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Mech Fuel Pump Issue I Cant Figure out,,,

u10072

Bronco Guru
Joined
May 18, 2007
Messages
2,249
Hello All,
Here is what I have going on-- Ive been working on a 73 for a few months doing some things to it and one being getting it running after sitting for at least a few years. So I swap out the carb, get it running- drive it a few miles and park it to just start on the rest of the project. I finish all the other things, charge the battery, prime the carb with gas and I am getting like zero fuel out of the pump. So I replace the mech pump with another and nothing. With the same replacement pump I add a clear fuel filter and there is literaly a dribble filling it up at the very best. I do this with literally three different Autozone pumps-- nothing. Go to an Oreilly mech pump which I believe is a repackaged Carter due to the name on it and there is nothing. On all the pumps I have taken a line from the pump down to a almost full 5 gallon gas can. The hose is all new on suction and on the pressure and the clamps all tight. Took the hose off the fuel filter just to make sure no obstructions and nothing. Take the pump with the hose in the gas can -- push down on the pump lever and gas goes flying out the end of the pump. Yes for sure the suction side/pressure sides are correct. When mounted the forward with the stamped barb is suction-- the side with the fitting is pressure which is toward the rear axle.

The engine ran when parked with literally nothing done to anything but the suspension. Has anyone ever seen the eccentric ever go bad? I mean there is literally only one way that a pump can go in and bolt up. I wanna keep the mech pump but at this point we are at electric pump with a blockoff to get this finished.

If you all have any ideas please let me know because I am at a loss at this point unfortunately.

thanks,
Matt
 

jw0747

Contributor
Bronco Guru
Joined
Nov 22, 2006
Messages
2,434
Loc.
San Antonio, TX
eccentrics are not prone to wearing out. sometimes they are left out of an engine rebuilt. shine a flashlight into the f.p. hole to see if it's there.

you are probably not getting the arm positioned correctly against the eccentric. usually when installing a pump if the arm is positioned against the eccentric correctly you will feel pressure on the pump when pushing it inward to line up the holes to start the bolts. lots of pressure on the pump if the arm goes in against the eccentric on its wide side. if the pump slides in easily without any pressure being pushed against it the arm is probably not positioned correctly.
 

gnpenning

Contributor
Bronco Slave
Joined
Dec 26, 2011
Messages
1,921
Loc.
I have more questions than answers.
You might try putting a gauge on the pump both suction and pressure sides while cranking. NOt sure but it sounded like you only put the suction side in the 5 gal tank then tried it by hand??? Sounds like you may have something farther back. Put the inlet line in the gas can then crank it and see what happens. Keep working back till you find it. Do you have dual tanks? If so checkout the switch valve and position, does it flow in both directions? What is the fuel level in the tanks, don't trust the gauges. Maybe clogged pick up? Etc.
 

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,343
Matt, I had the exact same issue/symptoms. I replaced several fuel pumps thinking that was the culprit. Turned out to be the fuel pick up unit in the gas tank. The mesh "sock" was old n clogged. Do yourself a favor...order the whole pick up unit, install it and be done with it.
 

casadejohnson

Bronco Alchemist
Joined
Jan 21, 2005
Messages
3,587
In High school, a buddy of mine had a Bronco that had the same symptoms. Like you did, we eliminated the bronco tank and fuel lines by running a fuel line directly into a gas can. In our case, we found that the eccentric indexing finger was sheered off and the bolt was just loose enough that the eccentric could spin and as a result was not working the fuel pump lever. Its something to check at least. I would think you could stick a screw driver in there and see if the eccentric moves around at all.
 

Sporto

Sr. Member
Joined
Oct 10, 2005
Messages
903
When I was in high school, I replaced the camshaft in my Bronco, and even though I used the recommended torque settings, and Loc-Tight, my eccentric fell of the cam and left me stranded - twice. I had enough of that and I removed the eccentric and did the electric pump with the block off plate and never looked back. Still run the same pump today and that was 28 years ago. Never had an issue with fuel delivery ever again.

The Carter 4070 electric pump is as solid and as reliable as they get. Make sure to get an oil pressure shut off switch so if there is an accident and the engine stalls, the power to the pump is cut off and there is no additional fuel being pumped onto the scene. Holley makes one and it sells for about 20 bucks. Cheap insurance. Also make sure to add a relay and pull power from the battery to the pump, I had another vehicle that would get vapor lock on hot days from not having enough current to power the fuel pump. (it was not a Carter though) I rewired it through a relay and never had the problem again.

I also agree with the other post that the camshaft pin may have sheared off, and the eccentric is just sitting still instead of pushing the cam lever on the pump. I also had this happen as well...I had the pin removed and replaced at a machine shop. Kind of a pain, but not that big of a deal.

Needless to say, I was an expert removing the TC cover and pulleys on my Bronco!

Good luck!
;D
 

DirtDonk

Contributor
Bronco Guru
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Nov 3, 2003
Messages
43,772
Two other problems I can see possibly causing your symptoms Matt.
Of course, first thing is to check what the others have said and make sure the eccentric is not loose and that you're installing the pump arms up against it.
That said, having done nothing to an engine that's been running fine for years, the likelihood that the eccentric is loose is lower.

