My 76 fj40 will sometimes not idle, when working fine it idles at around 550 rpm, but for some reason it will sometimes decide not to idle. So after reading some posts I decided to change the idle solenoid with a NOS I bought off EBAY. Once again I am having the same problem. I checked the solenoid and it does click, I noticed nothing moves externally when voltage is applied, isn't their a pin or something that is supposed to move out when activated? Can someone explain how this thing works and it is supposed to do?
How does the idle solenoid work? (2 Viewers)
- Thread starter makomark
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1911
chupacabra
The purpose of the fuel cut solenoid is block the idle circuit with a small plunger at times when the "Emission Control Computer" deems it necessary, principally when the truck is under prolonged deceleration such as when coasting down a steep hill with the throttle closed (i.e., braking utilizing engine compression). The FCS is powered at all times the ignition is on, but is opened and shut by the ground being controlled by the ECC. The ECC is a circuit board in a black box just behind your main fuse block on the driver's side kick panel, under the dash. The ECC takes input for the FCS from several things, but chiefly the vacuum switch that is connected to the base of the carb. The ECC circuit board is cold soldered, and the connections become brittle and weak over time, especially those where the wiring harness connector is attached to the circuit board. Many people have reported success by heating each of these twelve connections on the circuit board with a soldering iron and carefully re-flowing the solder. An alternative is to add a jumper wire from the White w/ Red spiral wire (ground wire from FCS) at the connector to the ECC to a convenient ground. The result of this will be that the FCS will be grounded and open at all times the ignition is on. You will lose the functioning of the FCS on deceleration, but your 2F will always idle.
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Connect and disconnect the solenoid from the carb with ignition on engine off, do you hear it click? if you don't hear it click try connecting directory to the battery.
As 1911 pointed out the issue might not a bad solenoid but with ECC, I had the exact same issue and I found this out the hard way...
As 1911 pointed out the issue might not a bad solenoid but with ECC, I had the exact same issue and I found this out the hard way...
- Thread starter
- #4
wow, thanks for the reply. Its pretty technical and it amazes me that this old vehicle is that sofisticated. I will try what you mentioned and hopefully that resolves it.
It may not be the solenoid at all. 550 is pretty low for the idle speed. I would try two things:
As suggested, run a temporary jumper from something that is on when the ignition is on-to the solenoid and see if that fixes the problem. It's easy to grab 12v at the coil (or the ballast resistor if you have one).
The other thing I would try is to bump the idle speed up a little. 550 is awfully low and all it takes is a little schmutz in the idle circuit to cause a stall.
If you determine that it's the ECC that's causing it, you can bypass it for the purpose of the idle solenoid and just run a permanent wire to the solenoid. That will not affect your idle emissions since the solenoid should always be energized at idle.
Good luck.
Makes me glad I've got a non-usa model (no ecc, no vacuum switch).
As suggested, run a temporary jumper from something that is on when the ignition is on-to the solenoid and see if that fixes the problem. It's easy to grab 12v at the coil (or the ballast resistor if you have one).
The other thing I would try is to bump the idle speed up a little. 550 is awfully low and all it takes is a little schmutz in the idle circuit to cause a stall.
If you determine that it's the ECC that's causing it, you can bypass it for the purpose of the idle solenoid and just run a permanent wire to the solenoid. That will not affect your idle emissions since the solenoid should always be energized at idle.
Good luck.
Makes me glad I've got a non-usa model (no ecc, no vacuum switch).
- Thread starter
- #6
I connected the idle solenoid directly to the coil and it did click, then I connected it to the normal connection and it also click the same. Does this mean it is functioning properly? I also took out the ECC (its the black box on the firewall behind the clutch pedal) I looked at it, it has capacitors, resistors and transistors, so I just cleaned it and put it back without attempting to do any soldering since their are so many connections on the printed circuit board.
I would hook it to the coil and leave it there for a while. See if the problem goes away.
If it does, the problem is probably in the ECC. And, if it were me, the solution would be to make a permanent connection to the solenoid.
If it does, the problem is probably in the ECC. And, if it were me, the solution would be to make a permanent connection to the solenoid.
i wired my FCS straight from 12v and truck ran great at idle. got out and check everything after warming up and fuel is pooring out of charcoal canister line (rubber hose not on) and there is no visible line of fuel level in bowl somit is flooded out. 2/79 CA stock
I have been chasing a no-idle condition for weeks. when wired normally the FCS will not click. suspect bad ECC. Need help thanks guys
Update: removed air horn and inspected, float must have been hung up?? No more flooding separate issue great timing. Had it off just before wiring FCS
I have been chasing a no-idle condition for weeks. when wired normally the FCS will not click. suspect bad ECC. Need help thanks guys
Update: removed air horn and inspected, float must have been hung up?? No more flooding separate issue great timing. Had it off just before wiring FCS
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I don't think the fuel cut solenoid was controlled by the computer until 79. Before that I think it was powered off the BY wire from the engine fuse.
