87 930.. Engine just died on the highway.

[HFR_Racer]

Guys..

Symptoms are as follows:

I had been driving for approximately 30 minutes all seemed to be going well. The engine simply shut down. Seemed like loss of fuel or ignition. I had been having symptoms similar to loss of vaccum (some stumbling) and low on power, but this evening it was running fairly well.


UPDATE from 4/16/2011...
My 930 still has no spark.


The original issue seemed to be the CDi box but I later traced this to the fact that I was not getting an AC pulse from the pickup coil located inside the distributor. I found that the actual pickup coil was flaky and sometimes did not provide an AC signal to the CDI box. I rebuild my distributor and installed a different pulse coil. My GREEN wire from the pulse coil to the CDI box is now providing a signal to the CDI box.

The symptom now is that the CDI box does not provide a 460 VAC pulse to the ignition coil "A" terminal. Thus you would think that the CDI box is bad. Not likely since I installed another CDI box in my car that is proven good from another Porsche.

I know that I have 12+ bolts from the ignition when the key switch is in both the START (engine cranking) and RUN position going to the CDi box. I've tested this several times. I've also tested for spark with my tach disconnected as suggested in the service manual. I'm convinced that this is not fuel related. I simply do not have spark. My fuel pumps run and I also tried to install a new "yellow" relay in the engine compartment just to humor myself. I've been told that this isn't OEM alarm related. I would assume that I wouldn't get an ignition signal ( 12+ VDC) to the CDi box if my vehicle alarm was flakey. Correct?

The root issue is that there is something preventing the CDI box from sending a high voltage pulse to terminal "A" and it's not ignition switch and not tach. I need to know (based on a wiring diagram). Does the white wire from teriminal "A" of the CDI box go directly to the "A" terminal of the coil of does it run through a relay? I checked continuity of this wire and it tested good.

Also... I don't seem to have an "overboost sensor". I've read several threads that tlak about the overboost sensor "white" wire must be grounded. Where does this wire come through the harness on an 87 930 so i can check to see if it's actually grounded?? I'm running a Kokeln intercooler and the only sensor attached to it is my dash boost gauge sending unit.

[Ronnie's.930]

There is no DME relay on a 930 (DME is not part of the K-Jetronic system these cars use - DME is a component of the Bosch Motronic EFI systems found on other model 911s of the era) . . .

[equality72521]

Yellow relay in engine compartment. Replace it with a spare from the front.. like the horn relay.

[RarlyL8]

Quick check is to look at the coil wire and ignition box plug in, make sure they are both plugged in solid. Next pull a spark plug and lay it (plugged in) on the engine. Hit the key and see if you have spark. You should smell fuel, if not jumper the fuel pumps, put the key in the run position and listen for the circulating fuel.

[HFR_Racer]

My kind neighbor is going to tow-strap me home in a few.. A least I'm out of the woods on getting her home.

Thanks Brian for the initial advice on troubleshooting.. I'll try all of those items..

I do have a new yellow relay for the engine compartment and I already tried that. That didn't get her to start.

I also see a round black relay in the engine compartment (next to the yellow) relay. What is the function of the round black relay. I'll try to swap it out when I get home..

What about the ignition cut-off relay?? If the ignition cutoff relay were bad then I should not get 12+ VDC to the CDI box with ignition on. Correct?? So I can rule this realy out, correct?

Coil wire and ignition box plug-in checked ok. I was running newly purchased fuel pump relays from our host. I swapped these out for the good OEM relays and I hear fuel pumps running with either of the relays installed. I don't think it's fuel. I'll check spark next.

Spark + fuel = RUN BABY!!! I must not be sparking. If I lost spark suddenly, then what should I suspect? Ignition relay?

[HFR_Racer]

Ok... I've got her home now.

I swapped out the black relay (engine compartment) with a known good one from the boot (fuse panel). Engine still doesn't start.

I pulled a spark plug and it's wet with fuel so fuel delivery should be ok. I assume no spark at this point.

NOTE: No spark was confirmed.


Based on the Pelican parts listing I only have a pickup in my distributor (no condesor or points). Is that correct? At least that's two less parts I need to worry about.

Pickup coil in the distributor wasn't sending a signal. This is now fixed and still no spaek ( due to lack of high voltage signal to the ignition coil).


Thanks everyone for any assistance your offering.

[wjfk32]

Happened to me........also..

Do everything they said ^^^^^^^^^^

Chk the ohms on the coil-10.5-12ohms good and distributor-coil-600ohms-good...This was my case--My coil had a slight leak-changed to epoxy one..Distributor coil--orig.(changed it),,Make sure u mark your distributor Cleaned distrb. cap & tested rotor-5-ohms..Also took the distrib. apart-(clean) crud inside...

