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Discussion Starter · #1 ·
Hopfully yellowbullet guys can help.98 T/A LS1 head/cam/intake motor.Stock lower.Wont start somtimes.Crank and crank, then finally just starts.When its cranking it has no spark.I pulled a wire off the coil(MSD) yesterday while cranking and nothink.Then we disconnected the battery few times and banged on the maf/map and it started.What do ya think?
 

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Try swapping out the 'ignition' relay under the hood with another one (there are a few of the same relays around, just swap them to check).

Also the ground wires behind the drivers side head can be getting loose.

Did the car start doing it after was something was just done or was it fine then just started acting up?
 

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Try wiring the MSD box stright to the battery. It may not be getting 12 volts while turning over. Rod
 

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cam sensor
 

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Hopfully yellowbullet guys can help.98 T/A LS1 head/cam/intake motor.Stock lower.Wont start somtimes.Crank and crank, then finally just starts.When its cranking it has no spark.I pulled a wire off the coil(MSD) yesterday while cranking and nothink.Then we disconnected the battery few times and banged on the maf/map and it started.What do ya think?
Do you have an RPM signal when cranking?
Do you have injector pulse?
Is your reference voltage correct?
Power and Grounds test correctly?
 

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Throwing any codes?
Has a CP relearn been done?
 

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Try swapping out the 'ignition' relay under the hood with another one (there are a few of the same relays around, just swap them to check).

Also the ground wires behind the drivers side head can be getting loose.

Did the car start doing it after was something was just done or was it fine then just started acting up?
X2.I had this happen 2 years ago.Had to tow the car home from the track.Took 2 weeks to find out it was a $12 relay.
 

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Discussion Starter · #11 ·
Try swapping out the 'ignition' relay under the hood with another one (there are a few of the same relays around, just swap them to check).

Also the ground wires behind the drivers side head can be getting loose.

Did the car start doing it after was something was just done or was it fine then just started acting up?
No changes.Problem stared out of nowhere.We'll try the relays.Thanks
 

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Those darn LS1Tech folks. :)

So the car will crank, but sometimes not fire up? But it will crank right up? Once it's running it's fine or it idles weird, or idles high, or sounds rich or lean?

Kevin (kp) is a great trouble shooter, keep asking him, so I'd check that relay like he said. If the MAF is messed up (oil got on it?), it will start crappy, like if you have a nitrous backfire and mess up the MAF it will be very hard to start. You can borrow a MAF from another car to test. You should also be able to start the car with the MAF unplugged.

Did you change any stuff recently, like heads/cam? Those grounds in the back of the head if not put back on will weaken the electrical system to the point where the car will have problems starting.

If you changed the intake, or had a nitrous backfire, you might have an intake that is not sealing right. If you scan it, it will show negative L Trims, and I think if memory serves -25 would be the max correction beyond that it's maxed out. If you see unequal Ltrims like -25 on one side, and say 0 on the other the intake is not sealed on the big negative side.

Okay, now the crank sensor wire runs in a bundle down the driver's inner fender between #3 and #5. also in that bundle is the starter power wire. If that bundle is right on the header it can melt and fuse the wires together. I suggest looking at that crank wire if the car shuts off at WOT ie. when you are making a pass.

Swap the MAF if it's got a code, or also try unplugging. I'm sure Kevin will correct me as needed he has a better memory.

John, cofounder of LS1Tech
 

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Discussion Starter · #18 ·
Those darn LS1Tech folks. :)

So the car will crank, but sometimes not fire up? But it will crank right up? Once it's running it's fine or it idles weird, or idles high, or sounds rich or lean?

Kevin (kp) is a great trouble shooter, keep asking him, so I'd check that relay like he said. If the MAF is messed up (oil got on it?), it will start crappy, like if you have a nitrous backfire and mess up the MAF it will be very hard to start. You can borrow a MAF from another car to test. You should also be able to start the car with the MAF unplugged.

Did you change any stuff recently, like heads/cam? Those grounds in the back of the head if not put back on will weaken the electrical system to the point where the car will have problems starting.

If you changed the intake, or had a nitrous backfire, you might have an intake that is not sealing right. If you scan it, it will show negative L Trims, and I think if memory serves -25 would be the max correction beyond that it's maxed out. If you see unequal Ltrims like -25 on one side, and say 0 on the other the intake is not sealed on the big negative side.

Okay, now the crank sensor wire runs in a bundle down the driver's inner fender between #3 and #5. also in that bundle is the starter power wire. If that bundle is right on the header it can melt and fuse the wires together. I suggest looking at that crank wire if the car shuts off at WOT ie. when you are making a pass.

Swap the MAF if it's got a code, or also try unplugging. I'm sure Kevin will correct me as needed he has a better memory.

John, cofounder of LS1Tech
Thanks John.Not Knocking Ls1tech,but I rarely get answers from them.Maybe I post in the wrong sections.Yellowbullet always moves so fast.I always get advice.Anyone that knows me knows I dont bash.I figured the title of this thread wouuld get some attention.;)Now back to my brothers car.Nothing has been touched in 2 years.It started this after bringing it out this spring.Once it starts its fine.Doesnt run bad or anything.It only does it once in a while.Its only driven couple times a month though.It hasnt been to the track in 2 years and it has never been sprayed with nitrous.the car is constantly hitting the rev limiter(6850) so I told him not to spray it.These are other issues we will deal with later.For now I will try all the great ideas you guys have suggested.Thank you again.Sorry if I offended any LS1tech people.I dont think I did.Hope not.:smt083
 

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I have had a few customers melt the wires near the starter going to the crank Sensor. It will start with out a cam sensor but not with out a crank sensor.

I never saw your post or do not venture into the sections you were asking ;)
 
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