more ECU woes..possibly..

mdslngr77 · 12-18-2012, 12:18 PM

I am working on a 1.6l upgrade to a samurai chassis project. In my case I have taken the frame and running gear of the samurai and transplated a 90 geo 1.6l engine and body to it. Swapped with complete wiring harness so I am basically working with a GEO as far as my running problems. After initially getting it installed it ran fine, starts easy and after some tlc ran well. A month later I pulled it out of the garage for some suspension tests and then it died. No injection pulse. Fuel pump runs fine, 36 psi pressure, good fire. Will run off fuel poured into the TB but no injector action. Ohmed the harness to the inj. no shorts to ground, inj ohms @ 1.2. Jumper the diagnostic and I get a twelve KOEO non cranking. This evening I am going to check TPS output and cranking codes. I am leaning towards bad ECU. My original is 33920-60a31... I have parts from some others and was curious if they would interchange. they are 33920-56b50 and 56b30 respectively. Thanks in advance for any help.

colonelhogan44 · 12-18-2012, 12:30 PM

Crack the ECU case and take some pictures. 99.9% of the time it's just bad capacitors (which leak all over the board) which can be fixed with 5 minutes behind a soldering iron.

mdslngr77 · 12-18-2012, 01:32 PM

Ruby caps so I figure they are toast. no swelling but evidence of leakage. don't really seen any "visible" trace damage. Don't have the means to test the drivers

colonelhogan44 · 12-18-2012, 01:58 PM

Get replacement caps (a local shop stocked them in my area, but lots of folks get them online), being careful that they are the same value as the ones in there. Also be careful when installing them that you get the polarity correct! make notes on how they are installed, as the polarity was NOT printed on the board in my ECU (and likely that'll be the case with yours).

Bex · 12-18-2012, 02:19 PM

The ECU would appear to be working properly if you are getting the code 12, the CEL is on with key on and off when cranking, and you can run with test fuel. Normally injector drivers in the ECU fail/short out due to wiring problems. Have you performed a noid test? Done a compression test to make sure that the timing belt hasn't slipped (or broken?)

mdslngr77 · 12-18-2012, 02:29 PM

timing is on per timing belt marks.. compression fine... going to attempt a noid test tonight if the local parts stores have a light.

mdslngr77 · 12-18-2012, 07:39 PM

OK update for the evening.. I took my good Fluke meter home from work and stopped by Azone and got noids. Let the testing begin... retested the injector.. seems that it may be bad tested @ 33k Ohm this time, may have been the cheapo HF meter I used last time... rechecked the inj circuit to the ECU - good no opens/shorts. jumper diag- KOEO =12.. cranking 10/20 seconds, still 12.. good fire @ all 4 plugs. TPS has 5V reference and .12v closed throttle, goes to 4.02v open. Noid tests give no light @ all KO/crank. fuel pressure still good @ about 34 psi. fuel pump only runs for about 1-2 second @ key on, but runs entirely during crank. I double checked the data tag and this is a build date of 07/89.. So now I've come to the conclusion this is a ECU AND injector problem and the other two ECUs I have will not work, they seem to be 91-maybe 92 models .. do I seem to be on the right track?

Bex · 12-19-2012, 04:45 AM

If your noid test fails, check the red and yellow wire to the injector. Can you hear the injector clicking (with stethoscope/hose) when you are cranking?? Resistance of the injector should be 0.8-1.8 ohms with injector connector disconnected. If so, disconnect the green connector at the ECU (ignition off) and check the #8 to #17 pin of the disconnected connector for 0.8-1.8 ohms as well. If you do not get this reading, check the red and yellow wires to the injector for open/short to ground/poor connection. Also advise what compression 'is good' means. What are the numbers?

mdslngr77 · 12-19-2012, 07:38 AM

Quote:

Originally Posted by mdslngr77

OK update for the evening.. I took my good Fluke meter home from work and stopped by Azone and got noids. Let the testing begin... retested the injector.. seems that it may be bad tested @ 33k Ohm this time, may have been the cheapo HF meter I used last time... rechecked the inj circuit to the ECU - good no opens/shorts. jumper diag- KOEO =12.. cranking 10/20 seconds, still 12.. good fire @ all 4 plugs. TPS has 5V reference and .12v closed throttle, goes to 4.02v open. Noid tests give no light @ all KO/crank. fuel pressure still good @ about 34 psi. fuel pump only runs for about 1-2 second @ key on, but runs entirely during crank. I double checked the data tag and this is a build date of 07/89.. So now I've come to the conclusion this is a ECU AND injector problem and the other two ECUs I have will not work, they seem to be 91-maybe 92 models .. do I seem to be on the right track?

compression @ 185-180-179-183

colonelhogan44 · 12-19-2012, 10:46 AM

I'd try replacing the caps. It's cheap, easy and will need to be done anyway at some point.

That's always one of the first things I do -- I'd rather not get stuck off the pavement on some back road in the mountains.