Chris2012 Posted November 2, 2013 Report Share Posted November 2, 2013 Repetition to facilitate searches by those who will follow ... I payed some little monkey years ago to get my car started. He allegedly was an ASE tech, but couldn't lay off the juice, and even arrived at my house stanking. Anyway he properly diagnosed the bad icm, and replaces it successfully (or so I thought), but nearly every time it rains and car sits for 4+ hours it won't start until I put a heat lamp or heat gun on my wires for (usually) a very brief time. When this started to happen, I assumed it was his shoddy workmanship. Could I be wrong? I'm also reading that the icm causes spark to be generated, at least in the beginning of a start. I'm not getting fuel. This is a fact (1992 3.1 mpfi Lumina). Could a shoddily installed icm be the reason the injectors aren't firing? As in ecm doesn't know engine is turning. I think this is more a function of the crank position sensor, but icm and cps are connected, no? Quote Link to comment Share on other sites More sharing options...
Schurkey Posted November 2, 2013 Report Share Posted November 2, 2013 I'd pull each connector body out of the ICM to verify that the silicone rubber seals are still in place on the connector body. DO YOU HAVE SPARK at the point where you still don't have fuel? First Guess: You have no spark, you have no fuel, the ECM doesn't know the engine is cranking. Alternate: Engine has to crank long enough to build oil pressure because the fuel pump relay circuit isn't working properly. Fuel pump doesn't run until oil pressure switch bypasses fuel pump relay. Quote Link to comment Share on other sites More sharing options...
Chris2012 Posted November 2, 2013 Author Report Share Posted November 2, 2013 DO YOU HAVE SPARK at the point where you still don't have fuel? - There is spark. But I'm not exactly sure what you're asking. First Guess: You have no spark, you have no fuel, the ECM doesn't know the engine is cranking. Alternate: Engine has to crank long enough to build oil pressure because the fuel pump relay circuit isn't working properly. Fuel pump doesn't run until oil pressure switch bypasses fuel pump relay. - fuel pressure is in excess of 40 psi. Car starts w/ether or gasoline vapor (don't ask). No codes. Fuses good. Swapped fuel relay with one to the left of it, no change. Haven't checked fusible links at all, not sure if that could be at fault. When car dies originally, this was after jumping and running for 5 minutes. Threw it in gear and it shut off. That's all she wrote. Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted November 2, 2013 Report Share Posted November 2, 2013 Well, a couple of other possibilites. The crank signal passes through the ICM, which will give you spark, but a bad ICM could not be passing that as a "reference" signal to the ECM. If the ECM doesn't see the reference signal from the ICM, it will NOT power the fuel pump. Additionally, if you're not getting the proper count of crank signals to the ICM, the ICM will not pass a reference signal to the ECM, again preventing the ECM from powering the fuel pump. I'd be tempted to go to a junkyard, and pick up an ICM. They're cheap and plentiful on 60* V-6's, from what I understand all flavors of the 60* V-6 use the same ICM. Quote Link to comment Share on other sites More sharing options...
Chris2012 Posted November 3, 2013 Author Report Share Posted November 3, 2013 Well, a couple of other possibilites. The crank signal passes through the ICM, which will give you spark, but a bad ICM could not be passing that as a "reference" signal to the ECM. If the ECM doesn't see the reference signal from the ICM, it will NOT power the fuel pump. Additionally, if you're not getting the proper count of crank signals to the ICM, the ICM will not pass a reference signal to the ECM, again preventing the ECM from powering the fuel pump. I'd be tempted to go to a junkyard, and pick up an ICM. They're cheap and plentiful on 60* V-6's, from what I understand all flavors of the 60* V-6 use the same ICM. My fuel pump isn't my problem though. That said if the icm has nothing to do with the operation of the fuel injector circuit, other then perhaps pulling it out to check the seals or whatever, I don't think I need to worry about replacing it at the moment. Quote Link to comment Share on other sites More sharing options...
Chris2012 Posted November 3, 2013 Author Report Share Posted November 3, 2013 You see it really does help to reread your own posts before calling it a day. Especially when you're crazy. What my question was according to what I read somewhere was that the icm not only creates spark, but at the beginning of a start, the icm is *the* controller (not the ecm) sending pulses to the injectors.presumably until the ecm is set up and can take over. 2nd question. Just curious, is there any danger applying a solid 9 - 12 volts dc to a single injector at the points beside the plenum? Just so you could totally eliminate the injectors as a problem. With key ON the thing would start pouring gas into the cylinder (and sniff), or you could monitor fuel pressure at Shrader valve Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.