78 FJ40 2F Idle Problems (1 Viewer)

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SliderJack

SliderJack

Joined
Oct 6, 2010
Threads
19
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394
Location
Sevierville, TN
Rebuilt truck and motor. Got it back on the road last year. Runs great for a period of time but now wont idle without choke. Aftermarket Trollhole carb. Took it apart and cleaned out ethanol gunk from jets. Was good for a bit, but rough again. Been running non ethanol and additive.

New gas tank and lines. Fuel bowl stays full at sight glass level. Holley electric fuel pump, two filters.

Stock distributor but found electric wire looks questionable. Photo attached.

Checked valve lash. Timing at dot. Played with adding 5 degrees advanced. One vacuum hose from carb to distributor. Pulls vacuum between 10 and 15.

FWIW has reground cam little hotter than stock.

Aftermarket coil.

Carb idle solenoid is seeing constant 12volts and clicks, seems operational.

Tried second new carb with similar results.

Tried adjusting carb mixture and idle. Wont idle under 1000 rpm. Needs some choke to stay running. Dies at stop signs and hard to restart. Needs choke to start even when warm. Running aftermarket gauge cluster.

Plugs were black from running with choke. Replaced with E3s I had lying around. A little better but not much. Have a new set of plugs but need to check gap.

Checked spark with light. All plugs causing light to flash. Took plug out and getting a spark. Not super hot but I can upload a video if it would help.

Ideas or thoughts to try? I could do compression test. Have maybe 100 miles since rebuild. Thanks in advance. I'd love nothing more than to get this baby running and reliable.
 
Last edited:
Check for vacuum leaks ... manifold ... carb base... booster

Check for intake manifold under carb crack
 
Check fuel delivery: carb sight glass, fuel filter, fuel pressure
 
10-15” of vacuum is insufficient to make the idle circuit work properly.
Of course this chicken/egg situation assumes the rings are seated. If not, you will not get the necessary vacuum. And you run the risk of washing the rings, in which event you may never see good vacuum.

Which is to say this is serious business!

Do you have any friends with good running Landcruisers you might borrow a carb and dizzy from?

Also, for break in, try cranking the advance WAY up to see if you can cheat in enough vacuum to get your idle speed down and onto the idle circuit.
 
Thanks for your replies! I did a little more work tonight. See comments below.


JohnnyC said:
Check for vacuum leaks ... manifold ... carb base... booster

Check for intake manifold under carb crack
Click to expand...

I've sprayed carb cleaner in these areas and didn't hear any change. Is there a better way? I don't have smoke. I did look over the intake manifold when I assembled, but not lately. Would I still pull vaccuum 10-15 if there was a leak? Should I observe some change when I plug the PCV valve? The couple connections on the intake are plugged. The hose to the booster has suction and a noise when disconnected.

billmc said:
Check fuel delivery: carb sight glass, fuel filter, fuel pressure
Click to expand...

I have two filters, one before the holley electric fuel pump and one after. The after is glass and is full. The sight glass on the carb seems to be at the proper level while running and maintained at faster speed. I do not have a pressure gauge.


65swb45 said:
10-15” of vacuum is insufficient to make the idle circuit work properly.
Of course this chicken/egg situation assumes the rings are seated. If not, you will not get the necessary vacuum. And you run the risk of washing the rings, in which event you may never see good vacuum.

Which is to say this is serious business!

Do you have any friends with good running Landcruisers you might borrow a carb and dizzy from?

Also, for break in, try cranking the advance WAY up to see if you can cheat in enough vacuum to get your idle speed down and onto the idle circuit.
Click to expand...

I'll try adjusting the timing advanced to highest vaccuum. I tried another brand new aftermarket carb and it ran the same.

The truck ran well after the rebuild. I got it on the road and drove it probably 150 miles, idled and ran great. I started having a problem getting it to restart when warm. I had a problem with it sitting a bit, took the carb apart and found gunk in the jets from ethanol I'd guess. Cleaned that all up. Ran good again, took it to the store and forgot I had turned off my fuel pump as a safety precaution. After getting it restarted, it hasn't run well since. Took the carb apart again, seemed fine. Tried that other new carb after this and wouldn't idle .
 
Last edited:
Those numbers are consistent with unseated rings.
 
“Took it apart and cleaned out ethanol gunk from jets. Was good for a bit, but rough again.”

How long is a bit?

You may just have a piece of smegma still f-ing up your idle Jets ?

Try the take apart thing again ... did you fully remove the carb and blow it out?or did you just remove the top and get what you could?
 
65swb45 said:
Those numbers are consistent with unseated rings.
Click to expand...


I’m curious, Mark... I stumbled onto this thread a few years back and filed it away for...

www.jalopyjournal.com

How to get rings to re-seat?

Iv been driving my ol buick for a while now, and its got alot of blow-by. The motor only has bout 50k on it, so i highly doubt that the bore is worn...
www.jalopyjournal.com www.jalopyjournal.com

What’s your take on the use of Bon Ami through the carb, to re-seat rings
 
JohnnyC said:
“Took it apart and cleaned out ethanol gunk from jets. Was good for a bit, but rough again.”

How long is a bit?

You may just have a piece of smegma still f-ing up your idle Jets ?

Try the take apart thing again ... did you fully remove the carb and blow it out?or did you just remove the top and get what you could?
Click to expand...
Thanks. Totally stripped it down. Shot carb cleaner through everything and followed with compressed air. I didnt dip it though or use a sonic cleaner, which I'm considering.

Tried another new carb recently though and had same results. But I'm willing to do whatever is needed. Weird that the acelerator pump seems slow to return. It sits for weeks on end without being started. But I put ethanol treatment in the gas and last two times I've added non ethanol gas.

Just weird that it ran so good for the first 100 miles and doesn't now.

I have a leak down tester, I hope to do it tomorrow. I'll look at the carb again too.

Thanks again.
 
Last edited:
Jets appear clean and not gummed up.

Accelerator pump plunger is a little sloppy. Replacement plunger fits the bore tighter but a bit shorter.

Top center, should power valve have that washer? Washer seems galled. I dont see it in carb diagram.

20200220_213656.jpg


Original plunger looks a little rough.

20200220_215338.jpg
 
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I’m now rechecking that (gasket) on mine (even though I’m positive I had that right) because I rebuilt mine and same issue as yours still ... I have to adjust my float anyways because it was off 2mm
 
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