fuel cut out problem

[Johnny Blaze]

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?

[68nate]

Have you removed the gas cap when it's acting up? Maybe a problem with the fuel tank vent/fuel cap? If the fuel tank can't vent the fuel pump could be pulling a vacuum on the tank.

[Johnny Blaze]

Does not affect it.
I have actually driven with out the cap on, and it still did it.

Does not matter if it has a full tank or low on fuel.

[megaladon6]

low fuel volume?

[Johnny Blaze]

low fuel volume?

What do you mean by that? fuel pump not suppling enough?

Changed pump, did not affect it.

SOmeojne suggesting raising float level, they are right at the sight plug now, as per recomendations, but will raise it more, and see what happens.

[megaladon6]

yeah i was thinking the fuel pump or the float level.

[Johnny Blaze]

Gonna try floats in morning.

[NOT A TA]

Not sure if your truck has it but some vehicles had a filter in the tank. Rust build up over the years plugs it up. Driving on the highway with the engine running at higher RPM the fuel isn't able to get through the filter fast enough.

[68nate]

Remove the fuel cap and blow compressed air through the fuel supply line at the pump back to the tank. If it has a sock on the fuel pickup it will usually blow it off. This will eliminate a problem with the sock without having to drop the tank.

[MrQuick]

yeah, could be the sock, you really should drop the tank and check. Thats after you check your float level.

Even if you use compressed air to check the sock it could still exibit a feed problem. Also are the lines still stock? 5/16" line?

vince

[Jim Nilsen]

I have a 77 C10 and unless you have a plastic tank it is definately the sock full of rust and crud. Your symptoms are exactly what happens when they are the problem.

I like the idea of blowing it off with the air but if it is not deteriated enough it will just clean it off instead of detaching it and it will get clogged back up again more than likely. Pull the tank and check it. Have fun with the bolts, cutting them and putting new ones on is the easiest.

Goodluck

[Johnny Blaze]

Raised floats. Did not change anything.

Will check out the tank, its behind the seat.

[paul67]

It might be the rubber fuel hose rotted and collapsing inside.

[paul67]

Are any fuel lines ruuning close to heat also have you the rubber gasket uder the carb might be a vapour lock.

[Johnny Blaze]

Could be the section of rubber hose before the pump. Gonna change it.

Fuel line are on passenger side, header and exhaust on left, so I don't think its vapor lock.

Intake has a spacer as well as being water cooled.

Intake has been on truck for 2 years and problem is new.

Thanks.

JEremy

[MonzaRacer]

dont forget ignition and charging system checks, bad coils can over heat and loose power. also bad condensers if points.

[Jim Nilsen]

dont forget ignition and charging system checks, bad coils can over heat and loose power. also bad condensers if points.

It's been so long since I have work on a points and condenser car i forgot all about the condenser going bad like that.

You could have nailed for the cost of going to the right friends garage like mine and digging out a condenser, I have seveal new ones that never got used because of the Borg Warner electronic ignition my dad gave me way back when.

[68nate]

He installed an HEI distributor.

[andrewb70]

I like the clogged tank sock idea. If there is another inline fuel filter, I would replace that as well.

Andrew

[Johnny Blaze]

I don't think the tank has a sock from what I have seen in the catologs.

Fuel filter has been replaced.

I changed the fuel hose between the metal line on frame and the pump.

Did not help either.

Tach and voltmeter do not do anything erratic when it happens either.

when it does it, I slow down to 45 and it runs fine, you try to tip in the pedal any and it just 'bogs' for lack of better description.

You can drive for miles at 45 and it is fine, but it will not go over that once it has happened.