LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

no start, good spark and injecter pulse

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Old 06-14-2007, 10:51 AM
  #61  
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Originally Posted by popstoy
isnt there a switch that doesnt let the car start in gear maybe thats messed up.or the connection from the after market security system you disconnected that might of closed a circuit to your ignition switch.
the neutral safety switch in an automatic tranny would not allow the starter to turn over unless in neutal or park, I have a std tranny with a clutch pedel switch, which is working fine.

the aftermarket security system was not connected to any ignition wires. Only the power windows, door locks and rear hatch release.
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Old 06-14-2007, 11:50 AM
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Ok, so we've painfully established that the car is not wired backwards. It's starts in the correct direction but rolls backwards when the key is released. Does it do this when the car is warm or cold? Does it do it when you release the key immediately to the off position?
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Old 06-14-2007, 12:28 PM
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Originally Posted by TheBoerg
Ok, so we've painfully established that the car is not wired backwards. It's starts in the correct direction but rolls backwards when the key is released. Does it do this when the car is warm or cold? Does it do it when you release the key immediately to the off position?
it hasn`t run in weeks so it does this cold. It usually needs to be tried 3-4 times before it starts doing the backwards thing, but it then does it nearly every time.

It does it immediately when the key is released from the 'start' position to the 'on' position.
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Old 06-14-2007, 03:33 PM
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Let's forget about the "running backwards" thing for the moment. Suppose voltage is dropping out to something like the PCM when the key is in the "crank" position but the voltage is there in the "run" position. Might explain why the engine starts when pushed.

However it doesn't explain why if you did like I suggested and left the key on and externally jumped the starter, it didn't start.....Unless you did it incorrectly.

Why don't you look for voltage dropping out to the PCM while cranking????

Last edited by Guest47904; 06-14-2007 at 03:42 PM.
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Old 06-15-2007, 07:14 AM
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Originally Posted by speedygonzales
However it doesn't explain why if you did like I suggested and left the key on and externally jumped the starter, it didn't start.....Unless you did it incorrectly.

Why don't you look for voltage dropping out to the PCM while cranking????
I agree, with the purple wire to the starter cut and jumped directly to the battery, it should have started.

Which plug and wire is the battery voltage feed for the ECM? The Haynes manual doesn`t give pin locations.
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Old 06-15-2007, 07:37 PM
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PCM pin outs or should I say voltage in are:

Black connector, pin 30 pink wire
Blue connector, pin 3 pink wire
Black connector, pin 15 & pin 31 both orange wires

Last edited by Guest47904; 06-15-2007 at 07:39 PM.
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Old 06-15-2007, 07:51 PM
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You say it runs fine when push started, but how fine? Will it buck, jerk, or backfire if you get on the throttle? If so, then I would almost bet the timing has jumped a tooth. A few people have mentioned it already, why haven't you pulled the timing cover off and check?
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Old 06-16-2007, 05:06 AM
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A valid point regarding the timing chain however you don't have to pull anything other than a valve cover and a plug to tell if it's off.

Use a wooden dowel or pencil in the cylinder to follow the piston while observing valve movement. Also, move the crank back and forth while the valves are moving to see if there is any slack in the chain by observing delay in the valve movement.

However, I have given some thought to your problem and I don't believe it's voltage dropping out to the PCM. Your "correct" purple wire test with the key on would have proven that. Although at this point it would still be a good idea to check the 4 voltage connections at the PCM.

I too would like to know how it runs when it is started by pushing it. Are there any dead cylinders? I think you should test all of them to see if any are not firing. But you have to do it while the engine is running. It is this that I think prevents you from starting with the key.
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Old 06-16-2007, 07:19 AM
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when you push start it it runs fine, no misses or bucking, not at all like the chain has jumped. That`s why I haven`t taken the timing cover off.



"It is this that I think prevents you from starting with the key."

It is what?? cylinders not firing?? It hits on all 8 when you push it.



The positive cable is about the only thing that is left. I suppose if the voltage is dropping right at the cable at the battery, that may cause it. I may throw one on here today if I get a chance.
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Old 06-19-2007, 10:55 AM
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I isolated the starter load with another battery. The cars battery and wiring are not effected at all by the starter, and it still doesn`t start.
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Old 06-19-2007, 03:14 PM
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Here's a stretch...

If the starter engages it cranks fine. When the key is released, the engine turns backwards. What if the starter drive gear isn't releasing? Then it would drag on the ring gear.

When the key is released and if the drive gear is engaged, then may armature would generate a field in a reverse flow and backfeed power. Windings don't care which way they turn, they will generate electricity. Then, if the armature is backfeeding power through the starter, it reverses polarity and causes the engine to reverse direction via electronics.

Testing a starter on the floor is one thing, testing it under load is another. Try a different starter or have it load tested (if Autozone, make sure they test your starter under flywheel resistance/load... not free spin).

Since it runs fine when you pop start the clutch and doesn't run fine when you crank via key, then the issue is likely the starter circuit (electronics/mechanical).
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Old 06-19-2007, 03:15 PM
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My post above was referring to a possible solenoid mechanical shifter bind/jam to the driven gear.
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Old 06-19-2007, 10:45 PM
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Check #4 &#6, #5 &#7 plug wires, could be wrong. PS- starter drive will not engage FW if its turning backwards. Danny Mc
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Old 06-19-2007, 11:22 PM
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If he's starting the car, then he's engaging the pinion of the drive gear. If the drive gear is binding into the flywheel, then perhaps the drive gear is not release from the flywheel. If it doesn't release, then it will spin the armature and perhaps generate an electric field. Then the electric field would back feed.

Again, this thread has gone on and on. I've stated that I'm stretching on this one. He hasn't swapped the starter motor.

If the wires were crossed, then it wouldn't run fine when he bump-started the engine.
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Old 06-20-2007, 07:03 AM
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Originally Posted by Wild1

Again, this thread has gone on and on. I've stated that I'm stretching on this one. He hasn't swapped the starter motor.

If the wires were crossed, then it wouldn't run fine when he bump-started the engine.
I`ve already stated, it`s the third starter in the car in the last few weeks. It hasn`t started on it`s own for the last two starters. The motor has always turned over the correct dirrection, and has now all but stopped the backwards running thing......This car is really frying my brain, I`d love to fix it and get it out of there. I just can`t figure out what`s so diffrent when it`s pushed.
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