jdmasonn

Forum,

This is my first posting, but i've use info from here and let me first say thanks. The short version of this story is that I have a 928 S4 that won't start. Cranks fine but won't start. So far I've done the following:

Replaced fuel pump relay.
Rebuilt LH module and had it retested.
There is fuel getting to the fuel rails.
There is spark at the #1 Cylinder.

The car was towed to my local porsche dealer who had it for about 2.5 months and was unable to find the problem. They are still suspect of the LH module but it has been rebuilt by Electronik Repair, Inc (Mesa, AZ) and retested by them.

They believe at this point that no signal is reaching the fuel injectors. I now have my 28 at home and have begun rechecking signals and wiring.

Question: I've attached a picture of a connector which is located above the fuel rail on the passenger side of the engine. I have not been able to identify this connector in the wiring diagrams and was wondering if someone could help?

Also I am also a little suspect of the car's alarm system which i understand would also stop the car from starting and this to me would be the logical way to do it. Any help would be greatly appreciated. Thanks in advance.

Jim bailey - 928 International

I think first I would replace the L H relay and ignition relay ...then buy a" noide" light (few $$ at autoparts store ) and see if the injectors are pulsing... Often we are finding that the crank sensor connector has fallen apart and the computers do not know the engine is turning so no pulse, no fuel ...no run.

oups59

Knock sensor connector

worf928

What year is the car?

jdmasonn

Thanks Jim, I should have added those items to the list, which have been replaced. I'll check the crank connector and get a light.

jdmasonn

Dave C.

It's and 89 S4

brutus

The 1989 is the first year for the ignition monitoring system with the clear relay outside the LH brain . That relay shuts down half of the injectors if it thinks those cylinders are not firing but I have heard that it can fail and shut down all the injectors. Just another possibility.

AO

Yep that pic is the knock sensor, but this would not stop it from running. The knock sensors would cause the car to run 12* retarded, but it would still run... just low on power.

If one of the injectors is grounding, I believe they all go out. I believe Bill Ball had an experence with that. I think I may have it in my saved threads - I'll check.

worf928

Ok. You are in luck. Do this the easy way: Hook up a Bosch Hammer or JDS Spanner or Theo's software to the 19-pin diagnostic port and have the car tell you what's wrong with it.

If the dealer still suspects the LH ECU then they cannot have hooked up the Bosch Hammer (that's the Porsche factory tool for diagnostics starting with '89 models) as it would have likely told them if the LH was bad. I find it unsurprising that a dealer wouldn't know enough about 928s to know that '89+ has built-in diagnostics.

Some Rennlister in your area should have one of the above and if you sweet-talk them they might do a house call for you. You can also call the dealer that worked on your car and ask them if they bothered to hook up their diagnostic computer. (I'll bet they'll tell you that your car doesn't have any way to hook up their computer...)

AO

You may want to review this lengthy thread about an 89 exorcism!

https://rennlist.com/forums/928-forum/271232-gt-exorcism-in-san-jose-on-saturday.html

John Speake

If the car has not started since last reconnecting the battery, then there won't be any stored fault codes to read with a diagnostic tester.

Do you have spark ? Does the tach flicker when you crank the engine ? Have you swapped out the EZK relay ?

worf928

Yes John. But a Hammer will be able to indicate if the various sensors and actuators are functional. And with one attempted-start, an ECU fault significant enough to cause a no-start will be stored.

I've played enough with my Hammer to know now how invaluable it is.

SteveG

Ahh, grasshopper has reached enlightenment.

jdmasonn

This is more info than I received in months and yes the dealer did say to me that my car did not have built in diag's. Is the connector located near the LH? Is there a description of the software or Hammer in a posting anywhere? Andrew I'll also check out the link you sent. I'm working on it guys. Thanks...

worf928

Ha. What do I win? Seriously, people wonder why us 928 folks look down on Dealers and why we all become our own technicians. Thank Dunkle for Rennlist or we'd be screwed.

The 19-pin port is located under a black screw-on cover between the amplifier and the fan controller. All of these are located under the "carpet hump" between the passenger seat and the passenger's door.(*) The newer Porsche diag computers (aka Porsche Workshop Information System - PWIS) come with the 19-pin connector. So, assuming the dealer hasn't misplaced the connector, then theoretically all components except knowledge are in place. (And, yes, the PWIS-II with the proper 19-pin connector will talk to an '89 or newer 928.)

(*) On top of the hump is the remote hatch release (possibly). If the carpet hump is to be completely removed (not necessary for 19-pin port access) then the two electrical connections must be removed from the underside of the cover first. Or, whoever pulls the carpet hump out will be buying a new ~$90 release switch. To get to the port all you have to do is unscrew the two black plastic screws on either end of the hump and move it slightly towards the seat.

Instructions on use of the Bosch Hammer are in the Factory Workshop Manuals, various other factory documentation supplements and the CD-ROMs available, unofficially, via a Rennlister. Obviously a 'dealer' should have the former two on-hand. On this forum, questions about using the Hammer usually are answered with "look at the manual"

Information on the non-factory software is available here: http://jenniskens.livedsl.nl/

and is discussed in (at least) this thread: https://rennlist.com/forums/showthre...=Theo+software

While the built-in diagnostic capability is usually a time saver and usually will give useful indications of issues, what we have available on the later 928s is the first generation of such technology for Porsches. It may not lead you directly to a cause. However, it will tell you what works and, therefore, at least tell you what you don't have to check and narrow down the possibilities.


Since you are on Post 5 as I write this reply, I've no idea of your wherewithal to chase this issue yourself. Almost all of the items that the tool or software checks - in this no-start context - can also be checked with a multi-meter in conjunction the "LH/EZK Test Plan" - another document that a dealer should have and one that is on the aforementioned CD-Roms for DIYers. The Hammer and software are time-savers but, with the Test Plan, a multi-meter and some reasoning they are not absolutely necessary.