pingman

Hello all,
I have an '87 911. I have posted one other time and am not too good at it. I have not been able to crank my baby since Oct '06. I can't find why I have no spark to plugs. I have replaced the DME relay, coil, rotor , dist cap, both the speed and reference sensors, have had the ECM analyzed twice, once on the bench and in two different cars. everything checked out fine. I have checked the continuity on the grounds and sensor wires. I checked to make sure the distributer is turning the rotor. I have tried different plugs to check for spark. I have closed the hood at night and turned the engine over to look for something going to ground. I have changed the fuel pump because I had a spare. I have gone over most of these things twice or three times to make sue I did not miss anything, obviously I am. Any help anyone can give will be extremly appreciated. The folks at Systems Consultants were very helpful in tracing out some of the connections, thanks. If anyone has any ideas...
Thanks, Mark

Wachuko

Alarm messing with you?

panchosouth

Is the starter working? lots of juice? buzzers and lights working? alarm sounds like a good gremlin as well

Droops83

Air gap set correctly on crank sensors?

---Chris A.

PorscheMD

May I ask how you had the ECU analyzed?

pingman

Thank you all for the ideas! First the air gap on the sensors. I am trying to eyeball 30 thousandeths in a hole a little smaller than a jalapeno pepper. I did move the bracket in a little but no change. The alarm I thought about but never use it. I did turn the key in the door just for fun, which this rapidly becoming NOT. As far as the ECM analyzing, I asked a nice guy at predominatly german auto shop to test it, he stuck it on another Porsche and it cranked. Not satisfied I sent the unit to Systems Consultants in Calif. and they bench tested it as well as put the unit on another car and it checked out fine. They also gave me some voltage numbers to check on the pins in the connector to the ECM. Again everything checked fine except the voltage on the reference sensor. I keep talking to people and we seem to come back to the reference sensor and the possibility that it is bad. It was bought brand new, OEM. Again thanks for the input. I'm all ears, right now they're big as Mickey's!
Thanks, Mark

rbcsaver

Mark,
Please help me (us) to understand your problem in clearer terms. You say "it won't crank." That means when you turn the ignition key that the motor won't turn over or attempt to start. I think you mean that it turns over, but won't start. What was the history? Was the car running fine one day, parked then suddenly wouldn't start. Or, did the car sit for a long time, get a tune-up, etc before the problem. The most and clearest details you can give us the better. Also, it would help if you posted your location in your bio so that we can refer you to others for help. How do you know you don't have spark? regards,
Steve

pingman

Thanks Steve, here it is. I live in middle Ga. Closest Porsche mech. (who is an independant) is fifty miles away. Porsche dealership is in Atlanta @ 125 miles. I am mechanically inclined and can fix most anything, I am not so sharp on electronics. I have owned the car for six years, and never had any trouble with it. I drive it on sunny days to the golf course, bank etc. every week or so. In oct. '06, I drove to the package store, it was a little sluggish starting but cranked ok. after my purchase, the car cranked fine, I backed up and it shut off. I tried to crank it, the engine will turn over, but it would not crank. I towed it home, looked everything over and found that it needed a tune-up, the dist. cap was slightly pitted and rotor was slightly pitted. I changed these, I had changed the plugs a year earlier due to a cylinder drop out problem, which happened to be an internal failure of a spark plug.
I cranked the car and it started fine and ran so well. I drove it to the parts to store for another project, made my purchase, cranked it up, backed up, it quit and has not cranked since. I keep the battery charged so it has plenty of juice. The engine will turn over. Went to my trusted manual and started with the fuel pump, I had a spare, so I installed it (new). No start. I then moved on to the ignition system, because I knew that I had fuel due to the aroma of gas in and around the engine.
I replaced the coil, checked plug wires, plugs, fuses (replaced most of these, esp in the engine compartment), removed the ECM and took it to the mech in Macon which was the 50 miles, he did not have an analyzer, but happened to have an '86 911 sitting there. He put it on the car and it cranked up. My manual listed about five things to try one of which was a spark plug test to see if the engine was getting fire. I tested and there was no fire to the plug. Now I replaced the speed and refernce sensors, new from Atl. dealer, no spark, replaced the DME relay no spark. I never use the alarm system, but turnrd the key in the door to see if something was making contact that should'nt.
No change. Not confident that the ECM was not the issue, I sent the unit to Systems Consultants in Calif. to be annalyzed. They bench tested it and put it on a car and it checked out fine. They gave me some voltages to check on the pin connector to the ECM. I checked these and everything looked like the way they said it should be except the voltage on the reference sensor. I tried to adjust the clearance on the sensors but cannot quite get to them. I bumped them in a little partly due to an opinion that through engine wear may have increased the gap and the fact that the voltage on the speed sensor was 1.6 volts A/C and S/C said it should be 2 volts, I thought that maybe too wide a gap would decrease the voltage. I have checked all the grounds on the car again through the advice of systems consultants and rennlist members, I checked continuity between the wires from the sensors to pin connector to the ECM, made sure that I had not reveresed the sensors. Tried different spark plug wires, closed the engine cover turned the engine over at night to see if something was going to ground, there was none that I could see. Although this list seems long, I have done a lot more trying to solve this problem. I do not wish to waste everyone's time, but I do not want to give up. I do not know what to check on the alarm system, it may be in the manual, and I am still wondering about the voltage reading on the referance sensor, could it be bad from the dealer? It is OEM with Porsche #'s. By the way when I first looked at these two things when I touched the wires the insulation fell apart, this is one of the reasons I replaced both. Thank you'all for the help, Mark

