Ken P

Tom,
Correct, to a point, there are other things that could cause the car to not have spark, ie. no power to the EZK computer.

But, to have spark, the EZK (Ignition) computer must receive a good CPS signal.

Stan said;
This is probably the easiest test to see if you have spark.
If you do, then you need to move on to why you are not getting fuel.

Do you have a copy of the Factory Service Manuals? There is a great section on troubleshooting the EZK and LH for no start conditions.

So in the cars current condition, can you verify if it has spark?

Ken

tbt

Ken...... I pulled a plug wire attached a spark plug to it... grounded it on the engine...cranked the engine & the plug fired. a strong spark....I do have the factory manuals so I will proceed to attempt to troubleshoot the EZK & LH...

Many thanks to Dr. Bob & you for your generous input & patience with me!

I'll keep you posted as to my further progress...or lack thereof!

Regards,
Tom Taylor

John Speake

Does the rev counter flicker when you crank the engine ?

tbt

John....tach needle does not move any when cranking engine stays at pegged at zero

Ken P

John, I have read about this several times from various posters. When I was helping Barney with his car, I tried this out on my car, before going up to try it on his car.

I pulled the fuel pump fuse on my car and cranked it. I did not notice the tach flickering at all.
I was wondering if this test may be year or transmission type dependent or if I just did not look close enough. I was expecting a perceptible wiggle or even it bouncing up to a couple of hundred revs.

I also tested this on Barneys car and did not see any tach movement at all.
The CPS signal on both cars was fine.

I'm just wondering if there is something I am missing in looking at this test?

Thanks,
Ken
'89 928 GT

davek9

Find the Wire in the CE that feeds the Tach and disconnect it, it is in one of the CE plugs on the right side by the ECU's. Can't recall the pin number. This could be a BAD Tach holding the signal down.

On the Auto Kick Down relay:
The fuel injector signal runs through it as said, it is a smart relay (kind of) it senses how fast the engine is turning. If the engine is turning slow (cranking speed) and the kick-down is engaged, it will STOP the fuel injection from working.

This allows you to CLEAR out the cylinders of a flooded engine (foot to the floor and no fuel going in

EDIT: I do not know when this "feature" was added and how it was addressed in the manual cars.

EDIT: quick search cam up w/ this, "... the wire that goes to the tach in the dash is pin w11. (plug W pin 11) on the fuse pane..." (Note: I'm sure this is year dependent)

Dave K

John Speake

There's usually some movement on the cars I have seen, but maybe there are variations I don't know about.

dr bob

You can easily test for injectors firing with a simple readily-available tool called a "noid light". It plugs between a fuel injector and the wire that normally feeds the injector. The 928 LH is a "batch fire" system, so if one is getting a trigger then they all do. Wiring faults/failures tend to be with shorted conductors, when a short in any one pair will short them all. Noid Lights come in flavors dictated by the connector -- Look for one designated for "AMP mini-timer" connections, or just pull one connector, take a picture of it and the injector connection, and go shopping at the local parts store.

There's a distinctive clicking that happens when an injector opens and closes. If you have a decent mechanics' stethoscope you can listen for that as your trusty assistant operates the starter. You can sometimes feel the clicking, or use a long screwdriver with handle to your ear as a listening aid.

Know that a somewhat common symptom of LH brain failure fires the injectors even before the starter is cranked. With key on (position 2 for normal engine RUN), you'd notice a buzzing from the injectors.

The injector tests above, in concert with fuel pressure test, should help narrow down the possible-causes list for your no-start.

dr bob

Again, if the CPS has not been replaced, now's a great time to do it. It's a regular PM item with 80-100k expected life. Most common failure mode is wiring and connector, as I shared in post 14 above. A little searching will net you pictures and some tips on removal if it's stubborn; do NOT pry on it.

worf928

Just so that it's clear: a 5-speed '87+ should not have anything in the kickdown relay socket. And there should be a bridge in the starter lockout relay socket.

Next, if there is verifiable strong spark then the CPS is not the culprit for a no-start.

tbt

I am still looking....have decided replace the crank sensor (it has been replaced but I don't remember how long ago...I'm sure it has close to 100K miles on it

Where would you recommend I send the LH brain to have it checked out?

tbt

Would it make sense to also get the EZ and the airflow meter also checked out.???

Ken P

Dave said;
You said;
So you can change the CPS, but do not expect it to fix your current no start issue, if you currently have a strong spark.

Do you know of anybody local to you with an 87+ 928, your computers can be swapped into their car, to verify if they are OK.

The airflow meter should not keep the car from starting. This could also be rebuilt to improve its function, but again do not expect it to fix the no start issue.

There are several places that you could send your LH to for testing. A search should bring up Louis Ott (https://www.performance928.com/products.html), Rich Andrade(http://www.electronikrepair.com/home.html), 928sRus (http://www.928srus.com/), 928 International or 928 Specialists may be a good point of contact as well.

There is a thread on testing the LH and EZK, https://rennlist.com/forums/928-foru...nt-thread.html

Ken

davek9

Did you disco the Tach yet and see if it starts?

Like I said a bad tach will stop the Fuel Injection from working, I've seen it, BTDT

dr bob

Post your location. If another 'lister is near you with a S4+ car, you can plug your brain into their car for a quick test. Otherwise, in the US the pieces go to Roger at 928SRUS for functional testing, or to Louie Ott at Ott Performance for evaluation or rebuild. 928 International has rebuilt pieces. Rich Andrade at Elektronicrepair in Phoenix did mine and several others for SoCal locals when I was there. I keep a spare rebuilt LH for local testing if you happen to be in central Oregon.