1996 LT4 Will Not Crank
Thread Starter
7th Gear
Joined: May 2011
Posts: 7
Likes: 0
1996 LT4 Will Not Crank
I have a 1996 LT4 and the car will not crank. I have been through the electrical and installed the correct VATS bypass and I still have no luck getting the engine to crank. There were no warning signs leading up to this problem... Just one day the car wouldn't start. When I turn the key to the run position, all other electronics inside the car turn on, but as soon as I turn to the start position, the "Brake Pressure" light on the dash comes on. I have checked the brake reservoir and the fluid is at the proper level and the sensor is connected. I am running out of ideas and wonder if anyone out there has any ideas as to what would keep the vehicle from cranking? Thanks everyone.
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
prove out whether its the solenoid / starter or the wiring leading to it
put vehicle in neutral (or park), run a wire from the solenoid on the starter; touch the other end to the positive terminal on the battery; the solenoid should engage and starter turns
if no action; bad starter or bad solenoid (or bad battery / battery cable)
if starter turns; the problem lies in the wiring
put vehicle in neutral (or park), run a wire from the solenoid on the starter; touch the other end to the positive terminal on the battery; the solenoid should engage and starter turns
if no action; bad starter or bad solenoid (or bad battery / battery cable)
if starter turns; the problem lies in the wiring
Racer
Joined: Jan 2004
Posts: 286
Likes: 1
From: Madison WI
You did the Vats bypass and then it wouldn't start or you did the bypass and drove it a few times since the bypass before it quit starting? If it's not Vats related then it's likely the solenoid or starter as previously mentioned. Could be as simple as a loose connection too.
Drifting
Joined: Aug 2004
Posts: 1,709
Likes: 285
Well is it posible the crank position sensor has gone bad?
I have replaced mine on my LT4 as a maintenance item. But it could mess with the start it is bad.
A little tricky to replace but not hard. Best thing to do is buy one (cheap part) to see what it looks like and where the bolt hole is. I replaced mine without going under the car.
I stood on the passenger side of the engine leaning over the tire, reached down on the right side of the power steering pump to the underside of the motor. Feel around, you will feel a wire/plug. That wire/plug goes into the backside of the CPS. Unplug it. I used a small 8mm (I believe) closed wratchet ..found the top of the bolt head with my fingertips and placed the wratchet on the bolt head and removed the bolt. The CPS can be wiggled out of the hole at this point. The tough part is doing this all by feel and not sight. That is why I suggested buying one to see what they look like.
Just another thought...
Good luck,
trebor
I have replaced mine on my LT4 as a maintenance item. But it could mess with the start it is bad.
A little tricky to replace but not hard. Best thing to do is buy one (cheap part) to see what it looks like and where the bolt hole is. I replaced mine without going under the car.
I stood on the passenger side of the engine leaning over the tire, reached down on the right side of the power steering pump to the underside of the motor. Feel around, you will feel a wire/plug. That wire/plug goes into the backside of the CPS. Unplug it. I used a small 8mm (I believe) closed wratchet ..found the top of the bolt head with my fingertips and placed the wratchet on the bolt head and removed the bolt. The CPS can be wiggled out of the hole at this point. The tough part is doing this all by feel and not sight. That is why I suggested buying one to see what they look like.
Just another thought...
Good luck,
trebor
Thread Starter
7th Gear
Joined: May 2011
Posts: 7
Likes: 0
The voltage does not drop in the run position or when the key is turned to the start position. I will check the starter and solenoid to see if there is a problem there. The car wouldn't start before I installed the VATS bypass and it still wouldn't start after the bypass was installed.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
prove out whether its the solenoid / starter or the wiring leading to it
put vehicle in neutral (or park), run a wire from the solenoid on the starter; touch the other end to the positive terminal on the battery; the solenoid should engage and starter turns
if no action; bad starter or bad solenoid (or bad battery / battery cable)
if starter turns; the problem lies in the wiring
put vehicle in neutral (or park), run a wire from the solenoid on the starter; touch the other end to the positive terminal on the battery; the solenoid should engage and starter turns
if no action; bad starter or bad solenoid (or bad battery / battery cable)
if starter turns; the problem lies in the wiring
You can do it this way. Or you can connect a voltmeter to the solenoid wire (and ground) and measure to see if is getting any voltage. You can use a long lead wire and bring the meter to top of the car to view easily.
