Hey everybody, first time posting on this forum. I'll get right to the point, I swapped a 1997 351w and zf 5spd. into my 1966 f-100 several months ago and just got it running about 2 weeks ago. I have pretty much everything working properly except for the fueling system. I bought an inline fuel pump from napa which seems to have developed some problems, it has an acceptable and normal hum on start-up (no starting issues) but as the vehicle warms up over the course of 10 minutes it continues to grow louder until its screeching constantly. The engine also develops a noticeable hesitation when i floor it that gets worse as the pump gets louder. It also will not idle properly at this point (the pump begins to surge, going silent, then growing louder and then silent again) and the engine also surges i believe because the pump is diving below the regulator pressure. also note that the pump is not hot to the touch at this point that I can feel, even though it is very close to the muffler.

So basically there is a lot of surging going on at idle, a very unhappy pump, and a noticeable hesitation when you stomp on it. My fuel lines are all hooked up as they were except I have the return line plumbed in to the pump feed line as my tank doesn't have a port for a return line in it. The pump was deadheaded multiple times for about a minute each time before i had the engine running as my fuel lines were reversed, maybe i wrecked it doing this? Just for info, it made the same noises deadheaded as it does now that it is plumbed properly. Any thoughts welcome!

 

1. It could be a defective pump.
2. Debris could've gotten sucked into the pump and broke some impeller blades.

 

Were assuming it's carburated.

 

It is an OBD1 efi system.

But I did some trouble shooting over the weekend, and found that my plumbing was faulty. The return will have to have its own separate line right to the tank instead of teeing into the pump feed line (the tee was like two inches before the pump so maybe it is was too close?). The only reason I plumbed it this way was because my tank has no option for a return line. I ran the return into the filler neck and started the truck and the pump worked nicely (ran at 30psi at idle), so now I'm going to space the sending unit up and put a return line in through the spacer instead of having to drill holes in my tank and eliminate the tee completely. (I have modified the sending unit so it still reads accurately while being spaced up). Blew a coolant seal on the weekend so I got to fix that as well.
Thank you for the replies

 

So I have actually still been having these fueling issues. I thought I had them fixed with my return line, but a Sunday drive proved otherwise. After about 5 minutes of driving she started losing fuel pressure and eventually died altogether (worse than it has ever been). So I replaced the fuel filter trying to find my problem and it was right full of rust chunks, like literally full. So I'm gonna give the tank a clean and flush all my lines and hope my pump isn't destroyed. I'm going to weld in a proper return line bung with a down line while I have the tank out. (don't worry it will be full of water while I'm welding). So I'm hoping this fixes my issues even though I feel it doesn't explain the pump running for 5 minutes and then quitting. I relocated the pump to the outside of the frame rail to get it away from exhaust heat and installed a new filter, but it didn't make a difference. Maybe the pump is done from rust going through it? I don't think any got past the filter. Is there anything else you guys can think of that i may have missed?


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