help with fuel delivery issue, please!

[OJ1988]

Okay, this is on my daily driver and is becoming an issue.

First vehicle info.

1969 Chevy C10 truck, original except where mentioned.
120,000 miles.
250 6cyl
3 on the tree

About 2 years ago, installed a
clifford intake,
450 holley mechanical secondary 4 barrel carb
split headers with glasspacks

about 6 months ago added new HEI dist.

carb was rebuild about 6 months ago as well.


Here is the problem.

When driving at sustained speeds over 50 mph, after a distance of 5 miles or more, it will fall on its face. Basically like you shut off fuel to the motor. Pulling over, stopping, and taking back off does not cure it. It will run at low speeds, under 35mph fine, but if you get on the gas it does nothing.

Now, I can drive around town for hours and it never does it.

Typically on the highway, I could make it about 10 miles, which is great, because I drive 8 miles in interestate to and from work. Sometims it will do this at mile 4 though which can be a problem.

It does not seem to be affected by temperature, or any other factors. Sometimes it does it sometimes it does not, but there never seems to be any corralation the times it does it.

When it first happened I changed the fuel pump, fuel filter, and sprayed cleaner in carb.

Any ideas?

[bigguy69]

i had something similiar happen to me. going down the interstate it would do they same thing. ended up that float on the carb was set to low. it would stick the free itself up. it finally got to where it would run a few seconds at a time. i had my friend adjust, been doing great ever since.

[OJ1988]

interesting. I will try and raise them, and see what happens.

[orangek5]

This sounds familiar It might be a crack in your fuel line from your tank, or it could be the module in your hei system. Im intrested in hearing what other might say because I also have the same Identical problem.

[68 C-10 Panel]

Im interested in what the "cure" turns out out to be also. Had some of the same problems with my 250 but i have the monojet still. Also not to hijack the thread, I wonder since you said you put on the clifford intake, and yours is a 69 I assume you do not have the integral head config. I have a 68 c-10 and it has the one pice head, intake, and exhaust assy. I wonder if this is stock original? If anyone has any info. And good luck on the fix.

[cdowns]

try taking off your gas cap the next time it happens

[LockDoc]

-
If the gas cap trick doesn't work try rocking the truck from side to side with the engine off. It may be sucking junk into the sock filter in the tank or the sock filter may have fallen off and a piece of crud is being sucked into the pickup tube. Could be a multitude of things. Plugged inline filter, plugged filter in carb inlet, rubber fuel line sucking shut or pinched, bad or weak fuel pump, just to name a few. HEI module as already mentioned....

LockDoc

[CCCC]

I take it that the engine never really quits - just runs at low/limited RPM when this problem starts. That would cause me to first look at other than electrical, and toward fuel supply. You say that ambient temp level does not affect the situation, so unless you have a fuel line up smack against something hot on the engine, we can probably elominate vapor lock.

Some good stuff from other posters here - maybe you fuel pump is trying to pull a vac in the fuel line/tank - a vent issue back there? Maybe a partial obstruction of fuel line, not after the truck sits for a while, but exacerbated by running it at higher RPM - sucking some crud or whatever against a filter screen? The poorly set carb float theory is interesting as something that could cause the carb to run out of gas after a period of steady higher flow, but have to doubt that as the culprit because your RPM are still limited even after you let it sit at idle for a while - which should fill the carb unless there is some weird hang-up with the float/needle-seat valve. Worth 2c - hope it helps.

[OJ1988]

Thanks for the input guys.

Tried raising floats. Did same thing.

Fuel filter is new. No filter in carb.
Engine does not quit, as said, so I agree with nonelectrical .

Have tried removing cap, as well as driving with no cap at all, and still did it.

Fuel pump has been replaced.

Stock fuel line, only rubber is small piece from frame to pump, and small piece at filter to carb.

When it does it, I can take off again, rev engine up and it will rev fine, but once I get above 45mph it will cut off again.

Bout ready to put this thing on craigslist.

[vasquezmrysvll]

how did you run power to your HEI? http://67-72chevytrucks.com/vboard/s...d.php?t=382778

[OJ1988]

12 gauge wire straight from fuse box.

[DennyB]

OJ,

I would also check voltage output/input as well to make sure your carrying enough volts at highway rpm to power the HEI.

Then maybe try a new coil if you got a good one laying around.

Do you have an electric tach? Does it malfunction when the problem occures?

Denny

[OJ1988]

Has electric tach, it does not do anything unusual when it happens.

[DennyB]

What is your voltage?

I had a bad regulator that drove me nuts with the weird things it caused before I finnaly checked the obvious.

Denny

[OJ1988]

Took the air ose to the fuel line and blw into it, and it worked. Runs great now.

Looks like I got some crud in the tank I need to clean out.

[C20-67_N_MO]

Cool!

Glad you were able to fix the problem.

[DennyB]

Glad to see you narrowed it down.