You *might* be able to get by with a multimeter in place of a scope when making some checks. Set the multimeter to measure frequency, connect one lead to a good ground, and the other into the back of connector W11 at the bottom of the fuse panel, so that the lead touches the terminal in that W11 position. That terminal gets the same RPM signal from the EZK that goes to the LH. Crank the engine while watching the meter. If you get a reading like that, it indicates that the crank position sensor and EZK are working as far as providing the RPM signal that the LH requires to operate. You might also see that by watching the tach in the instrument cluster while cranking the engine, since it also uses that same RPM signal source. If the tach is showing engine RPM, it also means that the crank position sensor and EZK are working to provide an RPM signal. Check the LH plug terminal 1 to make sure it isn't spread and makes good contact with it's corresponding LH pin when the plug is connected. If you find problems with that RPM signal when checking it at fuse panel position W11, it could indicate a wiring problem somewhere in that part of the wiring connected to the RPM signal between the EZK and LH. Because it's probably the fastest and easiest, I'd try unplugging the transmission kick down relay and seeing if it starts. That relay also gets the same RPM signal. I'm thinking it might be possible that if that relay has some kind of internal problem, it could mess up the RPM signal to the LH. I've never heard of that relay causing a no start problem, but if any part carrying that RPM signal shorts to ground, the LH won't work. The same RPM signal also goes to the diagnostic plug, so a short somewhere along the way to there will also keep the LH from working.

If you're talking about pin 18 of the disconnected LH plug showing 0 ohms to ground, that would seem to indicate a wiring problem causing a short somewhere between that pin 18 and at least one injector's ground side connection.

 

Dave: Thanks to you, Andrew and everybody else trying to help figure out this intermittant problem, however: NO GAS AND MATCHES! (although the thought has crossed my mind once or twice too) Andrew, I'm happy you are finally able to drive your beast. Dave, keep up the spirit.......somewhere there is probably an effen' rodent that died of indigestion from nibbling on german wire delicacies . Whatever part you need, holler; it'll be there ASAP!

Paul Barrera '91 $$$$$$4.......Yeah, the one these recent posts are about.

 

I didn't see any evidence of nibbling. There was a winter store of acorns, but that's all. This car is so frustrating because the fault does not seem to show itself. We know it's a fuel injection issue. That much is clear.

Brains checked good. Relays are good. CPS is good. Injectors test good. The Harness seems to be good.

You know a thought just cross my mind. We disconnected your aftermarket alarm, but we never disconnected the factory alarm which has an immobilizer feature that interacts with the EZK relay. I'm not sure but I think you can disconnect this and take it out of the loop. Never tried this, but it's worth considering. It's located under the passenger seat (which needs to be removed to get at). Just a thought.

 

Hi Andrew. You know that I don't know shiatt, but Iv'e always had a nagging
thought in the back of my head since we started this frustrating adventure.

A) Car sat for 3-1/2 years= shiatt in gas tank, fuel pumps (2), lines, & injectors.
Yeah.....I know you checked flow, but even though the in-tank pump was replaced, could either one of the pumps be pulling crap in and clogging, a hose pinched or a screen screwed up or something that could cause a relay or brain to stop intermittantly because of that? Were the pump(s) ever backflowed to remove any residual garbage from when the tank was drained? Simple and perhaps stupid thoughts but I dont know any better so I thought I'd ask. Thanks again for your continued help!

Paul Barrera '91$$$$$4

 

Ninespub,
Alan has posted before the method to disable the factory alarm by jumpering a couple of the terminals together at the central fuse panel. That would definintely be easier that getting under the passenger seat.

 

Paul- The problem is not with the fuel pump, lines, filter or anything like that. That was the first thing I checked and it pumped plenty of gas. I think I can still smell it in my garage. The issue is that the injectors are not firing. We have a test light (called a noid light) that shows when they get a signal... the light stays dark most of the time. The few times it has run, it lights up just fine. So the issue is something is preventing the LH computer from telling the injectors to fire. I tried my known-good computer in your car with a base chip and it behaved the same. We also swapped out the EZK just in case. Same result. We've swapped relays, checked for shorts (looks like there might be somethign going on at pin 18 on the LH), and countless other things. I can tell you it's not for a lack of trying! I just happened to think of the factory alarm as one more potential culprit, that we shoudl eliminate from the puzzle.

I'll check the archives to see how to disable the alarm for the 91+, but I thought you had to disconnect it.

 

Thanks Andrew. I probably should have asked that question in the Official Novice Question Thread, huh. I know you guys are busting *** trying to figure this out so I'll just lurk and be quiet while the pros make it happen!

Paul Barrera '91$$$$$4

 

Hi all and Happy Easter, our family celebrated yesterday so that left me with today to get back into the garage.
I built the voltage divider the other night and it works... (thanks Rennlisters) I was then able to use the Scope application for the PC's sound card on an old Notebook w/windows 2K, what you see on the screen is the Timing Pulse coming from the crank sensor on W11.

Oh and BTY it was running twice today for about < 1 min (30 sec).

Well I am looking at the wiring diag page 7 (digital eng elect) but am quite lost as to where to check next.

I’m going back out and will prod along but…. Please help with possible test points

and thanks once again...

DaveK9

 

Have you pulled the factory alarm? It's under the passenger seat.

 

go up near the factory ground points behind the passenger parcel tray, the alarm connection should be there (it is on my 87). Disconnect it and then you will have to make a loop connector of sorts to plug in, it wont start if you dont. You will have to dig up the wiring diagrams as i cant recall what pins to connect. I use this same point to wire in my "kill switch" My car came from the factory with out an alarm installed and there is a factory "loop/circuit" that replaces it.....a connector that simply plugs in where the alarm leads normally go..

ah ah! found it
https://rennlist.com/forums/showthre...ighlight=alarm

 

Sheesh Dave. This is turning into a real PITA for you! It's interesting though that there are a lot of "same thing, only different" issues cropping up recently; all with similar symptoms. Maybe there's a 928 "neurovirus" affecting the brains of our vehicals. I wish there was some kinda "marvel mystery oil" that we could pour on top of the engine and then after a dance in front of the 928 shrine, all the problems would go away. Ooops, I forgot.....the shrine is no longer around. Maybe that's the problem.
ANDREW! we need a new shrine! And no.....NO matches & gasoline will help my 928 (at least not yet). Thanks again Dave for all your patience and everybody else for their suggestions.

Paul Barrera '91 $$$$$4

 

Ok I wil disco the Factory Alarm, thanks for finding the link w/Pic's Tony!

Looking at the wiring diag, it looks like the output of W11 (signal on screen above) also goes to 1 of the LH and 13 of the EZK.
W13 goes's to Idle speed position and pin 4 on the ICC relay that feeds pins 2 & 5 to the injectors.
But pin 4 also goes to a Tank Vent ? and that goes back to the pin 27 of the LH. not sure but I am looking for anything that could be bringing this down (tank vent?).
I'll be back at it tonight!
PS: Paul sorry it took me soo long to build the scope, now at least I have a way to trace.

Thanks all,

DaveK9

 

The factory alarm changed in 91 to the same one as the GTS. This sits under the passenger seat. I do not beleive there is the connection point that Tony points out in his post. I think you will have to pull the seat and disconnect there. Sorry.

Paul- I was actually tracing out plans for a new shrine today...

 

Copy of my old post poke around this may help you on what not to do !
https://rennlist.com/forums/928-forum/357581-86-no-start.html

 

Also look at this!

https://rennlist.com/forums/928-forum/351135-inj-and-maf-wiring-testing.html

Good luck