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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Hi guys. 1987 Formula with an LG4. Choke doesn稚 work. Put on a new choke. That doesn稚 work. Choke dash warning light is on. If I unplug the connector choke dash light turns off. The electrical connector has 12-14 volts. But when connected to choke loses some voltage.
Any ideas? Perhaps a bad ground? But where do I look?
Check to see if there's a gasket under the choke stat. If so, take it out. The back side of the stat has a contact that must be grounded. Also check to make sure that the bowl the stat mounts in, is grounded. Check for continuity between that and some convenient known grounded thing like the alt case.
Also check the C-H fuse and the choke relay. When I was troubleshooting my choke problem, I discovered that a previous owner completely removed the choke relay.
All fixed now...
I was just looking at a 1985 LG4 manual, since I don't have one for a 1987 but I assume they're the same, and that's what I came up with. It looks like if the CH Fuse is missing/blown, or the choke heater relay is missing (good catch), then the choke warning light will get a ground from the choke heater and illuminate. This will also mean the choke doesn't work. When the engine is running and the alternator is powered up, it turns off the relay. When the relay is off but the CH Fuse is powered (hot in run), it passes through the relay and powers up the choke. This also turns off the choke light by removing the ground path for the light.
Here are the four pages from the 1987 Service Manual pertaining to the LG4 choke, for your analytical pleasure. I started to put them in the Electrical thread about your alternator, but then I remembered you had a thread for the choke somewhere else, so I figured I'd keep them each on topic. My scanner won't import to my laptop, so I clicked photos for you.
Here are the four pages from the 1987 Service Manual pertaining to the LG4 choke, for your analytical pleasure. I started to put them in the Electrical thread about your alternator, but then I remembered you had a thread for the choke somewhere else, so I figured I'd keep them each on topic. My scanner won't import to my laptop, so I clicked photos for you.
Thanks Tim. Once I get a second opinion on my alternator function, I'll reassemble and follow this flow chart. This stuff is me least favorite - but I'm learning as I go.
Thanks Tim. Once I get a second opinion on my alternator function, I'll reassemble and follow this flow chart. This stuff is me least favorite - but I'm learning as I go.
What a difference the correct wiring diagram makes. There's some bit of difference between the 1985 and 1987, so sorry for my part in that Charlie.
It doesn't appear the alternator is involved in the choke relay circuit for 1987, as it was in 1985.
One thing I would probably start with is the oil pressure switch. If the switch is not reading while the engine is running, you will get the Choke light on during engine running and no choke heater operation. I know you said you have voltage there, but you're likely reading through the choke light. You will also not have a working in-tank fuel pump, making the mechanical fuel pump do all of the work.
What a difference the correct wiring diagram makes. There's some bit of difference between the 1985 and 1987, so sorry for my part in that Charlie.
It doesn't appear the alternator is involved in the choke relay circuit for 1987, as it was in 1985.
One thing I would probably start with is the oil pressure switch. If the switch is not reading while the engine is running, you will get the Choke light on during engine running and no choke heater operation. I know you said you have voltage there, but you're likely reading through the choke light. You will also not have a working in-tank fuel pump, making the mechanical fuel pump do all of the work.
Hmmm...interesting in that I did have an episode where the oil pressure gauge went to zero. It freaked me out a bit. But after that it always read normally.
Hmmm...interesting in that I did have an episode where the oil pressure gauge went to zero. It freaked me out a bit. But after that it always read normally.
The oil pressure gauge will have its own sending unit. The oil pressure switch in the choke/fuel pump circuit is just an On/Off switch. They are two different devices.
It's possible the oil pressure switch is bad, or it's also possible you have an oil pressure issue based on you saying your gauge went to zero.
You're looking for an orange and tan/white wires for the switch side. I think some may be dual purpose (gauge and switch) but I'm not for certain on your specific application. The page that was posted above states the switch is at the rear of the intake manifold, so you're in the right spot.
Looks like you've found it. There's a T fitting between the sending unit and switch. The ignition control module will remain when you lift off the distributor cap so it might be more than just the cap in the way.
BTW, I don't know if it's the camera and/or lighting, but that one spark plug wire sure looks a little rough.
Looks like you've found it. There's a T fitting between the sending unit and switch. The ignition control module will remain when you lift off the distributor cap so it might be more than just the cap in the way.
BTW, I don't know if it's the camera and/or lighting, but that one spark plug wire sure looks a little rough.
Thanks JT. I've got new wires, cap, rotor and plugs waiting to go on.
06-17-2023, 06:38 PM
