924Board.org

[brian19600]

Here are some links to fpr discussions:

http://www.924board.org/viewtopic.php?p=289748

http://www.924board.org/viewtopic.php?p=289747#289747

http://www.924board.org/viewtopic.php?t=29881

http://www.924board.org/viewtopic.php?t=10360&highlight=rpm+limiter

http://www.924board.org/viewtopic.php?p=188463&sid=8b16fa541b0f2f16042f9439cdf45cc9
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78 924

[j03k64]

Brian, I figured it was likely a safety oriented feature to avoid the whole burning alive scenario... will check the links above! I only found one post with reference to the 3.300.300 on here during search. Thanks!

Neither of my cars function like this. The 79 (and this 80) both pump with the OEM relay in place, when the key is turned to Position 1. No need to crank the engine over. The OEM relays both had the ground tab on them. It may be the normal function now, but that hasn't been the case on my 79 for 16+ years now. I always let it pump until the pump tone changes and then crank it over, unless it's hot of course; starts flawlessly. Is that odd?

I managed to break both OEM relays while restoring this car (spring died on the 80, broke the solders on the one I borrowed out of the 79), so I'm stuck with the safety oriented relay now on both cars now. Maybe they were weak - not sure if that would allow them to trip more easily when you tumble they key?

It'll throw you for a loop if you're trying to troubleshoot the fuel pump and not use to it functioning like that - that's for sure! At least everything is clean now?
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1979 Porsche 924
1980 Porsche 924

[brian19600]

Strange!
Mine being a 78, the fuel pump will only operate when that air flow flapper is open.

That being said, when I was doing extensive cleaning up of the wiring and all the grounds (under the dash and engine), the fuel pump would run whenever the ignition was turned on. There were a few grounds and some of the fuel injection wiring disconnected.

I noticed it continued until everything was all back together. I did replace some of the fuel injection wiring so there could have been a short somewhere?

I just found out in a post somebody made last week, that with the ignition off, if the turn signal is on, the lights on that side will come on! I thought something was shorting on that side-until I checked the turn signal and problem solved lol.
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78 924

[j03k64]

Haha, I'm glad I don't have the flapper system on either car. I've heard it's a bit 'relativistic' when troubleshooting!

I found a spare in my bag of relays; I couldn't find the one in the shop trash. I'm pretty sure it was exactly like this. KRACKER AG <K> Audi - Kraftstoff fuel pump relay 24.1000.10. Looks like it was broadly used on Audi cars.



You're theory of a short somewhere may be legit - the fuel solenoid or HSV that might be dead is unplugged, yet I still have a strange electric noise coming from beneath the car. I'm thinking it might be the diode?

The CIS is contaminated, the fuel distribution head spent the weekend in an ultrasonic cleaning tank. The screens in two of the injectors are plugged up; I pounded the gunk out of them yesterday and put them in chemtool solution overnight. Fingers crossed...
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1979 Porsche 924
1980 Porsche 924

[j03k64]

Some good progress (delayed as per normal by work), now rather stumped...

I got the fuel pump relay situation sorted, ended up cleaning the fuel distributor in an ultra-sonic parts washer for a weekend, brand new injectors. Fuel system checks out.

Set timing to TDC, bumped it clockwise ever so slightly to try for -3. Spark wires all check out. Pushed it out of the shop and it started straight away. We ran it for about 15 seconds with the cam cover off to make sure that it's oiling the cam properly; all good. Pushed it back in as it was getting late that evening.

The next morning we were going to do run in. It won't start.

It cranks fine, battery is topped up, fuses are all fine, timing and wiring have not changed. I pulled the plugs after a few tries and they're flooded. It didn't pop at all, so assumed no spark; checked it with a tester and did not see spark. I had this happen before on the '79 and it was the coil; so I tested it. Tested it, a bit high from 1 and 15 (wavering at 1.3-1.5ohms), 1/15 to 4 is 7.48ohms. Checks out, but swapped the fresh coil off the '79 to this one to be sure. Nothing, other than it seems to crank slightly better?
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1979 Porsche 924
1980 Porsche 924

[j03k64]

Did the distributor, coil, ignition control unit troubleshooting in the Haynes manual today; all tests are within parameters. Swapped my dist cap and rotor to see if that was causing the issue; still no change. Used a spark plug, not the tester to check for spark - very weak faint yellow/orange spark - got slightly shocked in the process holding the wire?

Any ideas why it would start, run and now not function under these conditions?

