Only had car for about 3 weeks,an thanks to this board
I have learned mutch about my 1992 RS. Theproblem is
the servic engine soon light will not come on. Did a search
an found out about a fuel pump/ecm fuse next to the
battery. When I looked there was no fuse so I installed a
10 amp fuse.The SES light worked an it cranked right
up,before it was hard to crank,an ran great. Now with
the fuse in it wont shut off! The radio an all accessories
turn off with the switch,I can even remove the key
but engine wont shut off untill the fuse is removed.

 

sounds like a short is keeping the computer supplied with power through the fuse.....does your car have a tilt wheel? if so, you might want to run continuity checks on the column ignition wiring through the connector at the base of the column. Other than that, well.....just keep tracing and testing wires until you find it.

The reason I mentioned tilt steering columns is as wiring gets old, the wires get brittle, etc....and tilt wheels have been known to cause wires to break or insulation to rub off over time, causing shorts and so forth

another *possible* symptom with this is if the blinkers will work with the key off, though I'm not familiar enough with f-body specific wiring to say for sure, but IIRC the blinker fuse is off the same lead from the ignition switch

edit: typos

 

I bet you got a good deal on it. I bet now you know why.

Apparently somehow your ignition and ECM power circuits have come together. The ECM fuse you are pulling is the main power/constant hot for the ECM memory. The ECM also gets power from a switched hot off the ignition key. I don't have a wiing diagram in front of me, but i didn't think it was the exact same circuit as the ignition, but apparently it is. Either that or you have a REALLY interesting problem to sort out.

I hope you are good with wire chasing. Last time i had something this strange in front of me i had to rip most of a dash out and trace most of the harness. You need to get yourself some good wire diagrams (chilton's has exact copies of teh factory manual diagrams, don't even think of using the junk fake diagrams in a haynes manual for something this ugly), and a voltmeter and start checking everything related to those circuits. Easily a long weekend of work, and like i said, be prepared to have to practically gut the thing.

Sometimes you get what you pay for.

 

This sounds like what happens when somebody decides to "fix" the wiring. I'll bet you'll spend hours and hours tracing it, only to find somebody's pecker tracks in the wires.

First thing I'd do is get a schematic. You can get the Chilton's at the store, it has it in there, but it's harder to use than the factory manual. You may be able to order the factory service manual from www.helminc.com If not, you're kind of stuck with the Chilton's.

Trace the ignition feed back until you find where somebody "fixed" something, instead of "repairing" it.

 

InOx,

What year/model/engine is your car? Depending on the model, you may have a stuck/welded fuel pump relay or choke relay.

If you have an '85-89 TPI car, a welded MAF power and/or MAF burn off relay can backfeed power to the GAGE circuit and the rest of the ignition system. A completely fried ESC module could do the same thing.

All of these devices have constant power from Fuse 2, and could potentially backfeed power to the ignition.

 

The car is a 1992 RS with the 305 tbi and 5 speed.
I did get agood deal,it is in very good condition
and runs good without the fuse but is hard to start.

 

Without digging into schematics, I'd guess either the FP relay is stuck, or has constant power...could be the ECM driver is always low as well.

As mentioned before, get a wiring diagram, the circuit you need is not too difficult to diagnose.

Good luck.