MarkR (FAST)

Hi Guys,

I'm starting from scratch, offering a reward for help, and to keep the information as thorough and as accurate as I can, I dismissed most of my sleep last night to ensure a thorough description.

Personal background: I’m not stranger to Porsche’s or 928’s, having owned 3 prior models, a 2.8RSR replica, a 1991 C2 turbo (also very fast), a stock-turbo’d 944T (current play car). the world’s most powerful 2.5l 944TS street/track car back in 1996 (at the time), & my current 928.

Also, a friend of mine and I formed FAST (Forced Air Systems of Texas: www.f-a-s-tonline.com, a low-time-involved 928 Supercharging source for 928 owners, having sold over 38 kits since 2000.

This project: I Purchased an ’85 euro car (wrecked in front) out of Miami in 2000. Swapped out the entire interior, tuned the 2v motor, and was prepping it for painting when I realized that there was too much corrosion in the water neck to leave me confident with trying to boost this 15-year old 10.4:1 compression motor. I swapped the motor, computers, and engine wiring harness with a gentleman who had an extra ’85 US-spec motor with low-miles on the odo (or so he said).

I took my time over the next year and rebuilt this 32v motor following the manuals strictly, and with a bit of advice from Chris Carroll & David Raines from Powerhaus (also to follow the manuals). Every part was photographed, bagged, & labeled to facilitate an easier re-assembly.

Shortblock: All rotating parts spun balanced: basically a $400 waste of money as the motor needed nada according to the machine shop. The only thing I changed was the addition of the ARP rod bolts. All bearings, bolts, gaskets were OEM Porsche (new), and with the addition of the GTS oil pan baffle, I wanted the shortblock to be as stock as possible so I could prove 650hp out of the stock motor on boost. All parts removed from this M28/44 motor were reused, nothing had to be replaced (less bearings of course).

Heads: Stock castings, valves, springs, retainers, camshafts, chains, tensioners, cam sprockets, cam-sprocket hubs (cams are adjustable for fine-tuning), + new guldes reemed to spec, and about 40 hours of port matching, seat-blending, and polishing & a 3-angle grind + individual lapping compared to Porsche's 1-angle grind as we found.

Assembly: motor was assembled as a complete motor before installation into the car. Engine wiring harness was checked for breaks & damage, but none was found. I reused the MAS (mass air sensor) from the Euro car being that the manuals stated they were the same. A brand new clutch assembly was purchased for this high-powered motor as well.
Installation was a snap as everything went in as planned, no changes to note. The harness plugs right into the last lower-right socket in the fuse panel, ignition ignitor wires (one green, one white sharing the same connector) are the same between the the two slightly-different LH Jetronic Bosch systems, O2 wires (3) plugged right in, computers plugged right into the harness (connectors are slightly different as to keep mechanics from not getting them backwards), etc. All grounds were cleaned, and reused parts such as the ignitors & coils were checked to ensure they were the same between the two cars.

Here’s where I went wrong: When tightening the crank bolt on the front of the motor, my clutch was not yet installed, so I used a pair of vice-grips on the flywheel to hold the rotating assembly in place. By doing this, I had clamped onto the trigger wheel (which presses onto the perimeter of the flywheel) unknowingly, and spun it about 80d in retard. Of course, I had no idea as this information is somewhat unknown and proceeded with the final installation of the long-tube headers, full exhaust, clutch, etc.

When I was finally done, of course, the motor would not start even though it had fuel & spark. Closer inspection showed proper firing order, good spark, proper fuel from my 30# Bosch injectors (increased from the stock 24# units & necessary for the eventual supercharger). Finally, I went back to the basics to discover that with the help of a timing light, I was nowhere near the ~10d timing BTDC (at idle) at cranking. Mark Anderson suggested that I spun the trigger wheel, for which I was surprised and elated because that all made sense, though w/o a good reference, I consulted a Bosch specialist in my area regarding the proper repositioning of my trigger wheel. Yes, he was incorrect by about 27d but the car ran so great I didn't question the timing..it was close enough to allow the car to start right up and feel about as spunky as it should have been. I did not recheck my timing at this point, and proceeded to take the car to the body shop for it’s 13 month adventure there.

