Is the starter signal wire tied to the ECM on this GM bypass ignition system?

CHETSJUG

MEMBER
1993 BUICK CENTURY
95,000 MILES

Bringing a used car up to snuff for a sis-in-law. I just fixed a stalling problem where a fuel injector was shorted. In the process I changed the air filter, plugs, wires, fuel filter, fuel relay, ICM, CKP, TPS & flushed and tested the MAF. NOW: 3 times in a week since the car is on the road, the starter has continued to crank when the key is relaxed to the run position. When you turn the key off, the engine continues to crank for 45 sec- 1 min, then shuts off. If you return the key to run during the cranking time, the car will not restart. 1st time was after replacing the ICM (last thing I did besides the shorted injector). Q: is the solenoid signal to the starter going from the key thru the ICM, the ECM/PCM, OR is it a direct to the solenoid? What can cause a starter to stick ON like this on a 1993 GM V6 with *bypass ignition*

4 Replies

FIXITMR

MECHANIC
9,990 POSTS

You mean it has a bypass module installed?

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Sunday, March 11th, 2012 AT 11:02 PM

SATURNTECH9

MECHANIC
30,869 POSTS

Do you have a multimeter to see if the crank signal continues at the starter when releasing the key?

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Sunday, March 11th, 2012 AT 11:03 PM

CHETSJUG

MEMBER
2 POSTS

@fixitmr. The early 90's GM cars used a "bypass" style of ECM. The ICM actually runs the engine during cranking and for a few minutes during warm up when everything is in a default cold engine setting. Then hands over the engine to the ECU/PCM after the sensors are coming online. Early Ford EFI engines had a similar system.

@saturntech9 That is a very interesting question. At first I want to say "Duh" there would be signal if the starter is cranking. And then my brain kicks in and tells me wellllll, there is a chance that the solenoid sticks but the signal has stopped. This is something I'm going to have to check. But it starts 30 times normal before doing this.

Then there is the fact that I just got an email from Scotty Kilmer (dot-com). He said that the signal wire is direct to the starter and definitely does NOT go thru the ICM or the ECU. This is a fairly low mileage rebuilt starter so I'm just flustered over this whole car.

Anywho, I've rebuilt a hundred GM starters and can do it with my eyes closed. I'll just go through it and put on a Borg Warner solenoid.

Thanks guys :)

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Wednesday, March 14th, 2012 AT 6:49 AM

SATURNTECH9

MECHANIC
30,869 POSTS

Another thing you can do since it doesnt happen all the time is a make a feed back device from a blub and socket run the power wire to the purple wire at the starter then ground the other wire. Have the bulb and socket inside the car so you can see if it stays lit up when the starter continues to run. Just a thought I have used them on very intermintant no crank no starts to find bad starters.

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Wednesday, March 14th, 2012 AT 6:49 PM