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91 Toyota MR2 wont start after messing with ignition switch

Tiny
PEDROVESTEBANORELLANA
  • MEMBER
  • 1991 TOYOTA MR2
  • 108,130 MILES
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!
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Friday, August 10th, 2012 AT 2:06 PM

13 Replies

Tiny
ASEMASTER6371
  • MECHANIC
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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
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Friday, August 10th, 2012 AT 2:17 PM
Tiny
PEDROVESTEBANORELLANA
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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?
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Friday, August 10th, 2012 AT 2:25 PM
Tiny
ASEMASTER6371
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I would look at the modules first.

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

Roy
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Friday, August 10th, 2012 AT 2:35 PM
Tiny
PEDROVESTEBANORELLANA
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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.
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Friday, August 10th, 2012 AT 2:45 PM
Tiny
KHLOW2008
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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.
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Friday, August 10th, 2012 AT 2:46 PM
Tiny
PEDROVESTEBANORELLANA
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  • 7 POSTS
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.
https://www.2carpros.com/images/external/34g0w0p.jpg
Now I regret it.
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Friday, August 10th, 2012 AT 3:02 PM
Tiny
KHLOW2008
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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.

https://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.

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Friday, August 10th, 2012 AT 4:05 PM
Tiny
PEDROVESTEBANORELLANA
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"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!
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Friday, August 10th, 2012 AT 4:23 PM
Tiny
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If you have sparks, check the fuel pressure and injector pulsing. Ensure fuel pump is running.
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Friday, August 10th, 2012 AT 5:15 PM
Tiny
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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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Friday, August 10th, 2012 AT 5:42 PM
Tiny
KHLOW2008
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You would need a noid light. Maybe you can try spraying some starting fluid into the throttle and test.
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Friday, August 10th, 2012 AT 5:53 PM
Tiny
PEDROVESTEBANORELLANA
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Seemed like the engine cylinders were full of gas I don´t know why!
All tests performed were OK so I decided to take the spark plugs out and then I saw it. I left the engine without the spark plugs for a couple of days, and then it started, couple of minutes running at idle and it was OK. Thanks so much for your help!
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Monday, August 20th, 2012 AT 7:47 PM
Tiny
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Non starting coupled with continous cranking would flood the cylinders.
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Monday, August 20th, 2012 AT 10:28 PM

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