spiderw31 Posted January 23, 2008 Report Share Posted January 23, 2008 To recap for thse that didn't look in my timing belt thread, I was "enthusiastically" driving the '92 GP 3.4 I just got a short while ago, when it just died on me. It had just shifted out of the top of first, and the revs dropped, the car stalled and wouldn't start. Initially I thought the timing belt had broken or slipped, but after some testing, I find that I have no spark. After charging the battery (it was very low from all the cranking in the cold recently), I've checked a plug visually for spark, also checked with my timing light, and got nada. I've also verified that I've got 40psi on the fuel rail, and the plug that I pulled for inspection had raw fuel on it so I know the injectors are firing. I've checked for codes, and I've got none other than code 12. Now I know that the car is dependant on the CPS as well as the ICM in order to start, but is it dependant on any other sensor input? IIRC, the injectors require signal from the CPS in order to fire, so that would lead me to believe that the CPS is OK... right? Does the early TDC use a camshaft position sensor, and if so, would that cause a no start situation? What other things should I be checking here? Quote Link to comment Share on other sites More sharing options...
joey b Posted January 23, 2008 Report Share Posted January 23, 2008 There is no CPS on your car. You have to look for signal to the ICM. One harness will have a 12V and a ground with ignition in the ON position. Another harness will have a fluctuating resistance (Ohmage) when the engine is being turned over. I noticed a fluctuation between 400 and 700 Ohms on mine. Maybe it was Kilo-ohms. Get a DIGITAL multi-meter (Digital ONLY!). You can pick one up for 20 bucks at most tool stores or for 10 bucks at an Harbor freight near you. As for the 5 wire harness, I don't know how to decipher that. But do those other 2 tasks before you go spending wasteful time and money on this problem. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted January 23, 2008 Report Share Posted January 23, 2008 the cps is a wear part. If in doubt.... REPLACE!!!!! I estimate them to have a 10 year life. past that and you asking for trouble Quote Link to comment Share on other sites More sharing options...
ManicMechanic Posted January 23, 2008 Report Share Posted January 23, 2008 There is a Crank Position Sensor, but no cam position sensors... I'm willing to be it's the ICM... Quote Link to comment Share on other sites More sharing options...
Crazy K Posted January 23, 2008 Report Share Posted January 23, 2008 There is a Crank Position Sensor, but no cam position sensors... I'm willing to be it's the ICM... x2, but I would inspect the CPS, if the plastic is cracked... replace. Quote Link to comment Share on other sites More sharing options...
DOHCRagtopguy Posted January 23, 2008 Report Share Posted January 23, 2008 There is a Crank Position Sensor, but no cam position sensors... I'm willing to be it's the ICM... x2, but I would inspect the CPS, if the plastic is cracked... replace. I agree with this, plus a new CPS is much cheaper than a new ICM. Quote Link to comment Share on other sites More sharing options...
ManicMechanic Posted January 23, 2008 Report Share Posted January 23, 2008 Much cheaper, however he did say the injectors are firing... Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 23, 2008 Author Report Share Posted January 23, 2008 Hehe sorry... didn't notice that crankshaft position sensor and camshaft postion sensor both abbreviated to "CPS" . What I was referring to when I said "CPS" was the crankshaft sensor. At any rate, is there any way to actually test the ICM for functionality? Any particular reason to stay away from an analog multimeter? Also, what is the fluctuating resistance a signal of? This woudl probably be a bit easier if I had a service manual of some type for this car, but I haven't found one yet Thanks for the help all... I'll be digging deeper this evening! Quote Link to comment Share on other sites More sharing options...
IRONDOG442 Posted January 23, 2008 Report Share Posted January 23, 2008 The crankshaft positioning sensor is PROPERLY abbreviated as CKP... Hosed ! Quote Link to comment Share on other sites More sharing options...
19GT92 Posted January 23, 2008 Report Share Posted January 23, 2008 DUDE change the crank sensor and it will fix the damm car i've had this same thing happen before Quote Link to comment Share on other sites More sharing options...
Q-Ball Posted January 23, 2008 Report Share Posted January 23, 2008 That car is turning into a lot of problems! Quote Link to comment Share on other sites More sharing options...
Turbo231 Posted January 23, 2008 Report Share Posted January 23, 2008 Having done this myself, let me tell you what to look for (from memory many years ago using the factory service manual, that I've since sold. This is for a 93 GP DOHC, so we're pretty close in year). The ICM is on the front lower part of the engine, the three sets of coils sit on it...actually, they bolt to it. I THINK there were two plugs into the ICM. It has 3 things report to it. The first is a simple 12 volt permissive...pretty much telling the ICM that the ignition is turned on. The second comes from the computer...telling the ICM it is good to start (also 12 volts). I believe they make up the first plug. The second plug is from the crank sensor. Now, you can't just read the voltage out of the crank sensor, but you can measure it's resistance. Without cranking it needs to fall within a value set. I don't think I was concerned with the value, just that it wasn't sky high or not at all. IF all those things are good, then you have a dead ICM. This is a random fail part...sometimes they last forever, other times they die quickly. The ICM controls the coils (duh) and all spark control under 400 RPM (starting), so it's death is the death of your spark. I think it retails for about $200, and can be had online for $125 or so. Another bet that it is NOT the crank sensor...when you crank the car, do you get the smell of unburnt gas out of the exhaust pipe? That would indicate that the injectors are getting permission from computer to fire, thus the PCM is getting a reading from the crank sensor...that was my logic anyways. Hope that helps. Ben Quote Link to comment Share on other sites More sharing options...
rockfangd Posted January 24, 2008 Report Share Posted January 24, 2008 x2 i would definately say the Icm is a very good possibility as i have been down that road many times with clients Quote Link to comment Share on other sites More sharing options...
z34duck Posted January 25, 2008 Report Share Posted January 25, 2008 any luck did you get this running yet? Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 25, 2008 Author Report Share Posted January 25, 2008 Unfortunately, no, as I've had zero time to get out and look at the car. I'll be out there tomorrow or saturday, and I'm hopeful I'll have it back up and running then. I had planned to do plugs and wires on the car shortly, but since I manged to break two plug wire boots in the cold, I'll be doing those. In addition I've got a new crankshaft sensor and ICM on order and they will be in tomorrow. I'll test what I can on the ICM and inspect the wiring and fuses and then start with replacement parts. Since electrical parts aren't returnable once installed, assuming other tests don't reveal anything, I'll try the crankshaft sensor, as it is the cheaper of the two. Then I'll move on to the ICM as needed. Hopefully that will take care of it! Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 25, 2008 Author Report Share Posted January 25, 2008 That car is turning into a lot of problems! Meh... not really... just one problem that I've not been able to give my full attention to Not to mention that it is a minimum 1/2 hour round trip to get any parts... kinda kills the time available in short order Quote Link to comment Share on other sites More sharing options...
spiderw31 Posted January 27, 2008 Author Report Share Posted January 27, 2008 I got it running today!!! To everyone that said ICM, you were dead on correct. Changed out the ICM, and the car started right up! I gotta say though... changing the ICM in 30 degree weather sure can be a pain Anyways, thanks for everyone's help! Quote Link to comment Share on other sites More sharing options...
ManicMechanic Posted January 27, 2008 Report Share Posted January 27, 2008 I wuz right fer a change! Quote Link to comment Share on other sites More sharing options...
rockfangd Posted January 27, 2008 Report Share Posted January 27, 2008 cool. i have seen it happen so many times its not even funny. sometimes when they go bad they will start maybe once out of 50 tries throughout time. Quote Link to comment Share on other sites More sharing options...
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