Any mechanics here or .....

[real69ss]

some one who has had a similar problem ?

I have a 68' short bed, that hesitates, like it's running out of fuel. It started at freeway speeds (50+ MPH) but lately it has started doing the same thing at surface street speeds.

I did a tune-up ( plugs&wires ,cap&rotor) and an oil change, and a fuel filter. The problem continues!

I have driven the truck daily for over 3 years with no major part changes/upgrades. It has been converted to an HEI, but that was already in place when I purchased the truck.

It has a carbureted 350 w/ a 700r4.

Any ideas?

Thanks!

[geezer#99]

Fuel pump is dieing or almost dead!!

[truckster]

It could also be the strainer on the end of the fuel pickup tube. They can collapse or corrode and block fuel delivery.

[Billett]

I had a similar problem, but giving the carb a once over with fresh gaskets fixed it for me. Mine would stumble around 45 or so like it wasn't getting enough fuel, and every now and again it would run fine over that and then just as suddenly die stumble again.

[SS Tim]

Sounds like a classic fuel pump problem. Have you downloaded the service and overhaul manuals?

[real69ss]

I have a service manual. One other thing I don't know if this makes a difference or not.

I can keep it in park or neutral and rev up the engine and there is no hesitation or similar type of symptom.

Thanks everyone!

[SS Tim]

The pump is probably not putting out enough flow to keep up with the engine under load. There is a big difference between reving and driving. If you have access to a fuel pressure gauge you would see a drop while driving at the fault speeds.

[real69ss]

I think I have a gauge, if I can't find it I'm willing to drop the $20.00 to see if it fixes the problem. I'll keep you posted!

Thanks again!

[SS Tim]

A fuel pressure gauge in itself will not correct the problem it is a diagnostic tool. The service manual should give both a pressure and a flow spec. the pump should meet.

If you decide to try a gauge it needs to be between the pump and the carb. inlet and before a regulator if you added one. It must be readable while driving, preferably by a passenger who can record the numbers for you.

[twich3136]

i had starving symptoms yet everything checked out, the pressure was there, the air was there, the spark was there.. that is until i got out on the road. it started off slowly since i bout the truck. i replaced a lot of worn out stuff but the symptoms were still there. until i unhooked my carb's electric choke. after that it ran like a champ..trace the wires and it was tapped into the coils power wire along with 3-4 other things.

what im getting at, is your coil getting enough voltage to keep up with higher revs?

it took me a full year to figure that one out.

[Boog]

It could be a failing ignition system.
Hook up your timing light and verify the timing is advancing as it should. If it doesn't gain advance look to the dist.
The centrifugal advance in the dist may be siezed up not allowing for full advance. The dist shaft can get gummed or a varnish buildup over time and finally it won't advance anymore. Been there once with an old 327. It got so bad it almost wouldn't pull itself anymore. The dist has to be completely disassembled to clean it up good or just buy a replacement. A remand hei was running about a $100.
You need to remove the dist cap and grab the rotor and turn it back and forth to check it. It should move with only a little tension on it from the advance weight springs maybe less than a quarter turn.

[Bluechevy68]

I had a 68 short bed that had a smiliar problem. It would completely die at random moments, mostly while going up a hill or something. However, it would also do it while in park and reving the engine. It would run great than just quit and often it would pick right back up again. I changed the fuel filter but it did not fix it. I did not really like the truck so I fixed its problems by selling it. I know I know before you ask the buyer knew of the problem, it died a couple times while I drove it to his house. He said if it made it to his house he would buy it and if not he would not. That was a long 10 mile trip.

[RexDodge]

You're going to get a ton of good advice to check this and that. Stick to to trouble shooting one system at a time (fuel, electric etc). Is the hei a stock GM unit? What carb/intake? Where is your fuel filter located (I saw you changed it). How does the wiring that the po did look?

[68gmsee]

I agree with RexDodge. List the fixes and do one at a time starting with the easiest first.

And add this to the list.. Since the HEI was there before you got the truck, trace the 12vdc wire to make sure it's not using the original resistive wire that came with the truck. If it does, you need to rewire it since the HEI needs a full 12vdc.
http://67-72chevytrucks.com/vboard/s...d.php?t=471270

[real69ss]

I never updated this! It was the carb.