** Just wanted to add, if you check for codes using a OB2 code scanner, it might show you if you had, or did not have a VATS event. Then you might not have to be concerned with it.
Last edited by pcolt94; Jun 21, 2011 at 04:53 PM. Reason: More info
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Well is it posible the crank position sensor has gone bad?
I have replaced mine on my LT4 as a maintenance item. But it could mess with the start it is bad.
A little tricky to replace but not hard. Best thing to do is buy one (cheap part) to see what it looks like and where the bolt hole is. I replaced mine without going under the car.
I stood on the passenger side of the engine leaning over the tire, reached down on the right side of the power steering pump to the underside of the motor. Feel around, you will feel a wire/plug. That wire/plug goes into the backside of the CPS. Unplug it. I used a small 8mm (I believe) closed wratchet ..found the top of the bolt head with my fingertips and placed the wratchet on the bolt head and removed the bolt. The CPS can be wiggled out of the hole at this point. The tough part is doing this all by feel and not sight. That is why I suggested buying one to see what they look like.
Just another thought...
Good luck,
trebor
I have replaced mine on my LT4 as a maintenance item. But it could mess with the start it is bad.
A little tricky to replace but not hard. Best thing to do is buy one (cheap part) to see what it looks like and where the bolt hole is. I replaced mine without going under the car.
I stood on the passenger side of the engine leaning over the tire, reached down on the right side of the power steering pump to the underside of the motor. Feel around, you will feel a wire/plug. That wire/plug goes into the backside of the CPS. Unplug it. I used a small 8mm (I believe) closed wratchet ..found the top of the bolt head with my fingertips and placed the wratchet on the bolt head and removed the bolt. The CPS can be wiggled out of the hole at this point. The tough part is doing this all by feel and not sight. That is why I suggested buying one to see what they look like.
Just another thought...
Good luck,
trebor
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Drifting
Joined: Aug 2004
Posts: 1,709
Likes: 285
This is from a reliable source:
"A bad crank position sensor can worsen the way the engine idles, the pistons fire, or the acceleration behavior. If the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires. Accelerating might be hesitant, and abnormal shaking during engine idle might occur. In the worst case the car may not start."
thanks,
trebor
Drifting
Joined: Aug 2004
Posts: 1,709
Likes: 285
You are correct, you can unplug it and the engine will still run, but over time, it will not run well and maybe not at all.
This is from a reliable source:
"A bad crank position sensor can worsen the way the engine idles, the pistons fire, or the acceleration behavior. If the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires. Accelerating might be hesitant, and abnormal shaking during engine idle might occur. In the worst case the car may not start."
thanks,
trebor
This is from a reliable source:
"A bad crank position sensor can worsen the way the engine idles, the pistons fire, or the acceleration behavior. If the engine is revved up with a bad or faulty sensor, it may cause misfiring, motor vibration or backfires. Accelerating might be hesitant, and abnormal shaking during engine idle might occur. In the worst case the car may not start."
thanks,
trebor
There is always room to learn something new..
thanks,
Trebor
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
OK ..after further research and having no practical experience with this, I am retracting my theory that it could be a bad CPS. From what I understand now, the Opti communicates with the coil and not the CPS in a '96 OBDII. The '96 crank sensor is only for cylinder missfire detection.
There is always room to learn something new..
thanks,
Trebor
There is always room to learn something new..
thanks,
Trebor
The opti (optical portion) drives the PCM (ECM) - The PCM drives the ICM - The ICM drives the coil - And the coil delivers the spark to the opti cap.
In this case "drive" is the key (better) word not communicate.
Generally communicate is used for items like a bus. You might say the CCM communicates with the PCM and EBTCM. You can also have analog or digital communication or can be a change of state.
Just thought I would add a little.
