All my plugs are fouled?

[Smniekamp]

1981 Chevy K20 350 with 4 speed manual 4x4 (70,000 on rebuild) stock.
Hey guys,
I was driving down the road when all of the sudden I felt a miss. The truck hesitated then kept running, about 200 yards later it started to miss really bad. It felt like a automatic trans that was about to die, slipping in and out of gear (however I have a manual). I ended up having to tow it home. It will start and run very rough, stumbling hard and missing. I can step on the gas and bring the rpms up to around 2500 and it will run a little better (less miss fires), but then will just completely cut out and die instantly. It almost sounds like its firing on half its cylinders. I threw a timing light on it and the mark jumps around on me a little. Ive replaced the plugs, wires, ICM, Coil, cap, rotor, fuel pump, accelerator pump in carb, checked the pcv valve, and checked to make sure rotor is turning (stripped dizzy gear). Still having the same issue.... Any other ideas? All my plugs were fouled when I pulled them out initially. Could a leaky intake cause all the plugs to foul? Head gasket? Any input would be awesome! Thanks!

[Alex V.]

What color/consistency was the fouling?

[cadillac_al]

My first thought was the float level is getting too high. It will usually leak out the vent if it gets high though. Is it a Qjet? Is it blowing black smoke? This is when it's nice to have a spare vehicle to swap a distributor or a carb with a known running one.

[4x4chase]

What your describing sounds like the timing chain skipped? Threw everything off. Can you get #1 to TDC and pull a valve cover to verify the valves are closed?

[Dead Parrot]

Was the timing near normal even if unsteady? Thinking if the timing chain jumped, the timing would be way off.

Oil pressure normal? Since the oil pump is driven by the distributor, if the cam/distributor gear stripped, should adversely impact oil pressure.

Brakes working normally? If power brakes, maybe the booster developed a bad leak.

Bad gas?

If mechanical fuel pump, check the pressure. Maybe the cam lobe that drives the pump push rod died.

Do check the float/seat setup. It only takes a speck of crap to cause a flood condition in the carb.

[tucsonjwt]

If fouling is black carbon, then it is running too rich.

If fouling is oil, then rings are shot.

[Smniekamp]

The timing was close to normal (aside from the variation that I saw). Oil pressure is still good. I haven't checked the brakes but did notice that the bottom of the booster showed signs of a possible leak, it appeared to be damp on the lower section of the booster. What would this mean, vacuum leak? The gas is good and I just had the carb apart (Qjet) a couple weeks ago to replace the accelerator pump. May just go ahead and do a whole rebuild on it. The plugs looked more oily than carbon build up. They were dark black and wet. Im not getting a noticeable amount of black smoke out the tail pipe. It has a mechanical fuel pump as well... really hoping the cam didnt take a dump on itself...

[100%Chevy]

Maybe there's trash holding the needle open making it flood.
Wet,black plugs is usually gas fouled.
Could also be a bad float letting it get too much gas.They're only about $6.00 new at the parts house.
Mike.

[El Dorado Jim]

any update?

[Matt Man]

I recently had the same problem....turned out my float level was way to high. The only thing I can think of is that my fuel filter in the carb fell apart and messed it up?

I would check the float level.

[100%Chevy]

This new govt.corn gas will dissolve the rubber and glue holding the paper element fuel filter together!
Already happened to 2 of mine.
Mike.

[Matt Man]

Originally Posted by 100%Chevy

This new govt.corn gas will dissolve the rubber and glue holding the paper element fuel filter together!
Already happened to 2 of mine.
Mike.

THIS!!!!! so irritating that a 3$ part messed up my carb, I'm replacing twice a year now.

[Smniekamp]

Hey guys, so I live in Alaska and its been -8 for about a week and a half. Once it warms up above 0 Ill get back at it! Im going to check to see if my brake booster is leaking first. It looks wet on the bottom like fluid is leaking out of it? Online a guy said that its a sign of a failed booster which causes a huge vacuum leak, anyone agree with that?... If its not that then Ill check the carb filter, I replaced the filter a month ago but you never know. Thanks for the continued help. Ill post another update as soon as I can!

[jjzepplin]

You could easily block all the vacuum connections to the motor and see if the symptoms still exist. Reconnect one by one and find the issue. Back when I smoked I would light one up and blow smoke through an open vacuum line and find the leak. Now I have to do things the hard way.

[Smniekamp]

Originally Posted by Dead Parrot

Was the timing near normal even if unsteady? Thinking if the timing chain jumped, the timing would be way off.

Oil pressure normal? Since the oil pump is driven by the distributor, if the cam/distributor gear stripped, should adversely impact oil pressure.

Brakes working normally? If power brakes, maybe the booster developed a bad leak.

Bad gas?

If mechanical fuel pump, check the pressure. Maybe the cam lobe that drives the pump push rod died.

Do check the float/seat setup. It only takes a speck of crap to cause a flood condition in the carb.

So it finally warmed up to 14 degrees today. I went out and plugged the vacuum line that goes from the carb to the brake booster and tried to start it. With a little stumble she fired up and ran GREAT! Looks like my brake booster is the problem (vacumm leak)! If it was you would you replace the booster and the master cylinder at the same time? Thanks for all the help guys! Glad to have my '81 running again!

[Nick_R_23]

Hey, cool to see another Alaskan on here! If your brakes work and feel solid and not spongy, I would leave the master cylinder alone, no need to replace it, it's working fine.

[Harley03joe]

I Found These Plugs On Ebay >>LEONARD OIL FIRING LR14 mm SPARK PLUG Also In 18 MM

What MM Is A 5.8 K Eng In A 1987 Chevy Silverado
Thank You
Harley03joe

[RotaryRocketeer]

Originally Posted by Harley03joe

I Found These Plugs On Ebay >>LEONARD OIL FIRING LR14 mm SPARK PLUG Also In 18 MM

What MM Is A 5.8 K Eng In A 1987 Chevy Silverado
Thank You
Harley03joe

You should probably start a new thread for this.