whalebird

You may be onto something here rus. IIRC the sensor stud is like a set screw as Scott posted??? My mind is clouded with visions of 944 parts however...which does use a "setscrew" instead of the cheesehead bolt.
paintmark was probably put there during an earlier service out-of-car. #12 is used for tuning only using the factory equip. Non functional to us in the field.
I don't remember, again, but the sensor screw for the referance sensor is not set at TDC. I think if you set TDC(front pulley/dist.) you will not be at TDC via the sensor...it may be some 12* advanced or so IIRC.
Worldpac lists 3 different flywheels all aftermarket:
OE aftermarket with sensor bolt as per your photos
OE aftermarket w/o ring gear (California??)
OE aftermarket (except California)
a search thru PET and confirming the right sensor screw(in the flywheel)would be the next-first step.
Cheers

Lorenfb

"but there is this intermittant problem of the fuel pump running with the engine off and key on.

I'm wondering if the reference sensor gap is off."

The reference pin issue will not cause the fuel pump to run in the no-crank mode.
Also, the gap of the reference sensor is not that critical, i.e. It can be off +/- 1mm or so.
The gap affects how fast the flywheel must turn before an adequate signal is generated.
So an improperly gaped sensor will only have an affect with a very low battery and in a very
cold environment.

Bottom line;
As is typical, when one source of a unique problem is found, it is assumed that it now
affects all other problems one has with their Porsche. Have to love the internet!

whalebird

^^^thats good info. I know on the 944 side of the universe, people obsess about the gap. However, the latest findings are relevant (stainless marker??)
As for the fuel pump's deal, This may be a "multi headed dragon" kind of problem. Fix the obvious and see whats left. That red relay in the trunk? maybe?
Rus, when it's back together and ready to crank, try to duplicate the pump-running issue. If you can get the pump to run when it's not supposed too, yank the fuse, pull the red relay(it is red, not black?), jiggle the key, etc. Certainly check all the grounds - under seat, trunk, engine compartment etc. Remember the ground cluster on the intake manifold Doyle diagnosed after his epic engine-pull? Similar "hunting" at idle etc.

Lorenfb

"If you can get the pump to run when it's not supposed too, yank the fuse, pull the red relay"

DME cars don't have a separate fuel pump relay (red). It's in the DME relay.

whalebird

My bad. I shoot from the hip at times; disregard my misinformation.

Another hip-shot, doesn't two of the plugs(throttle switch/idle control, AFM or somesuch) interchange??? I doubt the car would run as it has if this were the case, but a general review would be prudent given the recent disassembly.

Lorenfb

"doesn't two of the plugs(throttle switch/idle control, AFM or somesuch) interchange???"

The idle/full load switch has only 3 pins, the AFM has more.

rusnak

There is a fuel pump fuse though, in addition to the dme relay.

I'm focused on the no start issue for now, but I am going to follow WB's lead and see if a switched circuit is touching the fuel pump circuit at some point either at the fuse panel or the ignition switch.

If the gap is not too critical, then I'd rather try it on the large side for safety.

rusnak

Yes, the reference and speed sensors do interchange. Luckily, I marked them properly before disassembly, so they were connected the same way as the factory had them.

whalebird

I think it's common in the field to epoxy a washer (for maybe a 4mm bolt) at the approx .8mm thickness to an old sensor. Install it touching the screw and adjust the sensor housing accordingly. then just install the new sensors.

rusnak

Yup, that's if you have the engine still in the car. I found a ~.85mm washer and glued it on one of my old sensors yesterday, that way today I can do the re-installation without a feeler gauge. I think I'll use the same sensor on the reference sensor gap, that way I can be sure that the reference sensor is set to the minimum gap before I hit the starter.

I used black silicone to glue the washer, that way I can save the sensor if I need it later for troubleshooting.

rusnak

**** UPDATE ******


I had time to sneak away from work and install the correct reference bolt, re-gap the sensors, and the motor purrs now. I mean, it is running PERFECTLY.

I forgot how much I like this fuel injection system, and how much I love the sound of that engine when it's running right. I don't think it would be possible to get the system to function any better than it is now.

I was thinking about that little reference bolt though. Can you imagine how many Gs are being pulled on that little bolt head at say, 6,000 rpm? I hope it was ok to tighten that thing down all the way. It looks spindly.

Anyway, time to adjust the shift coupler and give her a good wash and detail tomorrow. Back to work now.

whalebird

Outstanding. Go drive.
Stella from me to you...cheers.

User 4221

Glad to hear it, Rus!

rusnak

###### Second Update #######

Car continues to run flawlessly, and the strange fuel pump problem went away too. The fuel pump fuse is downstream of the dme relay, which is powered by the dme. As I mentioned, I keep a second brand new DME Motronic brain on hand solely for troubleshooting in cases like this. Both brains were triggering the fuel pump with the key on, and engine stopped.

It could be possible that a failure mode for intermittant ref sensor signals is that the dme might run the fuel pump. Could there be onboard memory processing that causes this? I'm not saying there is a link, just reporting what I'm seeing.

Lorenfb

"Could there be onboard memory processing that causes this?"

Remember, the fuel pump relay is not only energized once the speed/ref signal occurs,
but also when the #50 from the ignition switch/starter solenoid applies power to pin 4
of the DME ECM. Any signal noise or a poor ground on pin 4 will cause the fuel pump
relay to energize, thus running the fuel pump. A voltage as low as 4 volts on pin 4
will cause the fuel pump to 'run'.