If the solenoid on the carburetor isn't working will the truck still start and run?
Fuel cut off solenoid (1 Viewer)
- Thread starter igotta40
- Start date
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in my experience yes, but not well
it's not that difficult to make it working - take it off, clean it (multiple squirts of WD40 until the fluid is clear and the needle moves freely), test it off the carb (ground it on the truck and touch it with a tester wire you run from the battery), and if it clicks and the needle is moving with the click, it works - put it back on carb
it's not that difficult to make it working - take it off, clean it (multiple squirts of WD40 until the fluid is clear and the needle moves freely), test it off the carb (ground it on the truck and touch it with a tester wire you run from the battery), and if it clicks and the needle is moving with the click, it works - put it back on carb
Make sure the O-ring is there/not cracked.
x 3 on the cleaning part. Be careful when pulling away from the carb as you don't want to bend the needle.
I read somewhere (when I had the same trouble) that they rarely just go bad and often times it is fixed with a simple cleaning or lube.
I read somewhere (when I had the same trouble) that they rarely just go bad and often times it is fixed with a simple cleaning or lube.
If the wire off the wiring harness is missing, how would you recommend to hook it up.
If the solenoid has a wire protruding from it connect it to a keyed switched. The voltage regulator worked for me.
If no wire on the solenoid, you're SOL.
I'm interested in an answer to the original question as well... in various threads the solenoid is referred to as both fuel cut solenoid and idle solenoid.
Does it cut off all fuel to the carb or just what flows at idle? I suspect the latter but would like to know for sure
Does it cut off all fuel to the carb or just what flows at idle? I suspect the latter but would like to know for sure
From my experience, the idle circuit solenoid not functioning will allow the truck to run with the rpm's dialed up.
*I could increase my idle above 1000 and the truck would run, fast but it would run.
*With the idle set at normal, I would have to manually keep it from dropping off to the low end and shutting down.
I once had my jerry-rigged wiring come apart after hitting a bump. I restarted it while moving and maintained a higher rpm until I got home and reconnected it (about five miles).
*I could increase my idle above 1000 and the truck would run, fast but it would run.
*With the idle set at normal, I would have to manually keep it from dropping off to the low end and shutting down.
I once had my jerry-rigged wiring come apart after hitting a bump. I restarted it while moving and maintained a higher rpm until I got home and reconnected it (about five miles).
1911
chupacabra
Only the idle circuit. Truck will still run over 1200-1500 rpm, but it will start hard and not idle without the choke if the solenoid (or the "computer" that controls it) is bad.
the solenoid is just an electrically activated magnet - needle stays retracted as long as the key is in running position and there is juice on the wire to the solenoid - needle pops into carb passage and stops fuel flow when the truck is shut off
Mark W
Yep, it's true. I just don't care that much.
The "needle" in the solenoid is internal to the unit and can not be damaged during disassembly. The disruption of the fuel flow occurs inside the (the tip of) the solenoid
The "fuel cut" is a different part and has a different function that the Idle Circuit Cutoff Solenoid".
Very few of these go bad, it is usually the switching of the current to the solenoid that is the problem. Clogging is not common either.
The engine will start... it will not idle unless you have set the idle speed well outside of parameters and/or you have it choked heavily.
Mark...
The "fuel cut" is a different part and has a different function that the Idle Circuit Cutoff Solenoid".
Very few of these go bad, it is usually the switching of the current to the solenoid that is the problem. Clogging is not common either.
The engine will start... it will not idle unless you have set the idle speed well outside of parameters and/or you have it choked heavily.
Mark...
Mark, this was the same one as on mine, #75 in this diagram. I bent the first one I took off. See the needle passing through the gasket, that one.
1911
chupacabra
On later trucks (not sure which year it started), there is a vacuum switch that feeds data to the "emissions computer", a small soldered circuit board near the main fuse block. This "computer" will de-activate the solenoid when you are decelerating down-hill (with the throttle closed), thus saving some minuscule amount of fuel but making the spotted owls and snail darters happy. The problem is, the input connections from the wiring harness to the "computer" are cold-soldered and the solder cracks with age, resulting in an intermittent open in the ground circuit of the solenoid, which leaves the solenoid unactivated all the time and hence no idle. When this happens, you can either re-flow the solder in the connections with an iron and make the spotted owls and snail darters frolic again, or you can screw the little bastards and just ground the solenoid wire and have it be always activated with ignition. Then you can take off the vacuum switch with the rest of your de-smog too.
so the "fuel cut" is basically the same thing happening (ie the solenoid blocking idle level flow of fuel in the carb) but initiated by the emissions control computer based on input gathered from a vacuum switch
when the solenoid cuts off fuel because the ignition is off it's doing so as "idle cutoff" - largely to prevent dieseling
when the solenoid cuts off fuel because the computer tells it to (deceleration as detected by a vacuum condition) it's doing so as fuel cutoff - making the world a better place
am I understanding this correctly?
- Thread starter
- #16
Thanks for the replies, I'll check it out when I get home. I had been getting a miss like the carb was starving for gas when driving. I rebuilt the carb and replaced the gas filter. It seemed to run better but then it suddenly wouldn't idle. It will start and run but I can't let off the pedal or it dies. I didn't find any vacuum leaks.
Mark W
Yep, it's true. I just don't care that much.
Mark, this was the same one as on mine, #75 in this diagram. I bent the first one I took off. See the needle passing through the gasket, that one.
yes, I spoke incorrectly. (was wrong
) I always forget about the earlier carbs.Mark...
Thanks, I thought for a minute I might have had a 'Zuk or something else.
Mark W
Yep, it's true. I just don't care that much.
Nope...
The fuel cutoff valve is completely different from the idle circuit cutoff solenoid. Different piece, different place. It is only on the later carbs, not on any FJ40s or '55s unless that carb has been swapped on.
The idle circuit solenoid shuts fuel off at engine shut down and is also used by the emissions system. Early solenoids had one wire and only worked with the ignition. Later ones ha two wires and were also switched by the "computer".
Mark...
Mark,
great info- it may be the key to my problems...Thanks
great info- it may be the key to my problems...Thanks
