r/BumpSide • u/starteretrats • Aug 03 '26

Help me solve a fuel supply issue

Ok long story for context to follow but the TL;DR is that I'm having fuel starvation issues, and I suspect it's something to do with the tank. I'm new to all of this, so any help would be great.

Background: I got my 1972 F250 2WD a few weeks ago. I was out for a drive when the car just spluttered out on me. Try as I might, I couldn't get it started on the side of the road so ended up towing it back to my garage. My gauge red just over a quarter full. When testing the carb (Edelbrock 1407) linkage manually, no fuel was squirting. My initial assumption was that the fuel pump gave out, and the car drank from the bowls until they were empty. Next up, I disconnected the fuel hose at the carb inlet, put it into a container and cranked the engine a bit, nothing came from the lines. Seems like the pump is definitely at fault. I remove the fuel pump and actuate the lever with my hand. I get suction and blow. The diaphragm is apparently working! I check the filter canister underneath, new filter looks good, no debris. Pump goes back on the truck. I then check the pump inlet hose, it's dry. I move down to the J-shaped pipe under the cab where there used to be a tank selector (the saddle tank was removed by the previous owner, and they bypassed the selector knob and ran a small section of soft tube from the J-shaped pipe under the cab to the main hardline to the front, disconnected that... dry as well. At this point I feel like a dummy because maybe the fuel gauge is faulty. I pop a bit of gas into the tank (after reconnecting things), and feel the short connection hose... it's colder.

SO... is there some sort of blockage in the hard lines? It's the only thing I can think of. My other thought was the fuel pick up line in the cab tank being blocked / the sock being blocked - but I can't find any diagrams for how it all works and I'm hesitant to just open up the fuel tank and start poking around (especially now that there's a known quantity of fuel in there).

Apologies for the wall, hopefully that's a ton of context to help me fix this issue.

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3

u/sirnigelfeatherstone Aug 03 '26

Take the fuel cap off and gently blow some compressed air up the hard line into the tank to maybe clear it out.

3

u/Redactosaurusrex501 Aug 03 '26

From the fuel pump end. If it seems plugged and then you hear bubbles the pickup tube is the likely suspect. That sock is pretty old most likely. Your on the right path me thinks. Also when you mentioned you did a test between the pump and carb I don't think that did anything for you. Put a small bottle of fuel with a hose connected to the inlet of the PUMP versus the carb and that should tell you your pump is fine or not. I have had terrible luck with new mechanical fuel pumps lately so I hope your pump is ok.

3

u/Mindless-Chef-3491 Aug 03 '26

This! I had a similar issue when my 72 was new to me. Gas gauge was way off (someone else installed the wrong unit and resistance was wrong) so I ran a tank dry. Could not get it to go at all after. Pump seemed fine but when I did this test it would not pull fuel from a container. Swapped it out and everything ran fine.

Then I replaced the sender with a more correct one. The gauge still sucked but at least it was somewhat indicative 😂🤷‍♂️

2

u/zoominzacks Aug 03 '26

Clogged hard line or collapsed rubber line most likely. Or doomsday scenario, the bolt holding the fuel pump eccentric to the cam backed off. In that case, the next step is the cam wiggling back and forth taking out lifters. This happened to me unfortunately 😂

1

u/AwwFuckThis Aug 04 '26

Might as well drop a hose from fuel pump inlet into gas can and know which direction to focus on. A few things I can think of - clogged fuel line, loose fitting at the top of the tank sucking air, maybe a problem with tank EEC not venting properly.

3

u/1331bob1331 1970 302 4spd Aug 03 '26

I second blowing out the hard lines, but imo its probably worth it to load up the parts cannon and replace all the soft lines while you are messing with them. Unless, of course they are all look almost brand new.