Gevo

Hi Guys, thanks for the responses! I'm located in LA area, Souther CA of course.

Ok, so, Ive been stupid again. I had an hour or so to spare yesterday so I went over to my parents house to test the spark with the VAFM disconnected.. since I read that it starts this way for a short while. While I was there I decided to test the VAFM again and as soon as I pulled up the schematics from the FSM, I realized I had made a mistake the time before. I had pulled up the FSM page for the 22re vafm which has a different pin out. I checked everything with the new pin out and sure enough the VAFM is all within spec.

Back to square one. I am going to spend all of my saturday on this problem. It's now an embarrassment that I can't find the issue.

These are the tests that I have done so far.. in summary.

Coil within spec (both circuits)
-Igniter is getting power.
-VAFM within spec.
-black-blue wire is good between igniter and ECU and I tested against ground as well.
-New distributor (within spec of course)
-ALL ground triple and double checked, have temporary ground wires running to all components
- Checked tachometer wire not shorting to ground
-Tap test confirmed spark going to distributor.

SO.. short of a bad ECU, what else can cause the ECU not to send the signal (IGT over Black-blue) wire?

My plans for this weekend are to check all of the wires from VAFM and Distributor pickups to the ECU. And will be using an oscilliscope to check IGT signal from ECU. Perhaps there is a signal which is weak therefore not working. Because, I tested the black-blue wire during crankign and it WAS gettign some voltage to the igniter....

I need this to run soon cause my wife is tarting her new job and will need the second car! I really have a feeling it's either a very minor problem (could be in harness since it was worked on) or the ECU at this point. I don't know what would have cause the ECU to break though.

Gevo

SOLVED!!!!!! My oh my how happy I was when that little test light strobed

Here is what the problem was.

if you don't wanna read all my thoughts below, the problem was that E2 wire was shorting with the Vc wire within the harness at the TPS connector.

No spark condition after Engine rebuild. I tested every component involved in the process and they all checked out except the distributor. I replaced he distributor but the problem persisted.

I did the 'tap test' that another forum member had posted some time back here https://www.yotatech.com/forums/f2/n...89-95-a-10543/

This test proved that my igniter and coil were working and that the problem was the IGT signal. The IGT signal was not making it's way to the igniter. So, I started to test the continuity and resistance of the wires involved in the system. All of the wires checked out. I then went to check the VAFM (air flow meter) connections. I had checked out the resistance of the VAFM earlier and it was all within spec, so I set to test the wiring in the system. All of the wires check out in continuity. I stopped this and decided to check the codes. I jumped the terminals and turned the key, no check engine light at all. his distracted me for a few hours while I tried to find the problem in that circuit, everything I checked was working fine. I was about 2 minutes away form calling it a bad ECU, but decided to keep going with the previous work. I went back and re-checked everything from the sensors to the ECU. As I was checking the resistance of the wires I saw that the E2 to the VC wire had .7 Ohms. This caught my attention, as it seemed odd that a sensor wire would be grounded (the E2 is a ground from the ECU) . I researched the wiring diagram and found that the VC wire has two end at the throttle position sensor and the VAFM. I unplugged both and tested the wire only within the harness and I had continuity between the two. I spent quite a bit of time thinking this through making sure I haven't missed something (again) and going over the wiring diagram. After some thought I decided that I'm sure the VC shouldn't be shorting with E2 within the wiring harness and went about to find the location of the short. I unwrapped the wonderful wiring work m friend had done on the harness at the TPS connector. I saw one of the wires (yellow white) was hanging on by a thread but I knew that, and the rest didn't really look suspect to me. I was DREADING the rest of the task of unduing the harness and following the Green-Black wire but at this point it was either that or go buy a new ECU assuming that would be the problem anyway. I started to check the continuity of the E2 to Vc wire at the ECU connector, and after I had unwrapped the TPS there was no continuity. Not wanting to bring my hopes up, I checked them again at various points and found that now, the wires were not shorting. I looked back at the TPS and figured that must have been the issue since it was the only thing I changed between tests.

I plugged everything back in and jumped connectors at data link for check engine light and codes. To my utter amazement it flashed. Two codes, ECT and VAFM. ECT was disconnected at this point and VAFM... I dunno why that happened. I connected and checked both items and checked codes again, this time just ECT (22). I need a new ECT connector, I knew that, but meanwhile I checked the ECT wires for shorts and continuity up to ECU, and it was good. I put my spark tester on the distributor wire, held my breath and cranked. I literally was floating when I saw the litkle light flicker.

I quickly connected it all back together and cranked for just 3-4 seconds before she came to life. For the first time in MONTHS and after a complete rebuild. I let her run for a few seconds and she died. Timing seemed way off, so I adjusted the distributor until it sounded a bit better. I let it warm up for just a few minutes and shut it down. I need to follow strict breaking in procedures

I will go back to my build thread now and post further developments there. I do need a new ECT connector, new TPS connector and new VAFM connector.

Once more, thanks for everyones input and guidance!! Past and present

RJR

Congratulations, and Merry Christmas! That has to feel very good!

One of the hardest circuit faults to troubleshoot and find is a conductor-to-conductor short. They cause all kinds of weird behavior but often don't show up with a continuity test or a simple short-to-ground check. Glad you finally tracked this one down. Your troubleshooting methods were logical and thorough; kudos on that.

Gevo

THanks RJR, MErry CHristmass to you as well and indeed it is now for me

I spent so many hours trouble shooting this!!

Also, I have to add one more thing for any future reference. The reason why I didn't call it a dead ECU was because I set to test all of the ECU connectors. I printed the FSM page and started to go down the list. I found that 5 different low voltage signals were erroneous. Now this may look like a dead ECU, but these 5 were from different circuits and sensors. My logic was that it is not likely the case that multiple parts of the ECU circuitry burned out from one instance of voltage spike (assuming there was one). I would probably have ordered a new ECU had I stopped checking at the 1st or 2nd bad reading, but boy... I'm glad I went on.

RSR

Bravo Gevo.

Gevo

Incase anyone uses this thread to troubleshoot similar symptoms. Today I found that actual location of the short, same problem, same short with the same wires, just not the TPS connector. It's part of my big post here.. https://www.yotatech.com/forums/f199...15/index9.html