91 WONT START AFTER MESSING WITH IGNITION SWITCH

1991 Toyota MR2

Tiny

pedrovestebanorellana

August, 10, 2012 AT 2:06 PM

Hi, I have a 1991 Toyota MR2 3sge REV1. I was doing an experiment the other day so I could install a numeric keypad in order to start my car with a code. When I was doing some tests with a multimeter so I could determine which positions of the key were the ones in the ignition switch, my curiosity went ahead and I jumped terminals ST2, IG2, and AM2 briefly. The car almost started, but after that, when I connected again the ignition switch it didn´t. The starter engine works fine, just the sound is not as "good" to hear as before, but engine won´t run. I´ve checked all main fuses, all main relays, fuel pump, diagnose codes
and spark with my workshop manual. On the first second after trying to start, it wants to run but then the start engine seems like it´s out of power, though it´s still running with that unusual noise. Also I´ve opened the ECU to see if I might have blown something inside it but it seems ok. I do have an extra ECU, and my next guess is to try it and see if it runs. Do you guys have any idea of what is going on? Do you think I might have short circuited some of the installation and that´s the problem? Please help me!

13 Answers

Tiny

ASEMaster6371

August, 10, 2012 AT 2:17 PM

It may have spiked the ecu or the ignition module from you jumping out those wires. Voltage spikes are not good for these modules.

Roy

Tiny

pedrovestebanorellana

August, 10, 2012 AT 2:25 PM

Thanks for the answer. Yeah that s was my thought. Damn, I m gonna try replacing the ECU with the spare one I have and see what s up. Other wise I will start ordering an ingnition module. Do you think the distributor could have been damaged as well?

Tiny

ASEMaster6371

August, 10, 2012 AT 2:35 PM

I would look at the modules first.

Does the check engine work when the key is on, engine off?

Roy

Tiny

pedrovestebanorellana

August, 10, 2012 AT 2:45 PM

Yep, the check engine light appears as usual before starting the engine. Is there any special procedure to check the ignition module? I already checked for spark disconnecting the cable which leads to the distributor and grounding it to the chassis while starting the engine.

Tiny

KHLow2008

August, 10, 2012 AT 2:46 PM

First thing is, are you able to crank the engine with the ignition key?
Since you have a multitester, did you check the various wires of the ignition switch for battery voltage with ignition ON and cranking?
With a shop manual, you should have been able to distinguish which wires should be for waht.

Tiny

pedrovestebanorellana

August, 10, 2012 AT 3:02 PM

The starter runs, the engine does not crank, and yeah, it s done with the ignition key.
I did check all the wires with the tester, but it was confusing since there were more than one at the same time with 12 Volts.
My mistake was putting those cables together like in this picture IG2, ST2, and AM2.
http://i50.tinypic.com/34g0w0p.jpg
Now I regret it.

Tiny

KHLow2008

August, 10, 2012 AT 4:05 PM

Starter runs means the engine is cranking. It is not firing up.

Do you have ignition sparks? You mentioned checking but did not say if you have sparks.

http://www.2carpros.com/articles/car-cranks-but-wont-start

With ignition off, do you have battery voltage at AM1 and AM2?

With ignition turned to ON, do you have battery voltage at IG1 and IG2?

Your putting the wires together shuld not have caused anything other than a burnt fuse.

Tiny

pedrovestebanorellana

August, 10, 2012 AT 4:23 PM

"Starter runs means the engine is cranking. It is not firing up." Yeap, sorry that s what I meant, my English is kind of rusty and I get confused sometimes, specially with technical terms.
I do have ignition sparks, I checked taking out the ignition lead from the distributor and grounding it while starting the engine.
I will check again in a couple of days since I m out of town and post here the results. Thank you!

Tiny

KHLow2008

August, 10, 2012 AT 5:15 PM

If you have sparks, check the fuel pressure and injector pulsing. Ensure fuel pump is running.

Tiny

pedrovestebanorellana

August, 10, 2012 AT 5:42 PM

Fuel pump works fine, I tested it following the steps in the workshop manual by jumping two connectors of the diagnose connector. I need to test the injectors though.

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