Mass air conversion issues March 05, 2010, 10:11:44 AM So the swap went real well. Heres what I dealt with.Its an 88 mustang gt convertible. I changed the SD ecu with an 89 A9P.I swapped the ecu harness with one that I was told was from an 89 car.The car runs great when it runs. Recently I have an interminent issue with the fuel pump. It has cut out while running before. Mostly the relay won't kick on key on. I've heard stories with 90+ mass air harnesses wrecking havoc on FP relays due to those cars with air bags. Did this guy who sold me the harness lie about the year it came out of? Or is this a seperate issue? In the case of incompatible year harnesses shouldn't the FP relay just not work at all, not intermentantly? Or should I just replace the relay and this is freak coincidence? Any advice or links would be greatly appreciated, spring is near and I wanna park the big diesel. I'm not sure where to proceed next. Thanks in advance fellas. Quote Selected
Mass air conversion issues Reply #1 – March 05, 2010, 12:44:41 PM I should have added, with enough key on key off cycles, I can get the relay to finally kick. I'm stumped Quote Selected
Mass air conversion issues Reply #2 – March 05, 2010, 02:03:14 PM Ignition switch ever been replaced..? Quote Selected
Mass air conversion issues Reply #3 – March 05, 2010, 02:32:19 PM I don't think so. I couldn't tell ya what the last owner did though. Quote Selected
Mass air conversion issues Reply #4 – March 05, 2010, 03:34:25 PM Since you had the problem before the swap, I wouldn't think the harness would cause it. An Ignition switch can play havoc on a few problems. The other option is to test to see if you get juice to the relay repeatably. Quote Selected
Mass air conversion issues Reply #5 – March 06, 2010, 04:10:41 PM No, no problems before the swap. Immediately after the swap the car ran fine. Its intermittent. Ran all day yesterday, today I got to my destination and it cut out, after a million key cycles I couldn't get the relay to pick, so I towed it home. Now the car runs fine again. until next time. Quote Selected
Mass air conversion issues Reply #6 – March 07, 2010, 10:43:51 AM Why did you swap the harness instead of just adding the MAF wires to the 88 harness? It is really easy to just add the MAF wires. Quote Selected
Mass air conversion issues Reply #7 – March 07, 2010, 10:45:01 AM Have you tried replacing the relay and checkin grounds to the relay?? I thought there was a wire that had to be run to the back the fuel pump relay when a car was swapped over to mass air Quote Selected
Mass air conversion issues Reply #8 – March 07, 2010, 11:08:50 AM where on a mustang is the relay? on the harness you changed or under the seat i'm asking to see if the fuel pump monitor wire the mass air computer wants is hooked up or not. i'm in the middle of a mass air conversion (stupid speed densidy harness) during an carb to Efi upgrade (84 fila tbird)351w 5 speed from carb aod and i'm having lots of fun with wiring right now also. Quote Selected
Mass air conversion issues Reply #9 – March 07, 2010, 11:46:39 AM I changed the harness altogether to try and solve another issue that I had, which seemsto have worked. I did not run the FPM2 wire, the relay is under the drivers seat, I already changed it. Quote Selected
Mass air conversion issues Reply #10 – March 07, 2010, 12:06:25 PM You do not need to run the wire for the fuel pump monitor. You'll get a code 95 for the fuel pump monitor but it won't affect the operation of the EEC. I didn't run that wire when I did the MAF swap and it runs fine. Did you run the wire for the speed sensor? If you didn't you should or you'll have some stalling issues on deceleration. Quote Selected
Mass air conversion issues Reply #11 – March 07, 2010, 04:18:25 PM I did not run the VSS, Haven't looked to see if I even have that sensor yet, its a non-cruise equipped car. Everything sounds like that the culprit, but when that reported stalling issue takes effect, why the hell wont the fuel pump relay pick again. I can put my hand on it and nothing happens with it, which is why I changed it itself first. The car renders itself useless for a while and I'm stuck borrowing a tow truck. Then hours later after its home, it'll work again. If I get time tonight I'll run the VSS to try. My next suspect was going to be the ignition switch. For $11 its a cheap thing to change. The key and cylinder doesn't seem perfect, it works fine to the rest of the car but for some reason my mustang ignition key, is a one-sided tooth key. Never seen a ford like that in all my life. During pulling codes on a fresh batt hookup I obviously got no continuous codes, just the ones that I should for thermactor and egr since that stuffs has long been removed from the car. Not once have I gotten a FPM2 or VSS code yet. Yesterday the pump relay ped out for a second so I unhooked and rehooked the batt and it seemed to have got it working again. So far thats the roadside persuasive fix but this shiznit has gotta stop. Any other thoughts or ideas welcome, next step I'm gonna run VSS I think. Quote Selected
Mass air conversion issues Reply #12 – March 07, 2010, 06:10:58 PM Keep at it, you'll get it! Make sure you post up the fix to help us that haven't done the conversion yet. Quote Selected
Mass air conversion issues Reply #13 – March 07, 2010, 11:18:07 PM Still didn't investigate further yet but the car has been getting me around all day. Quote Selected
Mass air conversion issues Reply #14 – March 09, 2010, 07:13:54 PM 3 days it went with a new batt/eec reset. Failed today at work in the parking lot. Took about 75miles I'd say. So I'm running FPM2 right now, pin 19 is empty in the harness. When I get to VSS, there is a green wire in pin 6 at the eec. Pin 3 is empty. What the hell is pin 6 doing there and why is it green? Any ideas? Quote Selected
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