RJM fuel injection harness question

[Stevenb]

I have swapped them all twice just in case it was that. No change. I’m wondering if it could be a bad inertia switch?

 

[DirtDonk]

From Jame’s description of the factory layout, no it should not be a relay (sorry, a switch issue) issue.
But I imagine it’s possible that Ron Francis or RJM re-oriented the switch wiring to trigger the relay rather than be a simple pass-through for the pump power.
The wire run is much shorter with the switch inside on a kick panel, so maybe Ryan reinvented the wheel.

If you unplug the inertia switch does the relay kick in for a couple of seconds when you turn the key on?

And speaking of which… Are you taking those voltage measurements with the key just on, or with the engine running? Remember that when everything is working correctly with the computer your fuel pump only comes on for a second or two to prime the system.

 

[Stevenb]

With the key on. I run the two pump system and the low pressure pump by the tank runs almost constantly normally. The wire from the bottom of that relay kicks on at 12v for only maybe 1/10th of a second. Then drops. It does it every time you turn the key on. The relays all click back and forth then stop. I will try unplugging the inertia switch tomorrow to see what it does.

 

[jamesroney]

With the key on. I run the two pump system and the low pressure pump by the tank runs almost constantly normally. The wire from the bottom of that relay kicks on at 12v for only maybe 1/10th of a second. Then drops. It does it every time you turn the key on. The relays all click back and forth then stop. I will try unplugging the inertia switch tomorrow to see what it does.

OK. Let's get this fixed.

What are you saying? "With the key on, the low pressure pump runs almost constantly normally.." That is gibberish. If the low pressure pump is measuring 2.9 Volts, then it isn't "normal." If it runs constantly, that is also not "normal." How is the low pressure pump wired?

How are you establishing a constant fuel pump signal? When you turn the key from "off" to "on" the fuel pump only runs for 1 second, and then the computer turns it off. What kind of volt meter are you using, and how are you establishing your measurement? You only get to count to "one-mississippi" and it's all over. When you say that you are seeing something at 12V for 1/10 of a second...WHAT wire are you measuring?

Type slowly, and assume that I am an idiot. (or maybe just assume that I'm in 3rd grade) You won't hurt my feelings.

a. Unplugging the inertia switch will do nothing.
b. It is not the computer.
c. There are four wires on the fuel pump relay. They are Red, Pink, Orange, and White.
1. What is the voltage profile of the Pink wire measured at the relay when you turn the ignition switch from off to on?
(You should see 0 volts, then you should see +12V for 1 second, then you should see a fast decaying, noisy, counter EMF back to 0VDC.)
2. What is the voltage profile of the Red wire measured at the relay when you turn the ignition switch from off to on?
3. What is the voltage profile of the White wire? (probably don't need this, but since you are there...might as well measure it.)

That should be enough to get you working in the right direction.

 

[Stevenb]

First, I like you already. I will try to work on it and write it out but I have to make 17 pizza doughs, fresh sausage and sauce for those 17 pizzas tomorrow, then I have to cook them Wednesday. Nephews birthday and he asked for my pizza. I greatly appreciate your help. I will get on it Thursday. Thank you for the help and patience.

 

[DirtDonk]

Oh great! Not only do we have to wait, but now we’re jealous we’re going to miss your nephews party!
New business opportunity. Uncle‘s pizza and EFI troubleshooting business.
Have a great time.

 

[Rustytruck]

Just what is more important here? Pizza or Broncos, boy you gotta get your priorities straight. You need your Bronco running to deliver 17 Pizzas. You have a Pizza oven in your Garage? Damn kids always get in the way. Have fun 17 pizzas is allot of Pizza. you use a rising Dough? I sure miss a good pizza. California cant make a good pizza.

 

[Stevenb]

OK. Let's get this fixed.

What are you saying? "With the key on, the low pressure pump runs almost constantly normally.." That is gibberish. If the low pressure pump is measuring 2.9 Volts, then it isn't "normal." If it runs constantly, that is also not "normal." How is the low pressure pump wired?

How are you establishing a constant fuel pump signal? When you turn the key from "off" to "on" the fuel pump only runs for 1 second, and then the computer turns it off. What kind of volt meter are you using, and how are you establishing your measurement? You only get to count to "one-mississippi" and it's all over. When you say that you are seeing something at 12V for 1/10 of a second...WHAT wire are you measuring?