The only damage that found the car at the body shop was a damaged mass-air screen where someone was messing with the car, but the car really did feel like the 360hp it was supposed to have (before break-in & aftermarket computer chips). When driving the car for the first time to fit the exhaust, alignment, etc, I was sure the tuning just needed tweeking as there was a surge (bucking) to the driving during low vacuum, lower RPM driving. The car had great power though, roasting the 285's through 1st & 2nd w/o issue. This led me to the following:

-Tried 3 other used mass-air sensors, including one off a 30k mile GTS, no difference
-Different fuel injectors: swapped in 24# units as my fuel consumption was horrible for no reason...wrong impedence??
-3 different sets of computers, 4 different sets of chips, even putting my computers in another ’85 car to ensure his car drove normally
-different grounding straps
-different plug wires from my custom MSD wires (way back when the car wouldn't run....maybe I should check again??)
-hard-vacuum-lined the entire car, computer.
-removed the valve-covers and went over cam-timing & triple-checked part numbers.
-confirmed part numbers for the flywheel, harmonic, cam sprockets, caps, rotors, crank trigger.
-put about 300 miles on the motor in this current state of untune, as I was eager to get it broken in and though it would be a simple fix.
-dyno-testing with stock chips to read my fuel curves & determine bucking only revealed about 280rwhp/280rwtq, and the curves were not out of line…just way shy of what I considered I would get (and my horrible surging continued under low pedal pressure).

Finally, again, the timing light showed my problem: 37d timing (BTDC) at idle: I was about 27d advanced as the manual states 10d +/- 3 (odd, no detonation ever…) My Bosch-expert’s advice was way off, but still enough to get the car running. So, from consulting Mark Anderson & his online store’s photo of my flywheel, and with another reference flywheel from the same year car (US), I again removed my clutch and flywheel, correctly repositioned my flywheel’s trigger ring: knowing I was 100% correct when I found a dual-gouge mark “carefully” placed by a previous mechanic as he crammed the heavy clutch assembly against the flywheel so many years ago. Overlaying the reference flywheel (as well), I had a perfect match.

So, I installed everything with a smile knowing I had it all right at this point, but, the car would not start. Timing light (yep, using it regularly now) showed my timing to NOW be flashing at cranking to about 90d BTDC. Now I’m baffled as I had already checked everything, so I continued on by checking the cam sprockets, cams again, switched the ignitor harnesses back and forth, checked grounds again, continuity in the harness, switched out crank trigger sensors a few times, but still no avail. I re-confirmed my flywheel position of the trigger wheel again (correct), but ended up swapping in my buddy’s ’85 flywheel to ensure I did not damage anything, but did not, car would still not start with this arrangement. After about 20 emails and untold hours trying to figure this out, I patched this hole in my timing by indexing my trigger wheel on the flywheel to MAKE the #1 wire flash at cranking & show up on my harmonic at about 8d BTDC so that at idle, I would be within the spec of 10d +/- 3d. This worked great! Motor started right up, idle was under control & needed fine tuning, and the motor sounded more like a 928 (for a change).

I now had a distinct lope in my idle, and this lope was also a vibration upon driving the car that did not increase nor decrease with rpm’s. I (possibly) contributed this to the long-tube headers probably hitting my bellhousing as I had an incredibly hard time getting these to fit. Of course, that was not the issue, and when driving the car, it was obviously down on power, maybe to 280 flywheel hp/tq. I contribute this to my patching of the timing black-hole, and am still stuck with this solution as 3 more months of research have not yielded any new information. My last hope was a whole-new exhaust system to see if the unequal-length headers had contributed to the pulse, but this expensive solution did nothing but allow me to construct a higher-hung, not-even-close-to hitting-the-bell-housing system that could allow clutch removal w/o touching the exhaust.

In my search to fix this issue, I tried the following:
-5 total mass-air sensors
-2 NTC sensors, both spec’d correctly
3 crank trigger sensors
-2 air temp sensors
-3 sets of computers, 4 sets of chips within.
-2 sets of new injectors, one 30# set, one 24# set, impedence checked against the factory
-2 TPS sensors, both good, but original was full of old oil (weird)
-caps & rotors spec’d out correctly
-spark plug wires are properly aligned at the caps & cylinders (4671, 5238 from left to right from standing in front of the motor).

