Engine cranks and back fires, but will not start

[Dan Thompson]

I had driven the car and it ran just fine.

I parked it in the garage and a couple of days or a week later I try to start the car and after about 5 or 10 seconds it had one very big back fire.

I've "checked" the crank sensor and it 'looks' okay, it does not appear to be rubbing or damaged.

The cam sensor is tight and the connectors are all tight.

So I am at a lose as to what the problem might be.

I don't have any codes right now as I need to replace the battery.

Any ideas?

TIA

 

[JCotton]

Remove thw cover from the cam sensor, the cup with the window on it most likely moved. There is a little keyway in there that breaks and the cup spins, throwing the timing off. If it spun, we now have a part to easily repair that, you won;t have to remove of replace the whole unit.

 

[turbov6joe]

That would be the interrupter ring Jack is talking about...mine did the very same thing a few years ago....shear pin broke and the ring moved out of time causing all the things you mentioned.

 

[Dan Thompson]

Thanks for the replys. I'll check it out.

 

[Dan Thompson]

Pull the cam sensor cap and the cap "looked" okay. Since I have not had the cap off before this, I did not see any broken parts in the cap or on the cam 'ring/rotor'.

I checked to see if the cam 'ring/rotor' was lose and it felt okay, about the same as moving a distributor rotor, not much play in it.

So I am ready for the next step.

Thanks for your help

 

[JCotton]

Dan, go back and check the interuptor ring, "the gold colored cup with a cut out in it". 99% of the time a car exhibits what yours did, loud backfire, that ring has spun on the shaft. There is a very small hole where the key way, or shear pin is located that has to be carefully examined to be sure it is still there. It's difficult to see and easily overlooked as ok if you aren't sure of what it is supposed to look like.

 

[Dan Thompson]

I removed the "the gold cup " and washer. On the bottom of the cup is a small (1/16") 'pin'. With the washer in place there is only about 1/32" available to engage the 'rotor'.

The screw was very tight and had been installed with some type of locking cement.

This is the orginal cam sensor and the car has 113k miles.

 

[JCotton]

Was the pin definitely in the hole?

 

[Dan Thompson]

I believe so, because I tried to rotate the 'cup' when I took the cap off and it did not have much play.

There are no marks that would indicate that the cup was slipping. When I re-installed the cup I check the rotational play it was about 1/32" or less.

Thanks for all your help.

 

[S10xGN]

Dan,

See if the bolt holding the cam sensor down has become loose and allowed the sensor to turn. A mis-adjusted cam sensor will cause the EXACT problems you describe.

 

[19gn87]

When timing gears 'let go' it almost always happens on start-up. Just a thought...

 

[Dan Thompson]

I checked for play in the cam sensor, I couldn't move it at all, solid as a rock.

The timing change was replaced about 13k miles ago, so that should not be a problem.

This whole cam sensor system has not been touched since I bought the car new. I don't think the cam sensor connector has ever been disconnected.

 

[19gn87]

Dan,

Maybe back to basics. Take a minute and go to Steve's site ... click on troubleshooting. It's some good stuff that may well help.

 

[Dan Thompson]

Well I got everything back together and a new battery installed.

I was checking out the start sequence.

I turned on the ignition and could hear the FP pump up 40 psi, saw pressure on guage.

With the engine not running, but with the key on, I could hear a 'sparking' sound when I pressed the gas peddle.

I got under the hood at this point and could hear the noise again when I open the throttle. I could not determine where it was coming from, but I thought it might be the IAC. Does this seem possible?

I pulled the #1 plug and it was not wet and was a nice shade of gray.

Any more ideas?