I have an 84 Fiero 4 cyl, fuel inj, w/AC, 90K miles, ran great till last week. Repair History- replaced alternator last year, replaced AC compressor last month. Here's the problem- started fine, drove about 2 miles with the AC on. At that point, I noticed that the charge rate on the gauge went really low, but was still running fine. then I thought I got a whiff of smoke, so I shut off the engine immediatly. Checked for fire, found none. When I went to start it again, it just cranked like it was out of gas. No blown fuses, all electrical devices seem to work, no check engine light staying on. Getting good spark, but nothing out of the injectors. Next, I pulled off the breather and poured some gas into the throttle body. It then started up and ran fine, except that the charge rate still looks very low. When I turn on the AC or blower, the charge drops more and it dies. Will not restart without priming it the same way. I could use some help diagnosing the problem before I start swapping out parts. Does this sound like a wiring/fusible link problem? ECM? I am assuming that the fuel pump, relay and injector are OK since it runs fine when primed. Am I wrong? I can hear the fuel pump hum briefly when I turn on the ignition and crank it. I'm no expert, but it sounds normal to me. If it is a grounded/burned wire, where should I start to look for it? Any likely spots in the harness? If I knew which 2 leads on the ECM went to the Injector I could test or even rewire them. Anybody know the color and/or position of these wires as they enter the ECM? Diagnose this problem and I'll name a child after you. Any help greatly appreciated.
rdr, here's the deal. You are now the latest of a looooong line of people who have had this problem, but modified somewhat. Usually this will show up after the eng has been run for a while, and will go away after the eng cools down. I suspect that worn components in that 18 year old car, that results in slow build-up of oil pressure--and that your fuel pump relay circuit has been bad for a while. Since the OP switch will send voltage directly to the fuel pump after it closes @ 4psi, it is bypassing the fuel pump relay. When you pour fuel into the tbi, & turn the key, the engine starts immediatly in a very rich condition.(higher idle) This brings the oil pressure up quicker than if you're just cranking the engine over, closes the OP switch and turns the fuel pump on to maintain the running of the engine. The fuel pump relay is located on the eng firewall, just to the left of the left decklid hinge, on the top right row of the 4 relays.(if no a/c, then you only have 3 relays, & the 2 bottom relays are for your rear lights). I would start with the fuel pump relay. Here is a diagram of that circuit. PM me if you have more questions or post here. Don
After re-reading your post, I would definitly check the wires at the starter solenoid. On the 84 there is a fusible link there, 2 on mine. I've always suspected that the cause of the problem was an over heated & nearly corrupt ECM, but am not in the position to test mine (no scanner). I've had the same problem, but the eng always started ok after it cooled down for 15 minutes or so. I changed the OP switch, fuel pump relay, & a wire that goes to the ecm from the starter solenoid. So far, I've not had a re-occurance of the problem. The fact that the eng starts ok on pouring fuel in the TBI is no guarantee that the relay is good, since you are basically turning on the fuel pump with the oil pressure switch, rather than the FP relay. The a/c relay and the FP relay are identical, so you can switch them out to check your fp relay. & welcome to the forum. Don
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GTDude Member
Posts: 9056 From: Keysville, Virginia, USA Registered: Nov 2001
------------------ GTDude OVER 25 years GM experience
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Jul 11th, 2002
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Report this Post07-11-2002 11:31 PM
rdr
posts Member since
How would it change the diagnostic picture if my check engine light were not coming on at all. Not when the ignition is turned on, not when I crank the engine. I thought it was working, but I just checked it, and its not. Does that indicate ECM, or is it probably still a fusible link? Been working since I posted this and havn't had time to check it out further. Thanks for the ideas.
