930 electrical gremlin

[VA Turbo Guy]

When I installed a fresh battery in my 1989 930, the fuel pump came on and the starter tried to crank the car with no key in the ignition! I disconnected the ignition switch completely and the same thing happened. I have eliminated the starter solenoid as the problem. Also believe the problem is between the electrical box in engine compartment (left side of engine) and starter/fuel pump. The problem apparently started when car was sitting in garage due to discharged battery. The car is driven maybe once a month and has 22,000 miles.

[javadog]

Disconnect the electrical portion of the ignition switch and see what you find.

I don't think it will have anything to do with the rear relay/fuse board.

JR

[T77911S]

with problems like this there is one important question. what else did you do to the car.

rats have chewed on some wires.

how did you eliminate the solenoid.

[VA Turbo Guy]

OK here's the complete story:
1. Removed original radio from car for repair - car ran fine
2. Connected Optima battery minder to Optima Yellow Top batt (as always when car sits) - no problem
3. Few days later took radio amp (under passenger seat) out for possible repair
4. Few days later noticed a "fault" indicator on batt minder - would not charge with battery in car
5. Took battery out and hooked up minder which (a) showed a deep discharge and (b) eventually achieve full charge
6. Put batt back in car and when neg terminal touched post the starter and fuel pump were energized - obvious reason for discharged batt!
7. Disconnected three accessory wires at + terminal on Batt - same thing
8. Completely disconnected electrical connections from ignition switch (or at least think I did) - same thing
9. Disconnected yellow wire at solenoid - fuel pump ran but starter didn't (believe that would indicate that solenoid not stuck???)
10. After disconnecting plug at rear of fuse/relay box at left rear of engine bay - silence
It is certainly possible that a mouse/rat/squirrel chewed on something but I have an an exterminator keep bait etc. in garage since i bought the car in 1999 and haven't seen any evidence of vermin of any kind in that time

I'm generally convinced that some wires are fused together somewhere, "probably" between the rear fuse/relay box and fuel pump and starter but wanted to see if there might be something out there before taking the intercooler off or worse!

[SpyderMike]

In my 1985 normally aspirated car that I just rewired, the closest location for the two systems (other than the ignition switch) is in the trunk near the fuse panel. The starter wire from the ignition switch is yellow medium gauge. It comes from the bulkhead behind the dash and it passes down through the hole below the fuse box in front of the brake booster where it enters the central tunnel and goes the the starter. The fuel pump wire exits the fuse block and passes down to the gas tank area to the pump.

Both are powered through the ignition switch. The fuel pump is powered through the DME relay then to the fuse box then to the pump. The starter power goes from battery to ignition switch to starter solenoid.

Interesting to note the the power feed for the radio at the ignition switch is yellow and is hot in all key positions but off. The starter solenoid power feed is also yellow but only powered in start position. Did anyone possibly switch these wires while work in on the radio? Is the electrical portion of you ignition switch plugged in correctly?

See here:

understanding the ignition switch

[pors1968]

Did you try to start your car with low volt battery .The starter selenoid might stuck and you have voltage to system throught yellow wire.

[T77911S]

at fuse 8, there is a red or blue wire.( i cant see the color on my diagram), (its blue on the 86).
remove that wire and see if the FP runs.

power goes from the ign sw to the fuse panel. it does not go thru a fuse. it feeds power to the FP rlys to energize them and it feeds power to the speed rly. it also feeds power to the delayed action rly that keeps the ignition on for a few seconds after you turn the key off.
i believe the wire from the ign sw is red/blk.

it looks like there is a 6 pin(?) connector after the ign sw you could unplug but i dont know where it is. that would further isolate the ign sw.

[SpyderMike]

The six pin is most likely one of these through the bulkhead underneath far left of the dash (in the background):



Here is the ignition switch pigtail:

[gomezoneill]

In the engine compartment on the left side remove the black cover for the relays and fuses. Replace the round relay on the rear of the panel see if that cures your problem. Had the same issues your having with a 77 930 I was working on. Don't remember the correlation though.

[SpyderMike]

ran across this on another thread about a 1987 930 that wouldn't start about the round relay:

The mystery black relay in the engine compartment does indeed play a role in the power supply to the oxygen regulator/sensor/lambda circuits. I was mistaken when I thought it caused my fuel pumps to shut down when removed. I had forgotten that I still had the lambda frequency valve connected (even though I don't have the O2 sensor itself hooked up), and when I pulled the black relay the pumps continued to run....but the awful racket of the frequency valve suddenly stopped(in my frustration the other day I mistook that for the pumps running). So, mystery solved...your frequency valve will not operate with the black relay removed.

