Choke light stays on

[da_raabi]

Any idea why the choke light on my '86 C30 stays on all the time? It only turns off when I shut the truck off. It does not seem to effect the way it runs (runs like a friggin champ for almost 30 years old) its just kind-of annoying since its a big orange light on the dash. Any ideas?

 

[chengny]

Diagnosis & Testing:


Possible conditions for the electric choke not operating properly ( as indicated by the "CHOKE" light coming on are listed as follows.

Use a voltmeter to check oil pressure and choke coil circuits:


1. Low or no engine oil pressure.

2. Faulty oil pressure switch.

3. No current to oil pressure switch due to:
a. Burned out fuse.
b.Broken wire to oil pressure switch.

4. No current between choke and oil pressure switch due to:
a. Broken lead wire.
b. Wire terminal not properly secured on coil terminal.
c. Faulty ground circuit between choke assembly and housing grounding plate.

5. Faulty choke coil assembly.

 

[da_raabi]

Ok, thanks. I'll check that. Would this cause some dieseling too? It dieseled a bit when I shut down last night, but has not done it since.

 

[da_raabi]

Actually now that I think about it I just replaced the power steering pump, and had to fuss with the oil pressure sender right next to it. I wonder if I wiggled a wire loose or broke something in the harness. It only started doing this after I did the pump, so that could be the cause of the problem. Thanks for pointing me in the right direction!

 

[MrMarty51]

Actually now that I think about it I just replaced the power steering pump, and had to fuss with the oil pressure sender right next to it. I wonder if I wiggled a wire loose or broke something in the harness. It only started doing this after I did the pump, so that could be the cause of the problem. Thanks for pointing me in the right direction!

Are You sure that the sender next to the P.S. pump, screwed into the head, is`nt the temp sender unit???

 

[da_raabi]

Its screwed into the bottom of the block, below the pump just above the oil pan, right by the front main. I figured that's all it could be, what else would be plumbed in off the bottom of the block? Plus it has a big diaphragm-like sender on it, not just a small temperature style.

 

[MrMarty51]

Its screwed into the bottom of the block, below the pump just above the oil pan, right by the front main. I figured that's all it could be, what else would be plumbed in off the bottom of the block? Plus it has a big diaphragm-like sender on it, not just a small temperature style.

OK, that would be oil all right, the galleys runs right up to there.

 

[da_raabi]

I did some additional reading, and it said the choke light may come on if oil pressure is lost, I cannot see how I have lost oil pressure as the truck runs fine, drives fine, stays in temp and shows pressure on the gauge. I'm thinking there's just an issue in the oil pressure to choke circuit. I'll check it tonight after work.

 

[chengny]

Ok, thanks. I'll check that. not done it since. Would this cause some dieseling too?


The electric choke assist is designed to help the choke move open immediately after the engine is started. This is to help reduce emissions.

In the early years of EPA regulations, GM used oil pressure to activate power to the electric choke assist.

When the engine starts, and oil pressure reaches about 10 psi, that switch closes and supplies power to the choke heater. If power is not available - via the purple wire - the choke may not open fully.

If the choke plate does not open fully, this results in an overly rich mixture/high idle RPM. Either of these conditions could cause dieseling.

 

[da_raabi]

Well I opened the choke completely by hand, it stays that way on its own now, leaving the light off. The truck runs a bit better too, it doesn't seem to affect anything negatively.