New fuel pump partially solved problem

[1972_Buford]

So I have had this issue where I am going down the road at about 45mph or more and the more sill sputter and stall out. Before I replaced the fuel pump it did this all the time. Replaced the fuel pump and took it out today to get gas. It ran perfect until I was on my way home. It stalled out once I was close to the house at about 50mph. Like I said in previous posts I believe I am chasing more than one problem at once and just going down the line.

Now it ran like a champ for the most part until I was almost home.

I have replaced- Fuel pump, plugs, wires, rebuillt carb with new accelerator pump.

Still need to replace HEI cap and rotor once I find out what to replace them with. Says AC Delco on it (ideas on what I need?).


I have no idea how old these are but the previous owner said he had not ran the truck in over a year before I got it.

Any more ideas?

[sleepertruck72]

I wouldnt use the AC Delco caps/rotors. They suck IMO. The MSD cap and rotor is inexpensive and reliable. Did you replace the fuel filter ? I would clean out the gas tank and replace the fuel filter if it sat that long. I would also blow compressed air through the fuel lines if at all possible, There may be junk in there and the sending unit "sock" filter if in poor condition may be letting it through...

[WadmalawJoe]

I had a similar problem, except it started with my tank, it had rust in it, and it spread through the lines of course. I replaced my tank, cleared my lines and a new filter of course and its been fine since. I would look inside your tank and do what sleepertruck said, clear lines and filter and blow through the fuel pump as well and see what happens.

[71 super]

Filter and try again. You might try a quality wix unit in line rather that the small stock one at the carb. If you have rust issues in the tank you might also think about removing and replacing the tank or at least having it flushed.
Posted via Mobile Device

[68gmsee]

Yeah, clogged filters and lines are a common problem on these old trucks. I would stsrt by removing the sending unit and checking the sock filter (personally, I prefer to remove it and install an inline filter).

I had a clogged fuel line between the tank and fuel pump that was so clogged with varnish that I wound up having to put a new line on there. It was restricting the flow to a trickle.

[rico7769]

similar problem with my 67 after purchase. Gunk in rubber line from hard line coming from gas tank through the floor and connecting the hard line to the engine compartment. Ruined two carbs because of the crap in the tank too. Cleaned it out with a gallon of carb cleaner, replaced everything rubber, new fuel pump, filter, and carb. Runs like new now.

[geezer#99]

Easy stuff first! Pull the gas cap off, take it for a drive. Could be simple vapour lock.

[68gmsee]

Originally Posted by geezer#99

Easy stuff first! Pull the gas cap off, take it for a drive. Could be simple vapour lock.

^ Also, if the cap is not venting properly it causes a vacuum in the tank which would prevent the pump from sucking fuel.

Picture shows where the vent valve is and it should move slightly up and down.

[1972_Buford]

Hmm interesting. The old pump had a return so i dont think vapor lock was an issue. It runs a lot better with the new pump and i put new rubber lines in. The old ones were clean. Could still be in the tank though. Also the carb wasnt all gummed up. I'll check the fuel tank next. I am wondering if the old HEI could also be a culprit. Also, some of the wiring to the HEI is cracked and i am wondering once it heats up if it is causing a problem.

[1972_Buford]

Dual post

[cdowns]

exactly what year and model truck r u talkin about?

71,72 have nonvented gas caps on models with the charcoal cannisters

HEI??? has a new wire with a full 12volt supply been trun? the factory original wire is a resistor and does not supply 12volts

[1972_Buford]

72 350. Funny thing is when i first got it it ran great and the stalling problem didnt happen until like a month later. I know full 12 volt or not. I'll check that as well. Problems start when it is fully warmed up. I'll work on the hei next and for venting at the gas cap. Dont see a charcoal canister fyi
Posted via Mobile Device

[1972_Buford]

So I pulled carb back off and opened it up. Found this little bugger sitting in the accelerator pump cup. Piece of old cup partially blocking fuel passage. Ran better this time. I think my last issue might have to do with the secondary tension spring allowing secondaries to open up before they need to. I'll test this tomorrow as i applied more tension on the screw.
Posted via Mobile Device