vanster

I agree with the pod removal as I mentioned, it does not appear to have been removed in the past.
Only the cover plate had been removed to access the yellow wire which is now re connected.
I haven't found any corrosion (yet) even in the engine bay. I will look for another LH. This car was last driven in May/June
of this year and it just stopped running. Rich did find the MAF in-op with a broken wire that would have prevented it from running which has now been repaired and the LH did fail on the bench which has been repaired. One would think that it would at least run even poorly at least.

Mrmerlin

I would suggest that you buy a good used engine harness,
928 INTL has them,
NOTE that cured my 86, the old harness breaks down and then you an spend lots of time and money replacing everything only to find out the harness was KAPUT.

Until this is ruled out you just dont know.

ALSO verify that the relays and fuses are all in the correct places,
and that also the correct part number relays are being used

hwyengr

See if you can borrow a good EZF. Everyone says it doesn't go bad, but it sends the signal to turn on the LH, and well, your LH doesn't seem to be turning on.

vanster

Stan,
I have an extra injection harness that came from Mark Anderson. I have not had the courage to yank the old one out and install the replacement. I was hoping to find an alternative solution but I am starting to stare at the replacement harness a lot harder. You mentioned you could do it in 5 hours, I spent 5 hours just looking at it, along with a 6 pack.

AO

So, does it run with the FP relay jumpered? It's not clear from the description.

On an 87 we have at our shark tank, we found that the tach signal feeding the LH was corrupted. And would cause a no start. We ended up having to clip that wire for now until we replace the tach or the circuit board (not sure why it's corrupted). I believe the 86 has a similar setup.

Here's the thread for that one: https://rennlist.com/forums/928-foru...corrupted+tach

Perhaps someone can you help find the same circuit for the 86.

vanster

It won't even fire, so less than trying to start and the tach needle does not budge with cranking
The key issue here is that the LH and fuel pump do not shake hands
Only way to get fuel pump to run is to jump it and it still won't fire. I guess you can say that the only thing that runs is the clock and the fuel pump only when jumped

hwyengr

This is a big development. The signal that drives the tach is exactly the same as the signal that turns on the LH. They come from the same pin on the EZF.

The LH does not turn on from the ignition switch. It gets a signal from the EZF. So, if the tach is not getting a signal, the LH might not be turning on. If the LH doesn't turn on, the fuel pump doesn't run and the injectors don't get fired. Dollars to donuts that you solve your dead tach and the car runs.

harveyf

I agree with Jeremy. Vann, looking at page 15 of the diagnostic guide, you have to obtain a signal at pins 7 and 19 of the EZF plug while cranking. See my previous post above. The usual failure point is the 3 pin plug mounted in a bracket underneath the air filter. See the figure on page 13 for the "3 pin plug for the speed/reference sensor". This plug can be "crumbly" i.e. it will fall apart when you handle it. Mine was like that, held together with electrical tape.

vanster

You saying to remove the pod and disconnect the tach?
I have a gauge cluster on my desk and I just took a look at the back of it and I don't see a way of isolating the tach to disconnect it.

John Speake

Did you check that there isn't a relay in kick down slot ?

If there isn't, disconnect the LH ECU 25way connector and see if the tach moves when cranking.

vanster

John, you are saying to remove the 25way connector from the LH or just disconnect it and crank it and if the tach moves we are on to something?
Do I have a kick down slot with a 5sp?

bureau13

There's a relay position for the Kickdown (I forget which spot) that is left empty with a 5-speed. And, reportedly, if a relay is placed there, it can cause no-start problems.

mark kibort

that is slot XV.... that solved a no start problem with the 6 liter of greg v's. (8 months of searching for a solution, but John S told us this nugget of info)

harveyf

Maybe I'm confused but I looked back at the thread and don't see that anyone is recommending that you remove the pod. The only thing in the pod that is mission critical is the heavy red wire from the ignition key that powers the "15" circuit in the CEL. If you do the 12V power checks in the diagnostic procedure you will rule in or out 12V power issues.

There is a remote chance that a "bad tach" is sucking all the life out of your CPS signal. Low probablity and the only reason I could see to remove the pod and disconnect the tach. And there are probably easier ways to disable the tach by attacking the wiring at the CEL.

Another thing to check: Look at WSM wiring diagram for Model 86 page 7, Digital Engine Electronics. Down at grid H/69 there is the "Separate Plug for the Alarm System". You need to confirm that terminals B23 and F25 on the CEL are seeing 12V. If the alarm is causing problems F25 will not have 12V and your EZF relay XVI will not be energized. A and F refers to the plug numbers for the plugs across the bottom of the CEL. The plugs are embossed with these letters. They start with A on the far left. The numbers like 23 and 25 are a little more inscrutable but armed with the wire colors (in this case sw/rt and ge) you can usually figure it out. The english translations are on the bottom of the diagram. I think there is a generic pin-out drawing for the CEL plugs somewhere in the wiring diagrams.

hwyengr

If you cut the wire coming out of W11 in the fuse panel, you will isolate the tach. That's the block that's furthest to the right. Left column, bottom wire.

Check that you don't have the kickdown relay first. Ideally you'd also check that you were getting a pulse out of the EZF before cutting the wire. It's possible the tach isn't bouncing because it's not getting a signal, period.

Edited to add: Got the pins backwards. See Wally's post on the next page for the correct orders