Carrera No Start - Help

[tom1394racing]

I have my friend's Carrera in my garage this week for the classic no start problem. He said the car was running funny, he smelled something and then it quit and would not restart.

The engine cranks fine but will not start. When I sprayed starter fluid in the airbox snorkel, it fired right up. Must be a fuel problem I figure. I jumped the fuel pump and it the pump seems to run fine. I removed the seat and listened to the DME relay with a stethoscope as I turn the key and it clicks. I had replaced the DME relay in the car several years ago.

Any good ideas on where to turn next would be appreciated.

[DRACO A5OG]

DME? I assume a 3.2, okay. check the OHMs on both speed and referrence sensors.

If you have a buddy with a known good 3.2, place your friend's DME into the buddy's 3.2 to see if the DME is the culprit.

When was the last time friend replaced the fuel filter?

[rusnak]

Voltage at the ICV harness?

Jumper the head temp sensor with a paper clip?

Check the fuel pressure?

Check for pulses with a noid light at the injectors?

[pors1968]

Check injector harness on engine or if injector open.

[rick-l]

I'll type until the experts chime in.

If you have a spark (it runs on strting fluid) the sensors that determine the position of the crank are OK.

A temperature sensor won't inhibit the car running espcially of you got it turning over with starting fluid.

Did you try to start it when you jumpered the fuel pump? Could you hear the fuel in the back flowing through the regulator? A fuel pressure test would rule all this out.

An open injector will just make the car run rough, a shorted one will keep it from running however.

[kidrock]

I once had the exact same issue, plenty of spark but wouldn't turn over until I introduced fuel directly into the intake.

Jumpered the fuel pump and could clearly hear it spinning, but the issue continued. Replaced the pump anyways, and the problem was solved. I guess that sometimes they can "run", but not necessarily deliver fuel.

Maybe checking for pressure at the fuel rail could give some answers.

[ischmitz]

Get a NOID light to check fuel injector pulses and verify fuel pressure at the rail (clogged fuel filter?) One or the other must be missing....

[tom1394racing]

Thanks for all the input.

I did try starting the car with the fuel pump jumped, no luck there. I also swapped in a good DME relay, no luck there. Next I will check for fuel pressure by cracking open one of the fittings on the injector rails and see if I get fuel.

[mysocal911]

Originally Posted by tom1394racing

Thanks for all the input.

I did try starting the car with the fuel pump jumped, no luck there. I also swapped in a good DME relay, no luck there. Next I will check for fuel pressure by cracking open one of the fittings on the injector rails and see if I get fuel.

One really needs to use a fuel pressure gauge.

[rick-l]

Originally Posted by tom1394racing

. Next I will check for fuel pressure by cracking open one of the fittings on the injector rails and see if I get fuel.

There is a cap with a ball in it on the drivers side injector rail where you are supposed to attach the fuel pressure gauge.

[Rodsrsr]

I hate these no start threads, because they can go on for days with tons of suggestions and then the OP never comes back to say what the problem was. Its like missing the end of a movie. That said, if the engine started using starter fluid, you have compression and spark, so its clearly a fuel issue. Agree with Rick-1. Put a fuel gauge on the injector rail to first see if fuel is at least reaching the injectors.

[rick-l]

Originally Posted by tom1394racing

he smelled something and then it quit and would not restart.

That smell wasn't something burning under the seat was it?

[tom1394racing]

Originally Posted by Rodsrsr

I hate these no start threads, because they can go on for days with tons of suggestions and then the OP never comes back to say what the problem was. Its like missing the end of a movie. That said, if the engine started using starter fluid, you have compression and spark, so its clearly a fuel issue. Agree with Rick-1. Put a fuel gauge on the injector rail to first see if fuel is at least reaching the injectors.

I do appreciate all the suggestions. I promise I will update everyone once I figure this out.

[tom1394racing]

I checked the fuel pressure at the injector rail while cranking. 37 psi as expected. So I guess the injectors are not firing.

Any ideas on where to turn next?

[tom1394racing]

I also checked the input leads to the DME relay and found the following:



12 Volts at pin 30 key off or on
12 Volts at pin 86 key on
0 Volts at pins 85, 85b, 87 and 87b key on or off
Continuity to ground at pin 85 only
Terminal 85b shows no continuity to ground

All of this seems correct to me except that there is no continuity to ground on terminal 85B.

Suggestions??

[DRACO A5OG]

Then I default to the Speed and Reference Sensors, check the OHM values

Also, just incase, what is the reading on the Battery, our baby's need 12.6 volts to start.

My Buddy's '86 had a no start issue, he suspected his DME. I put it in my car and it started right up.

Went back to his car, I smelled fuel and it would not start with his DME, then for the heck of it I checked the battery, it was at 11.7, too weak to have enough spark, we jumped with a 12.6 reading, it started right up. He was using a red top Optima with a warranty, went back and got a new one. No more issues.

[ischmitz]

Tom,

given that the engine runs with starter fluid tells me there is spark and hence CANNOT be the flywheel sensors.

Further, assuming the "smell" observed by your friend was electric and him saying the car "running funny" before it quit leads me to believe towards the DME, more specifically the fuel driver stage having burned down.

What happens is the output stage start loosing control and the injectors dump lots of fuel -> bad running. Then due to heat the output transistor opens and the car dies with no fuel. Sorry for the bad news.

Ingo

[mysocal911]

You need to verify that injectors have 12 volts (battery voltage) with the key 'on'.
You can use a test light for that. Next, as mentioned before, use a noid light
or a LED test light to check for an injector pulse.

Hopefully, your alternator wasn't overcharging as this will usually damage the
injector output stage. Also, eliminate the possibility of a shorted injector by
by disconnecting all injectors when testing for an injector pulse.

[DRACO A5OG]

As Doc Ingo stated, it may be the case but just to make sure place that DME into a buddy's known good 3.2. If it does not start, you have found the culprit. It would be time to rebuild the DME.

[mysocal911]

Originally Posted by DRACO A5OG

As Doc Ingo stated, it may be the case but just to make sure place that DME into a buddy's known good 3.2. If it does not start, you have found the culprit. It would be time to rebuild the DME.

Simple tests, as have been mentioned, eliminate the need to have to find someone
with another 911 3.2 to determine whether the DME ECM is bad or not. If it's found
not bad by use of substitution, the basic tests still will be needed.