I just acquired a 1978 F600 with a 361 industrial motor. The carb was rebuilt and runs great. However, when you start the engine it coughs and sputters. You cannot take off or the engine will die. But, if
you let it warm up it runs like new.

The choke, governor, etc. have all been checked and appear properly adjusted but something is very wrong.

Free pizza to whoever figures this out.

Thanks.

ken

 

The choke seems adjusted properly.... but is it working properly? This sounds exactly like not having a proper working choke

 

If everything is great after it warms up, I'll second the comment that it is likely something with the choke. I could never get my automatic choke to work correctly; hence, I converted to a manual choke & throttle.

 

Well, it is back to the choke. The promise of free pizza still stands.

Thanks.

 

That's an easy diagnosis. It's lean on cold start (which it should be) but the choke is not compensating enough. Manual choke cures that issue.

 

Pull the air cleaner off. Have someone else crank the truck, while you manipulate the choke plate by hand. If you can get it to run correctly, then there's the answer.

 

Make sure compression is good, and no vacuum leaks, and ignition timing is running at spec. A mechanic's vacuum gauge is the only way to fly for engine diagnostics and tuning. If engine won't pull 18" to 20" steady at idle, find out why. Carb calibration and tuning is basically impossible if there are any problems elsewhere, they are completely dependent on a strong engine manifold vacuum.

A carb choke doesn't really work the way people sometimes think, they don't block the air off so much as they increase the velocity of the air that does flow, and consequently extra fuel is "pulled" from the well for cold enrichment. Hardly any air flows through a carb at idle, it needs the manifold vacuum to atomize the fuel. So anything that buggers that up, incorrect ignition timing, late valve timing, vacuum leaks, will cause problems. "90 Per Cent of Carb Problems are Ignition Related".

 

I am very glad to have joined this forum. I feel much better about tackling this beast Saturday. Will let you know what the outcome is soon. Pizza for ALL!!

Thanks for the great advice.

Ken

 

Please don't send pizza here! My butt is wide enough. Just get your truck fixed.

 

Does anyone want Mike's share of the pizza?

 

Dangit!!!!!!!!

 

It sounds like your choke isn't working correctly. If you are running a stock carburetor, you should have a thermostatic choke with two tubes. If you have an aftermarket carburetor, you would have a fully electric choke with two wires.

What is your starting procedure? If driven daily, your truck should only require *one* pump to start a cold engine. A warm engine wouldn't even need that. You should never have to "pump" the gas to start the engine.

The next time your engine is cold. pump the gas once. Then, remove the air cleaner lid and verify that the choke plate is completely closed. If it isn't, it's not set correctly.

If that checks out, start the engine, but do not pump the gas pedal. It should fire off immediately. When the engine starts, the choke plate should crack open just a little and the engine RPM should be higher than normal. If it doesn't do that, something isn't set correctly.

As the engine warms up, the choke plate should gradually open. At full operating temperature, the choke plate should be completely open.

 

1978 F600 w/a 361 would have a Holley 4V carb. See pic below:

The 361 is not an industrial engine, per se...it's an FT engine. It was an option for 1964/78 500 and larger series trucks.

FT's also available 1964/78: 330 2V Medium Duty, 330 2V Heavy Duty, 391 4V

btw: In pic, 389 is a detuned for smog 391.

 

Great advice. Thank you! I feel like I owe more than a pizza. 🙂

 

You could send it "Air Fouts" to whoever wanted it.

Dan Fouts, former QB of the San Diego Chargers.