SOLVED: What is this part behind the ECU? (Eventual AFM issue) (1 Viewer)

[diesellibrarian]

Looking at the electrical diagram for the FJ62, it looks like most of the circuits in the ECU ground to the right front pillar. Most of these actually tie in to a common ground bus located behind the gauge cluster. There are probably 12 or 14 grounds tied into this bus, and when it fails, weird things happen (failure can be due to corrosion or a short circuit burning one or more connections on the bus). The latter is what happened to me, and it caused my dash lights and headlamps to turn off spontaneously while driving. I'll see if I can find a picture of the location of the ground bus. Might be worth checking, anyway.

(Also, putting dielectric grease on threads as mentioned above won't help to get a good ground. Dielectric grease is non-conductive, so if anything it will make for a worse connection)

 

[diesellibrarian]

The bus I'm talking about is the little orange connector below the defog duct. See how it looks all burnt? If you remove the bottom of the connector, you can take out the multi-pronged metal piece, clean it up, then reinstall, wrapping the whole thing with e-tape. Doing that ended the electrical problems I was having with my truck.

 

[Spook50]

The bus I'm talking about is the little orange connector below the defog duct. See how it looks all burnt? If you remove the bottom of the connector, you can take out the multi-pronged metal piece, clean it up, then reinstall, wrapping the whole thing with e-tape. Doing that ended the electrical problems I was having with my truck.

View attachment 3413562

This reminds me I need to inspect and clean mine today while I have my cluster off (forgot to plug the speedometer lights back in last time I had it off, d'oh). Not having any issues myself at this point but preventative maintenance is a philosophy I strongly adhere to.

 

[MustangOwl]

Busy month, back to the garage today. I read through all the helpful comments provided (y’all ROCK!) and dove into a few rabbit trails. Somewhere, someone posted a 3FE diagnostic thread that had a PDF with a 1991-92 3FE EFI diagnostic.

While not an exact match to my vehicle (FJ80 vs my FJ62), one of the simple diagnostic tricks mentioned for my CRANK / NO START / NO CEL issue was to unplug the AFM connector and then to put the ignition to the “ON” position.

I did this and the CEL lit up. This led me to check the resistance on the AFM terminals per page FI-62 of the FSM.

E2-VS tested perfectly

ES-VC beeped showing continuity, or a short (I’m assuming). Spec resistance is 200 - 400 ohms.

HELP! IS THERE ANYWAY TO REPAIR THE AFM? AM I ON THE HUNT FOR A NEW ONE?

Y’all have been amazing in providing the help. It seems we’ve zeroed in on the issue just in time for Cruiser weather. Thank y’all!!

 

[diesellibrarian]

There's nothing in the FSM that talks about repairing the AFM.

If there was a problem with the AFM, would it not throw a code? There seems to be a diagnostic code for the exact issue you identified with your multimeter (i.e. open loop between E2-VC)

In the VW Vanagon world, guys are always popping the dust cover off the AFM and messing with things (cleaning the sweep resistor etc.) to try to get their D-Jet injection systems to work better (or just work period). I have to say, though, in the few years I've been on this forum, I don't know if I've ever read about a failed 3FE AFM. It seems to be a very robust part. But if you've eliminated everything else and you trust your resistance readings, you might try sourcing a replacement I suppose.

One thought - if you jump B+ and FP on the diagnostic port, that should bypass the AFM, yes? If the AFM is in fact the problem, shouldn't your engine fire with those terminals jumped?

 

[MustangOwl]

SOLVED!!

Alrighty folks, just to tie up any loose ends in case another unlucky soul needs help with electrical gremlins tied to an AFM issue.

RECAP: CRANK / NO START / NO CEL issue. As I was beginning to run-down all the electrical gremlins, someone somewhere mentioned a quick unplug of the AFM to see if the CEL would turn on once the ignition was turned to “ON.” This did the trick for me and showed a problem with the AFM (I have no idea why or why not a code would not have been thrown, but no code was showing when the Cruiser was in diagnostic mode).

I tested the resistance as shown by the FSM (page FI-62, I think, of the 88 FSM) and found a short between two terminals (E2-VC).

The FSM recommended replacing the AFM. When I saw the prices of those suckers, I sought out Dr. YouTube’s help and found this beaut:


(AFM REPAIR, AFM REFURBISHMENT)

The above is a video on how to refurbish a very similar AFM. It was WAYYY less complicated than you think. I’ll likely do a deep clean as well.

SOLUTION: When I opened up my AFM, I found the reason for the short. Two of the internal leads were touching as one of the leads had somehow gotten loose. I separated the two, replugged everything, and the truck started up as if she was brand new!

I will be finding a friend who can solder well (I am no bueno at it) to make the solution permanent.

A big THANK YOU to everyone in the community that offered up wisdom and experience. All of it came in handy bit time!

BTW, here’s a pic of the opened AFM:

You can sort of see the golden arm sticking off of the center wheel is stuck on the loose Terminal lead.

Also, to encourage anyone out there, before I got the LC, all I knew how to do was to change oil, oil filters, and air filters. Just a heavy dose of GRIT and an honest, humble desire to learn along with the amazing Cruiser community and anyone can learn a ton!

 

[MustangOwl]

Btw, @MrMacdugal posted a link to @jonheld ’s 3FE EFI diagnostics above. While I believe it references a 1991 FJ80’s version of the engine, the simple diagnostic information and suggestions helped me to understand the system better and helped me to very simply and quickly identify the problem. So thank y’all to both of y’all!

 

[jonheld]

One thought - if you jump B+ and FP on the diagnostic port, that should bypass the AFM, yes? If the AFM is in fact the problem, shouldn't your engine fire with those terminals jumped?

That bypasses the fuel pump logic and fires the fuel pump directly once the ignition is in the ON/RUN position. Engine should fire if everything else is working correctly, but it may not run well if there's an issue with the AFM.