RED928

When it stops it is immediate. As you say like a switch is turned off. There's no sputtering or slowing down.

Mrmerlin

probably a relay or fuse connection or ground connection

soontobered84

When my 89 had these symptoms, it was the main engine ground underneath the car on the passenger side. Removed it, tested continuity, cleaned both ends of the cable, cleaned both mounting points, and reinstalled it. I never have had an issue again.
That said, I would still take Stan's suggestion and do a full-on intake refresh.

worf928

Yup. Possibly also power.

If someone put a gun to my head and said "throw a part at this problem or DIE!" I'd go with LH harness. Given the state of the front main harness...

However, I'm not an advocate of throwing parts at a problem.

RED928, given the info in the last few days... When you got it to start on starting fluid, was it in a no-start state that you'd just tested? Your post(s) indicate that you think it might have started anyway?

When it won't start, or when it dies after a start, what needs to occur in order for it to start again? Passage of time? When it won't start or dies is the engine always not shop-cold? When it starts is the engine shop-cold?

RED928

When I started it with starting fluid the other day it was in a no start state. When it dies or will not start time seems to be the key. The passenger seat is out and the fuse/relay wiring and computer harnesses are easily accessible at the moment. Hot or cold do not seem to play a factor. When it does start, even after sitting for weeks, it will fire right up and quickly hit a stable idle.

Thanks,
Steve

worf928

Ok. So. We can concentrate on the fueling system.

In what condition is the LH harness at the injector connectors?

Do you have means of testing that the injectors are being pulsed during starting? (With an '89 or newer you could use a Bosch Hammer or Theo's Tool, but with an '88 you need a test light.)

Something like this:
Also, it would be good to measure voltage during starting as close as possible to power source for the injectors. This is the W13 pin on the fuse panel on your '88 (but, double check the wiring diagrams to be sure yourself.) Check the voltage across the battery while cranking and then check the voltage at W13 against a fuse panel ground while cranking.

If the voltage drops below ~10.5 during cranking then you have a power problem. It should stay in the 11s.

worf928

Also, what condition is the battery ground strap in?

RED928

Thanks Dave,

Battery cable is fine. We're heading out on the boat for the holiday starting today. I'll check the harness connection and voltage when I return.

Regards,
Steve

docmirror

Ignition key asm. Or, LH relay, EZK relay.

RED928

Hi All,

When I returned from our 4-July boat trip I attacked the grounds again and that seemed to work. The car would start and run well. So I continued replacing the carpet and seats. After getting all the pieces in I moved the car to the driveway so I could work on my wife's Mercury. Couple of days ago I tried to start the 928 to move it into the garage for an oil change and a few other minor items and it's now not starting again. It had been sitting out for only 2 days.

It cranks just fine and when jumped (30-87) the fuel pump runs but the car will not start.

Dave - you mentioned LH connectors at the injector. Not familiar with that item. How best to trouble shoot it?

Thanks,
Steve

Mrmerlin

At this point I would suggest to remove the computers from your car and place them into a running car to verify the LH computer is still working correctly.
The EZK computers dont usually suffer faults.

Based on the condition of the engine bay,
the harnesses could be internally shorting and thus causing damage to the LH.

The connectors Dave is talking about are the fuel injector connectors these would get tested with a noid light plugged into one of the injector connectors.

I know you said the LH was rebuilt but if you put a good part into a damaged car it could damage the new part.

I am dealing with a similar issue with the 88 S4 i am doing an intake refresh on.
I found a frozen ICV, the pins shorting to ground on the Hall sensor, and the front knock sensor pins shorting to ground, and an over charging non Bosch regulator 18.6 V that was new in the alternator.

All of these parts have been replaced with new Bosch parts,
I also swapped in my test LH and now the engine starts right up and runs strong.

Previously it would start and idle if the throttle was opened then the engine would die,
BTW when the engine is running what is the charging voltage? it should be around 14.0 volts

RED928

Thanks Stan,

I've reached out to someone local. Hopefully we'll be able to test the EZK/LH modules I have.

For what it's worth. I believe I'm getting spark because it will momentarily fire with starting fluid. I verified the fuel pump is running both by jumping the relay and hot wiring it. In both instances, with the pump confirmed running the car would not start... not even try to fire. Does this indicate pressurized fuel not getting through? If so what could cause that. The pump is new, the filter as well, and the tank was cleaned within the past year. Your thoughts greatly appreciated.

Regards,
Steve