1948 Chev Pickup Mystery Tune-Up Questions
 

The engine, I believe, is a 235 straight 6 from a 1960 truck, with a very simple one-barrel carb.

It's been running fairly well until recently. Just this past week it started acting funny.

Awhile ago, I went through the carburetor and put in new gaskets, etc. And it ran just fine after putting it all back together.

Recently, it acts like it is running out of gas.

It starts easily with full manual choke, then idles nicely with the choke pushed in to the off position.

If I abruptly push the gas, it dies. But I can get it to rev up if I tap-tap-tap the gas. It revs better with the choke on.

It all feels like fuel starvation, but I'm not sure from where. Today I replaced the in-line fuel filter, but no change in symptoms.

I don't think it's the fuel pump, either, because the symptom of over lean is instant when the gas pedal is pushed.

I thought one of the cylinders might not be firing, but all the plugs look just fine.

I guess it's the carb. But am not sure what to check next or what to do.

Please let me know if you have any diagnostic advice.

thanks,

Did you fill up the tank recently? Try pumping the gas into a glass and see if it's clean.

I had dirty fue. After a fill up once in my 911 and it behaved somewhat like you described. The fill filter would load up and limit the fuel rate.

it sounds like the accelerator pump is either not connected or has a an internal leak or the outlets are clogged. Remove the aircleaner and operate the throttle see if gas squirts into the the intake by pushing the throttle if not then you have your answer, next would be to take the carb apart and inspect it .

I've found that on carbed cars that do this, if you rev it up and hold it, pul the choke on full, then turn the choke off, and don't let the engine die it will usuaully suck whatever is clogging it up on through.

When the choke is on, flloorboard it and hold it, it will try to die. Turn the choke off and keep it floorboarded until the engine starts revving up on it's own, and clears the flooding. Repeat as necessary.

dirty needle/seat?

Does sound like its running out of gas. The "tap tap tap" thing is getting the thing to rev up using the Accy pump, but the main jets are probably low on fuel.

I would pull the top of the carb off and see what it looks like in there.

As stated earlier, it's the acc. pump.

Another vote for accelerator pump. You should be able to take off the air cleaner, look down the barrel of the carb and see the pump put a healthy spray down the barrel when you manipulate the throttle by hand.

Sound good to me...or, perhaps a hole in the float? Float level off? Definitely sounds like a carb problem as long as you're sure the fuel pump is okay.

Check that the vaccum/machincal advance is working in the distributor.

Maybe a vacuum leak, just had almost the same symptoms albeit on a 4.2 liter 6. It will run a little lean because of the vacuum leak and when the throttle plate opens it goes too lean to run, tapping on the gas will dribble a little extra fuel then it catches up.

Hi y'all

It was a little gob of silicone goo that broke loose and stuck in the main jet.

Somebody... not me.. fixed the gasket with silicone sometime in the past.

then,, I must admit here,, I might have been a little lax on my clean-up during the last rebuild.. oopsies!

runs fine now.. life is good. :D

S.

Happy endings to problems are always good! :)

Glad to hear you figured it out! There is something uniquely satisfying about working on a car where everything is mechanical, no computer BS... this linkage does this and the device should do that. The more I work on modern cars, the more I yearn for my old '73 VW bug :)

" Happy endings" are always good! ;)

Way cool! I am glad you figured it out.