Fuel pump

GFFR57

MEMBER
1973 FORD F-250
6.4L
V8
2WD
AUTOMATIC
67,000 MILES

Mechanical fuel pump will not pump! Recently pulled my 390 out of truck listed above. Replaced all seals and timing chain/sprocket as well as oil pump, fuel pump, etc. Initially, it ran fine for twenty minutes or so. The next day, would not start. Was able to suck fuel from the tank through the lines. However, from the pump to the carburetor Nothing. Took apart timing cover again to check eccentric. There were signs that the cam dowel was not long enough to engage the eccentric and it was spinning on the bolt. Replaced with a slightly shorter pin and an eccentric that had a tab that went into the dowel hole. Put back together and the pump still will not pump fuel! It will run for a few seconds with fuel in the carburetor so everything on the cam side should be functioning properly. Does it need to primed? I cranked on it off and on for the better part of an evening. I am at a loss! Help!

5 Replies

CJ MEDEVAC

MECHANIC
11,004 POSTS

Is there a fuel filter attached to the carburetor? Internal in the carburetor? Maybe it is clogged?

Sometimes it might take a little priming to get the fuel through the line. I will use a spray bottle or a water bottle with a "sports" lid to either squirt or dribble fuel into the carburetor to keep the engine running until it gets its own fuel.

I strongly suggest when doing any of this stuff that I discuss in my answer. Do it outside! Away from the house! Away from other vehicles!

A soaking wet towel as your first defense and a fire extinguisher if things get bad.

You may never need them, but it is always a good practice to have handy if you should need them.

Check the inlet hose to the fuel pump (maybe the tank end too). See if the clamps are tight and you did not create a split or hole when you removed/ installed them initially.

If the line is old, moving them around may have created a hole/split.

If this is a new pump, is the arm length and design the same as the old one?

Have you taken a rubber fuel line loose between the pump and carburetor to see if it pumps to that point when cranked?

Can you connect a vacuum gauge close to the inlet side of the pump and see if there is suction while it cranks?

No vacuum gauge?

Install a new three to four foot piece of fuel line to the inlet of the fuel pump, drop the open end into a small gas can with some fuel in it. Take a rubber fuel line loose on the outlet side of the pump. Crank it while watching the open outlet line of the pump. Any fuel pump through?

Yes?

Reconnect the outlet line, now will it pump fuel to the carburetor from the temporary gas can.

If it is working now, you probably need to replace the fuel line from the tank to the fuel pump.

Your turn,

The Medic

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Sunday, January 28th, 2018 AT 6:23 PM

GFFR57

MEMBER
24 POSTS

The pump is new and looks somewhat different than the original (I have tried two of the same brand, thinking that maybe the re-manufactured pump was junk). My thought was, like you suggested, that perhaps the pump arm was not making contact with the eccentric. I threw away the original so I have no means of making a comparison. I have been through the fuel from the tank to the carburetor and all seem fine. As I said, I can suck fuel through them. I rebuilt the carburetor and the filter is new. I disconnected the fuel line from it and nothing came through. I disconnected the line on the intake side of the pump and put my thumb over it and felt no suction. I will try to fill the line with fuel as you said, but my best guess is that the pump is not being pumped for some reason. Thanks!

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Monday, January 29th, 2018 AT 10:28 AM

CJ MEDEVAC

MECHANIC
11,004 POSTS

At the end of my answer I "screenshot" part of rockauto.com.(you cannot do any clicking on my picture!)

They show various pumps in their catalog.

Go there, plug in your information, find what I screenshot.

Click into each one of the pumps and see if any look like your old one may have looked. If there are different views, look at them too. Read specs, look at the arm lengths.

Here is the link to get you started:

http://www.rockauto.com/

Maybe you will find the correct one. I have also looked at other online auto stores, most seem to have a long arm.

Have looked to see if the eccentric is "wobbling" up and down or is it not moving at all?

You might try a paint stir stick, trim its width to fit, stick it in under the eccentric, sort of gently lever off of the bottom of the hole the pump fits into. Gently hold pressure on the stick.Turn the engine over a few revolutions and see if "Your end" teeter-totters up and down.

Just for giggles, pull yours off. put it in a vise, pump by hand, feel for suction on the inlet hole.

Another possibility is a brand new defective fuel pump, it happens!

The Medic

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Monday, January 29th, 2018 AT 6:11 PM

GFFR57

MEMBER
24 POSTS

Well, I went back through everything from the tank to the carburetor. Removed the pump, checked the eccentric, checked the lines, so on and so on. Found nothing wrong. But, for some reason, it runs now. Ha! Do you have any tips on carburetor adjustment? It idles and revs fine but shuts off when I put it in gear, and bogs down when accelerating, at least until it is warmed up. I rebuilt the carburetor, but it was my first so I am pretty novice.

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Wednesday, January 31st, 2018 AT 7:29 AM

CJ MEDEVAC

MECHANIC
11,004 POSTS

I have a link to tuning a Jeep using mine as an example.

It's gonna basically be the same for any simple carb.

https://www.2carpros.com/questions/jeep-cj7-1985-jeep-cj7-stalls-when-hot

Disregard the stuff specific to the Jeeps.

I think you'll understand as you get nearer to the end.

Return to this thread with questions/ good news!

I'm glad it figgered itself out, you can still take credit when you talk to your friends! LOL!

Your turn,

The Medic

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