lsx68firstgen

iTrader: (22)

Ok, so I've swapped a ls3 into a 68 camaro using the gmpp standalone harness with my own ecu o had base tuned. I turn the key to the on position let the fuel pump prime and turn the key it starts but for maybe a second not even. If I keep cranking it starts to backfire a little not much threw the intake. If I turn the key off and back on it will do the same thing, start for a half a second and stall. I'm stumped. I've tried 2 different ecu. Anybody have a suggestion on what it might be? I havnt scanned for codes yet as I have to rent and I am going to most likely tomorrow but just though I'd try here to see if anyone could help. Thanks for any help.

1964SS

iTrader: (1)

VATS turned off?

1989GTA

VATS first and then do you have a good spark if VATS is ok. Make sure the ground wires for the coils have a good ground. I have seen cars actually run somewhat with the ground wire disconnected. Same for the injectors. Double check the ground and power wires.

lsx68firstgen

iTrader: (22)

Yup vats is turned off. I have checked grounds, power supply, literally un-loomed my harness the other day looking for broken wires ect. Could it be the map sensor? I'm using a map from a 2005 5.3 with a gmpp 58x ls2 standalone harness. But now that I think about it I don't think I told the tuner that.

lsx68firstgen

iTrader: (22)

He knows what harness I'm using but not the map.

1929chev

unplug the map and try to start. The car should start if it is unplugged. That would tell you if it is bad.

lsx68firstgen

iTrader: (22)

Tried unplugging the map and it did the same thing. Thanks for he help though any other things I can try?

tonypaul

iTrader: (2)

did you try spraying some starter fluid in it? spray a good shot into it and see if it runs any longer.

What throttle body do you have?

lsx68firstgen

iTrader: (22)

Yes it'll run if I spray gas or starting fluid in. I'm using a ls2 silver blade t/b which the tuner knows. Thanks.

tonypaul

iTrader: (2)

check the iac. try blocking it off.

lsx68firstgen

iTrader: (22)

I thought dbw doesn't have iac? I don't remember having one. I'll have to check in the morning thanks.

tonypaul

iTrader: (2)

your right, no iac for dbw... i was thinking you had dbc...
I have heard of stand alone harness' having wiring errors. I remember reading something about the wiring on some electronic gas pedals being different. Maybe worth looking into.

Where did the electronic gas pedal come from?

lsx68firstgen

iTrader: (22)

I was told it was pulled from a saab suv i bought the harness, ecu, and gas pedal used and i had the base tune done.

1989GTA

Have you checked your fuel pressure at the rail?

tonypaul

iTrader: (2)

i think this is what i remembered reading- https://ls1tech.com/forums/conversio...-ls2-swap.html

lsx68firstgen

iTrader: (22)

No I have not checked the pressure at the rail as I'm using holley rails with a/n fittings and don't know how to go about it. I did crack a line before I ever tried starting it to see if fuel was flowing and their was alot of pressure. But it might be worth checking out thanks.

tonypaul

iTrader: (2)

are you able to check for codes? I also remember something about that you have to have an approved throttle body part number for the gmpp harness and the aproved part numbers are in the book that came with harnesss...??? something like that..

I looked into the gmpp stand alone harness' awhile back but decided to go a different route..

lsx68firstgen

iTrader: (22)

I didn't know that im going to look into it thanks.

lsx68firstgen

iTrader: (22)

No I havnt read any codes yet but I was gonna rent a scanner tomorrow or Saturday

tonypaul

iTrader: (2)

sent you a pm