dat240zg Posted January 26, 2008 Share Posted January 26, 2008 Guys: I'm feeling like I should be really close to getting the Z started but am stumped as to what is not functioning correctly. Here's the situation: I now have power to all the correct areas: coil, icm, and injectors. The fuel pump primes and shoots a ton of fuel out, but then when it's done priming, it shuts off (0 fuel pressure) and the computer doesn't continue sending power to the pump - during cranking there is no power at the pump. The harness is a speartech harness and the fuel pump is wired using the relay from the stock ECU. Have I wired it wrong? BTW, thank you for the pm's regarding tips; I read the LT1 no start document and others that several of you sent. It could be that I'm missing something really basic. If so, sorry! Bryan Dat240zg Quote Link to comment Share on other sites More sharing options...
turbo81racer Posted January 26, 2008 Share Posted January 26, 2008 well if you have it wired using the computer controling the stock relay and signal wire to the pump, that should work. I used the painless wire harness and had to redo mine using the stock relay and signal to the pump. Does your computer have the VATS? well the factory key from the GM had that signal in it to allow the car to start. Check and see if you have that or the VATS module that will bypass the signal. I had to use that from painless. Quote Link to comment Share on other sites More sharing options...
dat240zg Posted January 26, 2008 Author Share Posted January 26, 2008 Well, in doing more testing, with the key on, I have power at the injectors (positive side). However, under cranking, I should be getting a pulsing signal through the negative side - which I'm not. Sends me back to the optispark. Maybe more to come. Bryan Quote Link to comment Share on other sites More sharing options...
turbo81racer Posted January 26, 2008 Share Posted January 26, 2008 well the injectors get there power from the fuse block and are grounded through the PCM, i would check the power supply to them, or just try a jumper signal. They get 12v, so give them direct power from the battery and see if it will start that way. Just have to jumper one wire, it will feed to all the other injectors. But I would check out the power to everything, injectors and optispark. I have an extra new optispark if you need one to test with. Quote Link to comment Share on other sites More sharing options...
dat240zg Posted January 26, 2008 Author Share Posted January 26, 2008 alright. Pulled the waterpump and the opti connector and have power at the yellow wire (No start document said red, but I don't have one). I'm guessing that I have a bad opti due to the fact that if I touch the first "pin" on the opti plug, my fuel pump continues to stay on. Hmm... Getting ready to replace the opti with a later vented style. Bryan Quote Link to comment Share on other sites More sharing options...
wheelman Posted January 27, 2008 Share Posted January 27, 2008 If the PCM is wired to control the fuel pump it will run the pump for 2 seconds when the key is turned on and then not run it again. This should provide pressure in the rail, if your's is zero you probably have a bad fuel pressure regulator. Once the rail is primed there should be enough pressure to start the engine which then builds oil pressure closing the oil pressure switch in turn running the fuel pump. There has been some discussion about how this is actually wired but that's how it is in my car. My engine and underhood harness came from a 9C1 Caprice. If the VATS has not been disabled the engine will run for a few seconds, then the PCM will kill the ignition and or injectors effectively killing the engine. Wheelman Quote Link to comment Share on other sites More sharing options...
deja Posted January 27, 2008 Share Posted January 27, 2008 Hmm... Getting ready to replace the opti with a later vented style. Bryan What year is your engine? You can't use the new vented opti on a 94 or earlier without changing the cam. Maybe MSD or someone makes a vented one that will work on a 94 but the stock GM for a 95 or newer will not fit. Quote Link to comment Share on other sites More sharing options...
dat240zg Posted January 27, 2008 Author Share Posted January 27, 2008 Guys: I know that there is a thread somewhere titled dumbest automotive screwups and this is probably going to need to be added to it. After all of the testing and checking and such it came down to me being an idiot. Last summer when I pulled the motor from the firehawk, I went ahead and switched out the coil and opti cover. I told the people at Jegs that it was a late '94 LT1 and so they sent me a vented cover. I didn't think anything of it until this afternoon. I had pulled the waterpump off of the car and was getting ready to swap in my new vented opti (Dale, you're totally correct - I now know that I need the timing cover, cam, harness, etc for the swap, not just the opti) and tested the optispark connection at the distributor for power and ground. Had both. It was then that it dawned on me about swapping out the cover and the fact that the connector for the early opti is different that the one for the later. Bottom line: the connector was just "sitting" in the plug, but not connected to anything. So to make a long story short, I'm an idiot. Sheez. So, until I can pull together the rest of the parts needed for the swap, I've purchased an early style opti cover to get the car running and I'll swap the other in when I do the hot cam kit. Live and learn. And kick myself. Bryan Quote Link to comment Share on other sites More sharing options...
drexel_j Posted January 28, 2008 Share Posted January 28, 2008 I used a Painless wiring kit with a 93 computer on my LT1 and what I found out was that when you try to start the engine the computer will turn on the fuel pump and if it doesn't start after 3 seconds it will turn it off. When the engine starts the computer will turn it back on. Your fuel pressure regulator should hold the pressure until it starts if it takes longer than 3 seconds. Connect a fuel pressure gauge to make sure you are getting correct fuel pressure. Quote Link to comment Share on other sites More sharing options...
deja Posted January 28, 2008 Share Posted January 28, 2008 Guys: I know that there is a thread somewhere titled dumbest automotive screwups and this is probably going to need to be added to it. After all of the testing and checking and such it came down to me being an idiot. Last summer when I pulled the motor from the firehawk, I went ahead and switched out the coil and opti cover. I told the people at Jegs that it was a late '94 LT1 and so they sent me a vented cover. I didn't think anything of it until this afternoon. I had pulled the waterpump off of the car and was getting ready to swap in my new vented opti (Dale, you're totally correct - I now know that I need the timing cover, cam, harness, etc for the swap, not just the opti) and tested the optispark connection at the distributor for power and ground. Had both. It was then that it dawned on me about swapping out the cover and the fact that the connector for the early opti is different that the one for the later. Bottom line: the connector was just "sitting" in the plug, but not connected to anything. So to make a long story short, I'm an idiot. Sheez. So, until I can pull together the rest of the parts needed for the swap, I've purchased an early style opti cover to get the car running and I'll swap the other in when I do the hot cam kit. Live and learn. And kick myself. Bryan LOL, well at least you'll admit when you screw up. I hate those "stupid, stupid, stupid" moments! Don't feel too bad. When I got ready to pull my Z28 in the garage for the swap it wouldn't start. I ran all those tests and concluded it was the opti. I bought a new one, ripped half the engine apart to change it only to find out that the real problem was the MSD ignition module and of all things the coil wire. No clue what happened to kill them. I didn't put the original MSD opti back on so I don't know if it was bad or not. I really don't like MSD stuff anyway, just heard too many horror stories. I bought all GM parts. If anyone wants that MSD opti I'll sell it cheap, no guarantees but I will refund the money if it turns out to be toast. Quote Link to comment Share on other sites More sharing options...
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