88 3.2 Won't Start

88911coupe · 05-22-2002, 07:48 AM

Here's the facts...88 3.2 106k, replaced plugs, wires, DME relay, cap/rotor about 10 months ago. New O2 sensor 3-4 months ago. Car has run perfectly since. Monday car would not start but motor turns over fine, but no start. Towed to dealer and would not start while in shop but started today...totally unexplained. Tech says he has no idea why it now starts since he had not done anything to fix it yet.
Anything I need to suggest they try? Any other 3.2 owners run into something like this?
Thanks,

Rick Lee · Rick Lee's Garage

Sounds like fuel pressure (lack thereof) to me. Just a guess.

ChrisBennet · ChrisBennet's Garage

I've seen reference sensors fail and cause this sort of thing. Just replacing the expensive reference and RPM sensors might still be cheaper than having a non-expert tech figure out the problem. (An expert would look at the sensor signals with a scope.) Out of 5 Carrera's I know of (mine and friends), 2 have had these sensors fail (both '86s with 120K+ miles) so I personally would't feel bad about replacing them even if it wasn't the problem.
-Chris

Joeaksa · 05-22-2002, 08:10 AM

I would switch out another DME relay and see if it still did the same. Just because a part is new does not mean that its working correctly. Did you keep the old one as a spare? Plug it in for a bit and see what happens... takes 10 minutes.

Second thing would be cylinder head temp sensor. I understand that you can ground it out at the plug above the motor and eliminate it from the system to troubleshoot.

My 85 did the same "start once, then not start the next time" game for a long time and finally traced it back to a bad cyl head temp sensor. Make sure that your sensor is the upgraded one (two wires going to the sensor and not one) and go from there.

Joe

Harold_89_911 · 05-22-2002, 08:23 AM

Do you have a factory alarm by any chance? My 89 has one but I thought it was the only year for Carerra's. I had a no start condition a couple of months ago and could not figure it out. Everything tested fine. So I brought it to the garage and they traced it to the alarm box. I did have my 12V on the DME relay when trying to start but it was fluctuating due to a bad contact. He replaced the box and all is fine now. I opened it up and one of the two relay contacts in the box was completely burned up. Just my experience.

88911coupe · 05-22-2002, 08:44 AM

I will have them confirm I have the newer cyl. temp sensor. Also, I have a aftermarket Clifford alarm...not the factory. It has been set on Valet mode for the last couple of months.
Thanks for the replies so quick

Joeaksa · 05-22-2002, 11:43 AM

Buck,

You can confirm the new sensor yourself. Look inside the motor compartment on the left side. You will find a metal bracket with three wiring connectors.

The cyl head sensor should be the top one and if you look on the right side of the bracket, the wiring going down to the sensor will have two wires if its the new style, or only one wire if its the old style.

Its a bear to change and I would make sure that you have the newer sensor, no matter what! Some Pelican tech articles below should help as well.

Joe

http://www.pelicanparts.com/techarticles/911_cyl_head_temp_sensor/911_cyl_head_temp_sensor.htm

http://www.pelicanparts.com/techarticles/911_carrera_start_troubleshoot/911_carrera_start_troubleshoot.htm

88911coupe · 05-24-2002, 05:04 PM

Update,
Ok, just got the car back from dealer b/c it suddenly started starting. They did nothing. Latest update...car started fine and then cut off 20 seconds later as if turned ignition off. Tried to restart an can definitely smell some fuel. Seems to be no spark. What can I tell the mech to look for.
BTW...I think the cyl temp sensor is original...is this the first thing to tell them to replace?
TIA

Joeaksa · 05-24-2002, 05:33 PM

Buck,

If the car runs fine one moment, then dies. Let it sit for 5 minutes and it starts up again... and so on...

Change the cylinder head temp sensor if its the old style ! This is what mine did and it drove me crazy for a week then guys on this board talked me through it.

Never faltered since...

