notnilc20

Good morning fellow 944 enthusiasts. I have a 1986 951. Car was running great then I decided to try to add more power. I just finished installing the following:
Vitesse MAf conversion (12v switched source from one of the dme power lines)
Vitesse stage 2 turbo
Vitesse piggyback (smt-6 from perfect power)
​55lb.injectors w/resistors
3 bar fpr.
tial wastegate
LR MBC
used a dme from an 88 turbo S w/ vitesse performance chip(because chip has 28 pins compared to my 86 dme with 24 pins).
UEGO 1000 closed loop wideband a/f ratio gauge

Now my issue is as follows;
Go to start car, engine cranks over and has tach bounce but no spark
see video https://youtu.be/xzN1Jkfn4Y4
Coil tests good using multimeter getting 12v from both terminals and measuring ohms and the one spark when I turn the key as seen in video.
I removed spark plug and smell fuel and connected a noid test light to one of the fuel injector plugs to verify they are pulsing.
tried the bypass of dme relay and still nothing.
I notice the factory immobilizer box gets warm in certain spots so I tried bypassing it as well with no luck still. (still wondering if that's normal for it to get hot like that.)

Reference/speed sensors checked out ok with ohm meter. However measuring resistance between terminals 25 and 78 and 8 and 23 on the plugs according to clarks garage info it says these readings should both be >1 M-ohm. Admittedly I didn't know how to read this on my cheap meter. I tried every setting but meter would only read 1. But the meter was always at 1 whether connected or not.
I tried plugging my original dme in to make sure the one provided was not faulty as well a spare klr. Still nothing.

Somehow the dme is not signaling the coil when to fire.

So now I come to the experts here at rennlist. I'm about out of ideas. Whoever comes up with a solution I will PayPal them enough money for a case of their favorite cold brew. Thank you for your time.

Chapman951

I replaced my o2 sensor once and accidentally fried the wires against the engine.
Did you do anything with the o2 sensor recently?

Chapman951

I watched the video.

My car would keep cranking but not start when the DME failed. I resoldered the connections and the car started up again.

Pushing down on the white connector would get the started temporarily. Or you could try smacking the DME.

notnilc20

Thanks for the reply. When I did the turbo install I removed the O2 sensor. But would that cause no spark ?

slivel

First i would re-confirm that the MAF and PB are installed correctly. Second, the PB has a bypass plug that you should insert and eliminate the PB as the problem. If no change when bypassed, remove the bypass. PB has the ability to do some logging and I would try to collect some data. I had this same system (minus the Vitesse turbo) installed on my 89, in fact it is still on the car but now it's owned by my son-in-law. As I recall the Vitesse version (proprietary) of the SMT-6 does not allow for ignition adjustments and only fuel curve changes so a no-spark condition may point to a bad DME. Since you changed so many things at one time this may be a difficult problem to solve but it sounds like you are methodical in your approach. Check end-to-end continuity of all wires involved in the MAF/PB install as a minimum and also the sensor inputs like reference sensors throttle position etc. A pushed pin in a connector can be hard to find but will cause a problem like you describe. Maybe get a better VOM for troubleshooting. I think John Vitesse monitors this board so maybe he can suggest something. I will say that although the SMT-6 PB is 20+ years old, it still is working perfectly in my SIL's 89. Good luck.

notnilc20

Hi There slivel thanks for your reply. A few things. I don't seem to have a bypass plug on my piggyback unit. Is there a way to do this?
the piggyback integrates between the factory afm signal and dme and converts it to a maf signal. So If I bypass the piggyback, that will kill all connections to the maf. Maybe I can see if I can get spark this way, correct?

John at Vitesse has informed me that they have lost all their back information from a fire, so there is no more support for this kit unfortunately.

I will say, the individual I bought the kit from has been helpful with sending me pictures and working out the wiring etc. However, there were some things in the piggyback wiring that we were not 100% on and we had to use old diagrams from Perfect Power but even so, Vitesse had modified the original smt-6 to make it their own I was told by PO. Is there any possible way you might still have any installation instructions or wiring diagrams? Or software?

Thanks again for your time.

slivel

If I remember correctly the bypass was a small circuit board that plugged into the connector that plugged into the PB. The car should operate with the bypass but with no additional signal massaging that would be done in the PB, so just whatever the chip on the DME is set for. I don't know what it would take to make a substitute for the bypass board.
I do not have the original documentation.

slivel

In re-reading your original post, I have a question. You changed to a 28 pin DME with a Vitesse chip installed. Was this intended for an AFM or a MAF? I think it matters. Also your recent post said "the piggyback integrates between the factory afm signal and dme and converts it to a maf signal". If you are running a MAF, you don't have an AFM signal - you have a MAF signal and the DME must be able to use this signal profile correctly. This is why the chip in the DME is important. The PB is a pretty simple device that will allow some massaging of the signal before it gets to the DME. Years ago when people started putting MAFs on 951's they tried compensating for the AFM profile by intercepting the signal and massaging with some potentiometers and filters. It was not a very good solution. Later chips were developed to handle the MAF signal directly. The PB just gave the ability to adjust for differences like 3" exhaust or different turbo, or headers, cam etc. Trying to dial in a PB as a substitute for a stand alone would be a very difficult task.

mwc951

...

Chapman951

I have connected/disconnected my o2 sensor many times and the car kept running.

notnilc20

The dme with the Vitesse chip installed is for the maf conversion. Thanks again.

michaelmount123

You haven't contacted Vitesse! That's where I would have started. His customer service is excellent!
MM

notnilc20

I have. They no longer support this kit. Also, he said all the info for this kit was lost in a fire.

fast951

Based on the information I was given, this product is about 18-19 years old. It was discontinued 16+ years ago! Documentations were lost due to a computer crash years ago (not a fire).
Due to age and the fact that this setup was discontinued and was superceded by a much more advanced setup, free support ended.
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It appears that many changes were made to the car at the same time. Finding the real cause will take time and a thorough diagnostic must be completed. There is no telling if there is a faulty part, mismatched components and/or improper installation.

Keep in mind, ​​​​​​​this particular setup differs greatly from later ones. What works on newer setup may not work on yours.

​​​​Did you verify the DME and KLR are functioning?

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notnilc20

KLR is functioning, a local indy porsche mechanic lent me a klr to swap and it gave the same symptoms.. I used the DME that was provided with the kit (88 DME with 28 pin vitesse chip) and I also reinstalled my original dme to see if the car behaved the same and it did. (Cranking, no spark, tach bounce present). If you have any info available I would gladly pay for your time.
We (previous kit owner and I) were going off some old pics he took from when he removed the piggyback from his car. We thought we had it all sorted out. But obviously something is not correct.