Hi there!
I'm new to the community, but I've had my 928 for almost 6 years now. It's given me very few problems (that weren't my own damn fault), and I generally couldn't be happier.

However, I need to find the engine speed sensor plug, as my car isn't starting, and I've checked the fuel system and I know there is power through both the B+ terminal and the EZK relay. The next step in the manual suggests testing the signal at the EZK connector, and if there is no signal there, to check the plug on the wiring harness. Where can I find this plug? Thanks!

Supplementary info:
Several years ago, I managed to bottom the car out, and I was able to helicoil the alternator back onto the block. This fix worked for several years, but finally gave out, so I pulled the engine, took it to a welder, and got it all fixed up. Now the engine is back in the car, and it cranks just fine, and the injection system has power to it, but I get no spark. I pulled off the spark plug wires on both sides and grounded them to the block and got nothing, so the problem is clearly between the wires and the ignition computer. I hooked up the EZK terminals as per the manual to an oscilloscope, and got nothing for the speed sensor, hence my question. There is a connector on the passenger side near the front of the engine that is mounted in a bracket. The male plug partially disintegrated in my hand, but enough of the plug remains that I thought I could plug it back into wherever the hell it's supposed to go. When I put the engine back together, I had one plug from the harness remaining, conveniently with three pins perfectly spaced to fit into my now-broken connector. If I had to guess, I would say that this is the speed sensor plug, and I obviously need to replace it. However, if it is NOT the speed sensor plug, then what IS it, and where does it go?

Thanks for the help, I can provide more info if needed.

Thomas

 

What year is your car?
On my 1988 the crank position sensor plug, which I think is what you are talking about, is located in a bracket that is just below the MAF sensor center rear of engine just above the throttle cable that comes from the linkage on the side of the intake and goes down to the throttle body. The crank position sensor sits about six inches lower and six inches rearward of the bracket that holds the connector for it.
The cable from the crank position sensor is only about 16 inches long and probably can't reach any other female connector of the same design.

On mine the sensor side (male portion) also fell apart and I was able to get it plugged in by taking the female portion out of the bracket, plugging them together and then taped them up with silicon self sealing tape and it is working fine.

 

Sorry, mine is an '88 as well. I'll retry the oscilloscope test and see if maybe I had it hooked up incorrectly. That still leaves the question about the plug on the passenger's side at the front of the engine and what it is supposed to do/hook up to. Thanks for the help!

 

The plug at the front passenger side could be the Hall sensor. See if the wire leads to a sensor mounted behind the passenger side timing belt cover backing plate at the front end of the passenger side cam cover.

 

The plug at the front passenger side could be the Hall sensor. See if the wire leads to a sensor mounted behind the passenger side timing belt cover backing plate at the front end of the passenger side cam cover.

 

There are two sensors in that general area. Make sure you get the right one. The oscope procedure in the manual works great for testing, I've done it myself.

Note that a short anywhere in that circuit will result in no waveform. I had to pull W21 to get my car running while trying to hunt down the real short.

 

Be sure and check all of the engine compartment grounds...

 

Grounds were the first thing I checked ; )

Ill go out tomorrow armed with this knowledge and see what I can find.

Thanks!

 

I gather that W21 is a connector on the harness? If so, which connector do I pull? It would be nice if I could get it fired up so that I know I didn't do something (else) stupid, then track down the faulty wires/connection/whatever.

EDIT: for ignorance ; )

 

Along the bottom of the CE panel (Central Electric) below the relays and fuses is a row of electrical connectors with numerous wires coming out of them. It's where most of the cars wiring harnesses terminate.
Each connector has I think ten places, two rows of five, where a wire or wires may be connected. Those connectors are labeled alphabetically. W would be one of the last ones on the right if not the last one.
The letter labels are hard to see and the labels for the individual numbered holes for the wires are even harder to see.

So W21 is going to be a particular wire hole in a particular connector. I think the holes are labeled 11 through 15 for one row of five and 21 through 25 for the row next to it.

 

Here you go, a picture of the CE panel shows W as the last connector, bottom right.
Thanks to 928 International for the picture.

EDIT: I can't get the picture to load so here's the link to it:
http://www.928intl.com/repair/Relay/earlyrelay2.htm

To release a connector from the board you pull out on the plastic tab that sticks out near the middle bottom of the panel. That will release the bottom of all the connectors, the tops of the connectors all have their own small tab that needs to be lifted up gently then the connector will come out.

 

Yeah, I replaced the harness while I had the engine out. Evidently there was some minor engine fire which partially melted the old harness (obviously before I owned the car), but it never gave me any problems. Since I had the engine out, I figured I might as well fix it while it was easy to work with. It's possible that the replacement harness is bad, but I doubt it (read: really hope it isn't the harness). How did you disconnect the wire from position 21? Is it intuitively obvious, or is there some special trick that I'll need to know when I get out there?

Thanks yet again.

-Thomas

 

One more thing:

The wiring diagrams out of the manuals show a "speed sender" which plugs into the EZK control unit. I searched the whole diagram and I can't find anything labeled "crank position sender" or some such. Are those two sensors actually just different names for the same thing? When I crank the engine, I get a reading on the tach, which, according to
https://rennlist.com/forums/928-foru...art-issue.html
post #15, that means my engine speed sender is working just fine. I would be thoroughly unsurprised if that hall sender was the culprit. I'm going to head out now and take a look at it and see what I can make out.

 

As far as I know crank position sensor and speed sensor are the same with the exclusion of the ABS sensors in the wheel that I believe also provide speed data to some system but not anything to do with the engine starting or not. Was there a dedicated speed sensor in addition to the crank position sensor on some models? I don't know.
The Hall sensor can cause lots of wierd problems from what I've read but I don't think it would cause a failure to start since people have problems with performance and later find the Hall sensor was bad.

I think at this point I need to back off and hope one of the guys who know for sure step in and answer for you. I don't want to send you down the wrong path...I'm still a rookie...
I think you are correct in that a tach working while cranking shows the crank position sensor is functioning.

 

Those are the same thing. If you are getting signal to the tach, it is working ok. I am surprised you aren't getting anything on the scope.

Yes W21 is one of the pins on plug 21 of the central electric. They are much much easier to get apart with the right pin pusher. I got my set from eagleday or ebay or something a long time ago so I can disassemble just about any kind of electronic connector without destroying it.