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Engine not running, starting problem...

This is a discussion on Engine not running, starting problem... within the General Help forums, part of the LSx Technical Help Section category; Ok, after countless hours in the garage trying to brainstorm and come up with the possible reasons my car is ...

  1. #1
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    Engine not running, starting problem...

    Ok, after countless hours in the garage trying to brainstorm and come up with the possible reasons my car is not starting, I have run out of ideas. I put in a rebuilt LS1 last summer and never got it to start up. Here is the problem:

    When cranking, the engine will crank without firing for the first couple cranks. Then, it will start to fire in each cylinder, one every couple strokes. Once I have been cranking it for a little while, there is firing in all of the cylinders, but its very rough and it wants to die out. The longest I can get it to stay running is only about 2-3 seconds, then it will cut out. It will also not start at all when I just touch the gas, as if more air is making it cut out completely. Right when I start it, it will fire a cylinder and a few others with no problem, after that it will just die out slowly.

    I have a custom harness and re-flashed computer from Speartech, but before I got the harness, I had the stock harness and un-flashed computer and it was doing the same thing. I know my harness and computer are good. I checked compression on all cylinders and it all checked out ok. I checked my grounds, all the sensors are plugged in, I checked plugs and plug wires, all looked good. When I checked the plugs, they were somewhat dark and a little wet. I am sure all my wiring is good, cause I get spark on all cylinders, and all my injectors pulse. Each cylinder does fire and gets good spark. I also checked to see if it was reading any codes, and no problem codes came up.

    I am out of ideas and am getting depressed because so much time has gone in, and its still not working.

    Please, if anyone can help pinpoint this problem it would make my year. this has been the one thing that has kept this car from being on the road. Please, let me know what your thoughts are and if you have any suggestions.

    Thanks,

    John

  2. #2
    TunedbyFrost.com Tuner Frost's Avatar
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    Can you see and verify pulses from the crank sensor in your scanner? how about cam pos? You can log the low-to-high-to-low transitions as counts.

  3. #3
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    No, unfortunately the scanner I was using was the one you can rent at autozone and it only would read codes. I have been trying to find someone who will let me hook it up to a bigger scan tool, but no one is willing to deal with a custom setup. So, as far as the crank and cam sensors, the only thing I did was disconnect and reconnect them and seeing if starting it while disconnected made any difference, and for the crank sensor it made it much worse. Cam, not so much.

  4. #4
    Veteran 0rion's Avatar
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    was the cam out of the car? It's dot to dot right? Was the harness a plug and play and labeled well and all that? No splicing required?

    Something I just thought of that Frost would know more than I do about is under what circumstances you need to do a CASE learn procedure.

    Nevermind, the car has to be running to do a case learn. duh.

  5. #5
    TunedbyFrost.com Tuner Frost's Avatar
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    There isn't a lot forum advice can do here, just gonna have to site down with a diagram and verify everything from sensor/injector to PCM.

    Case relearn issues or crank sensor sync issues won't keep it from starting as noted.

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    Senior Member Too Fast's Avatar
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    It sure sounds like lack of fuel. Have you double checked the pressure/volume?

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    it actually sounds to me like it's 180 out.

    what about coil packs? put those back on in the same position they came off? the have numbers on them.

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    thanks for the response guys.

    Too fast, I have good fuel pressure right before the fuel rail, I have it set at exactly 58-60 psi, and remains there while firing.

    Orion, the shop I bought the engine from had already put the coil packs on when I recieved it, but I have not really looked to see if they are numbered. Would it matter if the coil packs were mixed around? I am getting the engine to fire in every cylinder.
    It does seem somewhat of a fuel issue though, either not getting enough or getting to much after a little while. Could also be air though, cause once again, the plugs are dark and somewhat wet.
    Oh, also thought I'd note every time I fire it the exhaust is dark and very potent (smells rich). It made my clothes smell just starting it for a while...

    And, once again, whenever I just barely open the TB it wants to cut out immediately. So, extra air definitely doesn't help. When I was playing with the vacuum line right behind the TB yesterday I blocked the hole off on the manifold (where the hose from the valve cover goes) and tried starting it up and it ran very smooth for about 2-3 seconds then cut right out. Could it possibly be a vacuum issue?

    Any thoughts guys?

  9. #9
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    do you have any means of data logging the car? If it's not firing though and still getting fuel it'll soak the plugs and eventually foul them. I've seen that happen. You're positive you have everything hooked up correctly? MAP sensor, Temp sensor, and things like that? The temp sensor has the means to make a car really really rich. My buds temp sensor went out on his car and it would start in open loop fine then die as soon as it went to closed loop and it was flooded all to hell.
    The reason I said it sounds 180 out is because of they way you describe it firing...almost at random on the cylinders. It may not be that at all though. I would say at this point to start from the beginning and check EVERYTHING with a fine tooth comb to rule out as much of the small stuff as possible. I would at the very least start by cleaning those plugs if they looked fouled out. I wouldn't replace them just yet though because if they're fouling you'll just end up ruining another set. Just hit them with a little sand paper to clean them up. Then just start going over connections, vacuum lines, and any other little silly stuff it could be. Need to rule out as much of that as you can. Spark....fuel....spark/fuel at the right time. That's pretty much all you need to make an engine run.

