Question about checking current flow to the choke.

[Gpaw44]

Because I am electrical challenged I come before you asking this question. Do I put a volt meter between the choke plug and the pin coming out of the choke housing and then start the truck to read the voltage? If no Voltage the I am correct the assume the switch behind the distributor needs to be replaced. I wll check the fuse first . Thank you in advance.

 

[Ricko1966]

You pull the connection off the choke and read from the connector in your hand,to ground. The truck has to be running. The choke only gets power when there is oil pressure.

 

[Gpaw44]

Thanks Ricko1966. Since I am going to ground from the connector why not use a test light to just see if there is current? Or do I want to know the amount of voltage flowing?
The truck starts and only runs utility it floods because the choke is not opening. I can push on the choke plate and it open and shuts freely. I guess I can start it and hold the coke open a little till I get a reading. I have been having the choke light come on and staying on longer at different times so I am thinking it is the switch finally giving out!. Befor someone suggest other tests. I can see gas squirting into the carb when activating the accelerator linkage. I'm also getting a good spark looking at my spark tester before it dies.

 

[Ricko1966]

Thanks Ricko1966. Since I am going to ground from the connector why not use a test light to just see if there is current? Or do I want to know the amount of voltage flowing?
The truck starts and only runs utility it floods because the choke is not opening. I can push on the choke plate and it open and shuts freely. I guess I can start it and hold the coke open a little till I get a reading. I have been having the choke light come on and staying on longer at different times so I am thinking it is the switch finally giving out!. Befor someone suggest other tests. I can see gas squirting into the carb when activating the accelerator linkage. I'm also getting a good spark looking at my spark tester before it dies.

That should be fine,but you have to have the truck running. Choke should not be fully closed at idle as soon as it fires the choke pull off should open the choke about 3/16ths. I am assuming everything is factory and still a quadrajet.

 

[jcperformance]

To test it properly, you should place the voltmeter between the wire connector and a good metal ground on the engine while the truck is running. If you get no voltage there, then it is reasonable to suspect the fuse or the oil pressure switch behind the distributor is faulty.

 

[Ricko1966]

To test it properly, you should place the voltmeter between the wire connector and a good metal ground on the engine while the truck is running. If you get no voltage there, then it is reasonable to suspect the fuse or the oil pressure switch behind the distributor is faulty.

Not necessarily the oil pressure switch behind the distributor. Some use the switch behind the distributor for the gauge/light and a seperate switch above the oil filter for the choke. Some use a dual function switch above the oil filter,some put 2 switches behind the distributor,and some have a dual function switch behind the distributor.

 

[Old Guy Bill]

Start at the fuse box..use a meter to make sure they're good.

 

[Gpaw44]

If the switch is bad will it shut the egine off? I can open the choke and get it started but it will not run long enough for me to check the voltage at the choke.

 

[Ricko1966]

Put a test light on the choke lead somewhere you can see it from the driver seat. Keep the truck running with your foot. Does the light light. The choke hot wire should not keep your truck from starting and running cold. Have you tested your choke pull offs. They should pull the choke open about 3/16ths on a cold start.

 

[Gpaw44]

Alright, I have good voltage going to the choke but the choke plate is not opening. I can open the plate up and start the truck and it will idle but after a few seconds it will die. IF I try to give it gas it dies.
Does the choke filiment need to be replaced?
Why does it keep dying?

 

[Ricko1966]

Alright, I have good voltage going to the choke but the choke plate is not opening. I can open the plate up and start the truck and it will idle but after a few seconds it will die. IF I try to give it gas it dies.
Does the choke filiment need to be replaced?
Why does it keep dying?

The choke element has nothing to do with it for 10 or 15 minutes. Check the choke pull offs( vacuum pods that open the choke). Some have 1 some have 2 again I'm assuming you have a quadrajet.. They should open the choke plate, with vacuum about 3/16ths as soon as the engine starts..

 

[Radiohead]

Hey Rick, I'm going to get rid of that hot air style choke spring system for my quadrajet, and rob the electric version off the other parts carb. I have the plug for it, but can I just swap out a newer oil pressure switch to get the required element action? Admittedly I haven't sat down with the wiring diagram yet to see what additions I need to make. What's your thoughts about this?

 

[Ricko1966]

Hey Rick, I'm going to get rid of that hot air style choke spring system for my quadrajet, and rob the electric version off the other parts carb. I have the plug for it, but can I just swap out a newer oil pressure switch to get the required element action? Admittedly I haven't sat down with the wiring diagram yet to see what additions I need to make. What's your thoughts about this?

Yea it's easy. Buy a 2 prong normally open,I repeat normally open Oil Pressure switch. Screw it into the Block where ever you find most convenient,by the distributor or above the oil filter. Use a fuse to connect 1 prong to battery 12v+ connect the other prong to choke element,it is really that easy. Normally open it turns power off when there is no oil pressure. You can also do it with a 4 prong relay #30 to battery,#87 to choke #85 to alternator exciter lead #86 to ground when the alternator spins it closes the relay and turns on choke power.
PS126 Summit. Look at the 1* reviews!!!! People who bought,without reading specs or knowing how things work. Yes MOST but not ALL oil pressure switches are normally closed,but in some instances you need one that's normally open.

 

[75gmck25]

My ‘75 K25 has a mechanical oil pressure gauge, so no oil pressure sending unit. When I converted to an electric choke I tapped into a key-on circuit that was there for the dual battery charging relay. I think some folks also use one of the wires powering their wipers. The choke does not draw a lot of power.

Caveat - The reason GM used a dual-terminal oil pressure sending unit to power the choke is that it will only power the choke if the engine is running. With my setup I power the choke if the key is on but the engine is off, and there are cases where that might cause starting issues.

 

[83Stepper]

My ‘75 K25 has a mechanical oil pressure gauge, so no oil pressure sending unit. When I converted to an electric choke I tapped into a key-on circuit that was there for the dual battery charging relay. I think some folks also use one of the wires powering their wipers. The choke does not draw a lot of power.

Caveat - The reason GM used a dual-terminal oil pressure sending unit to power the choke is that it will only power the choke if the engine is running. With my setup I power the choke if the key is on but the engine is off, and there are cases where that might cause starting issues.

I also run power from an ignition/key on only source if you don't have the "necessary" electrical oil sending unit. I've done this with many trucks and never had an issue so far. I've ditched the dummy light sender on basically every single truck I've had and gone with a mechanical gauge. Yeah you can plumb in a tee and run both, but usually not a lot of room behind the distributor and it looks funny with both plumbed into it.