Majestic Moose

Yes that seems correct, though I don't remember if there is a direct link between the starter and alternator. I think they are connected through the 14 pin connector.

Socal_Tom

Thanks!

Actually got an injection pulse this morning, nothing changed except battery on trickle charger overnight and I reattached the + and - battery posts. The pulse on the Noid light was pretty faint - I'd expect it to be brighter like it is when I tested it off the car. That suggests bad power or ground to me. I have power and grounds checking out on the pin out, and AFC relay is fine and no change when I jumpered it.

Will try cleaning all of those a third time and running an additional battery ground and see if that helps.

Socal_Tom

Picked up two new fuel pressure regulators and installed them. Mark/Tom didn't have a damper handy, but I pulled mine off and sprayed some cleaner though it and it ran clear into/out of all three openings. I know that isn't a formal test but at least it wasn't blocked.

Have had the battery on a trickle charger overnight, still not 100%. It is likely that some of my electrical issues were simply the battery being run down.

Form a line to give me a dope slap related to the battery being run down when I was testing....

Rob Edwards

The easy solutions are the best solutions, even if arrived at circuitously.

Ladybug83

Not sure if you've already tackled it, but if your waiting for the battery to charge, you may want to pull the CE panel in the footwell and clean all the contacts.

Although they are already marked, I mark each plug with a sharpie as I unplug it from the panel. They are all lettered A-Z. Then once it's all disconnected (including the ground wires at the top) unscrew it, pull it out and take a picture of the relays before pulling them out. Make sure to label any other connections before unplugging. I like to take pictures too for later reference.

This is good opportunity to inspect the wires on the back of the panel for damage or "modification" make any repairs, check the relay orientation against a picture from the manual (or Alan has them too I think) and clean each contact. I used a fiberglass pen to scratch them clean on both sides, then a drop of DeoxIT D100L on each contact (male & female). Reassemble. I found a relay out of place, and a jumper wire attached to the wrong contacts when I did mine. Also some hack radio wiring seems almost a given on most of these old cars.

Also clean and deoxit the ground contacts above the panel before reinstalling. Clean all other grounds throughout the car as well if you haven't already. It can make a big difference. A new ground strap at the battery is recommended. And a new ground from engine block to body as well.

Tedious but easy and rewarding work. Just go slow and take photos and notes so it goes back together correctly.

Another thought, if that doesn't help, you may want to think about unsheathing your wire harnesses for inspection and repair. Another tedious job, but worth it to know everything is in order. I've done it on two cars now and both times I found small repairs to be necessary. New sheathing and new connectors are cheap. Mostly a time investment.

Also, check for the red light to come on the bottom of the volt gauge when you turn the key to the "on" position (not start). If it doesn't, that means something's amiss in the alternator circuit. Could be just the bulb in the gauge, but the bulb actually completes the exciter circuit and if it's burnt out, the car will do wonky things. Removing the pod and gauges is again, tedious, but not that hard and there are some great write ups to guide you along.

Keep it up.

Socal_Tom

I get a light below the volt meter when it switch the ignition on.

I pulled the CE panel and nothing looks burned or obviously hacked on the back of it.

I am using a replacement FI harness from one of the big 3 vendors.

I've used two different ground straps to the battery, both cleaned. Leads from positive side of the battery are clean and I have 12+v at the injectors and pin out reads correctly.

I'm going to check volts at the injector when the starter is engaged - long shot but wondering if the draw from the starter is dropping the rest of the system below what is needed. Like I said, lomg shot because I think I am dealing with a ground issue.

Socal_Tom

OK gentlemen - I think I found the issue. I have two bad FI harnesses. The one that was one the car was bad, and it turns out the replacement one is bad too.

The one that was on the car never got the noid light to fire, it was also showing variable resistance.

The replacement one briefly fired the car, then didn't, and now after pushing on the connectors on the drivers side and movingnthat side of the harness around the noid light faintly pulsed. After moving it again, it didn't.

I think this is my key issue - they're will be others for sure - but this is a big one.

I suppose now I need to pull this harness off and deal with the short.

bigd64

Kind of a long shot. Most fails are in connections. Oxidized contacts and such. Have you tried running a gnd from the cam cover to the battery?

Socal_Tom

Good morning, thanks for the response and idea. I have done that based on much appreciated coaching that I've received here, pretty confident that I have located the part of the harness that needs to be addressed.

Thanks again, and welcome to the forum btw!

Landseer

Ground strap ends are not the problem on 928 usually, its actually braid corrosion at crimp and/or beneath plastic covering. Surprised evev the best of the troubleshooters on this forum. Very common for the car to evev be be disabled due to this, and intermittently.


84 running is very sensitive to timing. Can be manually set by feel, iteratively. One 13mm bolt, easy adjustment. I've chased all kinds of crazy zebras, only to find it needed a minor change to distributor position.

Socal_Tom

I think we should make this part of a standard no-start test if no injector pulse.


I checked my timing, in the range but not optimized. It will be a good day where I can worry about that!

Landseer

on leakers, the ground strap corrodes on the hatch side. On dry cars that sat, maybe those on tenders, the presumption is that battery related gas or fluid conducts into the battery side. both cause same issue. Voltage might test fine, but it wont pass enough current at certain conditions. Can actually take running car down when hitting a bump. Can act perfect, and be totally dead 5 minutes later on a restart attempt. Can show 12.7 volts between bat teminals, but only 3 or 9 or 12.4 or whatever, less than 12.7 from positive to shock terminal.

Not usually an injector test check, though ground strap / grounds are first item on ljet test plan in WSM..

Sounds like you are making some progress, but not sure your harness is the problem you think it is. Usually they work or are shorted and don't work. Might get wonky with heat, but again, usually all injectors work or don't. No in between. But you sound like you have a pretty good handle on this!!!

Landseer

Good work btw, keep posting up the solutions as you see them, it brings 16V stuff back out to the surface in a better format for all of us including the 16 v guys that follow you!!!

Socal_Tom

Did a fuel pressure test, was at 36 PSI.

I believe the manual calls for 2.5 bar +/- .2, which I think translates to 36 PSI.

Is so, then I think I can call at least this part good. It's the only part, but hey, I'll take it.

Need to source yet another FI harness apparently.

Socal_Tom

Well, not sure I am good on fuel pressure. Pressure builds quickly but drops off quickly too, sometimes instantly when the pump is shut off (I am using a jumper on that relay for testing). That suggests a check valve problem I believe, since the damper and regulators are all new.

I am also getting a FI pulse now on the Noid test light on #8, significantly brighter than before. Need to check the other batch fired for pulse.


Still not running except on cold start and fluid however.