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    I wish I had my own scan tool, but the only one I have had access to has been the ones that only read codes (no engine rpm or sensor details). I was supposed to trailer the car into a shop that was going to help me scan it this weekend but it didn't work out. That is my next step, to see if any of the sensors are reading anything out of the ordinary.
    I am positive I have all my electrical and sensors plugged in and hooked up right. I think my vacuum lines are right, although I was playing with vacuum and it ran better but still cut out. I swapped my temp sensors and still no luck.
    I will clean the plugs again, but I just replaced them a little bit ago just to make sure they weren't the problem.

    Engine gets spark, gets fuel, and I think gets air for the 2-3 seconds it runs. When I open the TB just a bit, it cuts out completely and quickly. Would this be a sensor problem that would just not adjust the mixture right? Or, could it possibly be something such as my vats still being on. I had speartech reprogram the computer, so I am pretty sure that wouldn't be it. I don't think they would overlook vats. If I didn't have my ECU reflashed already I would almost be certain it was a vats issue. But I just don't think thats the case.

  11. #11
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    One of vats functions is to kill the fuel pump I do believe. The other is the starter. So unless it's set up out of the ordinary I think you can rule out vats.
    I think you will get much further in a hurry if you can hook a scanner up to it and see exactly what's going on.
    Is the motor completely stock? You say it's a rebuilt motor? What was it out of? Not really pertinent, I'm just curious. Does it still have all the stock parts? MAF sensor and intake tubing with the IAT sensor and all that?

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    Alright, glad to hear its probably not still vats.

    The scanner is the next step, I was supposed to do that this weekend but didn't work out.

    The motor is rebuilt with a few upgraded internals, but stock as far as externals. I do have a ported TB, but I don't think that would make much difference. All sensors are OEM.

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    I was thinking about a possible scenario... Could the placement of the fuel pressure regulator (before vs after the fuel rail) cause an improper reading of fuel pressure, therefore allowing the engine to cut out and starve for fuel? Would putting the regulator and gauge before the fuel rails cause a improper reading?

  14. #14
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    I'm not sure. I know the stock location for 98+ is at the pump in the tank. The 97 vettes had the regulator between the rails. What kind of car is this in and how is your fuel system set up now? What pump are you using?

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    Its in a datsun 240z, but I am using the stock fuel rails with the regulator on it and the fuel rail has a return line. I am using a holley inline electric fuel pump that supposedly pumps at 100 psi.
    Here are a couple pictures of my engine bay.
    http://forums.hybridz.org/attachment...3&d=1204608427
    http://forums.hybridz.org/attachment...4&d=1204608569

  16. #16
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    I really don't know enough about the fuel system to be much help to you there but it's definitely something I would investigate. My opinion would be that as long as you have 58psi on the rail it should be fine. That set up sounds pretty close to the vette set up and I can't think of a reason why it wouldn't work but like I said my knowledge of the fuel system is pretty limited.
    I'm assuming you've watched pressure as the car is cranking and it's still 58psi? Have you pulled each wire off and watched spark to make sure it's firing everytime and not sporadically?

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    yea, I checked the spark and it looks consistent. Also, watched the psi while cranking and it remained at 58-60 where it was set.

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    I would think that your timing is way off. It's exibiting the same symptoms of my old truck. I would double check the cam timing with the motor at TDC in cylinder one and see where the dots on the chain sprockets end up first.

    The plugs are wet with fuel so the motor is basicly flooding out as the fuel isn't hitting the cylinders at the right time.

    Or it could be something as simple as bad crank or cam postion sensors.

  19. #19
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    Quote Originally Posted by Orcus79 View Post
    I would think that your timing is way off. It's exibiting the same symptoms of my old truck. I would double check the cam timing with the motor at TDC in cylinder one and see where the dots on the chain sprockets end up first.

    The plugs are wet with fuel so the motor is basicly flooding out as the fuel isn't hitting the cylinders at the right time.

    Or it could be something as simple as bad crank or cam postion sensors.
    that's why I originally said it sounded 180 out or maybe a tooth off or something.

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    I don't have words to describe how I'm feeling right now. I just started up the LS1 for the first time.... I just came home to work on the car and to relocate the regulator to after the fuel rail instead of before, where I had it. It worked! Started right up!

    I am so happy right now!

    Thanks for all the help and response guys, I really appreciate it. I should have posted my problem a long time ago, but I'm just glad to have it working now.

    Thanks everyone.

    John

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