Starving for Gas and getting worse!

[Fleeting65]

I'm at my wits end, guys, and I don't know where else to turn...

My '65 C10 has been experiencing an elusive and worsening case of bogging, choking, and now shutting down as if no fuel is getting to the carb. Carb is a Rochester Quadrajet sitting atop a refreshed 1970's 'Vette 350 engine with stock cast iron intake under the Rochester 4B. The engine also has HEI.

I've already performed the following over the past several months, but none have resolved the mysterious issue:

> replaced the (OEM) fuel filter
> replaced the mechanical fuel pump (twice)
> removed the gas tank "sock" (even though it was not clogged
> had the Quadrajet professionally rebuilt with all new parts by a carb rebuild shop
> NOTE: It hasn't been so hot that vapor-lock would be a diagnosis, because it did it during Jan/Feb too.
> I just tried starting it again, and it fired right up...but I know what will happen when I drive it again.

It used to run fine following its 2017 engine rebuild. Then, one day I floored it on the freeway from a 60 roll. It hit about 70 and suddenly stalled out and starved for gas. It's been doing that at high speeds since then. I'd let it settle down and she'd run fine at 45 or 50. But now it's been getting progressively worse & worse-- at 50, then at 45, then 40. Today, after installing the freshly rebuilt Rochester, I started it up and it idled perfectly. I took it on the road... within 5 minutes of driving it starved for fuel at 35mph. I tried to nurse it home, but it finally gave up ~2 blocks from the house, and it wouldn't restart. THAT was a first! The fuel indicator shown over 1/4 tank, and I can hear fuel in the cab's fuel tank when I rock the truck. Walking home I grabbed some fuel, then primed the carb, and it started up. I limped it back home at slow speed.

Any thoughts and/or suggestions from the experts would be very much appreciated.

[ghackett1]

Check the flexible fuel line coming from the tank that runs under the truck or along the side of the frame. They can cave in when deteriorated.
If you are sure all the lines are clear and you did everything you said you did including new carb then check the fuel pump push rod. They can wear down believe it or not.

[72Mountaineer]

By the OEM fuel filter do you mean the chunk of sintered whatever at the fuel line fitting on the carb? If so, that was always the first thing I canned on a Qjet. Also, get a pressure reading on the pump(s). Did you talk to the rebuilder?

[cwcarpenter98]

Another place to check since you have an HEI:

Break out the trusty multimeter and check the resistance on your coil and ignition module. A failing ignition system can make you think there's a carb problem

[bhap]

Vented gas cap ?

[bsarts]

Ditto on the flexible lines, I'd replace all the rubber hoses.

[Chevy Fleetside]

Originally Posted by cwcarpenter98

Another place to check since you have an HEI:

Break out the trusty multimeter and check the resistance on your coil and ignition module. A failing ignition system can make you think there's a carb problem

I 2nd this. Sounds like the Module is going out.

[Fleeting65]

If it indeed was the coil & ignition module, would it still allow me to start the truck after a period of 5-10 minutes? While the problem has gotten progressively worse -- meaning the "starving for fuel" symptom has now been occurring earlier and earlier at lower speeds -- it still starts hours later and the next morning as if nothing was wrong.

I'll be discussing with a mechanic today, then crossing my fingers that it can make the 3-4 mile drive without breaking down again.

[Bears63]

I had a very similar experience once and it was a bad pickup coil in the distributor. Do you have another distributor you could try and see if it makes any difference?

[Fleeting65]

Bears63 - That's another possibility! Thank you as well! While I don't have a spare HEI handy, I'll add that to the list of remaining sources when I take it in.

[64shortbox]

You might also check into this - the fuel pump eccentric at the front of the camshaft that runs the fuel pump might be worn. This happened to a friend of mine with his Chevy van that had a 350 motor in it. He installed an electric fuel pump and all was well.

[Braunschweiger]

You've probably already checked the float level in the carburetor,
because if there isn't enough fuel in the float chamber at higher speeds, the engines tend to starve and then pick themselves up again at low speeds.

[theastronaut]

I've read here that the in-cap HEI distributors can overheat the coil. I think weak coils will lose spark as they heat up, and if it's dying then it would explain why it's happening sooner/at lower speeds.

