1984 3.2 will not start

[198491132]

Good Day all....4 hours later and still can not get started. Any advice would be appreciated...here is the situation:

Battery is fine, no spark to plugs. Tested 12 volts at coil with ignition on, replaced coil. Replaced DME relay under drivers seat. Replaced fuel pump relay in luggage compartment. Cleaned dist cap and rotor. Tested ohms of both reference and speed sensors - readings of those tests are 1025 ohms between pin 1 and pin 3 (Bentley manual says this is OK). Between pins 1 and 3 and 2 and 3 I get "OL" on the meter, I also believe this is OK.

Car ran great last time I had it out about three weeks ago. Been extremely hot and humid.....

98K miles with orginal DME unit.....

Any advise would be greatly appreciated, Thanks...Dave

[Larry Herman]

You seem to have covered the obvious stuff.

Before I went nuts re-checking every little thing, I would find someone with a Carrera and try your DME brain in their car, just to make sure that the problem isn't with that.

[198491132]

I am thinking I may ask for that Larry, I seem to be running out of ideas. Anyone have a DME I can test with for 24 hours?

Additional test results:

Fuel pump turns on during "start" only. I also jumped fuse #6 with twelve volts, fuel pump runs....but did not start the engine.

Idle control valve does vibrate with key in the "on" position.

Additional general info - low fuel light was on - added 1 gal of fuel before all this testing (vapor lock issue?)

I found a loose plug wire.....almost too loose to be running the cylinder..(shorted out the DME?)

There is an ignition cut off switch. My tests show it cuts the 12 volts to the coil when active.

The only sure failed test, is there is no spark at the plug..I tested two seperate cables.

Thanks for your support, Dave

[198491132]

Larry, is it the same DME for all years? Most likely not......

Dave

[MylesD55]

Larry,

Does an 84 have a flywheel position sensor? I had a no spark condition in my 88 when the flywheel TDC sensor was not positioned correctly (gap was too wide).

Myles

[Larry Herman]

Yes, the 84 was the first year with the motronic system, and the flywheel sensor.  I know that the brain changed (I think in 86) from a 2K memory chip to a 4K, but it was only a jumper on the board, so I think that any year (84-89) will work.

[198491132]

Thanks Larry...Hey Myles...you helped me last time this car wouldn't start....with the DME relay...years back...I am over in Green Lane, white 911.

I was told if you got a good gas smell from the exhaust, after cranking it over, the sensor was working. I also verified ohms through both sensors, checked against the Bentley manual. If the fact that you smell gas at the exhaust is true, then the spacing of the sensor is good. Has anyone heard that? 

Measured coil resistance as well ... .6 to .7 primary, and 6.58k secondary. Tried the orginal coil I had on the shelf, no spark.

Changed out the dist cap and rotor with shelf spare (used before)..no spark.

Measured resistance on the coil wire.... ok at .2 ohms.

Out of ideas.......possible DME ignition output side????

Hoping to find someone to test with, either mine in a like car or like DME in this car before I ship it out and pay the big $$$$$

Dave

 

 

 

[JoeP]

It's a long shot, but did you test the DME relay?

http://www.dietersmotorsports.com/tech/2001/DME_relay_failure.htm

 

 

[198491132]

Yes, replaced the relay with two spares. But thanks for the thought.

Dave

[Darren]

The ground on the coil, I believe, is controlled by the DME so your logic makes sense.  You might want to check the ground locations and make sure none of them are corroded, especially the ones that run to the DME.  You should also check continuity between the DME and the coil, maybe there is a break in the wire someplace.