LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

New gm847

Old Dec 2, 2006 | 06:40 PM
  #1  
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New gm847

I just got a 847 cam and brand new opti, well i ran it for 2 days and never once mashed on it yet due to the weather. Well parked the car 2 nights ago and im in illinois so we had bad weather. Anyhow today went to move it and it wouldnt start, just crankeddd every now and then id get a fire out of it but it wouldnt be enough to get it going. I put a fuel pressure gauge on it and it said i think 35 psi but was slowly falling. So I believe theres fuel going through it but i cant really smel it. Wonder whats the chance that a brand new 2 day old running opti just went bad again? Thanks
Old Dec 2, 2006 | 07:26 PM
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Thats what it sounds like to me...or a bad coil wire?
Old Dec 2, 2006 | 07:30 PM
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well like i said im in decatur illinois and i came back from work the other night it was raining like all hell and huge puddles the only thing i can hope for is that when it decides to warm up in a few days that maybe it can dry out if its wet. also i got the opti from dal slavada i think it is , does it carry a 1 year warrenty through gm and how do you go about getting it replaced?
Old Dec 2, 2006 | 11:36 PM
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Is the car tuned properly? When my car wasent tuned properly it wouldn't start and when it did it would barley run.
Old Dec 3, 2006 | 09:29 PM
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no im still waiting for my madz28 tune to be emailed, but i mean it ran before so the only thing i can think of is that the opti is ****ed or wet unless it can dry out .
Old Dec 3, 2006 | 11:04 PM
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check and see if your getting spark.
Old Dec 3, 2006 | 11:47 PM
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not being dumb but to check for spark wouldnt i hold the wire just a small distance from the plug, also im going to check plugs tomorrow im sureee their fouled to hell. how does a car run with fouled plugs or will it at all? it makes attempts like it wants to start and i can now smell the fuel its pretty wild. so its either plugs or the opti if it is the opti im tempted to get the ltcc setup.
Old Dec 3, 2006 | 11:49 PM
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eather get a tester or stick the plug in the wire and turn the car over and watch for spark.
Old Dec 4, 2006 | 12:48 AM
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dont know for sure but i also changed from stock 24s to 42lb injectors so i made a homemade tune waiting for madz28 so im sure now that i think of it that i fouled all the plugs pretty bad ill post tomorrow when i pull them.
Old Dec 4, 2006 | 08:01 AM
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Originally Posted by Wildwill2855
I put a fuel pressure gauge on it and it said i think 35 psi but was slowly falling.
KOEO, the fuel pressure should read ~41-47 psi and NOT bleed off. If it is bleeding off, then you either have leaky injector(s), a bad regulator, or the check valve in the pump is bad. Is the car hard to turn over (crank)? I also suggest making sure you got the opti on correctly. Verify you are getting spark by setting the spark plug and wire on top of the intake, so that you can see it when you're cranking the motor.
Old Dec 4, 2006 | 01:21 PM
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well so far ive swaped out 5 of the 8 plugs and they were soaked with gas, a few after sitting all night still had wet fuel on them but they were black and wicked smelling. so im swaping in autolites 104s gaped at the .035. im going to try to finish them up in a few but damn its hard workin on a car in 15 degree weather. so anyhow so far this is what im thinkin it is, like i said i dont have a real tune yet still waiting for the email to come through with it, but i switched to 42 lucas's so its super rich even though i tried to scale the pcm for them.
Old Dec 4, 2006 | 01:34 PM
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Originally Posted by Wildwill2855
well so far ive swaped out 5 of the 8 plugs and they were soaked with gas, a few after sitting all night still had wet fuel on them but they were black and wicked smelling. so im swaping in autolites 104s gaped at the .035. im going to try to finish them up in a few but damn its hard workin on a car in 15 degree weather. so anyhow so far this is what im thinkin it is, like i said i dont have a real tune yet still waiting for the email to come through with it, but i switched to 42 lucas's so its super rich even though i tried to scale the pcm for them.
I hear you on the 15* weather. I was out working on my car yesterday and it was 19*. How did you try to scale the PCM for the injectors? It's done in the ECM Constants table (in case you didn't know). Do you have the stock injectors to throw back in? That way you can eliminate one of the possible causes.
Old Dec 4, 2006 | 02:05 PM
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no i dont have the stock injectors anymore, i cant see the shop i went to messing up on the opti part they had so many nice custom lt1s and ls1s in their garage bays that are their own i just couldnt see it happening lol , i used this site to scale i found it through ls1tech,

http://www.carprogrammer.com/Z28/PCM.../injectors.htm

got 1 1/2 more to go and the plugs are swaped, i actually think this is the fastest ive done them before lol must be the weather motivating me

Last edited by Wildwill2855; Dec 4, 2006 at 02:07 PM.
Old Dec 4, 2006 | 02:37 PM
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Originally Posted by Wildwill2855
i used this site to scale i found it through ls1tech,

http://www.carprogrammer.com/Z28/PCM.../injectors.htm
I don't exactly follow what that table is saying, but I did some searching and it looks like the Lucas injectors are flow rated at 43.5 psi. First off, go in and undo whatever you've done. Then, go into the ECM Constants table and change the injector flowrate from 24.xx to 42. That should get the car somewhat in the region it needs to be in, fueling-wise. Then, post back and see if it runs. Do this BEFORE you start it up again, or you'll foul the plugs.
Old Dec 4, 2006 | 03:39 PM
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see i seen where it said to change the size to 42 and did that but that damn chart somewhere i read you use it? So i changed all the values. thanks man for your help so far ill go and reflash it and see what happens

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