Mike Murphy

I think this whole "cranking" verb that you're using is causing a misunderstanding. Instead of cranking, can you edit your post to include only the following two scenarios:

"turn over" = starter motor engages and spins the engine slowly (when your turn the key all the way to the right)

"start" = spark plugs fire and engine runs on its own power (you release the key and the engine still runs).

rbcsaver

Murphy, that's what I was trying to get him to clear up also. I "think" it's turning over, but not starting.
Pingman, please describe exactly how you tested/determined that there isn't any spark. Is it possible that the car has an old anti-theft mechanism such as a "lojack" that shut down the motor. When you turn the ignition key to the right, **before** the starter engages (to turn the motor over), are you seeing the alternator light come on, gages activate etc?

nineoneone

I explained in another post what I had to do for my 87.

Try this.. Take the ecm relay or (fuel pump) relay and remove it from the electrical connector.
2, Pull the cover off so you can see the small electronic board, (new or not won't matter)
3, fold a matchbook cover piece (the front cover only) fold in half
4, lay said paper down inside the cover so the electric board will fold it as in V----] the v is the paper the dotted lines are the board.

5 make sure you have it in correctly and snap the board back in the plastic cover
6, plug it in to the connector and try it.........

2 fuel pumps 2 relays and a boat load of down time taught me this trick and I have not had one bit of trouble with it since then. The fuel pump checks good after replacing , and so have the relays. weird I know

No harm no fowl.

dshepp806

Pingman,..

I, too, liive in middle GA. (Macon)...where exactly are you located?

Doyle

JV911

the way i read it is that the starter motor engages and spins the engine but wont "crank" (ie fire)

you mention this scenario twice - sounds like something is loose ie a ground/earth

theiceman

Yeah that is definitely the confusion .. " cranking" is commonly known to have the engine turn over , but a lack of gas or spark will prevent it from firing .. and there in lies the problem.

I have an SC with no computer ... "phew" .. but I have heard of issues with the CHT sensor , would this cause a no start condition ?

rbcsaver

I still want to hear exactly how he tested for "spark." Screw driver in the plug wire, a plug in the end, voltmeter or how. Then, it must br grounded to the motor to see a spark. If not spark seen while grounding to the motor, then an unpainted chassis surface. If it arcs to the chassis, but not the motor, than this would indicate a bad ground to the motor, and there are a few of them. The copper meshing will fail after a while. We just need more info and clarity, leaving out the "crank" term. Either the motor turns over and won't start, ot the starter never engages and it won't turn over.
Steve