I'm out of thoughts...
Ground causing weak spark?
Maybe the distributor pickup is dying? Tested okay at the ICU... obviously that's not under load. It's the reluctor type, not the hall sensor.
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1979 Porsche 924
1980 Porsche 924

[brian19600]

Intermittent ground/power problem? I can't imagine if starts and runs one day and not the next, that it is something major. Maybe try running power and ground jumpers right from the battery to rule out things?
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78 924

[j03k64]

Yeah, I was thinking intermittent ground causing weak spark. I'm going to replace the negative battery cable and make sure that ground point is clean. I'll double check the others.

I had an epiphany at work today. I put dielectric grease on a few of the grounds and electrical connections to prevent corrosion there in the battery box and the connector on the ICU box (as the plug is hard to insert). Perhaps that's causing issues by acting as an insulator?! I didn't think about it at the time, but dielectric grease has been known to impede high voltages (whereas it works fine on a hard to insert relay). Should probably clean that off and test it...

It has to be something stupid, I'm out of smart things. It's always humbling working on this thing.
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1979 Porsche 924
1980 Porsche 924

[j03k64]

Right, so cleaned off all the dielectric grease... don't ever do that.

I pulled the starter, had it tested; it's dead - assuming I fried the solenoid? I had a new starter on the shelf, installed it. The + battery cable was damaged/funky, replaced it. Cleaned up and confirmed the T3 alternator harness wiring for continuity; sewed it in a heat protective fabric. Ignition switch tests as okay, inspected it and the plug - all good.

Gave it a try... still dead as all hell.

If you turn the key on and bring the headlights up, they are bright. If you turn it to start and they go black; lights come back on when you relieve they key.

Assuming bad ground/s if all that's ruled out? Anyone know which are most suspect for this behavior? Or alternative ideas? It's just interesting that it would start, run gorgeous, then be dead on the next go...[/b]
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1979 Porsche 924
1980 Porsche 924

[Paul]

Sounds like a battery or grounding issue....double check engine ground (run jumper cable from negative post of the battery to the block).
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[brian19600]

Has the problem changed from no start to no crank? I wonder why the starter or starter solenoid failed?
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78 924

[j03k64]

Yes, changed from a start, to a no crank scenario.

I think it had enough residual ground to start initially from us cranking it during restoration, when it finally swapped to alternator power, it likely fried the chassis ground. I'm not even sure where that is located in an unmolested stock car. I would love to put it back there if anyone knows!

I picked up two insulated cables today. Planning to replace the exposed braided ground cable at the distributor bracket to the head; it's way too close to the fuel lines for comfort. I'll reground the block to the chassis tomorrow. Will let you know how it goes!
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1979 Porsche 924
1980 Porsche 924

[Paul]

Did you try using jumper cables from the negative battery post to the block? Easy way to find out if its a grounding issue.

The braided cable is the stock ground.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[j03k64]

Paul, I tried your trick with the jumper cable without result. I ran it from the negative battery post to the alternator bracket; later realizing that the bracket might have been painted during restoration.

I replaced the stock braided ground cable at the distro with an insulated one. I ran a second insulated ground cable between the AC mount and chassis. I also installed a third redundant ground. It's definitely grounded now!

Turn they key, still won't crank.

I swapped the ignition switch with a spare out of my parts bin. Same result, no crank.

Tried the headlight test to see if the result was any different. The lights still go black at start position, gauge lights still remain lit. This time the headlights failed to go down. The headlight motor, relay and MOLEX connector got very hot; unplugged it and the washer unit because it's on the same harness. Not sure why it's sending so much juice to that point...

Confirmed 12v to the starter's main post.

The black ignition switch signal wire shows zero with the switch off, 6.05v at 'on' and 'start' key positions; I swear I read somewhere that it needs to be 8v to trip the solenoid? Can anyone confirm this to be true?

According to the Haynes manual, there's a ballast resistor between the ignition switch and starter solenoid (the black ignition switch signal wire that tested at 6v). If it takes 8v to trip the solenoid, I'm assuming that this resistor has failed. It also fits my original thought that something 'solid state' died after first startup.

Interestingly, I have yet to find the mysterious ballast resistor in either of my cars after sixteen years. I do not have a transistor box, insulated terminals on either side of the coil, or the odd tower resistor depicted in the Haynes manual.

Can anyone direct me to it's specific location, so I can inspect it?
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1979 Porsche 924
1980 Porsche 924

[Paul]

Your car uses a fusible link which is built into the black wire's circuit. This wire does not go to the ignition switch, it goes to the ignition coil. You've already tested it.

You need to find your red/black wire and connect it properly.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.