Hello everyone, my first post here although I've used this resource many times. I have an '89 GT I've owned since 1992, it's a daily driver with almost 300K on the clock and along the way I've had to fix many things, never the short block though, but this time I have a question that's got me stumped. This all started over a no prime/no fuel pump situation a few weeks ago. Leaving a large antique it would only turn over, the pump would only make noise past run and into start, on the key, but before that starter engaged. After fooling with what I could without tools, came home on a bouncy rollback. After doing nothing more than checking a few connections, fusible links and spark, the relay clicked and the pump primed. Motor started and I changed the rely and fuel filter, had the filter already so... The next day I run errands and stop and start the car 10 times without problem UNTIL my last stop at Taco Bell. On the way through the lot were the T.B. is, I went over 4 speed bumps, thin but high, narrow abrupt ones, I was in a hurry, bang bang, bang bang. Well I come out to my car and the same thing as the day before, I call a friend, get my groceries home and start reading here. After some reading and going over the checklist I thought I might try the inertia switch since jolting the car seemed to affect it. Back to the T.B.. eliminate the inertia switch, ground the ECM, may or may not have helped more on that later. and my relay clicked and pump primed. Car starts and I go home, yea! All week, no problems, stop and start everywhere until I was leaving the flea market, same problem again. With a multi meter I find power on two of the 4 connectors in the pump relay plug. Looking in the bottom of the relay itself I have 2 large spades and 2 narrow and power in the plug on one of each. Jumping the larger connectors ran the pump but no start. Jumping the narrow connectors as well and the cars started drove home and back to reading here. So everything points to a bad ECM or rather the solid state switch that powers the primary power to the relay which in turn puts the power through to the pump, if my understanding is right. Replaced the relay again and still no start so as the work week loomed, I rigged up some spades on heavy speaker wire with some 12v toggles and replaced my impromptu jumpers under the seat and been driving it like that for a week, all the while thinking it must be the ECM, where I'm stumped right now. About 15 years ago my car wouldn't start, had fuel, must've had spark because the consensus was it had jumped time but before I took the front apart, I went to see a Mustang guy I knew who told me to go home and take out the little plug on the pigtail near the TFI module and it will start. Sure enough he was right and he said I had a bad ECM. At the time I couldn't source another ECM and had to send mine away to be repaired. With that plug out and the ECM in the shop states away, I drove my car like that for about 3 months. No computer in the car and no spark advance but it ran well enough I just drove around like granny until the ECM came back and everything put back together. My confusion lies here, if the ECM controls the the opening, or closing, of the fuel pump relay, how did I drive the car then with the ECM removed?? Back to grounding the ECM thing, I once had a no start situ where at work, our electronics guy who's a very smart person, suggested I "clear the computer" by taking the ground cable off the batt and touching it to the positive side, he said things can get "buzzy" on a computer board and that I was draining any residual power. The car started. In the end , I replaced the stator but until I figured that out, I would going down the road and the car would shut off after a half hour or so. I would have to get out and ground the positive side and it would start right up again. I showed a Ford mechanic, at Ford, and he could only scratch his head but I swear it! So when I think I have a computer bug, I'll clear it like I said above but my problem right now is the relay. BTW, same electronic guy just this week wanted to look at my relay and said it was bad, he took it apart and a strand of wire almost hair sized coming form the coil was off it's connection, so he solders it back and we test it on my battery and it's fine. I install it and no start back to jumpers/switches. A long enough read for sure but I wanted to cover everything. I'm a handy guy and know my way around the tool box but electronics, instead of simple wiring is a little over my head. Anyone have any insight? I really did drive without the computer, for months. Thanks for reading if you've gotten this far, sorry for the length.
Jim
Jim