ive got spark and fuel , not throwing any codes just acnt get it to run? could that cause it?

 

Not on an LT1.

 

no...

 

I've always agreed with the general concensus that the CPS is not needed for an LT1 to run. However, last year my car started running like crap - stalling and refusing to start. I ended up getting the car flat-bedded to my local Chevy dealer. I trust the guys in the service department there... in fact their lead mechanic also happens to be the guy who I trusted to build my 383.

They checked out the car, and tracked down the problem to a bad CPS. They replaced the CPS, and the car ran perfectly. I realize that this goes against what we all "know" about the LT1's CPS, i.e. it's only used for missfire detection. But like I said, I trust these guys - so if they "fixed" the problem with a new CPS, I believe them.

EDIT: Just to clarify... this all happened before my OBI conversion, back when the car was still OBDII.

 

The above just doesn't make any sense. Considering you can run around in an OBD2 LT1 w/ the CPS unplugged all the time w/ no issues.

 

Then how do you explain that an LT1 can run without a CPS even installed? Perhaps if it was shorting out in some way, it could affect something...I don't know. Maybe your mechanic accidentally fixed something else that was the real culprit.

 

I agree with what you guys are saying, I just thought I'd throw this story out there. Shoebox: You're probably right in that there was either a short causing problems with the system, or something else was the problem and was accidentally fixed.

Regardless, all that was done was a replacement of the CPS, and it "fixed" the car. It didn't make sense to me either, but I have no reason to doubt these guys. I mean, if there was a loose wire (easy fix) somewhere and they were trying to rip me off, they would have screamed "OPTI" or "PCM" and soaked me. In fact, I suggested that those 2 could have been the problem. They assured me that all they needed to do to fix the car was replace the CPS.

Weird, huh?

 

Weird stuff happens.

 

ok well can you guys please help me ,using all AC DELCO parts ive replaced the coil, icm, crank shaft postion sensor, And the optispark. my fuel pressure is correct according to the haynes manuel and using a spark tester i have fire to the plugs. The car just turns over burps a few times , could it be a fuel pressure regulator or something any direction for getting my car running would be greatly appreciated thanks.

 

oh yea im throwing no codes.

 

Sounds like the opti is installed incorrectly.

 

Well you need spark fuel and compression to run, so far you say you have spark and fuel, do you have compression?

 

The spark has to happen at the correct time too, so yeah the opti may be incorrectly indexed.