Choke - bad?

[yellomalibu]

The 84 C10 has been perfect, as long as the choke wire stays on the choke... This morning, however, the oil / choke idiot light came on and stays on... It's never been on while the vehicle is running, so it got my attention. Not low on oil and don't hear any signs of low oil pressure... so I head down the road.

Once it comes up to temperature and I try to go highway speeds, it starts running like crap. The Choke is still on - of course it runs like crap.
I double checked, and the choke wire is connected to the choke.
I manually opened the choke, and the truck immediately idled down and sounded fine... and stayed that way until I hit the gas again. grrr.

I am clueless about how to troubleshoot this, as I have never messed with this issue before. Any ideas, tips, or pointers?

I've got to run errands - busy day... so I'll check back a bit later. Luckily, mom let me borrow my Blazer back. :-)

[squirrel]

Check to see if there's voltage at the wire, with the engine running. I'm pretty sure it's wired so the two pin oil pressure switch sends ignition power to the choke once the engine starts and gets oil pressure. this keeps the choke from opening if you leave the key on but don't start the engine right away.

If there's no power, look for a melted wire or bad switch or blown fuse or whatever else might be causing the problem.

[SpiderGearsMan]

your primary vacuum break ok ?

[Barry Donovan]

I just went through a spell with rochester choke.
the choke wire reads zero. I moved it to another spot..it comes back later.
this tells me static pressure is non-diode (and ought to be). the choke is the main keeper for calm for the whole truck.

I remember the 84 c10 specifically..
the cat ended up being the culprit, after all the silly mystery electrical.

..and that 305 engine is egr scary.

1984 is nice v8 choke, it is a hefty one..versus chevettes which fit in the same spot. (you can swap all of them around)

I am going to try zener diode on the wire that feeds them.

[yellomalibu]

Thanks for the tips Jim... and Spidey, I don't know what the primary vacuum break is.
All was working normally yesterday when I parked it, then this morning: idiot light.

I have had a long day, and just now get a chance to sit down for more than a couple minutes. Will be hitting the rack soon. Hopefully tomorrow I'll have time to troubleshoot.

Again, thanks.

[Rocketman]

Probably a bad oil pressure sending unit...As Jim stated, this controls power to choke coil

[squirrel]

or it's just out of oil

[yellomalibu]

It wasn't out of oil - but it was a bit low, so I topped it off. Wasn't the problem.

First thing I checked this evening was the fuse, and low and behold, it was blown. Replace it, and the idiot light is no longer on. Yay.

Take it 3 blocks to the gas station, and it's still chugging and puffing black smoke. Grrr.

When I got home, I pulled the air filter assembly off, and flipped the choke lever on the side of the carb down, and it smoothed right out... until I gave it some throttle, then the choke closed again.
Checked the wire, and 0 volts. No idiot light, but no voltage to the choke.

It was getting dark, and the engine compartment was too hot to mess with it tonight, so temporarily, I tied the choke open with a zip tie. I'll investigate it properly as soon as I get time, but for now it's drivable.

[squirrel]

could be a melted wire shorted to ground? Sounds like a fun challenge

[yellomalibu]

Well it took me a month, but I finally got it figured out and fixed.

I tried to change the oil pressure switch last weekend, but the part was apparently mis-boxed (It really does happen) because the two spade terminals were an inch apart rather than 5/8" apart... so it obviously didn't make electrical contact with both terminals in the plug.

a few days ago, the idiot light comes back on. I know I have oil, so I ignore it until this weekend.

Put the correct oil pressure switch in, change the blown fuse (that's why the idiot light was lit again), and the new fuse blows instantly... Clearly Jim was right, and I have some wires to chase.

The wires run (ran) through a wire clamp that is held in place by one of the bell housing bolts. A few months back when I had the starter trouble and had to loosen all the bell housing bolts to un-crimp the starter wires, then re-tighten them... apparently the wire clamp rotated under the bolt head and squeezed the wires against the bell housing: a short waiting to happen. While fixing a wiring problem caused by a careless mechanic, I created another wiring problem by being a careless mechanic.


Today's lesson is to always double check for crimped wires.