Hey all, I have a safety question: I am about to compression check my LH0 V6 and have all the spark plugs out, ready to thread the guage in, and I have disabled the ignition system already. Now I need to disable the fuel injection system so it doesn't dump gas into the engine while I turn it over. Haynes says to unplug the fuse labelled "FP" in the fusebox, but there is no such label in my 90 RS. There are two fuses labelled "INJ1" and "INJ2" though. My best guess is that these are for the injection system, but that is just a guess.

My question is: Should unplugging those fuses do the job?

Thanks for any help!

 

they might.... but i would pull the ECM/Fuel pump fuse thats in the engine bay.. look on the fender near the batt.. theres a little plug into nothing... pull the plug off the cover and theres a fuse inside... pull that one.

 

That sounds like a better plan, I'll look for it. Thanks much!

 

If you have an automatic trans don't forget to do the idle learn procedure. You reset the ECM by pulling that fuse.

RBob.

 

I can't find the fuse mentioned above. Does anyone have a pic of it, or would it be in any other location on a 90 RS?

Could you elaborate a wee bit? Not familiar with that procedure.

Thanks!!

 

I didn't worry about it, just don't do anything stupid and make sure that the ignition system is disabled by pulling the wires that feed the coil. I wrapped them in electrical tape just to make sure they didn't accidentally come into contact with metal and spark, but most of the fumes go out the pipe so you should be alright. Just don't crank the motor for too long while checking because the CAT will heat up real quick and melt with all the raw gas. Just crank for like 3 or 4 seconds, then stop, check the reading and move onto the next cylinder.

 

he means the computer will forget what it learned about your car... so you will have to drive it a little bit so it can re-learn everything.....

so the first time you start it up after pulling the fuse, the idle may hunt or be off for a min.

 

Your pic of the fuse is correct, passenger side fender under the hood.

As for the idle learn it is more then just driving the car. Search on 'idle learn' & 'RBob'. It has to do with teaching the engine how to idle.

Pulling Inj1 & Inj2, or the fuel pump relay would be better. No idle learn is then required. You don't really want the injectors pumping fuel as you do the compression test.

RBob.

 

I definitely won't do the test with the fuel system running. Sounds like a recipe for disaster, lol. Now I see why I didn't find that fuse, my battery is located by the driver-side fender. Consistency was not one of GM's strengths.

Thanks for the help all! :hail:

 

You're supposed to wire the throttle body all the way open (or mash the go-pedal to the floorboards) while cranking. The injectors don't pulse at WOT, the TPS puts the ECM into "Clear Flood" mode.