87 No start - but haven't given up yet.
 

OK,

This is the diagnostics and work done to date...

Initial symptoms: 87 Carrera with intermittent start issues until finally not start at all. Symptoms began after getting a fresh battery, which may be coincidental

Work done:

• Replaced the DME Relay (twice). I think the one in there now is OK because I get two clicks from it: one on turning the key to run, and a second click on turning the key to start.
• Replaced both the reference sensor as well as the speed sensor. After that the car started and ran like a champ for 30 seconds then died like I pulled the key from the ignition.
• I had to remove bracket during the sensor install (frozen sensor), so I thought it might be the gap. I used super glue and washer trick at the end of an old sensor to get the gap right (0.8mm). That made no difference, no start.
  
• I replace the fuel filter. The pump filled the filter with fuel without any issue when trying to start the engine. So the pump is getting power and pumping, at least enough to fill the filter.
  
• Replaced the Head Temp sensor with the better 930 type sensor. This produced no results.
  
• Cleaned off the ground wires in the engine bay for the DME. No results.
  
• I am getting a strong smell of fuel at the tailpipe after about 20-30 seconds of cranking. So I think I am OK on the fuel front
  
• I tested for spark today on the number 3 cylinder. No Spark.
  
• Tested for Power at the mass airflow sensor to see if the DME was getting power. I got 4.9 volts.
  
• Double checked the connections on the tree which holds the sensor plugs.

OK, so where does this leave me? New DME? Coil? I don't mind springing for a rebuilt DME if that is what it really is.

Unfortunately I live in NH. 911's are not so plentiful in this part of the country so I don't know anyone who has another Carrera to test my DME for me.

What are your thoughts?

Thanks,

Matt

test for spark and fouled plugs
 

You may have fouled your plugs. You need to see if you have spark at the plug

disconnect the fuel pump so that you dont pump raw gas into a cylinder and cause yourself more problems by filling the cylinder with fuel.

take a spare spark plug, remove a plug wire from a plug put it on the spare plug
ground out the spare plug and have someone crank the engine. if you have spark at the spare plug then i think your plugs are fouled and need dried or replaced, I had this problem after i forgot to connect up the msd after doing some work,, the engined cranked and fouled all of the plugs,

I probably should have been clearer, but this is how I tested for spark. No Spark at the plug.

Did you check the plug connection behind the intake? The motor harness has a connection there, also check the harness plug under the black cover left side of engine bay. Order a new DME relay from our host and try that, good to have a spare in the glove box if that doesn't do the trick. Next, the coil could be culprit. I read some old post of yours stating that the DME relay you have in now was acting flaky; by tapping on it made the car start. I would replace it.

Replaced the DME Relay (twice). I think the one in there now is OK because I get two clicks from it.
Not sure if clicking is the answer if it's good or not.

This may be the last thing you want to try, but a DME unit.

I have changed the relay out twice and I think I have eliminated that as the issue, as I am getting power to the fuel pump and the DME (airflow sensor harness test).

I will check the other connections, you mentioned.

I have no power to my coil. Should it have some kind of reading when the key is switched in the ON position or does it need to be cranking to tell?

Thanks,

Matt

Bentley's has a good troubleshooting procedure for checking the coils. If you aren't getting power to coil with key in "on" position, check the ignition switch to see if power is leaving there. These go bad pretty regularly, I think. Good luck,

Don Ivey
'87 Carrera

I think you are probably right. It could be the coil, but when it runs, it runs great, no missing or anything. I will see if I can pull it tonight and check the board for cracked solder joints.

If I see any bad solder I will order a rebuilt unit. I could go at it with a solder gun, but I have no way to test it.

Is there more than two power leads coming out of the ignition switch? I am getting power to the fuel pump and DME and DME relay (2 clicks, one with on and another with start), so unless there is more elements to it, then I think the switch should probably be OK. I am I wrong about that?

If it is up the DME to power the coil, then perhaps it is the DME.

http://forums.pelicanparts.com/porsche-911-technical-forum/458417-87-carrera-ignition-stopped.html

heres a good thread

Its great that you have all those cool new parts in there but what you really need is to diagnose the problem rather than throwing parts at it. It seems to me that since it just totally died and now you have no spark then that is the trail to follow.
-It wouldn't hurt to check another plug to see if it has spark. While you're there you can check to see if its fouled (although I would think that fouled plugs would cause it to run rough as opposed to just shut down).
-Have you opened up the DME (not the relay) and looked for bad solder joints?
-Is your rotor button turning when the motor is cranked?
-Look around for loose or broken wires (especially around the coil and distributor). Make sure the speed sensors are properly plugged in.
-RU absolutely sure that you connected the speed sensors correctly? I would consider swapping out the connections to see if it fires (although once again I can't imagine it running for 30 sec and then totally shutting down)?
-When all else fails, swallow your pride and call a rollback and get it to a shop that knows air-cooled P-cars.

Last night I checked the power going to the coil and I am getting 12.2 volts at the positive terminal of the coil when grounding to the engine block. So the ignition switch is probably OK.

I removed my DME and shipped it off for diagnostics and a potential rebuild.

I will let you know what I find in the end. Thanks for all you help!

Matt

double post

Did you check the coil itself? Mine died recently.

DME was bad
 

Well, I sent the DME for a rebuild to Florida. They tell me the diagnostic revealed that it stopped sending a signal to the coil. They needed to replace more than just solder joints so I am glad I didn't try to fix it on my own.

They also offered a performance chip for an extra hundred bucks. I know it is not a Steve W chip, but if it helps the car have a little more pep, I am all for it. Hard to pass it up at a hundred bucks especially since it won't void the 5 year warranty they offer on their work.

I guess I am not out of the woods yet, the car is not running, but I am feeling better about getting closer to a solution. I should get the DME back on Monday. I will let you know what happens.

Thanks for all your help!

Matt

Just wanted to end this thread. The new DME fixed the issue although I think the it now idles a little too low at about 500 RPM. I dismantled and cleaned the ICV, which many have helped marginally and my throttle micro-switch seems to be activating. Waiting for my Bentley book to arrive before an go any further.

Thanks for all your help everyone.

I would remove whatever performance chip they put in there. Did you get the factory chip back?

Idle speed may have been altered (lowered in this case) by their chip, as well as idle and off idle timing.

Idle speed can be raised and lowered by twisting the screw at the base of the throttle body. It is an air bypass screw used for this purpose. The proper way to do it is to jumper a couple of test point connections near the coil, located behind the black plastic cover that is over the defroster fuses and relays; these points are jumpered and the adjustment is then made.

The benefit of buying a performance chip from a guy like Steve Wong is that he'll tell you how the car should be behaving against what he programmed. Incidentally, you can find the idle adjustment procedure on his website, 911chips.com.

850 is where a 3.2 should idle, 950-1000 is o.k. in a performance chip.

http://forums.pelicanparts.com/porsche-911-technical-forum/250438-idle-bounce-3.html

Everything you need to know!
Have fun

Long shot but worth checking. Look at the #6 fuse (from the driver end of the fuse box) and make sure (1) it is the correct fuse value, blue I think, (2) it is not corroded or otherwise not correct.

I found on a 87 Carrera the fuse had been replace with a white fuse and had some deterioration with resultant resistance. The car ran but would not start all the time. I believe that it must have run when the alternator was delivering a full 12 volts (or so) but when in the key was in starting position the drain of the starter lowered the delivered battery voltage below 7 or 8 volts which was not enough to kick off the fuel pump. Changed the fuse to the correct one and it hasn't failed since.

One symptom that led to this conclusion was that if you pushed the car it would start. No starter drain in that condition.