Type slowly, and assume that I am an idiot. (or maybe just assume that I'm in 3rd grade) You won't hurt my feelings.

a. Unplugging the inertia switch will do nothing.
b. It is not the computer.
c. There are four wires on the fuel pump relay. They are Red, Pink, Orange, and White.
1. What is the voltage profile of the Pink wire measured at the relay when you turn the ignition switch from off to on?
(You should see 0 volts, then you should see +12V for 1 second, then you should see a fast decaying, noisy, counter EMF back to 0VDC.)
2. What is the voltage profile of the Red wire measured at the relay when you turn the ignition switch from off to on?
3. What is the voltage profile of the White wire? (probably don't need this, but since you are there...might as well measure it.)

That should be enough to get you working in the right direction.

Pizzas were a huge hit. Then we got super busy and had bad weather. But today the sun is out. So here goes. My system is the two pump system from BC broncos. I swore that the rear pump (low pressure high volume) used to run almost constantly, but I’m guessing the was with the truck running. I know I could always hear it when I turned the key on.

Is there a possibility the rear pump is going bad? I can hook up my power probe and it turns on, but it doesn’t even turn on at all when the key is turned.

High pressure pump shows 0 volts key off. Follows exactly what the pink wire from the pump does.

Low pressure pump is weird. Shows a slowly decaying voltage from the last key on, but with the key off. Key on is a slowly climbing voltage only up to 2.15. Very slow. Sixty seconds just to drop to .40. Also, if I hook up the ground to the pump, ground my ohmmeter to the frame and touch the red probe to power, it reads .005 on the 2k range.

Both pumps are unplugged. Just testing at the wires.


Voltage on the pink wire. Key off, 0 volts. Key on goes fast up to an instant 10.46 to 12.39 to 11.3 to a steady 7.1. Sometimes drops to 6.99

Red wire. Voyage with key off is 12.4. Drops to 12 with key on.

White wire is light tan on my harness. 0.01 with key off. With key on. It starts slow. .98 volts, 10.98 after almost a full one-one-thousand, then11.05 to 11.48 .

Orange wires that loop between relays is 0.01 key off. Key on jumps to 8.08, 11.01, then steady at 11.45. Drops back to 0.01 right away with key off again.

Does any of this point in any direction? I appreciate your help so much.

 

[Stevenb]

OK. Let's get this fixed.

What are you saying? "With the key on, the low pressure pump runs almost constantly normally.." That is gibberish. If the low pressure pump is measuring 2.9 Volts, then it isn't "normal." If it runs constantly, that is also not "normal." How is the low pressure pump wired?

How are you establishing a constant fuel pump signal? When you turn the key from "off" to "on" the fuel pump only runs for 1 second, and then the computer turns it off. What kind of volt meter are you using, and how are you establishing your measurement? You only get to count to "one-mississippi" and it's all over. When you say that you are seeing something at 12V for 1/10 of a second...WHAT wire are you measuring?

Type slowly, and assume that I am an idiot. (or maybe just assume that I'm in 3rd grade) You won't hurt my feelings.

a. Unplugging the inertia switch will do nothing.
b. It is not the computer.
c. There are four wires on the fuel pump relay. They are Red, Pink, Orange, and White.
1. What is the voltage profile of the Pink wire measured at the relay when you turn the ignition switch from off to on?
(You should see 0 volts, then you should see +12V for 1 second, then you should see a fast decaying, noisy, counter EMF back to 0VDC.)
2. What is the voltage profile of the Red wire measured at the relay when you turn the ignition switch from off to on?
3. What is the voltage profile of the White wire? (probably don't need this, but since you are there...might as well measure it.)

That should be enough to get you working in the right direction.

Fuel pumps were wired as the old RJM manual showed, Pink wire front high pressure pump, Green wire to rear pump. It’s ran great for ten or more years until now.

 

[jamesroney]

IGNORE THIS POST.

 

[jamesroney]

OK, I went out and tried to verify the Green wire on the low pressure pump. I dug out my old Ron Francis wiring installation manual. Where are you seeing a green wire? I can't find any refernce to a secondary fuel pump on the ron francis TDZ-Bronco 75 Ford EFI harness.

Now I DID find a green wire as an auxiliary power wire in the Centech Body Harness. Are you using a Centech harness in conjunction with your Ron Francis EFI?

If so, then yes... the Centech harness has a green wire that is under the hood and is a switch ignition power source. It will be Hot at +12 in the ON position only...not ACC.

 

[Stevenb]

OK, I went out and tried to verify the Green wire on the low pressure pump. I dug out my old Ron Francis wiring installation manual. Where are you seeing a green wire? I can't find any refernce to a secondary fuel pump on the ron francis TDZ-Bronco 75 Ford EFI harness.

Now I DID find a green wire as an auxiliary power wire in the Centech Body Harness. Are you using a Centech harness in conjunction with your Ron Francis EFI?

