fast377

iTrader: (52)

I have this posted in another thread, but I think it is buried too deep to get exposure.

The problem I have is my car (2000 Z28 for the most part) won't start unless I have the scanner plug connected to the diagnostic port (no start meaning fuel pump won't kick on to prime the system). Would this be a ground not connected (or maybe a hot)? If so, which one and where?

John_D.

iTrader: (2)

That's kinda weird that plugging in the scanner lets the fuel pump come on.
I don't know that you can use that to diagnose the problem.

Might be better to back up a step and get into what all you've done to the car.
"2000 for the most part" suggests some re-wiring/hybrid setup.
Could be vats, could be a ground. The two dash grounds get overlooked sometimes. A vats mismatch between the pcm and bcm could be a possibility.

LS1curious

Sounds like a security system issue.

wait4me

iTrader: (10)

What did you do to your car when this problem started?

slow

iTrader: (7)

check the grounds, make sure pins 4 and 5 (of the OBD2 port)are both independantly grounded, if one is not, the scan tool can short them out, allowing the system to be grounded.

Ryan

fast377

iTrader: (52)

You guys are right about the hybrid part. It's a 91 Z28 with an ls1/t56. I used ALL wiring (engine, body, lights, dash, etc) out of the donor. I don't think it's the vats...I wired in the appropriate resistor for that. The pcm and the bcm don't match, so I guess that could be a possibility (what is the fix for that...bend over at the dealer and re-program it?) Any way to check that for sure? I was kind of leaning toward one of the grounds on the dash. How many are there supposed to be on each side?

wait4me

iTrader: (10)

Sounds like all the black wires on the PCM are not grounded. you need to fix that and it will start then.

fast377

iTrader: (52)

Are the black wires on the pcm the ones that go to the lower dash bolts on either side, or the back of the heads? I'll check both (I just need to figure out how many are supposed to be on the dash.) The is the strangest thing. It starts and runs with the scanner plugged in. Hell I can even tune it with no problems.

John_D.

iTrader: (2)

There are a few black wires coming out of the pcm. Almost all of them end up being spliced together into a couple of major ones somewhere in the wiring bundle. So the final ground points are the 2-3 on the dash mount bolts, and 2 or 3 behind the heads.

fast377

iTrader: (52)

Cool, thanks a bunch guys. I'll check all of them and see what I find. Any one know how many are supposed to be on the dash and heads? I think I have 2 or 3 on the heads, and maybe 2 on each side of the dash.

fast377

iTrader: (52)

I fixed it!!! Thanks to everyone for their help. Turns out there was a ground wire that I think was supposed to be on the back of the driver head, but had been spliced and relocated to a stud on the coil pack bracket. So I moved it to a spot on the firewall and bingo! Everything works.

It runs kind of bad though. It doesn't want to rev...stumbles and wants to die. I've played with the tuning a little (still learning though) and it is a little better. It kind of feels like there is a miss...and I'm sure I need a fresh set of plugs. Is there anything specific I should be looking for in the scans? If anyone could help me with a baseline tune that would be great too. Thanks again!

fast377

iTrader: (52)

I forgot to mention a couple of dtc's.
[PCM] P0443 - EVAP Purge Solenoid Valve 1 Control CKT (Old) (Current) (Immature)
[PCM] P0803 - 1-4 Upshift (Skip Shift) Solenoid Control Circuit Malfunction (Old) (Current) (Immature)
[HUD] U1301 - Class 2 Short to Battery (History) (Immature)
[HUD] U1000 - Class 2 Communication Malfunction (History) (Current) (Immature)


The first two I am not worried about...I just forgot to delete them. The U1000 I think is from no abs and no cruise and no srs. But what is the deal with U1301?

Also, the first time the car started the other day, right before it started it kind of backfired through the intake. Not a loud pop, just like a big gush of air. I don't think it killed the maf but you never know. (no dtc's reported for it though)