While I was at it-chked all front-hood fuses connections-tested-ohm meter.
Used pet-jelly to electric inserts..Chk green wire for electric output also-(connected to distrib)...
IT takes time and good light to see..Make sure you have a nice chair to work with..

The worst case scenario if your CD-BOX FAILED.

Walt

[willtel]

Try grounding the wire that goes to the overboost sensor. It is unlikely that it would just die but it is also easy to eliminate.

[JFairman]

the aluminum color bosch ignition coils made in Brazil are sometimes not reliable and upside down on the fan housing is one of the worse possible places for an oil filled coil.
that or the CDI or the green coaxial primary wire going to the distributor may have quit if you have no spark.

the round black relay you fiddled with is for the 12volt heater element in the oxygen sensor to get the lambda emission system working faster and that has no effect on what you're dealing with.

[HFR_Racer]

willtel.... I already tried my new "yellow" relay and that didn't fix the issue. I'm digging much deeper today and I'm generating more questions...

My coil is new last year and yes it is mounted above my fan in the stock location.

How do I test the coil to eliminate it as an issue? I can pick up enough signal from my spark plug wires to make my timing light oscillate but I do not have spark at the plug.

It's either got to be the condenser in the CDI, coil or no good diode in the ignition cut-off relay causing the alternator not to function... Do these ideas sound logical?

I have the following questions.. Sorry for the all caps..

1) HOW CAN I TEST THE VOLTAGE OUTPUT FROM THE PICKUP IN THE DISTRIBUTOR WITHOUT AN INTERMEDIATE CONNECTOR. I DON'T SEE AN INTERMEDIATE CONNECTOR ON MY VEHICLE BETWEEN THE CDI AND DISTRIBUTOR? MAYBE IT'S UNDERNEATH THE BROWN HARNESS PROTECTIVE SLEEVE? SHALL I START CUTTING?? I HOPE NOT.

- INDICATED READING ACCORDING TO THE SERVICE MANUAL SHOULD BE 0.1 VAC. DOES THIS CORRECT?


2) HOW DO I ENSURE THAT MY COIL (IGNITION VOLTAGE TRANSFORMER) IS OK FOR THIS VEHICLE?

- SHOULD I CHECK THE RESISTANCE BETWEEN THE COIL OUTPUT WIRE TO THE DISTRIBUTOR AND TERMINAL #1 ON THE COIL?? HAYNES BOOK SAYS IT SHOULD BE 650~790 OHMS. HAYNES BOOK SAYS TO CHECK RESISTANCE ACROSS TERMINALS #1 AND #15 ON THE COIL BUT THE STICKER ON THE COIL SAYS OTHERWISE (DANGER). WHATS UP WITH THIS? I ASSUME THAT I CAN ONLY CHECK RESITANCE FOR EACH SIDE OF THE COIL (PRIMARY WINDING AND SECONDART WINDING. I ASSUME THAT THIS IS DONE BY OHMING OUT EACH OF THE SMALL POLES ON THE COIL TO THE COIL OUTPUT WIRE? I'M NOT GOING TO DO THIS UNTIL SOMEONE OF EXPERTICE TELL ME TO... I'M NOT LOOKING TO BUY PARTS BECAUSE I FRIED THEM DURING TESTING.

3) HAYNES ALSO SAYS TO JUST DISCONNECT THE MAIN COIL WIRE FROM THE DISTRIBUTOR AND HOLD IT 10MM FROM AN ENGINE GROUND, THEN IGNITION AND CHECK FOR SPARK. THIS SOUNDS DANGEROUS AND ALSO THE 6 PIN CDI THREAD ON THIS SITE WARMS AGAINST NEVER DOING THIS....

[RarlyL8]

There are many electrical connections that can cut the spark. One that is not so uncommon in our old cars but typically overlooked is the ignition switch. The switch can wear out to the point that the starter engages but the ignition doesn't light.
A very quick check is to jump the starter and see if you get spark. If you do get spark your car will start on the remaining 5 cylinders so be ready for that.

[pkabush]

I went through similar issues on my 81 930 a few years ago.
I was lucky enough to be working on my car about a block away from an independent Porsche mech. I don't think you can bench test the CDI. He plugged mine into a 911 and it was fine. Turned out to be the green dist. wire. Apparently this is a common failure.
Good luck

[HFR_Racer]

Brian B...

I checked that I have good voltage to pin # 15 of the CDI box. This should prove that the ignition switch is still good.

My green wire is good as well. My green wire ohms out between the two pins at 587 ohms. As checked from terminals "7" and "31d" from the harness going to the CDI box.

I also ohmed out the primary and secondary windings of the coil at 712 ohms. Therefore the coil should be good as well.