The more I think about this issue, the only place both start circuit and fuel pump circuit are connected is in the ignition switch. If you are not sure you disconnected this, then you may not have isolated it. Were you able to pull the back of the ignition switch from the mechanical switch:



This video shows you how to replace the part of the switch that could have failed:

https://www.youtube.com/watch?v=DmBrBf0y0QU

[VA Turbo Guy]

Thanks for responses - I'm out of town and can't do anything until next week. Will do some additional trouble shooting and see if I can apply some of the suggestions.

[VA Turbo Guy]

When I got back to troubleshooting here is the current situation:
1. Ignition switch completely disconnected from electrical system
2. Car does not crank now after sitting a week plus (it DID try and start about 10 days ago with ignition switch disconnected - I have a witness)
3. There, however, now strange "electrical noises" coming from area of fuel pump - it now appears that FP is not running and may be kaput
4. When the engine wire harness is removed from the relay/fuse panel from at left rear of engine bay, connecting NEG terminal creates clicking noise - apparently coming from one of the aluminum relays (?) NOTE: on this panel are what appear to be four relays, a round red one, square yellow one and two aluminum ones (these two bolted to the support bracket); there are three fuses on the side of the panel. The clicking noise continues with both the yellow and red relays removed. I haven't had time to remove the two aluminum relays. NOTE: I can't find any black relays in engine compartment as mention by SpyderMike

ADDITIONAL NOTES:

1. I forgot to mention that I did wash the car several days before the problem appeared.
2. I can find no evidence of any vermin activity thus far
3. I have had some on-site assessment and advice from a very experienced Porsche 6-cylinder (air cooled) mechanic (including Turbos) who is the first to admit that while he knows a lot about the mechanical stuff, he is not that knowledgable about electrical issues. I'm worse yet.
4. The above rebuilt the motor several years ago and removed the emission control gear. There have been no issues until recently.
5. I will next follow up on some fo the suggestions mentioned earlier
Thanks

[VA Turbo Guy]

Update:
After looking at electric diagrams, concluded that problem could be in alternator (bad diode?) so when removing alternator, discovered that severe electrical meltdown occurred in engine wiring harness - all wires in vicinity of alternator (between fan shroud and alternator) were burned through (except ground wire) and there was significant scorching of the shroud. It appears that there is also some melted wires outside the fan shroud but the intake manifold and associated widgets have not yet been removed so full extent of damage not known - nor is the cause of the meltdown? Visible damage explains what was going on RE fuel pump and starter!

Does anyone know where to get an engine wiring harness? Believe part no. is 930-607-016-01 and it is no longer available from Porsche.

Thanks

[Ronnie's.930]

^^^

Dennis (timmy2) makes wiring harnesses, connectors, etc. I've never bought from him, but would in a heartbeat as I have seen many pictures and very positive commentary regarding his work over the years.

Pelican Parts Technical BBS - View Profile: timmy2

[RSTarga]

Timmy2 here can rebuild your harness

[Bob Kontak]

Originally Posted by gomezoneill

In the engine compartment on the left side remove the black cover for the relays and fuses. Replace the round relay on the rear of the panel see if that cures your problem. Had the same issues your having with a 77 930 I was working on. Don't remember the correlation though.

Aside from the cooked harness, I think this is good approximate information. Perhaps just hip pocket info for now.

I tried jumping the fuel pump relay the wrong way. I wrapped wires around the legs of the FP relay and plugged it in rather than jumping the holes in the female socket. Starter engaged. No key.

As gomezoneill says, not sure of the correlation, and that is the same for me. I could do research and explain why, but you can do that too. Probably best you do the grunt work for your comprehension of what you are faced with.

The 930 has two fuel pumps. I don't know if they have two relays or one relay with two fuses.

Timmy2 can whip you up a harness.

[Ronnie's.930]

Originally Posted by Bob Kontak

The 930 has two fuel pumps. I don't know if they have two relays or one relay with two fuses.

Two relays and one fuse in OEM, dumbass idea, trim, Bobasoaurous.

[javadog]

They have a second fuel pump fuse. It's the one in the pack of spare fuses that you install when you also install the new fuse holder block, once the original part has gotten hot enough to ruin it.

JR

[Bob Kontak]

Originally Posted by Ronnie's.930

Two relays and one fuse in OEM, dumbass idea, trim, Bobasoaurous.

Speaking of trim, how many years since you got some?

[Ronnie's.930]

^^^

Ask yer sister, Bro!!!!

Javadog; ha! Yep to the "2nd" fuse!