Engine Died While Drive - Will Not Start

[beren]

Hi All,

I have an 88 911 3.2; The other day while driving home from work the engine cut out (tach dropped straight to zero). The car will crank, but not start. I had it towed home - but it will not start.

I was driving at 55MPH on the highway. Everything was normal. The car has never done this before and never had any kind of starting issues.

I did search around the forum,but this seemed pretty different from other issues/threads I could find.

Any suggestions would be appreciated.

beren

[Joe Bob]

High percentage chance the DME relay. Buy and replace, avoid URO products.

Assume you have checked for spark, fuel and air?

[Discseven]

Fuel pump buzz'ing (or not) is an easy check.

[rick-l]

Originally Posted by Joe Bob

Assume you have checked for spark, fuel and air?

+1

Is the idle air control vibrating?

[glewis80SC]

Had this happen twice with my SC...it was a bad coil each time.

[Rodsrsr]

Check the obvious first. DME relay as others have said.

[Rodsrsr]

Originally Posted by Discseven

Fuel pump buzz'ing (or not) is an easy check.

Thats not an easy check on a motronic car, because the fuel pump only turns on while the engine is cranking. You have to jumper the fuse (#3 I think) to see if the pump comes on with key in run.

[beren]

Thanks guys - appreciate the help. I'm decent with the basics, but by no means an expert. I'll order a DME replacement.

It does seem like the fuel is not getting to the engine. After 30 seconds of cranking away I would think you would smell something at the tail if fuel was flowing. I would think if the pump failed I would have had some sputtering or something. In this case I was driving for about 30 miles and it just went dead.

I'll check for a spark tomorrow - I guess I'll just yank a plug from the right hand bank and get the wife to turn the engine over and see if there's a spark. Battery looks good on a voltmeter and I don't see anything wrong with fuses.

[cnielsen]

DME relay is the quick obvious choice

Also check that the DME is getting over 12V and that it is grounded well (check the engine ground strap also). I can't remember the specific voltage but if it's even slightly deficient, it shuts the fuel injectors down.

[timchar]

Careful on excessive cranking in case you are getting gas, don't want to hydro lock. Tim

[beren]

Originally Posted by cnielsen

DME relay is the quick obvious choice

Also check that the DME is getting over 12V and that it is grounded well (check the engine ground strap also). I can't remember the specific voltage but if it's even slightly deficient, it shuts the fuel injectors down.

How do I do that? pull it off and check the terminals? What position do I need the key in to do this?

[patz]

Give the intake a shot of ether/quick start when cranking. No start, it's the DME. If it tries to start it's the fuel pump.

[beren]

I really don't think a cylinder ever actually tries to fire. The engine is cranking away, but it never really sounds like it is trying to start. In all the years the car has started right off - 2-3 seconds and vroom, even after a few weeks of no driving in the winter. I never drive in bad weather or terribly cold stuff.

[rick-l]

Before you do anything turn the key on and put your hand on the IAC

[JJ 911SC]

Originally Posted by patz

Give the intake a shot of ether/quick start when cranking. No start, it's the DME. If it tries to start it's the fuel pump.

+ 1, fastest way to find out if you got sparks.

[Rodsrsr]

Originally Posted by rick-l

Before you do anything turn the key on and put your hand on the IAC

Do this.^^^ Turn key on and see if the Idle control valve is vibrating. If it is then jumper fuel pump fuse to see if it comes on with key in run. (I believe it is jumping fuse 3 to 4) If car starts the relay is bad. Or you can just wait the 2 days until your new relay arrives and see if it starts.

[Irhmsd]

If you are a novice, wait for the new DME relay, plug it in and let us know.

[rdrr]

This just happened to me tonight - pulled the distributor cap, scuffed up the points, and voila - she started right up! Time for a new cap and rotor.

[Walt Fricke]

The DME controls the fuel injectors and the spark. So if the DME relay fails, the DME doesn't get its 12-13VDC supply, and you won't get either a spark or fuel because no signal is sent from the DME to the injectors to open, or to the spark coil to fire.

The cylinder head temperature sensor can fail, but that usually means really hard starting, and I think generally the engine will run, albeit not very well. If you are getting spark (easy to check) and fuel (not quite so easy), then I'd look at CHT replacement. The ether squirt will be diagnostic here. Your '88 should have the two wire CHT sensor, which is said to fail less frequently than the single wire ones the '84s had.

[Joe Bob]

Put your hand on the relay and turn the ignition to run. You should hear or feel a click. If not, it's not getting power or it is defective. Check the fuse that supplies power, pull the relay and re-install or replace it.

While I keep a spare just in case, my no start on my 3.6 was caused by a defective fuse.