No power to fuel pump inertia switch, 91 MTX

[tompumped]

I haven't had time to find wiring diagrams. I have a lot going on right now and I could really use the help or guidance.
This is my first 91 and the wiring is different than the three 92s i've owned. Full disclosure I just got done installing a different motor with the same original complete engine harness. I did a 3g alternator upgrade using the factory alternator charging wire harness from a '95. I was able to use the yellow/white wire with 20ga fusible link from the 95 alternator charge wire harness and solder that to the original yellow/white wire over by the starter solenoid. I completely eliminated the original charge wire, and the yellow/white wire with fusible link that was attached to it. I also did a gen 2 starter upgrade. It will crank, the S terminal for the starter is part of that 95 alternator harness.

I can not get power to the fuel pump. If I put power to the pump at the intertia switch it primes. The CCRM is coming on and sounds as it should. Turning on for a few seconds then the fuel pump relay kicks off. This 91 also has a yellow wire with 20ga fusible link that is directly attached to the positive battery terminal. The CCRM will not activate without that wire connected.

The brown wire that you connect to the ECM test terminal to get the CEL to flash to count codes should be a ground IIRC but when I check for continuity or use my power probe it isn't.

When I have more time I will see if I can get the fuel pump to activate from that ECM test plug, but I need to find a pinout of it. I will also double check the voltage readings at that plug, but I think I had low voltage there. The ground is connected to the back of the intake, the ground that is part of the harness for the ecm test plugs is also connected.

I have no clue what i'm missing or what I did wrong. It's not the ecm/ccrm, I have known good spares. Thank you in advance.

 

[zoomlater]

here is a link with pins for the CCRM from a D code and M code (from NoSlo)

https://shoforum.com/index.php?threads/fuel-pump-cutting-in-and-out.141701/#post-1543789

 

[tompumped]

In the stickied how-to thread the person stated that you have to provide power to the old alternator charge wire. I did try putting power to it initially and I thought it would've caused the fuel pump to prime, but that wasn't the case. I falsely assumed he did this, because at the solenoid end of the charge wire there's a yellow/white wire that is spliced into it. I had the same yellow/white wire attached to the larger 1995 charge wire so I never applied +12v to the old charge wire. If i'd cycled the key while providing power to the old wire it would've worked as it should.

The way I found out it was that was I grounded the fp terminal at the EEC test connector and then applied power to the old alternator charge wire. The strange thing was I was getting five volts at the fp pin on the eec connector. When I would check the voltage there it would cause the relay to cycle, and i've never seen anything like that happen. Same thing when I grounded the terminal.

I started to tear into the harness to try and find the splice where the old charge wire powers up whatever wire it does and I can't find it. I think if I find the splice number in alldata I can then find it's location without stripping all the tape off the loom and searching. That's the first and last time in my life I wont try and find the wiring diagrams first. It only took a few hours to figure it out but it could've all been avoided.

 

[tompumped]

If anyone happens to know where the splice is on that alternator charge wire that would be great. I can't find my prints that show the splice numbers. I'd rather find the splice and just put voltage to it than leave that charge wire powered. If I can't find it I doubt i'll tear apart the whole loom to find it,but i'd rather do this the right way.

 

[TimboSHO]

If anyone happens to know where the splice is on that alternator charge wire that would be great. I can't find my prints that show the splice numbers. I'd rather find the splice and just put voltage to it than leave that charge wire powered. If I can't find it I doubt i'll tear apart the whole loom to find it,but i'd rather do this the right way.

Did you ever figure this out?

 

[tompumped]

Did you ever figure this out?

Give me a minute to remember, but I figured out where it was. I'll have to go take a look at the vehicle and just by being by it i'll know.

If my turbo audi wasn't taking priority and my bike i'd remember all of this because my mind is usually a steel trap when it comes to this ****. Either way they were right. IIRC I followed the old charge wire back to the splice cut it, heat shrinked it and then just connnected the other end that was originally connected to a solenoid IIRC, but hang on a min

 

[tompumped]

All these years I thought it would be more difficult to do this swap and the only issue I honestly ran in to was the fact I assumed I knew better than the person who wrote a write up. I figured that I was using an altogether new charge wire why would I need the old charge wire, but the fuel pump will not power up without it.

The hardest part of the swap to find is the small bracked that bolts to the front of the alternator. I got lucky because I had purchased a '95 that turned out to be scrap. I have a spare bracket that bolts to the block if anyone wants me to find it, but you'd have to fab up a bracket for the front I believe which isn't anything if you can weld and use metal burrs, cut off tools.

I was lucky to have the original factory wiring harness to see just what gauge was used for the 3G alternators and how it was wired. I was able to retrofit the charge wire harness with exciter wire(s) from my 95 onto my 91. If anyone wants me to explain in detail how it was wired and anything else I did including pictures let me know.

This tape is an absolute must when tearing into harnesses. I thought Tesa tape was the best, but FOD tape is as good if not better than the OEM harness tape, i'm speaking of the heavy duty fabric type tape. https://www.amazon.com/gp/product/B079SRY4Z4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I used to just use super 33 and corrugated tubing but that FOD fabric type tape is infintely stronger. There are also products that are infinitely better than corrugated wire loom, Caterpillar uses it for harnesses and if you've seen it's amazing. IIRC flexo tight weave is comparable depending on what you order, but I don't know.