Head Swap complete ... Check Engine Light

[Red91GSX]

As some of you may remember, my head recently got warped and I bought the head off Josh (BatmanGSX - thanks) that he had for sale. So, Cody and I worked hard all weekend swaping heads. As we had figured, my old head was warped badly to about .13 (service limit is .08). Anyways, after starting the car and letting it idle for a while, the check engine light came on. We drove the car about a mile up the road and back, then shut it off. We read the code off the ECU and it says it's the Engine Coolant Temperature Sensor (21). We then did a compression Test, the numbers were good. 145, 158, 150, 145 now and before = 95, 100, 110, 95. After the Test, the car would not start again. It cranked, but wouldn't rotate. We left it at that and went out to eat. We return about 2 to 3 hours later. The Car started right up and the check engine came back on, it still gave us the same code (21). So, we swap out the Engine Coolant Temperature sensor with the one in Cody's 90. The check engine light went off. I tried starting the car, still nothing. It crancked, but would not turn over. This morning I started the car, the check engine light came back on, still telling me its the Engine Coolant Temperature Sensor. I let the car warm up a bit, then shut it off. As expected, the car would not start back up. Now we think that the car is dumping too much fuel into the engine, causing it to flood and that's why it will not start back up right away, but a few hours later. The Manual does say that if the Engine Coolant Temperature Sensor is damaged, it could affect the entire fuel injection system.

*** Cliff Notes - after shutting car off, it will not start back up. Check engine light proceeds to tell me it's the Engine Coolant Temperature Sensor even after swapping it out for Cody's. ***

Any ideas would be very helpful. - Cody, if you have anything to add that I might have forgotten, please post it.

[XakEp]

Just a thought, but when the car starts up the ECU can be set in "COld Start" mode, which means that you'll have fuel dumped in to get it to start... If the Coolant Sensor thingie is broken it may KEEP it in that mode and KEEP dumping fuel in, this flooding the engine...

THoughts?

[Red91GSX]

Well, Now I am starting to get a little frustrated. The Car now does that exact opposite then before. It will not start when cold, but will start fine when warm. I can get the car to start by applying a little gas while crancking, giving it some fuel. The check engine light of course is still on, and is still giving me the same code (21 - engine coolant temperature sensor). Now, the check engine light does not come on until about 1 minute after turning the key on the ON position. (well it does, but it turns right off like it's suppose to). It shows me all short pulses (normal) until the light comes on.

Any Ideas?

I have ordered a new sensor, even though the one out of Cody's car can't be bad, since he does not have a check engine light, but we'll see I guess.

[DSMxTSi]

Ok, here's my theory. The engine coolant temp sensor is being a bitch and thus it's dumping too much fuel for the short time it runs, then will not start right back up. I remember Brian had a problem with his coolant temp sensor just after his rebuild and it had wierd starting and operating problems, but Benji's GSX is just having starting problems and seems to run perfectly fine regardless of the CEL when it does start. Maybe it's a differance with a MAS (GSX) versus a speed density system (Brian's GS)? But why is the GSX "destroying" engine coolant temp sensors suddenly?? I think mine was just fine in the '90 as it never had a CEL, but now it throws a CEL in Benji's GSX. In hindsight I'm thinking that maybe the Technomotive ECU in the '90 possibly doesn't throw CEL lights anymore?? Not sure, never had the problem, but maybe I did and didn't know it and that's a reason why the '90 is running super-pig rich. I wish we had a datalogger cable! Also, I remember that Benji accidently touched the terminals on the battery with a wrench while he was putting the positive cable back on. Could that have made a short in the system somewhere?? I have accidently done that before on other cars and never experienced any problems afterwords.

Cody