1989 Turbo Auto - 1.37V at IGN Fuse, No ECU power, More details inside

[Chambers]

Hi all,

I got a chance to work on my 89 turbo automatic car over the weekend. The goal was to see if the engine runs, and basically address whether its better to part out or attempt to fix. When I started working on it, the engine would crank but would not produce any spark/fuel and the EFI main relay was not energizing. I also noted the CEL was not turning on. So my first thought was ECU, so I checked the ECU, BATT was getting 12v, but M-REL was not, and IGN was not getting anything with the key in the "ON" position, so hmm. Heres your sign, checked for a 7.5A IGN fuse and found there was none, so I plugged one in and checked voltage and only got 1.37V:aigo:. So I tried it anyway, I checked at the ECU, and sure enough I was getting 1.37V at IGN on the ECU and obviously that wasn't enough to energize the EFI main relay etc... So, to test it I jumped 12V to IGN and the engine started on the first turn of the starter, upon removing the jumper it died as it should. I also checked the voltage at pin 17 on B-1 Black-Orange wire and only got 1.37V, so maybe there is an issue with my ign s/w?

I managed to put a band-aid on it to get it to run to work out any issues, I found on the drivers side the Black-Yellow wire running from the ign s/w had already been tapped with a inline fuse for something that was not installed anymore and that was getting 11.6V when the key was on so I ran that over to the IGN pin on the ECU. First I pulled the IGN pin out of B-1 and just wrapped it together, the car would not start. So I put the IGN pin back into B-1 and touched the tap to the IGN pin on the ECU and bam, it fired right up. From that point I did a tap into the IGN wire so I could continue checking over the engine.

So, I'm a little perplexed by this, I reached my goal of seeing if the engine runs witch it runs quite well, but now I'm faced with this 1.37V IGN stuff and I want to find the issue. As usually I'm open to all comments, suggestions, or ideas on what to check/test. I plan to continue troubleshooting this but I figured I'd ask around too.

Summary:

Was getting no CEL, power to ECU, no spark, and fuel.
Checked ECU grounds on the intake manifold - They are good and tight.
Coil pack ground - Replaced it to eliminate it.
EFI Main Relay - Checked out ok when I jumped the correct pins.
EFI 15A Fuse - Good.
IGN 7.5A Fuse - Good, installed missing unit. Replacement did not yield a start.
Getting 1.37V at IGN 7.5A Fuse, IGN pin on ECU, and Black-Orange pin 17 on B-1.
Band-aid 12V when the key is "ON" to IGN wire installed at the ECU.
Runs with band-aid.

Thanks all!

 

[MKIIISupraGuy]

Interesting situation. I wonder where the voltage drop is coming from ? You said the blk/yellow ign wire was tapped and you ran it over to the ecu pin... does that mean you cut it , or did you use a jumper wire ? Personally I would of removed that wire with the inline fuse, then soldered the connection back to where it mates again with the black/yellow wire. If you can get a close-up pic of your ignition harness and wires, that would help a lot too.

 

[firegumby]

I had similar problem with no cel or spark. I bought a ton of stuff and it ended up being one of the 2 main relays, brown or round silver in the engine fusebox. The only other thing I did was unplug and re-plug the ecu. Hope that helps.

 

[Chambers]

Sure, any comments and ideas are appreciated. I checked the EFI Main Relay (Round Silver) but didn’t check the brown rectangular one. I will note that and see if it’s functioning.

Thanks, I may be toying with this latter in the week.

 

[Scruggs86.5T]

I would have to say check the 30amp fusable link in the engine fuse box. That doesnt really make any since though because you would end up having the 1.37 on the +batt of the ecu. But if could be that someone before you messed with the wiring for the ecu and ran the +batt to somewhere else. If this is not the case then you would need to look at your connections between the fuse box and the ignition switch to the ign fuse, basically just follow the white and red from pin 1 of 2b in the fuse box, through the ignition switch to the ign fuse. I am thinking someone before you messed with the wiring somehow and left it for you to clean up. By the way you explained what was going on it seems like you have an ewd handy and know your way around electrical systems. Hopefully that helps out, good luck.

 

[3p141592654]

Based on what you say, something in the AM2 circuit of the ignition switch is bad. First thing to do is find where the missing 11V is hiding. Most likely culprit is the ignition switch itself. Measure across White-red and Black-orange at the ignition switch (colors are from 1989 so yours should match). Ignition off, should be 12V, Ignition on, should be 0 V. If ignition on gives 11V across those two terminals then the switch is bad. Easy fix. Let us know.

 

[Chambers]

Thanks for the replies. I do have a EWD handy, It’s my second favorite book! .

When I get back to the car I will take some photos and do some more testing. I'm still in that "I like a challenge" mindset, so here’s hoping that it pans out.

Thanks again.

 

[Chambers]

Started at the fuse box, checked fusible links and they were all good. So I went to the IGN switch plug, everything looked good. Then I took a peek at the back of the IGN switch and lo an behold a bad wire corroded and missing its insulated jacket, see photo, I have no idea how this happened but replacing it did solve the CEL problem.

Now I have a blinking check engine light when cranking, it blinks every time the engine fires witch is intermittent. This thing is weird, it ran amazing before I found the problem, a guy actually bought it (he was told it had problems), he drove it home then out of nowhere it crapped out. So I have to continue the trouble shooting.

Pic:

 

[Chambers]

I started to address the strange CEL blinking when its cranking. It would crank then fire one cylinder, then the CEL would turn off, then it would continue to crank until the CEL came back on (within a half second) and the engine fired again, rinse and repeat... So I checked the CPS, upon giving a tug on the connector the wires pulled right out, they all showed signs of bad corrosion too. I exchanged the CPS at TDC. Now the CEL is solid during cranking, and after adjusting the timing more I was able to get it running again. All I have left to do is fix the band aid on the CPS wires and adjust the timing some more and it should be good!

Thanks all for the support, comments, and suggestions!