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94 Z Issues. W/ Video Ok I'm still trying to figure out why my car won't start ( 94 z28) It seems like it's really out of time. I have had the motor apart, but it's back in now and I have had it running. Ran great, started up several times, went to start it again and it would hit a few times sporadically but won't start. Checked for spark and it's getting plenty. Double checked the wires, they are all correct. I know that the opti and timing set are installed properly. So Question #1 Is there any other reason it could be out of time? Fuel: Seems to have some kind of pressure problem. Pressure is great until the pump goes off then it immediatly drops to 0. From what i understand there should still be pressure for a good while after the pump goes off. I can't find any leaks, changed the fuel filter, injectors aren't leaking. I tested with an FPR today that I know was good and it still does the same thing. Here is a video. I'm just running the fuel pump. As soon as I turn it off the pressure drops. http://youtu.be/8QrKFhojj9s So Question #2: Does it seem normal that it won't hold pressure? And what could be causing this? Thanks guys. |
If it was running great and starting without issue id tend to lean away from the asumption the timing is out. Fuel pressure should hold steady when the pump is done priming. Id be willing to put money on it being the fuel pump. My camaro did this to me also. Wouldnt start worth a shit. Took over ten seconds of cranking to get it to start. With the fp guage on it, priming would yeild maybe 10 psi first time, 20 some 2nd time, and finally almost 45 ish the 3rd time. Would fall back right to 0 right away. On the highway at wot the guage would drop to 22 psi. I pulled the pump and found the plastic hose between the pump and the top of the pump assembly to have a hole in it and was draining back into the tank as fast as it was being pumped out. Pull the fuel rail and prime, if no fuel drips out of the injectors, order a pump kit EDIT: watched the video, noticed the rails off already. Order a fuel pump kit. racetronix, etc. DO IT! |
You might have more than one issue going on, but first things first. Few thoughts: -------------------- 1) Regarding your video, I would tend to agree with 97LT1 above. To be clear, no, the fuel pressure bleeding off like that is not normal. Unfortunately, in order for the fuel pressure to bleed off that fast, it's most likely the check valve within the fuel pump. You have the fuel rail off, so you'd probably notice if the injectors were leaking or if the FPR diaphragm had failed. Unless your neighbor's cat has chewed through the fuel line, the pump is the likely culprit. As I'm sure you are aware, there are two ways to get at the pump -- either by (carefully) cutting through the trunk's sheet-metal, or by dropping the tank. I opted to drop the tank when I upgraded my pump, and it wasn't my most pleasurable experience in life. I'd recommend just biting the bullet and cutting the sheet-metal. -------------------------------------- ***You should probably fix the fuel pressure issue before further diagnosis, but in the event that you do and the problem persists: 2) Do you have an SES light / any DTCs? Check your fuses? Don't forget the simple stuff. Not going to get too far down the road if an injector fuse committed hari kari. 3) You used the fuel pump prime connector to kick on the pump. Do you also hear the pump prime when putting the ignition key to the "on" position? (This might be indicative of a fault in the PCM fp relay trigger circuit.) 4) You said you have spark, but there are different ways of testing for spark -- what exactly did you do? I'd consider having someone else crank the engine over at night (in the dark) while you check out the engine -- see if any spark is arcing out of the coil or coil wire -- and thus not making its way to the cylinders. I'd also remove a few spark plugs to see if they are fouled. 5) When I built my engine and got it back in my car years ago, I had a no-start condition. I went on a big long goose-chase to find out I didn't have continuity on one wire between the PCM and the optispark. One of the terminals had failed within the opti harness connector along the passenger side intake, yet I was still getting spark, which is what threw me off. As I understand it, the fuel pump won't run without the optical signal (more specifically, the PCM wont trigger the fuel pump relay without the low-res pulse, or something to that effect). So, double-check that if all else fails. 6) Worst case scenario, you say that you know for certain that the timing chain and opti are okay, but don't rule it out unless verified. Never know. I've heard of old/loose timing chains jumping a tooth. I suspect the problem is elsewhere, however. That's all I got. Hope you get it figured out soon! |
Thanks for the replys guys. Alex94: to answer your questions, 1. I don't have any ses light and I have double checked for codes on the laptop and that checked out fine. Also the pump primes with the key. 2. I haven't checked the fuses, I'll do that today. I have plugged up a couple of the injetors with the rail off to verify that the pcm was firing them, they sprayed. Only checked a couple though. 3. Spark: I just pulled a few wires and tested with on old plug. I have read about the check ball causing problems on shoebox site. I changed the fuel pump about 500 miles ago, so I already have an access panel cut. I was leaning away from the pump because it was so new. But the car sat all winter though so i'm guessing some trash in the tank may have triggered the fuel issues i'm having. I'll check the fuses. (Is there one for each injector?) and have someone crank it in the dark tonight. Thanks again. |
I believe there is one fuse for each bank of injectors -- comprising two 4.5A fuses. The fuel injectors are always supplied +12vdc, but the PCM's injector drivers decide when to ground them out, thus firing them. What's strange here is that you've verified both spark and fuel at the cylinder, which should be all you need to get the engine running. Only thing you've left out of the loop are the spark plugs themselves, and odds are slim that all 8 failed simultaneously. As such, hopefully fixing the fuel pressure issue will resolve the matter. Was this a stock GM replacement or aftermarket pump? 500 miles on a new pump is pretty ridiculous, if it indeed failed. Perhaps one of the hose connections failed as 97LT1 suggested, but if it's the pump, hopefully the vendor would honor a warranty claim. |
It was a stock replacement made by Airtex still under warranty. Either there is not enough pressure to support all 8 injectors or one of the fuses is bad. IIRC I only checked a couple injectors on the right bank so the other side may not be firing. If fixing the pressure issue doesn't get it running: 1) Can the opti or PCM fail in such a way that it would lose timing? 2) Is there any way a brand new chain would jump a tooth? Edit: Happy 4th! |
deff a fuel pump |
I got my pump warrantied yesterday and just put it in. Fuel pressure is good now, but I still can't get it to start. Does the same thing.... checked the fuses and everything is good. Really tired of this POS. |
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Pics of plugs http://i546.photobucket.com/albums/h...d/IMG_7231.jpg http://i546.photobucket.com/albums/h...d/IMG_7232.jpg Are these fouled? the don't have any grey on then. All black and smell like gas. Which makes sense. Would fouled plugs keep it from starting? Edit: pics are fixed |
May possibly be the ignition switch on the column under the dash... |
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