WHY DIDN'T ANYONE TELL ME THAT THIS RESISTANCE VALUVE WAS NO GOOD??? 712 OHMS IS CLEARLY A NO GOOD VALUE.. IT SHOULD BE AROUND 10,000 OHMS. NOW I KNOW. IT WOULD'VE SAVED ME $250 IF SOME WOULD'VE SPOKE UP.

THE PRIMARY SIDE OF THE COIL SHOULD BE APPROX. 0.7 OHMS OR LESS.
THE SECONDARY SDIE OF THE COIL SHOULD BE APPROXIMATELY 10 K OHMS.


I am not getting high voltage the the white wire ( terminal "A" ) at the coil. My CDI box has good input ( 14 VDC) to terminal #15 but no-good output to the coil from terminal "A". I am only getting 0.1 VAC output to terminal "A" of the coil.

I've purchased another CDI box from a fellow Pelican and I should be running in a few days. I'm going to take me other CDI box apart and troubleshoot the internals once I get the replacement box.

Thanks for everyones help on this topic.

[lucittm]

I had a similar problem, she just stopped. It took me awhile but I found a burnt wire under the forward fuse panel. Run a jumper from the battery (or other known good +12V source) to the + side of the coil and see if she starts. If she does, you have a broken wire somewhere.

My burnt wire should have been a 3mm wire but it was .5mm. A rare Porsche factory mistake.

Mark

[HFR_Racer]

Your serious???????? The "A" pole of the coil is supposed to get ~460 VAC. I'm not sure that 12 VDC is gonna do it sir. Have you truly tried this or are you blowing smoke up my A$$

I'm not likely to try this duct tape solution on my 930 anyway, but I'm curious.

[lucittm]

My mistake, you don't have a + terminal on your coil because your cars model years used a CD or Permatune box so the coil has an "A" and a "B" terminal. It would not have done any damage but connecting your coil A terminal to +12V would not allow your car to start either.

My 1977 911 S had a CD box. I never cared for the high pitched whine.

Mark

[HFR_Racer]

Help please... I've revised my intial post above. CDI experts help please

[oilonly]

That wire splits off from the same spot as the wire for the boost gage sending unit. Its the whiter one that must be grounded if you don't have an overboost sensor or car will not start. Strange you don't have one.

[oilonly]

HFR, here is a thread from a poster whose problem was a bad overboost switch.

Sudden & Abrupt Boost Loss

[HFR_Racer]

Thanks guys.. I confirmed that I do not have an overboost switch. My white wire is grounded at my fan near my ignition coil..

I changed a few things and now I have "very weak" spark:
1) Fully charged battery. I had 12 volts. Now 12.9 volts. Does the CDI have an interupt that looks for low voltage? A low voltage cutoff?
2) I installed my fuel pump relays. Does the ignition circuit drop out for the CDI box if the fuel pump circuit is interupted? I don't think so since I was getting 12+ VDC to "15" on the CDI box with my fuel pump relays removed. There is nothing in the vehicle wiring diagram that indicates this.

NOTE: I've confirmed that you can get spark and have the fuel pump relays pulled out of the fuse panel located in the boot area of the vehicle.

3) I found that my coil wire from my distributor was not fully seated into the coil. But this wasn't the true issue. Maybe it was why I didn't see spark at my plugs but not the ROOT issue of not seeing high voltage from my CDI to the "A" on the coil.

More tomorrow.


April 17th, 2011 ( 6 am):
1) Output voltage from either of my CDI boxes is no good less than 20 VAC. I now believe that both of my CDi boxes are damaged. I'm not sure how this could've happened.
2) Confirm resistance readings from the ignition coil. Coil resistance from the coil terminal "A" to the coil output "4" is approx 700 ohms. Coil resistance from coil terminal "4" to coil terminal "1" is approx 700 ohms.

April 21st, 2011 (6:30 am):

SHE RUNS!!!!!!!! BETTER THAN EVER. NO MISSING!!! TURBO SPOOLS HARDER THAN EVER SINCE I FIXED ALL OF VACUUM LEAKS!!

I determinec that my ignition coil was in fact no good. The method that I was using to test my ignition coil was faulty. I understood the warning sticker on the ignition coil to mean that you shold not put an electrical meter accross the two smaller terminals. THIS IS NOT CORRECT..

You properly test the primary side of the coil by placing your meter leads on terminal "A" or "+" and the output to distributor terminal "4". This reading shoud be approx. 0.7 ohms.
You properly test the secondry side of the coil by placing your meter leads on terminal "A" or "+" and the "-" terminal of the coil. This reading shoud be approx. 10,000 ohms. I used the 20K ohm setting on my multi-meter to test this.

IMPORTANT NOTE: You should fully disconnect your coil from the vehicle prior to testing.