tubby

'97 t/a lt1
car will crank but no start no spark
next day fires right up runs great several times in a row hot or cold.
next day no start and so on.
car has never quit while running. could there be a circuit that if closed will allow the car to start but not kill it if the car is running? what about a relay? theft deterent? coil?
i believe have eliminated the computer by swapping back and forth and had same symptoms with both. also had it diag. and no problems were found.
thanks

Fastbird93

VATS maybe?

tubby

from what i've read about VATS it seems that the motor would'nt turn over. is this correct?
thanks

FRDnemesis

Have you checked the Opti-harness that runs parallel the intake and down behind the water pump to the opti? I have seen this a few times where it had gotten moisture in there and caused corrosion on the pins. Whether it started or not was "hit and miss". Its worth a shot.

Jeff

tubby

i have not but i will. i had problems in that area before and have since but a new harness on. i will check again
thanks

tubby

opti cable checked okay. same thing, car started right up yesterday just cranks today. driving me insane. any other ideas?
thanks

Hotwire

is the fuel pump kicking on? have you checked power to it from the fp relay? have you checked the signals coming from the opti? power to the coil?

is the intake on tight? my truck wouldn't start unless the intake (rubber elbow) was firmly secured to the tb, otherwise air was getting in behind the maf and it wouldn't fire.

good luck.

FRDnemesis

Two things to check here:

Pull a plug out and place it up against some metal (with plug wire still connected) and have someone watch it to make sure its getting spark while you turn it over

The other obvious thing to listen for is to make sure your pump is powering up when you turn the key forward.


Jeff

slverbullet

hey, FYI: my car was doing the exact same thing when my fuel pump died. it had only 85k miles on it. one day it would start right up. next day it would just crank with nothing. you could always get it checked. hope this helps. just an idea.
dave

tubby

thanks for the input, here's what i see:
fuel pump is coming on with good pressure at the gage. raw fuel smell after cranking a while.
but will the relay effect more than just pump?

no spark present.

i have a digital tester but absolutly no idea how to check electrical items such as power to the coil and opti signals.

car is set up for FAST comp. with no MAF needed how ever i did temporarily reinstall the factory setup and had the same result ( start sometimes no start sometimes)

when it is in the mood to start the motor won't even hesitate to fire and like i said earlier it has never died while running or not run well.

Hotwire

i've heard of people having problems w/ the crank sensor on obd2, the pcm doesn't see the rpm from the crank, so it doesn't thow any signal to the ignition control module. Check this site for instructions on testing opti signals and ignition module. good luck

http://csce.uark.edu/~jgbertr/rb/4th_gen_tech1.html

FRDnemesis

No Spark??????? Well that kind of narrows it down to Opti, coil, or ignition module right there!!!! Do you have access to a set of GM manuals? Do you have a FAX machine?

tubby

no manuals, fax 803-691-4322
i will try to do some testing tonight.
man i hope it's not the opti the thing is brand new though i know that doesn't mean much.
thanks for the help

FRDnemesis

I'm gonna go home tonight and find the troubleshooting chart for that system. My vacation starts after I get off of work today so I will not be back tomorrow. But I will try to get it faxed off to you tomorrow. What year is your vehicle?

Jeff

tubby

it's a 1997 t/a
thanks alot