I was thinking of using the gray wire that goes from my relay to the pump for the switch. However, will this work knowing that there is also an oil pressure relay involved?

Thanks,

Geo

 

The gray wire will work but you will have to tap into it downstream of where the oil pressure switch splices into it. This splice should be inside the engine harness somewhere as it goes across the firewall. A good location to tap into it would be after it goes thru the firewall which it should near the ECM.

 

That won't do much good. If you interrupt that wire, you'll only disable the ECM's control over the fuel pump. Once you crank long enough (2-5 seconds), oil pressure will build up in the engine and the FPOP switch will turn the fuel pump on anyway.

Instead of disabling something as simple as the fuel pump, I'd recommend disabling a circuit that CANNOT be bypassed by any retarded thief. And that's either spark control or injector control. Either of these will disable the engine 100%. The only solution would then be to tow the car.

Hope this helps.
Lou

 

Actually, the gray wire would work fine to disable the fuel pump, whether it be for security or safety. If the wire is accessed after it passes thru the firewall next to the ECM it will be downstream of the oil pressure switch and ALDL connector, making it as secure as disabling spark or injectors. This would also be the easiest place to access it as it wouldn't require running wires thru the firewall.

 

I see two problems with that:
A) the grey wire is nowhere near the ECM, it runs along the driver door
B) any idiot can power up the fuel pump with an alligator clip no matter how many switches you put in your car - that's why it's not a recommended way to disable the engine

Hope this helps.
Lou

 

I see two problems with your post.
A) No where does he say he wants to disable the fuel pump for security. Perhaps it's for safety.
B) If the switch is placed downstream of the relay, oil pressure switch, etc, say at the fuel pump, yes someone with an alligator clip could still bypass the switch by jacking up the car and finding it--and how is that any less secure than interrupting the ignition, etc. as any idiot could jumper those as well.

George90GTA,

Sorry if I've misled you on the routing of the wires. BigBabyLou obviously knows better than the component locations views in the GM factory service manual I consulted.

 

You're right, George never mentioned whether the switch would be for security or safety. However with dozens of posts every month asking about how to prevent theft by disabling the fuel pump, it's only assumed that it's not exactly for safety.

The fuel pump circuit is so simple (on-off 12V) that it can be bypassed with one wire (without jacking up the car, just fold down the rear seat). A spark or injector circuit is precisely timed by the ECM, there is no brute force bypass there. I've been repeating this here on TGO forever.

The GM FSM unfortunatlly contains many errors. And even more unfortunatelly, many other manuals (Haynes, Chiltons etc) simply copy the FSM so the error gets propagated further. We just have to learn to live with their errors and make corrections in our manuals.

Cheers.
Lou

 

The fuel pump wire does indeed travel down the driver's side.

 

I've found my FSM to be a very good reference material, but not 100% correct.

I've found mine to argue with itself, from chapter to chapter/section to section, on several things. Sometimes simple, matter things, to totally wrong, when trying to find the problem.

Way better than Chiltons/Haynes, but not 100% accurate either.

 

Thanks for the help!!!



I am using the kill switch to burn the remaining pressured fuel before leaving the machine.