I keep going through mechanical fuel pumps like crazy. It's a 1985 f250 with the 6.9 non turbo. I have checked the return line and there is no obstructions and the vent on top of the tank is good it will let pressure out. I can let the truck sit for a couple days and it starts up fine but for no apparent reason the pump will quit pumping I take the line off the filter housing coming from pump and all it does is push and then pull my finger with not much pressure at all not what it should b it should just push the fuel by my finger covering the fuel line. I then take the pump off get a remanufactured one install it bleed the air out of line before filter because filter is already full connect the line back on the filter housing and crank it with throttle pedal to the floor and maybe 10 to 15 seconds it starts. I'm not running any special fuel or additives. I put an inline filter before pump thinking junk from tank was wrecking pump but no luck it did last longer though lol. The pumps have never gonna bad when it has been running they seem to go after the truck has been shut off. If anyone has heard of or seen this happen I would like to know what could cause the pumps to keep going bad. I would also like to keep the mechanical one and not go electric.any help would be appreciated thanks

 

There are a few things you might try.
Try to place a piece of clear tubing in the suction line right at the pump so you can see what the pump is doing. If it is pulling/pumping air , now you know it is before the pump and work your way back to the tank.If there is any kind of crack/opening in the line you will see the bubbles.
Take a good look at the surface that contacts the pump arm and confirm it is not excessively worn.
If you are always using the same company/brand of pump there could could be a problem with their pumps.
There are check valves inside the pump and it sounds like they are not working all the time.

 

I have a clear plastic inline filter about 2 feet before the pump and it looks fine when it is running there are no air bubbles whatsoever even after sitting the filter is always full.. I know that there is no obstructions in the fuel line before the pump because when I take the line off at the pump and blow into it I can hear bubbles in the tank then I can siphon fuel back through the line with no issues. I use remanufactured fuel pumps the brand name is Precision and they do have a check valve in them which seems to be what is going every time. Why would 4 go bad though? Could this be a very poorly remanufactured pump. It is weird that it's gone through so many pumps.

 

Have you considered purchasing a NEW pump instead of the reman ones?

 

If the pump goes again I will end up spending the money and purchasing a new pump. I can not figure out why they go bad maybe the remanufactured pumps are just junk to begin with. However if something else is causing the problem than a brand new pump will just do the same. I have never heard of or seen this happen before I have heard of a remanufactured pump be bad after installation but never 4 of them going bad after 1 to 3 months of use so it has me baffled. It would be nice to find someone with the same problem because it really makes no sense to me. The truck runs great idles smooth starts amazing but out of the blue it won't start and I know what the problem is but I test everything before I rip the pump out and change it for another one