Finally I disassembled the entire front/top of the motor and re-checked everything: TDC, harmonic & it’s TDC references, cams & part numbers per-bank, cam-alignment (intake to exhaust), overall timing, but nothing to report, all was to spec, plugs all matched in burn patterns & color. I also did the dowel-in-the-#1-spark-plug-hole trick to ensure that TDC matched the crank (it did), and removal of the valve covers showed that I was indeed on TDC on the compression stroke. Cams were timed 180d out to ensure that the motor is indeed a wasted spark, wasted fuel system (yes, runs the same). Ignitor harnesses were swapped to ensure it was a wasted spark system as well, but of course, this did not change the running. Also, per the manual, the passenger’s side igntion rotor faces directly at 3-o’clock position as it’s aligned with the #1 cap-point for cylinder #1 when the harmonic is set to TDC (& the driver's side rotor faces about 2pm position).

My last effort was to swap in another engine wiring harness, not that I had doubts in the one I had, but just to rule it out. The consistent spark & timing mark indications did not leave me feeling uncomfortable, but I was out of options. A 4-page post on Rennlist and countless emails to Wally, Mark, and Marc still left me without issues, though I'm really appreciative of their time in assisting. Now, of course, with the installation of the good used harness, nothing has changed. My motor still runs as it did with my timing patch installed (trigger ring spun to match 11d at idle), where I was hoping that with the new harness, the car would not start and all I would have to do is remove the clutch (actually enjoy this now) and reset the trigger wheel.

Bottom line: all rotating/timing components to the motor are keyed in place: harmonic is keyed to the crank, flywheel is dowel-keyed to the crank, cam sprockets & hubs (same part numbers on each side) are keyed, so there’s no way to get them “off”.

Here is what I’ve NOT confirmed so far:
-crank: there is a difference between the pre-32v cranks and the 32v cranks up to the GTS. This 5.0 32v motor appeared to have never been apart before, but if (for some odd reason) it had in the past, and someone put a 2v crank in it, would the dowel-key be in the same relative position to the 5.0 motors? Unlikely, but I have to consider odd things now.

-Intermediate plate in the clutch assembly: I’m using an ’82 (new) plate as the “package” for 928’s covers ’80-86. On closer inspection, the ’85-86 intermediate plate is slightly different as it has a pair of reference dowels in place to tell the extra TDC sensor (extra TDC sensor is not used by the LH or EZK modules as it doesn’t even wire up to anything, it’s just for mechanics to use in determining TDC…why??) where it’s at. Other Rennlister’s have disclosed that they too have this extra TDC sensor removed. My difference from them is that I do not have the correct IP, but the posts are not supposed to be magnetized, so there should not be any interruptions in the magnetic field generated by the timing ring & crank trigger….but who knows at this point.

-front harness: front harness to the ignitors remains euro-spec LH Jetronic, for which the US Jetronic is slightly different by nature…can something with this harness explain my near 90d advance at cranking? Probably not, but who knows at this point.

Last night (it’s almost morning now) I did some measurements on my harmonic as I marked the spot (approx 90d BTDC) where my timing light was flashing to see how close it was to 90d exactly. My theory: if it’s EXACTLY 90d off, then there’s some mechanical issue here, as 90d is exactly one cylinder off in my firing order being that 4-stroke motors require 720d of rotation for one complete cycle of 8 cylinders to occur. I found that my ~90d mark (at cranking) was exactly 90d before the 7d mark at cranking that it should be at on a normal motor.

Previously, when “making’ my engine run by my hack-indexing, I shot for 8d at cranking and got 11d at idle (at 800rpm), so there’s a 3d difference between cranking and idle. 90d back from my mark on the harmonic is exactly 7d, where it should be.

Ok, my eyes hurt as I’m sure yours do as well. Do you have any idea why my motor wants to fire 90d too soon? Weird thing: mechanically, the passenger’s distributor rotor is in between cap-points 4 & 1 when it’s firing to #1, so, it’s mis-firing to the #1 about 90d too soon, meaning my last cylinder in the sequence, #8 (1,7,3….4,8) is (should be) correctly firing at TDC. I need to borrow back the timing light to confirm this.

Another hack could be to rearrange the wires so that my firing order is advanced by one cylinder, but with the results of my last hack-job, I really don’t want to solve the issue like this (since it’s not solving anything). Whoever leads me to the resolution of this problem will get a multi-hundred dollar gift certificate to anything they want: Porsche parts, Pizza, Beer, I don’t care, I just want my beast to run correctly so I dyno well at the local Porsche club dyno day in two weeks, let alone to drive my 4-year project car!!

Thanks again, I've been sick for much of this last week, and may not be able to respond to posts on this timely as I'm still recovering, but if you are sure of my issue, call me, I'd be delighted to take such a call regardless of my fever.

