Instrument Cluster - Hard Start and not Functioning

[SanDiego928]

Last year I fixed the starter problem and replaced the intermediate steering shaft (cracked) and all bearings. I put the pod back in and gauges are not working properly and it is extremely hard to start.

I unplugged each one of the 3 connectors (1 at a time) and with each removal the car started more easily and ran better. Starts immediately with the 3 connectors not connected. I plan on trouble shooting by using just the cluster and plugging each connector in 1 at a time and see what is happening.

Is there something in these connections that would cause the hard to start condition?

Any suggestions for trouble shooting the non-working gauges and hard start condition? A person told me that the top connector excites the alternator so unconnected the battery will drain while driving, any truth to that one?

I would like to get this working and pass smog so I can enjoy the 928 experience once again.

Thanks, Mark

1981 5 speed

This is an auto to manual conversion by a Indy Porsche shop owner here in town. Just an FYI

[5l32v4c]

This is a real shot in the dark. I had a hard starting issue myself not so long ago and it turned out to be a loose connection (in the engine bay) to the temperature sensor. If the computer can't work out the temperature, it can't configure the engine properly to start. Could it be that the temperature guage connection is where the issue is? Again, this is a wild-ass-guess, but it's something to consider.

While I think of it, another signal the computer needs to start the engine comes from the flywheel sensor which also feeds the tach. I can see why bad connections at the pod could, theoretically, cause starting problems.

Check to see if your fuel pump is spinning when you try to start the car. The computer will not send voltage to the fuel pump unless it has input from various sensors. If you have someone crank the car while you have your hand on the fuel pump (under the tank) you should be able to feel if it's working. If the fuel pump does not spin, also check your fuel pump relay as these can randomly go bad and have you chasing your tail. On my '85, the fuel pump relay is the same as the horn relay, so you can swap it out for troubleshooting. Trying to troubleshoot with a relay that is starting ot fail can drive you nuts as it might work intermittantly.

[SanDiego928]

^^^^^ thanks for the info, much appreciated and I will check into your suggestions. Before removing the instrument cluster last year for the steering shaft fix all instruments were working properly so I was thinking that it should be definitely related to the instrument cluster connections but you never know with this old semi-molested car.

Mark

[stepson]

Mark,

Check that the 3 connections on the back of the pod are connected to the correct 3 plugs. IIRC, the car will not start if they are inadvertently swapped.

IIRC, the plugs are marked. Even if they aren't, you can look at the wiring diagram and find out which one plugs into which socket by wire color and function.

[tmpusfugit]

the car should run with all 3 connections unplugged. As it is an '81 it has no flywheel sensor, so that is not the issue. I would unplug all 3 connections and see how the car starts and runs. In my limited experience I don't see any path where the instrumentation would cause the problems described.

[SanDiego928]

Originally Posted by stepson

Mark,

Check that the 3 connections on the back of the pod are connected to the correct 3 plugs. IIRC, the car will not start if they are inadvertently swapped.

IIRC, the plugs are marked. Even if they aren't, you can look at the wiring diagram and find out which one plugs into which socket by wire color and function.

Hi John - The instrument clusters 3 conn. are connected to the plugs as I found them. The wires are semi-permanently routed due to age (wire stiffness shows they are correct) but they could be mixed up from way before I got the car. The car always had been hard to start but ran good before removing the pod and all gauges worked very well.

Last week I was able to start the car with much cranking of the starter and I mean a lot of cranking and engine ran badly for about 15 seconds with all 3 connectors connected to the instr. cluster.

After unplugging the 3 connectors the car started immediately on first turn of the starter and ran much better and even sitting for a few days. The flexible ribbon circuit is in need of some repair and maybe shorting somewhere perhaps. Ill take some pics later to share.

I will take notice of the printed names on the ribbon circuit and will check the connectors for any markings so I can match them up, thanks for pointing that out.

I may need a wiring diagram for a 1981. The instrument cluster is for a manual and the car was an auto if that makes any difference.

Mark

[SanDiego928]

Originally Posted by tmpusfugit

the car should run with all 3 connections unplugged. As it is an '81 it has no flywheel sensor, so that is not the issue. I would unplug all 3 connections and see how the car starts and runs. In my limited experience I don't see any path where the instrumentation would cause the problems described.

Yes, with all 3 connectors unplugged the car starts immediately and runs very well. With all 3 connected, has a lot of trouble starting and no gauges seem to work correctly.

I will try some things that John described above for mixed up connectors to plugs and clean the copper edges of contact points and spray some cleaner into the plugs.

Mark

[SanDiego928]

Connecting the 5 round plugs into the pod and then connecting the 3 connectors to instrument cluster is a real ***** and I needed the wife with smaller hands to help out..... Oh my gosh.... I am sure it gets easier with practice which I am getting....

[SanDiego928]

Fixed - my mistake. I mixed up the right and top connectors. It was a year since I took the POD apart to get to the steering and I assumed I knew which was the correct ones.

Now onto final installation of POD and then smog test. I am hoping the new CAT from 928intl. will take care of any issues hopefully.

[stepson]

I hope that you have now correctly marked the plugs so this issue never arises again.

This kind of thing can just drive me crazy.....and that's not a long drive.

Glad you figured it out.

[tmpusfugit]

I fought a bad ground wire connection in the pod connector for 5+ weeks of on and off testing, chasing wires all over the car, reading the so called '84 schematic, and trying to figure out why the instrument panel had so many goofy readings that made absolutely no sense. I must have had the panel in and out 20+ times....got pretty quick about it and finally just left everything hanging until one day I noticed the prongs on a wire in the connector itself were spread apart. Bingo, they were not connecting the ground yet all my testing of the grounds showed good because I was cramming a probe into the already too spread apart wire connector. Made contact with the probe just fine, did not make contact with the mating pin in the other connector.