doesn't fit" and "battery too weak to spin the starter" to "runs for a minute and then dies". You need to tell us EXACTLY what is & isn't happening.Because early EFI was optional on trucks, so the parts they shared had to work with both the new system, and the old carbs. That included the gas tanks, whose openings were sized for only a float. Not big enough for a high-pressure fuel pump and everything else. So Ford initially put a small "lift pump" into each tank, a tank-select valve (of some kind, on 2-tank trucks), sometimes a reservoir (sometimes integral to the select valve), and then used 1 external HP pump to supply the injectors. This shows the '87-96 systems, and yours should be vaguely similar:

Normal. The EEC watches the PIP (the sensor inside the distributor) to know if the engine is spinning or stopped. If stopped, the EEC doesn't turn on the FP relay because it's not needed (and to prevent fuelling a fire after a collision). But any time the PIP sends out a pulse, the EEC thinks the engine IS spinning, and turns on the FP relay (the click) for a moment.Possibly the spark from the coil passing through the distributor & echoing under the plenum; possibly some other actuator (like the CANP) cycling. I doubt that identifying will help you get the engine running, though, so I wouldn't worry about it.Yes, for ~1 sec. each time the key turns to RUN.They should be wired in simple parallel: both controlled by the FP relay and the inertia switch. I haven't found the specific diagram for your truck, but this one references it at the top (ZZ to fuel pumps). The bottom Right shows that the FP relay trigger wire (Tan/LG on that old truck) goes to the DLC just like later trucks, so jumpering it as shown here should turn on the relay & both pumps:

The EEC grounds them (in banks, but not the same as the engine banks) based on the PIP (for the timing) and several other sensors & internal programming (for the duration).Same as any other relay, but the short answer is: DON'T. Those early relays are known to be problematic, so the best thing is to just cut them off & replace them with the newer, more-common, MUCH-more-reliable Bosch/ISO/Tyco-style (cube) relays, as this caption & the NEXT few describe:

Not a dedicated one on most Ford trucks, but the bottom Left of this PDF suggests that it's fuse 18 on that early EFI.Pry the white button up to open the switch; push it down to reset (close) it. This shows the guts:

Follow this diagram, precisely:

No, those are the emissions controls, and the MAP. No fuses or relays there.

It should have 4, like this:



But the colors on a single-tank truck are probably different. Look at the top Right corner of this diagram:

Yes.

. Agreed! For the best applicability to such an old truck, look for a red cover that stops before '92, like the one in this pic:



Read that caption & follow the link.You can get some of the wiring diagrams (like the PDF I linked above) free here. But in 25 years of collecting documentation on these trucks, I've never seen a plumbing diagram for any of them. That's why I made the one I posted above.
Steve, Thanks for the information, attachments and links.

When I stated it won't start, that's is actually exactly what I meant - the event of combustion is not occurring within the combustion chambers. Since it has known fire at the coil, from the coil to the distributor cap and at each of the plugs, the fuel seems to be the component that is eluding us at the moment which is supported by seemingly dead pumps, which led me to the questions about the fuel system.
I found the '80 - '96 Haynes manual in my library of books (the blue one with the '87-'91 Bronco on the cover) so I'll study it and see what I can find.



Thanks,

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Old 03/19/17, 10:48 PM   #12
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It looks like the other guys answered your questions pretty well, so I won't add much.

The clicking under the intake is most likely the injectors firing as it get's PIP signal. It's normal.

Since it runs on ether, I'd say spark is good and timing is at least close enough to fire. So you're going in the right direction hunting down fuel delivery. You really should have a fuel pressure gauge on this thing. But, I'd say if you can't hear the pumps run then they probably aren't getting power.

Start at the inertia switch, it's easy to get to and the connector for it is a common point of failure. Unplug the connector and look for signs of the wiring or the connector melting. If it looks good then you'll need a test light. One of the terminals should have power (from the relay) when you prime or crank the engine, the other goes down to your pump(S). If there is no power on either one then you need to test at the relay. If one of them does get power then the next place to test is at the pump.

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Old 03/20/17, 08:00 AM   #13
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It looks like the other guys answered your questions pretty well, so I won't add much.

The clicking under the intake is most likely the injectors firing as it get's PIP signal. It's normal.

Since it runs on ether, I'd say spark is good and timing is at least close enough to fire. So you're going in the right direction hunting down fuel delivery. You really should have a fuel pressure gauge on this thing. But, I'd say if you can't hear the pumps run then they probably aren't getting power.

Start at the inertia switch, it's easy to get to and the connector for it is a common point of failure. Unplug the connector and look for signs of the wiring or the connector melting. If it looks good then you'll need a test light. One of the terminals should have power (from the relay) when you prime or crank the engine, the other goes down to your pump(S). If there is no power on either one then you need to test at the relay. If one of them does get power then the next place to test is at the pump.
Thank you sir, I will be back at the truck this evening to have another look and check / apply what I've learned from everyone here at CB.com

In the meantime, my BIL called to tell me that he found another relay... identical to the one under the hood beside the master cylinder - however, this one is located inside the cab, under the dash, driver side, right around the area your right knee would be if your foot was on the accelerator. He said it is identical to the one outside only black in color.
This truck does not have dual tanks nor does it look like it ever had. There is no evidence of straps, old hose, no fuel door in the bedside to indicate it ever had two tanks.
Could this second relay be for something else maybe? I haven't seen it yet, just relaying (no pun intended) what I'm being told, will know more tonight.

thanks again to All!



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Old 03/20/17, 02:41 PM   #14
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I pic would likely help. Depending on how big it is, it could even be the delayed wiper module. Not sure if or when they changed the design, but in the early years it was separate from the switch, and looked like a big black relay. Pretty big for a relay though, at about 2" cubed or so.

Just a thought. No reason that Ford would not have other relays under the dash too. Broncos got a rear window relay there somewhere, but pickups may have had some odd function or another that needed it.
Or a "chime" module for the seat belts and whatnot.

Paul

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Old 03/20/17, 06:42 PM   #15
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Long story short... the second relay is a carbon copy of the first, just different location and still not sure what its purpose is but will look into it further.
Started over at the beginning (battery) and worked our way toward the end (in tank pump).

Turns out that pump #1 on the frame rail was dead. Replaced the pump and replaced the fuel filter, engine started after only a few seconds of cranking... runs great.

Thanks again to all for the information and suggestions.


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