Hey all, I am slowly creating a To-Do list when Spring rolls around and I think the top of my list is the cranking/starting system issue I began having at the end of the summer. 

Story ahead, feel free to skip if need be. 

I purchased my 64 Fleetwood in late July of 2022. Prior to my purchasing and unbeknownst to me, someone had modified the oil pressure switch with an oil pressure kill switch. This is a switch that ties into the ignition and fuel system. For those that dont know, the whole point of this is to prevent the car from starting or continuing to run when there is no oil pressure. If oil pressure is not present after a few seconds after starting, or oil pressure drops while running, this switch will cut spark and fuel. This also required the factory fuel pump to be disconnected and and wired up with an electric fuel pump. The fuel system is something I plant to return to normal but not this issue at the top of my to-do list right now. 

So near the end of the driving season, I started experiencing an oil leak. It started slow and gradually began getting significantly worse. So bad over about 10 minutes of running, it would drop about 1.5 quarts of oil. I thought this was oil plug, checked and confirmed that it was not the issue. (I do have a replacement on hand). After investigation, I confirmed it was the oil pressure switch leaking. No big deal so I thought. Pulled the wires off, cleaned the area, put some thread tape and re-installed everything. Engine would crank, fire once or twice, and die. Pulled the strange pressure sensing oil sender and grabbed the part # for replacement (also ordered factory replacement as well). Before I continue, the block was fine, just needed the sender tightened down, no more leak. Wired everything back up with new part exactly how it was before, same deal. Cranked, fired on a few cylinders, and died. I trouble shot as much as I could wiring fuel pump and coil to to 12v together, separately, getting it to run different ways when wires connected in every which way. But it was NOT correct and not how it was intended to be installed. 

I confirmed there was oil pressure by replacing the new fangled switch with the factory switch and plugging the factory wire in. Oil pressure was good. So to be able to move the car around and to my storage shed, I wired the fuel pump and coil direct to 12v. I didn't drive like this for long, less than 50 miles all told, but I would prefer to return my starting/cranking system back to factory to prevent any further issues. 

Here is the area that actually contains my question, skip to here if you wish to avoid the backstory. 

Is there a wiring diagram that shows the starting system and provides wire colors? Any tips on how to proceed with this issue? Am I in for a lot of work or should this be fairly simple? 

These cars are still fairly new to me and I I desperately do NOT want to mess anything up. I am fairly handy but lack the confidence to just jump right in without some kind of guidance and direction. 

All help is more than welcome, but I am really looking for what wires are located where and where those wires need to be connected to. 

Thank you all again! Ill include a photo of the aftermarket sender so yall can see what I am talking about. 

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One red wire goes to Starter (solenoid I would imagine). The other goes to fuel pump. One yellow wire goes to coil and the final yellow with the factory plug is for the dashboard oil light. 


Not advise able to be putting tape on an oil sending unit into the block distorts the rearing I believe 

SB  a metal to metal fitting 

Some serious loss of oil pressure protection you have going on —a first for me to experience 

You should have a switch to shut down an electric fuel pump when using one in case of an accident 

Russ in one of our parts supplier on this site and he is extremely good with the wiring issues of our year Cadillacs 

Find him in parts Suppliers in the header 




Look for —-Caddy Shack 


There is a help page for Cranking Systems Basics at this link: - Cranking - Starting System Basics
The schematics are also on our help pages under wiring. 
The cranking system wiring will walk you through the how it is wired and how it works.

Thank you!

Figured I would update. 

I was having the issue where it would crank and fire once or twice and then die. I finally decided to tackle this issue and I fixed the problem. It was a bad resistance wire. So while cranking, the coil would get its full 12v. But then because of the bad wire, after the initial start, it doesn't need a full 12v. Replaced the wire and cleaned up all the connections, et viola, fixed.

A big headache gone! Now on to other projects...


Congrats on your repair and for sharing with our community 




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