Joe

88911coupe · 05-30-2002, 12:00 PM

Here's the update and I need help. The mech's have had the car all week and can't find the problem. Now want to charge me another $165 for diagnostic work. They put a new rpm sensor in that did nothing. I have suggested, (twice now) that it may be the cyl. temp sens and the mech. admantly says that it can't cause a sporadic no start condition. It would only cause the engine to think it was hot. This doesn't sound right to me but I'm not the master certified Porsche technician.
Any ideas?
thanks again

BrianH · 05-30-2002, 12:18 PM

My 84 began having a problem where it would "stumble" sporadically when it was cold. Then it started dying occasionally at low RPM, and finally got to the point where it would die immediately after start up. It would fire up and then die a split second later, did it about half the times I would try to start it cold, other times it was fine. Mechanic said he wasn't sure what it was, but the first thing to try was the head temp sensor, since I had the original one and they can "cause sporadic problems like that." He changed it and it's run fine since. Your problem may be different since it sounds like it is not firing up at all, and mine would start, but die right after. Still, it sounds awfully familiar...

Joeaksa · 05-30-2002, 12:38 PM

Buck,

If you have the old style cyl head temp sensor, ask politely for them to change it and if they refuse, then find a shop that realizes that the customer is important. The mechanic is FOS (full of something) when he says that it cannot cause this. It did it on my car!

You need the new style sensor... it will go bad eventually, period. There is a very good chance that this is your problem so eliminate this variable from the list of options. When my sensor was bad it would do it warm or cold... replaced it and it has never done it again.

Joe

stlrj · 06:49 AM

If you suspect the head temp sensor, you can bypass it by disconnecting it at the connector on the left side as mentioned and bridge a 1000 ohm resistor between the two terminals and see if it starts.

Cheers,

Joe

Gspin · 06-03-2002, 05:59 AM

Sounds like we need John Walker Workshop to come the rescue, maybe he can offer his 2 cents?

88911coupe · 06-03-2002, 01:54 PM

Update and bad news. Mech says its the DME computer and will be $1600 PLUS the 2 $165 diagnostic charges. I have to pay them the $330 diagnostic fees to get the car back even if I decide to get the DME computer somewhere else. Does Pelican sell these (I'll go check) or can they be had rebuilt? My bros. 95 318is had the same problem and I found him one for $300 but they only do BMWs.
I still think it may be better to at least try the head temp sensor.
I'm really bummed about this.

Thomas Owen · 06-03-2002, 02:45 PM

Buck - I have an extra dme for the '88 if you want to try it out. Send me a pm if you want to try this, but please, do not pay $1600 for one...
Regards,

Joeaksa · 04:12 PM

Borrow a DME computer and troubleshoot it, but agree with Thomas that you would get screwed by paying that much for a new computer.

Have seen them recently for sale used for $350 or so... there was a guy selling the complete DME setup for a reasonable price recently. Believe it was on Ebay but its not there now.

Joe

88911coupe · 06-03-2002, 04:08 PM

I have replied to Thomas very generous offer to help. I did find a place that says they will rebuild it for $450 since they don't actually have any rebuilt ones in stock. It's 20th St. Auto Recylers in Phoenix. Are there any other places.
Thanks for all the help

Joeaksa · 06-03-2002, 04:16 PM

Was just at 20th street last week. Bought and have them install a used windshield in my car. Good people and did a good job on the installation.

Not sure about "overhauling" a DME as there are not too many parts inside that can be reworked. If a wire has come unsoldered or the chip is bad I could understand that, otherwise it would take someone with a good electronics background.

Joe

Tim Polzin · 06-03-2002, 05:11 PM

I've had a few DMEs apart. The quality of parts are top notch. If the problem is intermittent, very likely it is a cold solder joint. These things are really quite fixable, not much in it to "rebuild". If you buy another one, keep the original and have someone check the circuit boards, most likely at the connector or larger components. The 944 DME (85.5 to ?88?) can be made to work perfectly on a 911 with a replacement Eprom and a few jumpers.

Tim