The other things are:

1. The carburetor's float valve is stuck closed. Surprisingly even a good pump has a very hard time pushing through a stuck needle-n-seat. Add some compressible air into the line and it just gets harder.
Blow some low-pressure air (5 to 10 lbs or so) through the feed line to make sure it's not stuck.
If it is, you can smack the top of the carb with something heavy but cushioned (heavy plastic handle?) and likely open it up.

2. The pumps are not priming. It's VERY common for a new mechanical pump to take more than just a little help to get it started. Even with the stock tank trying to push fuel up into the line via gravity, it's not a perfect method. Add a low fuel level and you don't have much help from gravity.
Is your engine cranking slow? If so, that's even worse.

I guess the easiest method would be to pour fuel down the suck-hose and hold it high to make sure that the pump is getting just fuel and no air.
If that doesn't work right away either, I've literally had to do the old "put your finger over the outlet to fool it" routine.
I pulled the carb end off the pump and held my finger over the port while someone kept the starter cranking the engine. That cured it in about 3 seconds.
Could have been all the other work already done of course, but it finally sucked fuel only after I got to that last step.
A fuel line from the port would be cleaner of course, as your finger over the port itself is likely to spew fuel in several directions at once. So safety glasses and a good aim are essential.

Hopefully you don't have to get to that point. But I'm thinking it beats the heck out of pulling the front of the engine apart to re-fit a pump eccentric!

Good luck

Paul
 

DirtDonk

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Nov 3, 2003
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43,772
Oh, and to add to number 1 above. Unfortunately, in my experience at least, if you have a needle-n-seat that are sticking, they're likely to do it again and again.
Not sure how many cures there are, but one of my old carbs sure looked beat up after a few months of hitting it with anything I had laying around to get going again. Even a plastic screwdriver handle will take it's toll after enough blows.

Paul
 
OP
OP
u10072

u10072

Bronco Guru
Joined
May 18, 2007
Messages
2,249
Ok I have the new mech pumps on the engine... With a hose going down into a full 5 gallon can and the outlet hose connected to nothing
. While cranking I am getting zero output from the pump. The battery is at full charge while cranking btw. You take the pump off the engine with the hoses still connected and press the lever and the pump pumps. It's getting the electric as I am not doing the timing cover tango :)
 

casadejohnson

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Joined
Jan 21, 2005
Messages
3,587
Ok I have the new mech pumps on the engine... With a hose going down into a full 5 gallon can and the outlet hose connected to nothing
. While cranking I am getting zero output from the pump. The battery is at full charge while cranking btw. You take the pump off the engine with the hoses still connected and press the lever and the pump pumps. It's getting the electric as I am not doing the timing cover tango :)

I understand not wanting to get into the timing cover and open up that can of worms, I would at least try to see if its loose in there through the fuel pump hole before you slap a cover plate on there. If the eccentric were to come off in there it could cause a whole new set of problems.
 

patterdale

Bronco Guru
Joined
May 24, 2010
Messages
1,246
Sounds like the eccentric is just spinning on the crank. As was said even if you slap a cover plate on you need to make sure the eccentric will not come off. Better to pull the timing cover and make sure what you have.
 

DirtDonk

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Exactly what they said. After all, if the eccentric is loose because the bolt is loose, that's your cam-gear retaining bolt and you're going to be in for a lot more headaches than a fuel pump issue if that comes any farther out.
Should be able to tell at least part of the story with just a quick finger in the hole I would think. Never tried it myself, but can't you get a finger in there enough to see what's going on guys? I would think so, even though it's likely at a somewhat awkward angle.

Good luck.

Paul
 

A4x4Junky

Sr. Member
Joined
Jan 9, 2007
Messages
550
Loc.
South Jersey
Exactly what they said. After all, if the eccentric is loose because the bolt is loose, that's your cam-gear retaining bolt and you're going to be in for a lot more headaches than a fuel pump issue if that comes any farther out.
Should be able to tell at least part of the story with just a quick finger in the hole I would think. Never tried it myself, but can't you get a finger in there enough to see what's going on guys? I would think so, even though it's likely at a somewhat awkward angle.

Good luck.

Paul

Had the same problem they mention with the fuel pump eccentric. On mine the bolt had backed out far enough that parts had started to rub on the timing cover inside. I understand not wanting to pull the timing cover, but I still think you should.

Anthony
 

roundhouse

Bronco Guru
Joined
Sep 5, 2003
Messages
2,870
Make sure you're getting the arm under the eccentric
If its easy to bolt the pump on the it's not under the eccentric

Holding the pump up and getting the bolts started while the arm is under the eccentric will take some muscle

I use some long bolts with he heads cut off or all thread rod
I start the long bolts in. Slide the pump on and run a nut up on it. Then you can pull them out one at a Time and replace em with real
Bolts
 
Last edited:

blubuckaroo

Grease Monkey
Joined
Jun 11, 2007
Messages
11,764
Loc.
Ridgefield WA
I agree with rounhouse. I'll bet the arm is on top of the eccentric instead of under it. I can see the old pump failing from sitting in the garage but the eccentric didn't come loose. A mechanical pump can be a bit difficult to install, especially if you have power steering. First, glue the gasket to the pump with Gaskasinch or contact cement. You need to direct the arm down and under the eccentric. You'll end up with the pump not able to fit squarely against the block. You'll have to press the pump down flat with one hand, and put in the bolts with the other. The first time you do one is really awkward but not nearly as bad as a Chevy V8 and their goofy push rod arrangement.;)
 
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