WallyP

Have the intake and water leg been powder-coated? That can prevent the Temp II sensor from being grounded.

Have you tried jumpering the fuel pump relay and the injection relay at the same time?

Are all wires on the positive post clean and properly attached?

If you use a mechanic's stethoscope on the injectors while the engine is cranking, do you get one click per engine revolution? No click = no run.

hwyengr

I wasn't joking about the tach wire. The CPS signal from the EZF feeds both the tach and the LH trigger. If theres a short in the tach, the amplitude of the signal to the LH trigger can decrease below the level needed to turn it on.

Bill Ball

We've got good spark, at least we did when I saw the car a few weeks back. So, to me that ruled out the CPS. Am I wrong? The injector leads did not fire as tested by noid light and observing dry spark plugs. We did generate fuel pressure when we jumpered the fuel pump relay, but with the injectors not firing, nothing useful happened. Hence, the suspect LH, as I mentioned, which was rebuilt but failed to fix the problem. So, anyway, it may be the LH is not getting the tach signal from the EZF. We didn't look at that specifically. I've not seen such a specific harness or EZF failure before. I've seen many injector harness shorts, primarily under the plug boots. That will take out all the injectors, as we see here, but that does not account for the fuel pump failure to get a trigger. The LH triggers the fuel pump. I suppose we should now trace that path back through the LH and EZF. Did not look at temp II, because we have problems beyond just hard starting. We need to get the pump running w/o a jumper and injectors firing first.

dr bob

Basic check for +12V at the injector harness while cranking. That confirms connections from the battery through the relay and such. Injectors, fuel pump, and more depend on great connections of their feedwires at the positive battery post. More than a few erratic operating conditions have been cured by cleaning and securing the smaller wires at the battery. Two of your symptoms (injectors and fuel pump) have those feeder connections in common.

Verify fuel pressure with a gauge. "It dribbled out of the rails OK" is not a valid pressure check. I had pumps running, fuel in the rails, and no start. Caused in my case by a weak fuel pump relay, diagnosed with the fuel pressure gauge. I modified a rail cap to accept a GM-style gauge fitting for testing, and used a H-F fuel pressure gauge kit. No magic or big cost to have this setup in your bag of diagnostic gear. Considering the car's history of extended storage, it's not unreasonable to suspect the fuel pump itself if pressure is low after all wiring is confirmed.

You can pinch the fuel return line at the rear of the engine if pumps are running and pressure is low, to check for a failing fuel pressure regulator.

Once +12V is confirmed at the injection harness, the Noid Light comes into play to confirm that the LH is grounding the low side of the harness. If it isn't, unplug all the injectors carefully, then use your DMM to verify that there are no shorts in the injection harness itself. Simple Ohms check from the LH connector in the footwell. Injectors are about 16 Ohms each, so you should see about 2 Ohms with all injectors connected; zero Ohms with them connected or disconnected means a short. It's difficult sometimes to see the difference between ~2 Ohms (OK) and ~zero Ohms (shorted) with the injectors connected.

Replace the LH and Fuel Pump relays if you haven't already.

vanster

I would have replied sooner but I went to the Rennsport event ( very cool) .
I am going to replace the Temp 2 sensor

This yellow wire has been cut under the ignition. Why would someone do this and where does it connect?

VehiGAZ

Oh man, Van! It's "Bill Clay" from BaT... I'm "VehiGAZ" here and other automotive forums, and "Bill Clay" on other sites.

You are really in for a challenge! Try not to jump at quick fixes. Whatever is ailing this car is a real stumper. Keep an open mind and consider that it may not be a problem anyone here has seen before.

The ends of that yellow wire don't look like they would reach each other. Perhaps they were connected with an in-line fuse holder or butt-crimp but not anymore?

My only useful advice is...

1) Double- and triple-check the relays and their positions by part number. The IX and XI relays in my car were inadvertantly switched, creating a devilish scenario in which a sticking window switch was killing the battery (it's not as clear as it seems which way those carets are pointing or which way the Roman numerals are printed!).

2) I would suggest to disassemble the under-dash area to get at the dash wiring and remove everything associated with the old alarm.

3) Do what Bill says - always!

Good luck!

harveyf

I had the pleasure of viewing all the Concours cars at Rennsport Reunion last Saturday with Vann. We figured that there were about a billion dollars of cars out there. No joke! When there are 50 unobtainable cars lined up it could reach those figures, if they were for sale.

Whatever, we of course discussed Vann's no start. I gave him a copy of the Porsche Test Plan for 84/85/86 cars.

Vann, if you haven't already, crank the car and check for a "tach bounce". Even better, on page 15 of the test plan, you can check for a signal at the EZF plug, terminals 7 and 19. I know they call for a scope but if you get a good digital volt/ohm meter that can sample at a high rate (my Fluke does 250 ms) and has a peak capture/hold function, you should be able to capture a peak DC voltage of > 2.5 volts.

vanster

Monterey was fantastic. Porsche along with Rennsport did wonderful job putting on a flawless event.
Mark Woodsma's white '81 was the featured 928 and of course it represents the mark well.
I think there were about about 6000 various 911's and 6 928's We are very special.

Thanks to Harvey that was kind enough to bring the shop manual and Rich Andrede and all his wisdom and experience the red car will run.

The yellow wire had been cut and there was a jumper hanging from it that was cobbled on. The leak in the fuel rail I found was my error, when attaching the injectors I nicked one of the O rings. Now fixed

Here is a list of what has been done from the back

1) new fuel pump and filter
2) new relays that relate to the problem
3) repaired LH
4) repaired MAF
5) rewired and replaced fuel injector wires and plugs (Bosch)
6) injectors cleaned by Witch Hunter
7) bypassed factory alarm

Suspect bits: Temp II, odd wires under the pod ( time to take off the pod) ( it doesn't appear that the pod has ever been off0 I would doubt that aftermarket alarm installers would have done this as it would be easier for them to just hack into the ignition switch from the bottom.

Van

bureau13

Do you have access to a known good LH? I realize yours has been repaired, but if you haven't seen it work properly, I'd still consider it suspect given the symptoms.

dr bob

The only yellow wire at the ignition switch is the circuit 50 wire that triggers the starter solenoid when the ignition switch is in the "crank" position. The 1986 wiring diagram calls out the yellow color as "ge". In the attached image, you can see the CE panel connections from the ignition switch contacts. That should make it easy to see where you can test for all ignition switch functionality with a multimeter or test light.

Bill Ball

Van: Pick a day next week and I will come over to take another stab at this. I think we've eliminated all the obvious: relays, LH, EZF, fuel pump, power to these components, CPS, alarm. Maybe not.

Did the LH repair at least get the fuel pump to run un-jumpered?

John Speake

You have checked that there isn't any relay in the kick down relay slot ?

vanster

I connected the yellow wire #1, fixed the fuel leak around the injector, put it all back together, checked the relay panel with the manual ( all relays are new)
Same thing. The only way the pump will work is if I bypass it.
Now I guess it's time to pull off the pod and look behind it.

Cosmo Kramer

It's a big job, but pull the CE panel. Check and clean all the contacts that connect to all the connectors. I have seen these green with corrosion. Also, look on the back of the panel and check for any burnt wires.

hwyengr

Not sure what you're going to find under the pod. If you've got spark, the 15 bus is getting energized from the ignition switch. Everything else is down at the panel.

I still think you need to focus on the LH trigger. Everything seems to work except that the LH isn't turning on. You can buy a cheap-ish USB oscilliscope, then follow the test plan from the manuals.

Question to the group, does the EZF process the CPS signal, or does it just pass through to the LH?