Mark Robinson
(512) 799-8479
’91 C2 turbo, 12.2@ 117mph
’85 928S euro, 32v swap (see description above)
’86 944t vette-teaser.


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Bill 86.5 928s

Mark......I am by no means a Porsche mechanic and am not that familiar with the dual distributor used in the Euro engines...But are they both identical and can be interchanged ? ...Is it possible that the left is in the right etc....maybe a diference there is causing the 90 degree shift....again I am no expert, good luck, I hope you find your problem before the dyno test......Bill

Old & New

"...the passenger’s distributor rotor is in between cap-points 4 & 1 when it’s firing to #1, so, it’s mis-firing to the #1 about 90d too soon..."

I think you are onto the problem right there - there is some problem with the timing of the cams, the position of the belt, etc.

Lagavulin

Hi Mark,

I was going to offer this during your earlier post regarding this same matter, but didn’t think it relevant as you were getting plenty of good feedback and assumed/hoped that the problem would be solved.

We had an eerily similar issue over here with ‘The Local 928 Racer’ Jean-Louis and his 84 Euro race car. I know it’s not the same year you are dealing with now, but something similar principle-wise will maybe inspire you to think of something you haven’t considered before.

Z, myself, and JL worked on that car a lot last year (..was truly lots of fun), so it’s hard to recount exactly what we were fixing when we came up against this phenomenon which took over 2 weeks and many hours to diagnose.

The symptoms were a rough idle, where the rough running continued up until about 3000 RPM, whereupon it ‘cleaned up’ and ran perfect with full power up until redline. This was also audible in the exhaust note as it did not sound right below 3000 RPM.

The timing light revealed that the timing was WAY off; I do not remember the actual numbers at this time. However, I do remember us thinking that it seemed like it was almost off by a cylinder.

So we attempted to time it correctly which did not work; took the distributor out and advanced and retarded it one gear-position and tried re-timing it; messed around with the sparkplug wire positions on the distributor cap; considered that maybe the plug wires were bad and cross-firing was occurring; etc. We checked, double, and triple checked everything, but could not figure out what was going on and were stumped; all of us a pretty good wrenches too.

To make a long story short, it was the innocuous little ‘green-wire’ which goes from the distributor to the brain! During the course of this journey, we went over and over and over again, 'what was different?!?', 'why can't we solve this?!?' And every time the answer was the same, the new green-wire was the only thing different. Finally, JL replaced it with the original one, and just like that, problem solved!

I don’t know if you are aware of it, but there was a bad batch of green-wires Porsche had shipped out, and JL got one of them.

I know you don’t have a green-wire, but maybe there’s something similar going on with your setup.

Good luck!

ViribusUnits

The green wire doesn't exist on that car.

Bill's idea sounds really correct to me. If cylinger 1 is fireing 90 degrees early, and when the cap is half away between the two points, then the comuter is fireing for the left side coil, but it's coming out of the right side coil for some reason. The plug dirictly before number 1 is number 8 right, and thats on the other side of the engine.

Have you tryed reverseing the wireing?

SharkSkin

I'm not an expert on these motors, not by a long shot. But I'd like to point out that your two cylinder banks are offset by 90º. So what this means is that your cylinders are not necessarily supposed to fire at exactly 90º intervals(are they?). Perhaps you have simply mixed up the two cylinder banks. Track down your coil connections. Yeah, the connectors all fit together, but track it down nonetheless. I don't know the system in-depth but it seems possible that you have the signals to either half of the ignition mixed up somewhere along the line.

PM me for an address to send the $$$

D

[Edit]Looks like VU beat me by a nose... I loaded the page then went & made coffee before replying [/Edit]

ViribusUnits

The engine should fire pretty much every 90 degrees of the crank.

In 2 turns of the crank, all 8 cylinders fire. They fire at even intervalls. If you feel like confirming this, jsut take a look at any 90 degree V8 with one distributer. The rotor, and the points are arranged in an even arrangement.

So take 360*2/8 = 90 degrees between each spark.

SharkSkin

Post-coffee, I see that I was not thinking clearly. but... I think the idea of having the sides switched has merit... maybe...

T_MaX

I didn't read anywhere where you verified your wire harness hook-up, did I miss this?

If not, I would suggest pinning-out and checking resistance of the wires with and without sensors/coils hooked-up.

Than check/swap brains if nothing out of the ordinary is found.

No reward required

MarkR (FAST)

Hi Guys, correct, no green wire.

