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. 

Views: 121


Reply to This

Replies to This Discussion

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 




  • Add Photos
  • View All


Correct rims and drums?

Started by Logan Robb in 1963/64 Cadillac Specific Discussion. Last reply by Tony and Ginny 429 3 hours ago. 5 Replies

As I am collecting items for a brake overhaul, I’ve have come across many posts about the aftermarket drums not being of quality like the originals. I am fairly certain the drums I have are not…Continue

cooling problem solved

Started by greg in 1963/64 Cadillac Specific Discussion. Last reply by Tony and Ginny 429 7 hours ago. 6 Replies

I have a 64 Fleetwood and in the summertime with the a/c cranking when I would be in traffic or going slow it would always run warm....close to the 3/4 mark sometimes.   I replaced the fan clutch…Continue

Powder Coated Rims

Started by Logan Robb in 1963/64 Cadillac Specific Discussion 21 hours ago. 0 Replies

I have a very reputable blasting and powder coating shop near me, come this winter, I am thinking of getting my wheels power coated in preparation for new tires in the spring. Is this a good idea? I…Continue

Dragging to one side

Started by Sammy in 1963/64 Cadillac Specific Discussion. Last reply by Tony and Ginny 429 on Monday. 9 Replies

Hi there, after a lot of work on my brakes - new cylinder, hardware, shoes, hoses, going back to old drums, the car still drags to one side. Does this for years now, but I hoped to get rid of it…Continue

Blog Posts


Posted by ANGELO MARTINEZ on July 23, 2023 at 10:44pm 3 Comments

  Hope someone can help me to find the harmonic balancer bolt for my 1964 Cadilac Deville 429 engine

in advance, thank you for your help.

Clock ‘64 DeVille

Posted by Matt Vander Hooven on July 23, 2023 at 7:36pm 2 Comments

Is there still a member in the Detroit area that refurbishes clocks?

Matt VH

Spark Plug Heat Range

Posted by Patrick Westphal on July 7, 2023 at 10:00am 3 Comments

I found a diagram that illustrates the main factor in determining a spark plug heat range that I was trying to describe to you during the chapter get together.

Here it is:


The main factor is the length of the ceramic insulator from the middle of the spark plug to the tip (where the spark happens)  

The insulator…


Lower Front End Ball Joints

Posted by Logan Robb on May 11, 2023 at 9:04am 7 Comments

Good Morning all! 

I took the 64 into the shop to have some adjustments completed and in the process decided to have the lower ball joints replaced as was recommended the last time I had it in. I ordered the parts and came into the shop. They quoted me nearly $500 to replace those lower ball joints requiring nearly 4hrs of labor. Now this is a reputable shop and they know me by name here and they will continue to get my business. I am just questioning what on earth is…



  • Add Videos
  • View All

© 2023   Created by Jason Edge.   Powered by

Badges  |  Report an Issue  |  Terms of Service