Car cranks but doesnt start

[f104g]

Hi,

Last weekend without warning, my 1986 C4 coupe stranded me at a shopping mall and would not start.

Got back into the car to go home, lots of cranking of the motor happening, but not on your life would it start.? .. had to get towed home.

I just want to be sure I am on the right track with identifying the problem.

What I have found out so far...

When I turn the ignition key on,
* The fuel pump is silent,
* there appears to be no spark getting to the plugs.
* The engine will crank over fine,
* there is plenty of power in the battery.

Is this the VATS system immobilizing the car? I have read some conflicting information in forums as to this .

The symptoms I've described above sound similar to a VATS problem I seen described in other posts, but I wanted to be sure.

Some state categorically that if the engine will crank over, then it's not a VATS problem.

Others say ...
"
If the engine WILL CRANK and a code 53 is displayed, that indicates that the VATS decoder module has detected a correct key resistance, and has grounded the relay coil negative wire for the start enable relay, but that the ECM is not receiving the VATS signal from the module. That can be caused by either a failure of the VATS module output which generates the signal, or Circuit 229 between the VATS module and ECM is open or shorted to ground.
"
I've tried starting the car again a number of times in the past 24hrs, and there is no change at all.



any similar problems experienced by others?

If it's not the VATS ... then are there any idea as to what else could suddenly knock out both spark and the fuel at the same time?

 

[John Robinson]

Ignition coil

If you do not have fire then check the ignition coil for continuity and if it is ok then check the pick up coil. I am guessing that since you have crank and no fire the problem is in these coils.

Also have you checked the oil level. Don't laugh GM in order to reduce warrenty cost on engines that burnt up for a lack of oil put a sensor in to detect and shut down the ignition and fuel if the car was excessivily low on oil. If the oil level is below the add mark on the dip stick put in enough oil to be over the add mark and try starting the car. If it is a low oil problem the car will start right up. Let us know what you find.

 

[f104g]

If you do not have fire then check the ignition coil for continuity and if it is ok then check the pick up coil. I am guessing that since you have crank and no fire the problem is in these coils.

Also have you checked the oil level. Don't laugh GM in order to reduce warrenty cost on engines that burnt up for a lack of oil put a sensor in to detect and shut down the ignition and fuel if the car was excessivily low on oil. If the oil level is below the add mark on the dip stick put in enough oil to be over the add mark and try starting the car. If it is a low oil problem the car will start right up. Let us know what you find.

Thanks for your feedback.

yep .. Oil level is fine ...

I'll try the checking through the ignition components one by one and see if anything is looks out of place. It's the obvious place to start. I'm probably on the wrong track with the VATS.

 

[JAKE]

Also have you checked the oil level. Don't laugh GM in order to reduce warrenty cost on engines that burnt up for a lack of oil put a sensor in to detect and shut down the ignition and fuel if the car was excessivily low on oil. If the oil level is below the add mark on the dip stick put in enough oil to be over the add mark and try starting the car. If it is a low oil problem the car will start right up. Let us know what you find.

From all I've read there's no such circuit on the Vette. The only oil pressure sensor that effects fuel is the secondary sensor that will energize the fuel pump once it sees at least 4 psi of oil pressure. It acts as a sort of back up to the fuel pump relay.

Also, on my 96, a few months ago, the oil pump drive gear failed; oil pressure instantly went to ZERO and the Check Gauges light on the dash came on. Engine continued to run even with NO oil pressure.

Years back I was changing the oil on my 5.7 TPI Trans Am and in mid-job decided to use a different oil than what I had bought. While at the auto parts store my nephew stopped by, fired my engine to show how it sounded to a friend of ours. By the time I returned, the engine has seized solid. Guess who wasn't a happy camper.

Jake

 

[John Robinson]

From all I've read there's no such circuit on the Vette. The only oil pressure sensor that effect fuel is the secondary sensor that will energize te fuel pump once it sees at least 4 psi of oil pressure. It acts as a sort of back up to the fuel pump relay.

Also, on my 96, the oil pump drive gear failed; oil pressure instantly went to ZERO and the check gauges light on the dash came on. Engine continued to run even with NO oil

Thats good to know thanks. What brought it up was I was in a garage the other day and they had a Buick that would not start. They were trying everything to get it to go. The mechanic mentioned it was low on oil but did not think that would keep it from starting and they were going to do an oil change later. I mentioned what GM did on the Vega with a low oil cut out. The mechanic put some oil in the Buick and it fired right up.

 

[JAKE]

When my 86 wouldn't start it turned out to be the ignition module under the distributor cap. AutoZone can check it for you for free.

Another time it was my coil which I dicovered by finding dark brown coloration right near where the wires exit the coil.

Could be a bad rotor too. Look for a burn-through hole under the meta tab.

Even if the fuel pump relay has failed, the pump should energize once the oil pressure reaches 4 psi (or so) while cranking the engine. Have someone stand at the back of car to verify if the pump is coming on or not.

Keep us posted.

Jake

 

[f104g]

The problem has turned out to me a burnt out fuel pump.

I was also completely incorrect about thinking it was the VATS obviously.