ViribusUnits

On further inspection, it apperes, at least to me that you need to switch the coil triggers, to get the rotors ligned up with the caps when the coils fire, and then switch plug leads, to get the distributers pointed at the right cylinders.

Here is the explinations.

The coils should not fire 16 times. The distributers are not set up for a waste spark system. As a result, when the "wrong" coil fires, it is going to put alought of voltage that is going to go somewhere. The most oivous place for it to go is to jump to some other cylinder. This however is not very controlable. It could also go through the coil wire insulation, the rotor, or the distributer. Thats bad, right?

If cylinder 8 is fireing to the wrong distributer, it will fire inbetween cylinders 4 and 1, right? Then it would jump to which ever cylider it likes best. Maybe thats cylinder 1.

So you need to switch the coil triggers to match the distributers. They are suppost to fire when they line up, right?

Now you have another problem. While the coils are fireing when the distributers line up, the distributers are sending the spark off to the wrong cylinder. Instead of the fire for cylinder 1 going to cylinder 1, it's going to cylinder 3. So now you need to flip flop the plug leads so the distributers line up with the correct cylinder.

And I hope that corrects the problem.

Vlocity

Mark:

In your last thread I suggested that you install the correct dowel referenced intermediate plate. I would really like to see you rule this out. At this stage I don't think you have anything to lose.

Regards,

Ken Bigham

heinrich

Best guess, the distributors are not installed correctly.

John V

Hi Mark,

I'm no expert on your car but a couple of ideas come to mind. Are you checking timing off the #1 spark plug wire? The reason I ask is that youv'e stated two things that I think are important. 1) you stated that at one point that the car ran pretty well (albeit with the gross timing still off from the Bosch guys info). 2) That when the trigger wheel is set up correctly, the timing is 90 degrees off.

Your car has twin distributers. I beleive the computer and trigger system on your car is only responsible for reading the trigger points and, making relatively minor timing adjustaments based upon engine load and sensors. From there, the computer controls the coil field collapse which generates the spark. That spark gets directed to the right plug by the distibuters, not the computer or trigger system.

We know that trigger functions are generating consistent coil firings becuase the car ran well at some point and I don't think that could have happened if the trigger pulses and computer were problems. Thats futher evidenced by your muliple swap outs with no change. I suspect your distibuters are causing the problem, althought I don't know enough about your particular setup to help fix it.

One thing is clear from your info, you are getting a coil firing at the correct point but, that spark is being directed to the wrong cylinder (90 degrees off -which coincidentally is one quadrant off on a 4 wire cap). I know you probably already know this but your rotor to plug wire orientation is not very critical when the computer is contolling the timing. The rotors alignment with a plug wire doesn't initiate the spark, the coils field collapse does. That feild collapse is contolled by the computer , not the distributer like in cars that had points or electronic ignition. I don't know how the distributers are driven on your engine... is it gears? Could you have the distibuters meshed slightly off or in the wrong spot? It wouldn't take much to have that spark directed one lead off.

Just a thought.

Jim bailey - 928 International

.....there is a two wire connector off the front harness which is near the fuse relay board , on some early prototype 85-86 engines which we had the wires were "reversed " from the later USA pattern (Euro ?? ) they are green and white wires and I think you need to try reversing them hook green to white ..white to green and see what happens.......I believe they trigger the coils . ........and that just might "fix it".

MarkR (FAST)

The wiring harness to the coils is independent from the engine wiring harness, and is also suspect as I think the same thing: if something inside the harness is rubbing, and causing both coils (ignitors) to fire at the same time, it would expain this. Unsure if there is another fire at another cylinder as I've not had a timing light handy to check this lately.

Though, swapping the harnesses backwards at the ignitors does not change anything: the spark is very consistent regardless of which ignitor is firing it. Though, I still suspect the harness since it's euro and the US harness may have slightly different leads to the ignitors. I'll have to look into this..

does anyone have a front wiring harness they can loan me?

Mark.

MarkR (FAST)

Hi Jim,

I too thought about reversing the green and white wires, but the same (I figure) would be accomplished by just swapping the ignitor harness leads at the ignitors right? I would have to make a wire bridge to try the reverse since the connector is one-way.

There is not way to change the distributors/rotors: the're either bolted on correctly or not, and the parts are interchangeable back and forth.

This car ONLY ran correctly with the euro motor installed, never with this US motor. I still suspect the front harness as being the culprit..the slight differences between the US and Euro LH jetronic systems might be evident here...

Mark

MarkR (FAST)

The three dowels for the intermediate plate are equally spaced, so even if my PP had the larger dowel to correctly align the PP, i would still be 120º off...though, I cannot 100% rule this out as nothing else seems to point me in the correct direction. Being that I've had the clutch in/out of the car 9x now, I figure I probably hit all three possible positions anyway.

Mark

ViribusUnits

Mark, are you getting 2 flash of the timeing light? ie, comeing up with two sides of the dampaner?

If you arn't, then you do not both coil triggers fireing at the same time. You just have the spark in the wrong place.

Next, you've got the spark at the right time for the number 8 cylinger, now you've gotta figure out how to get it to the number 8 cylinder.

I'm willing to bet that one of the other plug wires will give you the correct spark for the number one cylinder, you just have to find it, and get it to the number 1 cylinder.

I know, I know, shut up Viribus.

John V

in the first thread on this post you stated,


"Yes, he was incorrect by about 27d but the car ran so great I didn't question the timing.."

This statement was about the euro engine??

Jim bailey - 928 International

Mark I sold one of the new "prototype" engines to a customer when installed it in his 86 it would not run he reversed the wires .....it ran . We sold a second told the customer to reverse the wires ....it ran . Just use two JUMPER wires reverse the wires .........hope it runs !

MarkR (FAST)

John:
the 27º was blindly set on the euro motor (not a bad guess I guess): car started up and sounded mean..no vibrations, etc, decent acceleration, though, on dynoing the car it dyno'd low and there's a horrible surging issue at low rpm, high vacuum that cannot be tolerated..undriveable. Timing light shows 27º at idle. Luckily, no detonation.

Jim: I will try that tonight. gotta nice check coming your way if that's it...interesting though, I would think that by swapping the harnesses at the ignitors would have accomplished the same thing...we'll find out.

I did change the firing order on Sunday to 8-1-7-3... from the original 1-7-3..to see if by placing the #1 wire/cylinder on #8 (90d advanced) etc for all, it would run, but it didn't like that, started right up and immediately dropped cylinders until the motor died about 6 seconds later.
(wierd)

Mark.

Zandramus

progress?

Bill 86.5 928s

Marc....This is probably foolish to ask but a book I have here states that the 85 through 87 engine the firing order is 1-3-7-2-6-5-4-8 with cylinders 1-7-6-4 on the left side ignition system and 2-5-8-3 on the right side system. is there a chance any of those wires mixed...The wires that Jim was refering to are also in here and the white wire controls the left side ignition and the green wire the right. Still reading the the book ......good luck

MarkR (FAST)

My thanks to everyone for reading my book and posting thier ideas. Jim Bailey rom 928INTL hit the nail on the head: I had to reverse my white/green wires where they plug into the fuse panel...and reversing the harnesses at the ignitors did not change things initially, so I discounted trying to reverse the wires since I thought it would not change anything....I guess I should have tried.

My only issue now is it sounds like it's running on 7, and I have no (zero) continuity in 7 of my 8 plug wires (new), though my plugs all read the same and the injectors are new...any clues? Compression is even across the board...will try to borrow a set of wires to rule them out.

Thanks again,

Mark Robinson