75 Grand Lemans wiring diagram/starter

[Karnawgie]

I recently picked up a 1975 Grand LeMans as a project. It last ran in 2012 or so and sat in a warehouse until 2021 and has been passed around until it got to me.

It was mostly stripped and taken apart to be restored, but nothing was ever really done. I want to get it back on the road. This is the oldest car I've ever messed with. It's a 350 car.

I swapped the fuel line at the tank and connected a boat tank, disconnected the fuel line towards the carb to catch any old gas in the line. Threw a battery in it and got nothing.

I found the second smaller cable coming from the positive terminal of the battery lead to nothing, I assume it's supposed to connect to some sort of block with the rest of the harness.

I connected the wire from the battery to another matching connector in the harness and got some lights, and had the engine turn over some but never got any gas. After this, the starter never did anything.

So, I'm hoping someone can help me figure out what the cables by the battery are supposed to be connected to. And potentially a wiring diagram.

I also guess the starter is going out, it looks like a pain to replace.

Any input would be greatly appreciated, thank you guys.

 

[melsg5]

I recently picked up a 1975 Grand LeMans as a project. It last ran in 2012 or so and sat in a warehouse until 2021 and has been passed around until it got to me.

It was mostly stripped and taken apart to be restored, but nothing was ever really done. I want to get it back on the road. This is the oldest car I've ever messed with. It's a 350 car.

I swapped the fuel line at the tank and connected a boat tank, disconnected the fuel line towards the carb to catch any old gas in the line. Threw a battery in it and got nothing.

I found the second smaller cable coming from the positive terminal of the battery lead to nothing, I assume it's supposed to connect to some sort of block with the rest of the harness.

I connected the wire from the battery to another matching connector in the harness and got some lights, and had the engine turn over some but never got any gas. After this, the starter never did anything.

So, I'm hoping someone can help me figure out what the cables by the battery are supposed to be connected to. And potentially a wiring diagram.

I also guess the starter is going out, it looks like a pain to replace.

Any input would be greatly appreciated, thank you guys.

Main wire from battery positive goes to starter. Smaller wire may go to relay in engine compartment for power options such as windows. Find a factory shop manual which has the wiring diagrams.
It uses a mechanical fuel pump so not electrical related.

 

[B52bombardier1]

I never like to recommend the use of a lot of starting fluid / ether / "Explosion In A Can" but a little can be very diagnostic to tell if you have good spark and compression but really just a dirty carburetor.

Rick

 

[Karnawgie]

Smaller wire may go to relay in engine compartment for power options such as windows.

Would it be okay to keep these vice gripped? I got 0 power to the ignition/starter without these wires connected. I wanna buy the relay I need and slap it in. Put as little money into it as possible.

I was hoping I could find an electrical diagram online, again, being cheap but if push comes to shove I may buy one.

The starter was pretty weak when it was turning, never had it turn enough to get gas through the mechanical pump. If I buy a replacement starter, is there one that would fit any smaller than the stock size? I found some acdelco remans online for cheap. For example I know the low profile high torque starters from vortecs fit onto some sbc, any equivalent here?

I was told this was a unique 'Big block 350', any truth to that?

I never like to recommend the use of a lot of starting fluid / ether / "Explosion In A Can" but a little can be very diagnostic to tell if you have good spark and compression but really just a dirty carburetor.

This is definitely in the cards, charge up my battery again and see if the starter wants to work.

Thank you guys for the responses, I'll keep reporting here.

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[melsg5]

Unique Big Block 350??? Unless someone replaced the engine, Pontiac has one basic block design used from 326, 350, 389, 400, 421,428, and 455. Chevrolet has small and big blocks.
Since I can't see what you have vise gripped I can't say but it sounds like a recipe for a enormous short to ground.
Did you bench test the starter to make sure you don't have a cable or battery problem before buying another one. Not sure why you would buy a mini starter that is more expensive than a rebuilt original.

 

[Karnawgie]

Unique Big Block 350??? Unless someone replaced the engine, Pontiac has one basic block design used from 326, 350, 389, 400, 421,428, and 455. Chevrolet has small and big blocks.
Since I can't see what you have vise gripped I can't say but it sounds like a recipe for a enormous short to ground.
Did you bench test the starter to make sure you don't have a cable or battery problem before buying another one. Not sure why you would buy a mini starter that is more expensive than a rebuilt original.

I'll do more research on the engine thing, you've probably just disputed such claim.

I've only had the car two days, when I get a chance I'll do more tests but that starter is a bitch to get to on this car. Exhaust and suspension around it with hardly any clearance but I'll get it done if need be.

The vortec starters can be cheaper/the same price as a rebuilt original and more powerful. I robbed one off of a 4.3 for my tbi suburban. I was thinking it'd just be an easier replacment hence it being smaller and easier to get in there.

Below is a picture of the two wires that I believe should be connected to a relay of some sort. The ones I had vicegripped.

The red wire (although dirty) runs from the positive terminal on the battery, and it appears to need to be connected to the rest of the harness that runs across the intake beside the valve cover.

 

[melsg5]

Vortec is Chevrolet not Pontiac.
This is the part I mentioned. Do you see it anywhere in the engine compartment?

The Parts Place

1975 Pontiac GTO/LeMans/Tempest ALL GM POWER ACCESSORY RELAY/CIRCUIT BREAKER

www.thepartsplaceinc.com

 

[B52bombardier1]

Relays are usually connected by male and female spade connectors, not eyelets such as those.

The things that "melsg5" is referring to in the link above should most likely be bolted to the radiator core support sheet metal.

Rick

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[92 Sunbird LE]

Make sure your ground cables are clean and there is a block to chassis ground also.... Congratulations on your Grand Lemans, here is the 75 I owned as a winter car back in the 90's...$300 Special....

Doug in P.R.

 

[92 Sunbird LE]

Only 2 wires go to the starter, positive cable from battery and smaller purple wire to the solenoid from the neutral safety switch and ignition....

Doug in P.R.

 

[Karnawgie]

Completely dropped abandoned this forum, sorry guys.

Smaller wire may go to relay in engine compartment for power options such as windows.

This is the part I mentioned. Do you see it anywhere in the engine compartment?

The Parts Place

1975 Pontiac GTO/LeMans/Tempest ALL GM POWER ACCESSORY RELAY/CIRCUIT BREAKER

www.thepartsplaceinc.com

This was the thing that had helped me, I had no circuit breaker connecting the red wires under the hood for cab power. I connected them and the car cranks and runs now.

I've played with this project some and it is making progress.

Thank you guys for all the replies.