[Fleeting65]

TheAstronaut- Thank you for chiming in! As a longtime veteran, your expert opinion is always welcome!

Your suggestion now makes for the THIRD reference pointing to the "HEI distributor coil" as the possible culprit. Realizing that this can deteriorate over time, causing the fail to occur sooner at even slower speeds... just may be the correct path.

I'm giving a list to the mechanic and crossing my fingers.

[theastronaut]

Forgot to say this in my first post, check the plugs- if they're black its a sign of weak spark. Quick and easy way to see if it's weak spark or actually starving and running lean.

[theastronaut]

Another thing to check- thermal paste should be used to help transfer heat out of the HEI module. It's not the same as dielectric grease like some people recommend/use.

https://www.thirdgen.org/forums/elec...-compound.html

[Fleeting65]

Originally Posted by theastronaut

Forgot to say this in my first post, check the plugs- if they're black its a sign of weak spark. Quick and easy way to see if it's weak spark or actually starving and running lean.

Pulled plug #1. Seems to be a mess. It may be a weak coil. However, when it was starving for fuel, and I primed the carb, it fired right up and it got me home 3 blocks away. Is it therefore possible that I’ve got TWO issues causing this failure— a bad coil AND something fuel-related??
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[bhap]

Next time it dies, try opening the gas cap and see if it sucks air in. If you have the wrong type of gas cap on the filler, it will create a vacuum that is difficult for the fuel pump to overcome. I've had this happen on motorcycles with gravity feed, worth a try. I also had an electric fuel pump suck rust into the inlet screen and kill the engine at highway speeds. Waiting a few minutes allowed the rust to settle and the car restarted. Ended up replacing the tank and putting in an inline filter. Good luck!

[Fleeting65]

Originally Posted by theastronaut

Forgot to say this in my first post, check the plugs- if they're black its a sign of weak spark. Quick and easy way to see if it's weak spark or actually starving and running lean.

Pulled plug #1. Seems to be a mess. It may be a weak coil. However, when it was starving for fuel, and I primed the carb, it fired right up and it got me home 3 blocks away. Is it therefore possible that I’ve got TWO issues causing this failure— a bad coil AND something fuel-related??
Posted via Mobile Device

[Steeveedee]

Did you fill the float bowl after the engine died and you started it and drove it a ways? Did I read that right? If so, you definitely have a fuel flow problem.

[Fleeting65]

Steeveedee-

Yes, you read that correctly. Before I primed the carb with about 2 shots worth of fuel, I tried to start it one more time. It cranked strong, wanting to start. But you can tell it wasn't getting fuel.

Once I put just a little fuel in, it fired up and continued running long enough to get me home 3 blocks away. (It was still faltering, but it got me home nonetheless.)

I'm not sure if I have BOTH an electrical problem AND a fuel problem...or just a fuel problem.

[Fleeting65]

I wanted to thank everyone for all of your insights & suggestions over the past 24 hours.

Here's my plan:
1. I'm going to pull and clean all my plugs, having seen #1 looking sketchy.
2. In addition, my auto repair shop's lead mechanic has offered to come over with his arsenal of tools to the house Sunday A.M. to figure this out- electronic & fuel. (I suspect he's going over & above the norm because he was the one that suggested I get the Quadrajet rebuilt.) I'm impressed by such service!

I'll let you all know the ultimate source(s) once learned.

[The Rocknrod]

Something in the tank plugging the suction?

[franken]

I'd test the fuel delivery from the pump and have a look at the spark to a plug.
The OP describes things done but no description of testing--a sign of shotgunning rather than troubleshooting, which is a waste of time and money.

[geezer#99]

Don’t clean those plugs, replace them. Look oil fouled to me.
Do you know the casting number on your heads. Your plugs might be the wrong kind.
Do you have a dedicated 12v power for the hei.

What air cleaner? Crazy long air cleaner stud! The nut on the stud can hang up the secondary metering rods and air door causing a super big bog like you describe.

What year is the intake from? Could be the infamous hot slot intake. The wrong gasket causes super hot carb.

Does your manual choke hold the choke blade completely open. Or is that how it normally runs.

Have you checked timing? Checked weights and springs are intact and moving? Vacuum canister good?