Added another Fox to the fleet - 1985 Marquis LTS

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Re: Added another Fox to the fleet - 1985 Marquis LTS

Reply #75 – December 29, 2025, 08:05:07 AM

So, I dug into it a bit last night.

The program was commanding for fuel pump activation, but the ECU was not sending the signal. I discovered this while running the ECU with the Stimulator on the bench.

I've run into this before on these, so I hunted down the transistor for the fuel circuit. You can see the old one on the bench and the new one (next to the MAP sensor hose) ready for soldering.

Hooked things back up to the laptop and now we have FP signal (The LED on the lower right)

The weather is pretty gross today, but I may brave it for a few to plug this all back in and see if we can get signs of life out of it.

Re: Added another Fox to the fleet - 1985 Marquis LTS

Reply #76 – December 29, 2025, 04:21:23 PM

Well, I made an attempt earlier to start this thing, and while I have fuel pump function, it seems like the injectors aren't firing. Things check out with the Stimulator, and the adapter board is just a passthrough.

I need to trace forward to see if it's something in the harness, or what. Too cold and windy today to mess with it.

Re: Added another Fox to the fleet - 1985 Marquis LTS

Reply #77 – December 30, 2025, 10:49:09 AM

Wind is pretty crazy here too.

Hope it is a simple find and fix.

Re: Added another Fox to the fleet - 1985 Marquis LTS

Reply #78 – December 30, 2025, 10:53:07 AM

You have the patience of a saint, Chuck. Most of us would have no idea how to work through a complicated electronic issue like this. Kudos to ya.

Re: Added another Fox to the fleet - 1985 Marquis LTS

Reply #79 – January 01, 2026, 05:06:46 PM

OK. I had to finish up a house project by yesterday (Solar battery), but I decided to brave the chilly temps this afternoon to do some trouble-shooting.

I rigged up a couple test lights and set about to verify spark and fuel.
I had spark and the injectors were firing. I pulled a plug to check to check to see if it was wet, and it had some fuel on it.

I decided to recheck the timing. I rotated the engine to my 10* BTDC mark and popped the dist cap. Sure enough, I's somehow managed to get the timing 180* out. I pulled the dist up and rotated the rotor 180* and put things back into place.

Then it started to make the proper noises. I got it running, but couldn't get it to idle and I know I need to work on the tune.

By this time I was starting to get a bit chilly, and the laptop ran out of charge, so I took that as a sign to stop for the day.

Not a 100% success, but I know that my ECU and the adapter are good. Just need to fiddle with the tune now.

I still have to secure the fuel lines down, but the clamps I needed didn't show up until yesterday, so I'll get to those soon enough.