Technical Mechanical fuel pump problem Y-Block

I’m baffled. My mechanical fuel pump will pump when cranking. But once the engine is running it no longer pumps. This is my second replacement fuel pump. I have replaced the rubber lines and the filter. I dropped the tank and cleaned it. I replaced one of the hardliners that did have a pin hole in it. And it is still acting up.

This is a 292 y-block on my 1955 Ford T-bird. Any ideas other than install an electric pump?

 

It's possible you're still sucking air when the engine is running it's sucking air faster,
A lot of pumps that are sitting on the shelf that are Not names brand will have issues Rubber diaphragm cracking,/dried out new from the shelf use a name brand
(performance name or well known brand)
Fuel sock in tank?
To diagnose the problem use a 5 gallon jug in the back of the vehicle and hook it up to the hardline tank and see if it runs/ pumps .possibly Tank not vented.

 

possibly the hose is collapsing on the inside. old hose ?

 

gas tank vent is good?

 

what carb? I had the same problem a couple months ago. carb was plugged. and would only let enough fuel in to run down the street then die .AFB carb .far side screen plugged. couldn't see anything till we took the top of the carb off .Went with a Holley instead.

 

Add Y Block in your thread title to get more views.

Seems I've read about vacuum lines from early Y block fuel pumps being a problem.

 

Ok. I hadn’t considered the tank vent. I’ll leave the filler open and see what happens and then look into it if that helps. The carb isn’t the problem. It won’t let me upload a video but basically it pumps while cranking but not when I get it started and I know this because I disconnected the line right before the carb. Not saying the Holley 4160 on a 1957 intake couldn’t use a rebuild or attention. But the problem is verified before it gets to the carb. Then the only two parts that haven’t been replaced are the two hard lines that run the length of the car. I bought replacements and that will be the next step. But I blow out the lines already so I thought that they were clear. And all other soft lines have been replaced. And the last new replacement pump did suck because I hooked it up right from the pump to a fuel source without going the length of the car and it did pump but not enough to keep the car running. So that is why I got a second replacement. So the pump still could be bad but it seems all the top brand name pumps are out of stock so then I’m SOL.

 

Probably not your issue but this happened to me when I was 17 on my 56 Ford with a 292. The bolt that held the eccentric to the cam worked loose.

 

There’s 2 current threads on fuel pump problems on yblocksforever right now. So don’t feel alone. Bad diaphragms and check valves seem to be near the top of the list. New and even “name” brands don’t seem to be any guarantee.

Half way down is a post about the Casco rebuilt pumps. They won’t accept off shore pumps as cores. Got to be US, Canada, or Mexico. There’s a message there.

http://forums.y-blocksforever.com/Topic161558.aspx

 

Before you do anything further you need to "troubleshoot" the fuel system: Get a five gallon gas can and a long rubber hose, put the gas can in the car and run the rubber hose to the inlet on the fuel pump. If the engine runs OK, the problem is from the fuel pump back, if it won't run, the problem is from the fuel pump to the carb. Best of luck with your project.

 

Two bad pumps in a row would be unusual but not unheard of. Problems I've seen with a line or fitting sucking air usually cause hard or no start, but often pump enough fuel with engine running. I'd look at the fuel pump eccentric but that's a real long shot. If loose or damaged it could impair the pump stroke, but it seems like you'd hear some noise. Could probably check through the fuel pump flange at least by feel.
Is gas tank original? If so, I'd give that a hard look, especially if someone has used liquid liner in it. Clogged tank strainer will cause behavior you described. That can let enough fuel seep by to start but not run.
Vacuum gauge can tell you if pump is making enough suction or lines are sucking air. Cheap and effective tool to diagnose a lot of engine problems and adjust idle mixture. They are like a scan tool for old cars but way cheaper, less than $20.
Best way I've found to head off fuel problems is to stay away from gas with ethanol in it. I can get 93 octane "recreational fuel" for about a buck more a gallon. Extra cost is well worth it. Use it in everything I have with a carb and the improvement in starting and running is noticeable. Best part is that it doesn't continuously "clean" your fuel system and deposit all the gunk in the tank strainer and carb. Plus, ethanol deteriorates any rubber parts not formulated for it, but it can give you lots of opportunities to sharpen your carb rebuilding skills.