Side of the road question

[CruisinGA]

40 started stumbling while driving city roads at 40ish mph.

Engine starts easily and will stay running only if I continuously feather the pedal. Fuel level in float bowl is correct.

It’s the original Aisan @FJ40Jim rebuilt for me 16 years ago on the original 1.5F

Maybe trash blocking the primary jet?

 

[pithicus]

Maybe trash blocking the primary jet?

When that happens it will idle and that's about all it will do.
You can try cleaning the end of idle/fuel stop solenoid and blowing out where it screws in.

 

[Clutchee]

Fuel filter?

 

[CruisinGA]

When that happens it will idle and that's about it will do.
You can try cleaning the end of idle/fuel stop solenoid and blowing out where it screws in.

It will only run when accelerator pump is pumping fuel now

Fuel filter?

Normally would be something to check but I replaced it recently and float bowl is at appropriate level when this is occurring.

 

[Mtntopper]

I would start with cleaning those jets, most importantly the idle jet.

Remove these 2 bolts and squirt some carb cleaner through the 2 main jets.

Then, probably the thing that will make the biggest difference, the idle jet. You need to pull the the top case of the carb to get it out. Careful not to tear the main gasket, or lose the float's hinge pin.
Pull that jet and clean it, should be able to see light through it.

 

[Brew40]

Gas tank pressurizing? Unscrew cap and try?

 

[CruisinGA]

Gas tank pressurizing? Unscrew cap and try?
Checked that too, no dice unfortunately.

 

[pithicus]

My main primary jet blocks from time to time. but it usually still idles ok. Make sure there's power to the solenoid and it clicks when powered. It's easy to clean the solenoid and blow out/flush where it screws in.

another possibility is water in the fuel.

 

[CruisinGA]

I made it home last night by continuously rapidly feathering the gas pedal, I think because that was causing the acc pump to squirt fuel.

Is there a place in the carb that could become blocked and affect both idle and main circuit but not accelerator pump? I could only find a 2F flow diagram with vacuum secondary.

 

[pithicus]

Is there a place in the carb that could become blocked and affect both idle and main circuit

Don't know sorry. If it's still playing up after the primary jet and solenoid are cleaned, it might need to be pulled apart.

 

[pithicus]

Also, when my primary jet clogged, I could always limp home with my foot down and the secondaries would keep me going. It might pay to check out your secondary vac diaphragm too.

 

[Mtntopper]

When that idle circuit is clogged, the carb floods through the primary jet causing erratic running and backfiring. When you pull the air cleaner and look down into the top of the carb, if you can see fuel coming through the primary while you're not giving any throttle, then your idle circuit is definitely clogged. And the smallest part of that idle circuit, and therefore the first to clog, will be that idle jet.

 

[DesertFJ40]

Sounds like your idle selenoid?? Happend to me once on the interstate. I let go off the accelerator pedal and it would start to stumble then die. It worked as long as I fethered the gas like you described.... I got off the highway and it died when I needed to come to a stop at a red-light. The Fj40 would start up and continue driving as long as I kept giving it gas...

The original selenoid on the carb still works, all it was was the wire running from it to the ignition coil that was busted. Soldered it and wrapped electrical tape. Good as new.

Mine is a 1971 fj40 with 1f original carb

 

[CruisinGA]

Also, when my primary jet clogged, I could always limp home with my foot down and the secondaries would keep me going. It might pay to check out your secondary vac diaphragm too.

This has mechanical secondary. holding foot down to keep secondary didnt work, I had to keep pumping the throttle.

When that idle circuit is clogged, the carb floods through the primary jet causing erratic running and backfiring. When you pull the air cleaner and look down into the top of the carb, if you can see fuel coming through the primary while you're not giving any throttle, then your idle circuit is definitely clogged. And the smallest part of that idle circuit, and therefore the first to clog, will be that idle jet.

it was definitely not flooding.

Sounds like your idle selenoid?? Happend to me once on the interstate. I let go off the accelerator pedal and it would start to stumble then die. It worked as long as I fethered the gas like you described.... I got off the highway and it died when I needed to come to a stop at a red-light. The Fj40 would start up and continue driving as long as I kept giving it gas...

The original selenoid on the carb still works, all it was was the wire running from it to the ignition coil that was busted. Soldered it and wrapped electrical tape. Good as new.

Mine is a 1971 fj40 with 1f original carb

If it was just idle solenoid only idle would be affected. In my case it won't run unless the throttle is being "pumped" constantly.


This is all helpful, hoping to get to dig in to it tonight!

 

[DesertFJ40]

If it was just idle solenoid only idle would be affected. In my case it won't run unless the throttle is being "pumped" constantly.

That is what I was trying to explain, but perhaps yeah it is not the idle solenoid. It could be many things; but, the symptoms you explained are pretty much 99% of what I was experiencing . Mine also would not run unless I was giving it constant pumps for fuel.

Only other thing I could imagine is that your fuel pump is giving out and still managing to keep you going in its final stage of life. Luckily these things are fairly easy to troubleshoot and you should be able to figure it out it no time 😁

 

[FJ40Jim]

I made it home last night by continuously rapidly feathering the gas pedal, I think because that was causing the acc pump to squirt fuel.

Is there a place in the carb that could become blocked and affect both idle and main circuit but not accelerator pump? I could only find a 2F flow diagram with vacuum secondary.

Yes, the main jet supplies both the main circuit and the idle circuit. If the idle jet is restricted, then there's no idle, but will kinda run at 50% throttle. If the main jet is restricted, then it won't run at higher throttle but may idle weakly if there is enough fuel leaking through the main jet to supply idle circuit.

 

[mattressking]

No one has asked the obvious question, if your idle solenoid clicks solid and reliably have you measured vacuum at idle?

Random debris in a carb after 16 years of generally limited issues - I doubt it’s relative to that. My assumption is vacuum leak initially if it occurs out of nowhere.

 

[bikersmurf]

Had a similar issue with the Edelbrock on my SBC in my 40. The Idle circuit was blocked.

The solution was to remove the carb screws and spray some carb cleaner through the holes they came out of... I found one of them was blocked. I then blew compressed air through both holes and put the idle screws back in. In my case it resolved the issue and I've not needed to dig in any further.

Alternatively if its a vacuum leak, spray carb cleaner around the head, intake, and carb base while it's running. If spraying the cleaner around these areas changes the rpm, then you've found the vacuum leak.

 

[CruisinGA]

turned out it was a bad connection to the idle solenoid. The original bullet connector just needed to be unplugged and re-plugged.
I thought I was hearing the idle solenoid click but it turned out to be a relay I have that powers an "ign on" accessory fuse block.

 

[Xylonmedia]

Glad you got it solved!