I have pinned out most things, though not the coils/ignitors yet. I know they will probably check out ok, as they do work ok, just 90d off.

I removed my clutch and reset the timing wheel (again) to stock, did this in less than 2 hours! (thanks to the help of my new exhaust system, designed to allow clutch changes w/o removing the exhaust.

what I plan to do today is to rearrange my firing order to start with #8 first (where it tries to fire, though I need to retrieve my timing light as well.

anyone need to purchase a good used Engine wiring harness for an '85-86 US spec 32v motor?

Mark

MarkR (FAST)

Hi Guys, the coils fire a total of 16 times it appears: if you switch the wiring harnesses at the ignitors, nothing changes, meaning, both coils fire at the same time, both on the correct cylinder, and in between cylinders on the opposite bank (cap, coil).

Two months ago when a Porsche Mechanic suggested this, I REALLY thought that was it...but to no avail. I've switched them a few times JUST to be sure I really did it.

Mark

Kevin in Atlanta

I have a good 85-86 wiring harness in my garage. PM me. Here's a picture:



The wire to the t-belt warning is missing.

Steve Cattaneo

Mark,

Did you check each individual timing reference with a compression gauge installed I would bring the number1 piston to TDC and confirmed with a gauge that it is truly on compression stroke, also check that both valves are closed and that the rotor is ready the fire that corresponding spark plug. Check each cylinder the same way in the firing order of the motor. While the number 1 cylinder is at TDC look in the hole for the ignition timing sensor you should see the wide tooth gap on the ring gear. How did you index the cams; the cam marks should be pointing to the copper colored chain links.

good luck

MarkR (FAST)

Hi there,

Yes, two weeks ago I removed the valve covers, caps, timing-belt covers, and put the motor on TDC, verifying that the marked TDC on the harmonic really was TDC: compression stroke: intake valves were the last to close, exhaust were next to open, and #1 piston really was exactly at the marked O/T on the harmonic.

I have 100% confidence in the mechanical alignment of my entire motor, and am convinced that my issues MUST be electrical at this point because I've ruled out all other mechanical suggestions, INCLUDING the crankshaft as I referenced another '86 crank yesterday only to verify that my crank/flywheel alignment dowel was indeed in the same 5:30 position as my motor....ruling out my 2v crank suggestion (long shot anyway).

Yesterday i spent 2hours changing my clutch & re-spinning my flywheel to match the true-spec'd TDC location, as i have twin gouges that verify this, and again, the motor will not start as the light is flashing at exactly 97 degrees at cranking, whereas a healthy motor flashes at 7 degrees at cranking...

Mark

ViribusUnits

Let me ask you a couple questions.

1. Have you tested the cicurty up to the triggers for the coils, to be sure that each one has an indipendent feed? Looking at the wireing diagram, each coil trigger should have a independent feed, and a common ground. Maybe they're somehow jumping in the harness, and causeing things to get confused. (PS, maybe that is backward. common feed, independent ground, but I'm pretty sure that it's independent feed, common ground.)

2. If it is fireing 16 times per 2 revolutions, you should get two points on the dampaner where the timeing light fires. Are you?

2.a, Is the 85 one of the cars that you can hook the timeing light up to the engine wireing harness, and not use an inductive loop or dirict pick up? Are you useing the inductive loop, or dirict pick up, or the wireing harness?

3. Could you somehow have gotten the left distributer on the right side, and the right distributer on the left side? I know it sounds stupid, but it's worth checking.

A possible explination for the problem is that when you have the coil triggers one way, it fires the coil for cylinger 8, which then jumps to cylinger 1, giveing you 90 degrees of advance. When you switch the ignighters, they match the distribors. When it fires for cylinger 1, it is distributed in the other distributer to cylinger 3. However, it will not run, because cylinder 3 is at the exaust stroke. It should also send the fire for cylinder 8 to cylinder 1, but w/o the jumping. So, if you switched the distribors, (left to the right, and right to the left) and not coil triggers, when it fires for cylinger 8, it actualy goes to cylinger 8, instead of cylinder 1.

I don't even know if I should suggest it though, because it seems so stupid, and I'm not even sure if you can arrange the plug leads in that mannor.

PS However, after looking at pictures of the plug leads, and the fireing order, I'm fairly sure that you can run the plug leads backward. Also, there is apperently one PN for the distributers and rotors, so it deffently looks like you could get it backwards.

PSS, if you decide to try to flip them around, rember to try the coil triggers both ways.