If so, then yes... the Centech harness has a green wire that is under the hood and is a switch ignition power source. It will be Hot at +12 in the ON position only...not ACC.

No harness yet. I will be installing one soon, but right now the only new wiring is the RJM harness under the hood. By new I mean ten or so years old.

 

[Stevenb]

Yep, I could see where you were headed in your thought process. But remember that all of those Ford inertia switches were mounted in the trunk tail light panel, (near the tank) and the relays are mounted up front. So they do indeed sit on the load side of the relay and carry all of the fuel pump current.

The OP was asked to measure the voltage on the relay (line and load side) back in post #8 in the thread. Until he does that, I can’t help.

I’m measuring under the relay on the pink wire as well as by the pump.

 

[Stevenb]

Just what is more important here? Pizza or Broncos, boy you gotta get your priorities straight. You need your Bronco running to deliver 17 Pizzas. You have a Pizza oven in your Garage? Damn kids always get in the way. Have fun 17 pizzas is allot of Pizza. you use a rising Dough? I sure miss a good pizza. California cant make a good pizza.

I make my own dough, sauce, and sausage. It’s basically Nick and Vittos pizza from Chicago with finely diced green peppers added so it tastes closer to a Howard’s special from Great Falls, MT.

 

[Stevenb]

No harness yet. I will be installing one soon, but right now the only new wiring is the RJM harness under the hood. By new I mean ten or so years old.

So I looked at my instructions from forever ago. I must have spliced the green wire into the pink to run the two pumps. I have to chase down that splice. I know I soldered and heat shrink tubed every connection as well as used dielectric grease on them. As far as the orange wire floating, I’m not sure how to fix that. You guys are all so amazing to help me so much. If any of you ever come to Spokane I’ll make you pizza!

 

[jamesroney]

So I looked at my instructions from forever ago. I must have spliced the green wire into the pink to run the two pumps. I have to chase down that splice. I know I soldered and heat shrink tubed every connection as well as used dielectric grease on them. As far as the orange wire floating, I’m not sure how to fix that. You guys are all so amazing to help me so much. If any of you ever come to Spokane I’ll make you pizza!

OK, the instructions say to splice the secondary pump into the pink wire.

Now we just need to chase down that ground on the orange wire. Unfortunately, my dash is back in...so I can't open up my harness. (But we will get to that later...Lets see if we can bypass it for now.

Next step is to take out the relay cube, and apply a jumper wire direct from the battery positive post to the pink wire. That should make the pumps run as they should. You might want to put a 20 amp fuse in your jumper wire if you are not inclined to look for big sparks and yank the jumper out hot. (I usually just jump it hot with a small jumper wire. If I am looking at a dead short...it will just burn up my jumper...)

Odds are that your jumper will work fine. If it does work fine, then take a jumper and jump from RED to PINK at the cube connector. That should make the fuel pumps run "normal"

Give that a shot. You can text me at 831-484-4959 for faster replies.

 

[DirtDonk]

No main harness? I think that would’ve been important to know early on. Maybe I missed it.
Where are you sourcing power? You need main power to the relays on the heavy wire, and switched power to the RJM harness connector at the back of the engine, as well as grounds.
The grounds are usually included in the RJM harness and are typically sufficient for the EFI stuff. But for a fuel pump that need more battery power than can come through the computer, where are you pulling power for the relay array?
And how is the main system grounded?

 

[jamesroney]

So I looked at my instructions from forever ago. I must have spliced the green wire into the pink to run the two pumps. I have to chase down that splice. I know I soldered and heat shrink tubed every connection as well as used dielectric grease on them. As far as the orange wire floating, I’m not sure how to fix that. You guys are all so amazing to help me so much. If any of you ever come to Spokane I’ll make you pizza!

I'll get you info on the orange wire. It is NOT the dedicated ground. Don't Ground it!

 

[jamesroney]

This post is from the EEC-4 schematic. I will verify that the Ron Francis / TDZ / RJM Harness is the same...

The Fuel Pump Relay wiring consists of 4 wires. There is:
Big Red Wire = +12V from the RJM fuse block directly from the Battery.
Big Pink Wire = Switched +12V to the Inertia Switch, then to the Fuel Pump / Pumps.
Orange Wire = VPWR, +12V from the EEC power relay. also feeds the EEC pin 37 and Pin 57, etc. Hot when ignition is on.
White Wire = Sinking control wire to the EEC pin 22. Also routed to the self test connector. When pulled to ground, it energizes the FP relay coil.

 

[jamesroney]

There is a bank of 4 fuses included with the RJM harness. What is the voltage present at the fuse panel on the 2nd fuse down? Since it goes directly to the Battery positive, it should be +12V all the time. Please verify.