Blocked idle circuit help/fix

[Vernon]

4/73 FJ40 all stock, won't idle unless I choke it or hold the accelerator. T/P and idle solenoid ruled out. From the responses I received, it sounds like I have a blocked idle circuit. Not having attempted to fix this before, can anyone explain how to go at it? I tried the search, but no luck. Also cannot find help from my manuals. Thanks much....

 

[76FJ40]

The FSM will show the idle circuit path. I'm assuming you have power to the solenoid?

 

[Poser]

T/P and idle solenoid ruled out.

How did you come to the conclusion of ruling these items out?

 

[vk7ybi]

I've had some luck by removing the idle mixure screw and injecting compressed air in there.. The only real way to fix this is to rebuild and clean properly..

 

[Vernon]

T/P has vacuum and good movement when attempting to start,and when vacuum hose is removed. Solenoid clicks when key turned on and off, engine will die when power cut to solenoid. I am ruling these out just by trying what was found in previous searches. Thanks for your reply, any help is welcomed.

 

[Poser]

... engine will die when power cut to solenoid.

So would that not lead you to believe that your idle circuit is getting fuel and working as it should?

 

[Pin_Head]

It is more likely a vacuum leak than a clogged idle circuit.

 

[Vernon]

I don't know, wish I did I am having trouble making sense of this as I have not had to diagnose something like this before. Are you saying that the idle circuit is most likely ok?

I have tried to pinpoint a vacuum leak by using carb/choke cleaner around all gaskets, hoses, brake booster, base of carb. etc. I have not noticed any significant change in the RPM's. I am at the point where I should just replace the intake/exhaust manifold gasket just to eliminate the possibility..? Any other areas to check. Thanks.

 

[Pin_Head]

I wouldn't replace the manifold gasket unless you know there is a leak there. Other possibilities include a cracked manifold and a bad brake booster and any other vacuum connection.

It could also be a partially obstructed idle circuit. Remove the idle fuel cut off solenoid and idle mixture screw and blow them out with carb cleaner spray and compressed air.

 

[Hellebore]

sand...

I had exactly the problem you are describing.

I had a grain of sand lodged in the end of my slow jet (the long one pointing downwards closest to the plunger (took 3 weeks to find) you will need to take the top off the carb.



Cameron