F18Rep

EJ... what a nice, direct no-start thread.

This same thing happened on my first 944 (15 years ago) and I had to come up with reliable hack to get the thing out for a drive. I wish I had a pic bc it was so ugly. I opened up the boots, dug out the potting compound and taped the wires so they would stay separated. Then I dug up two carpenter's pencils, and splinted the "mess" so they would stay in position. It looked like hell....Bruce

EJZero1

Not sure I can put off getting it fixed. It's been months since I've been able to drive it, and can't stand the idea of wondering whether or not it will start next time I have it out for a drive. Past experiences have taught me these types of things only get worse. Had to get it towed home due to this problem once already. I just want to fix it.

I would love to have seen a picture of that!

Thanks to everyone for contributing! Will post up my fix action and the results as soon as I have time to do so.

Tom M'Guinn

Here are the quick, easy, and reliable solutions:

http://944online.com/index.php/944-r...r-harness.html

https://www.lindseyracing.com/LR/Por...4-HAR-REF.html

Or if you want to try your hand at replacing the connectors only, here's a thread with more than you probably want to know about the connectors:

https://rennlist.com/forums/944-turb...onnectors.html

I'm not terrible with wiring and electronics and I found it easier and more reliable just to get the replacement patch harness for $90. When you try to replace the connectors only, you end up with little wire to work with and have to deal with the shielding, etc., so it starts to feel sketchy. It can be done for sure, just didn't seem like the best approach for me. Just FYI, there is no "genuine" replacement other than buying a whole new engine harness (if available). Porsche will sell you the connectors and pins, but there is no real point in paying extra for such universal connectors...

EJZero1

Thanks for the info, Tom.

Although hesitant, I was going to try my hand at just cutting the bad connector off, and replacing it with a new one. The shielding issue you mention was one of the reasons I was hesitant.

Sounds like my best option would be to go with one of the harness repair products you linked to. I'm guessing there's some soldering involved? I've done some soldering in the harness during the install of my M-Tune and Zeitronix WB, so I'm not a stranger to it, just not overly comfortable...

If you (or anyone else) has experience with installation of these products, and could provide insight, I'd greatly appreciate it.

Thanks again.

NCLA951

Minimal soldering if I remember correctly, mostly pulling Pins out of the DME connector and replacing them with the new Pins.

Tom M'Guinn

Right, no soldering with those replacement harnesses.

Edit: here's a link to the installation instructions so you can see what's involved:

https://www.lindseyracing.com/LR/Parts/REFINSTALL.html

EJZero1

So, if I'm following the directions correctly, soldering just one ground wire? I can probably handle that. (I hope so, anyway. I've already ordered it!)

My only real concern now is this: I've done a bit of alteration to the harness to the extent necessary for the installation of the M-Tune and Zeitronix WB. Given that it only appears I'm soldering a ground wire in this installation, I'm hoping THIS installation doesn't alter anything done in THAT installation.

Thoughts?

Edit: Tom, I just reread your comprehensive write-up reference your own Zeitronix installation (the exact same write-up I referenced during my own install). After reading the harness repair instructions and your Zeitronix write-up, I didn't see any DME pins that were common to both projects. Am I missing anything?

Thanks again for all of the inputs!

Tom M'Guinn

I could have sworn mine required no soldering, but not sure I got mine from Lindsey. Sorry about that. Maybe practice on some spare wires before the big event. I don't think you're missing anything -- I can't think of any aftermarket part that alters or taps into the speed/ref wires.

EJZero1

A big thanks to Dave and his team at Lindsey Racing. Just ordered this late Monday afternoon, and at my door today.

Reading the instructions, I may have discovered why some may not have had to solder during their installation. These instructions indicate if you no longer use your factory O2 sensor, no soldering would be necessary. Alternativly, if you're still using the factory O2 sensor, the cutting and soldering of one wire is required.

As I've alluded to, I have installed a Zeitronix WB, to include the O2 sensor downstream from the turbo. I don't recall taking any steps specifically to discard the factory O2 sensor and its associated signal. It is still in place and connected.

My initial thoughts are to install this new sensor harness in accordance with the instructions for maintaining operation of the factory O2 sensor.

Anyone have a suggestion/rationale for the alternative installation?

Thanks again, everyone. I really appreciate the info provided here. With any luck I'll be posting an update this weekend of my 951 cranked up and ready to go!

EJZero1

Well, as much as I'd love to provide the happy ending update I was hoping for...it doesn't start. The same exact issue persists. What's incredibly frustrating is that it started last weekend. Took my wife out to the garage last weekend, excited to show her that after months of troubleshooting I thought I had at last found the problem. Started up then, too.

Installed the replacement harness today, climbed in, hit the key...and no spark. Confirmed again with the inline tester from coil to distributor.

Did an hour's worth of continuity tests. Just for the hell of it, I'll tell you the findings.

The pins in the connectors are undoubtedly numbered, but right now I'm too damn frustrated to look it up. Let's assume that we're looking at the connections at the sensor end of the harness, 2 "mating slots" at the bottom, single "mating slot" top center. In this orientation, let's number the female tab receivers 1-3, left to right.

I've got continuity from:
Forward (or "B" sensor):
Pin 1 continuity to DME pins 2, 4, 5, 16, 17, 19, 30
Pin 2 continuity to DME pin 26
Pin 3 continuity to DME pin 25

Rear (or "D" sensor):
Pin 1 continuity to DME pins 2, 4, 5, 16, 17, 19, 30
Pin 2 continuity to DME pin 27
Pin 3 continuity to DME pin 8

I'm assuming pins 1 at each connector are for ground. Continuity at remaining pins matches installation instructions. I checked these connections at least half a dozen times, to include after I slid the DME plug cover back on to make sure it didn't pull anything loose.

While I was down there, I checked continuity from DME pin 1 to the coil. Good continuity.

To say I'm frustrated is an understatement. I've gone from looking forward to taking my 951 out for a drive finally, to back to square 1 after exhausting all of my trouble shooting efforts.

In summary, all continuity from sensors to DME checks out, and I've still got no spark.

Please help. My next purchase for this beautiful, but non-running 86 951 will be a "For Sale" sign.

F18Rep

That Lindsey kit looks good. Please say how you got the old pins extracted...Bruce

86 turbo

NCLA951

This is one of the reasons I ended up going VEMS, a system that tells you how it's doing vs stabbing in the dark at potential causes.

DME/KLR test plan is prob your best bet if you stick with DME. But you need an oscilloscope.

Tom M'Guinn

Bummer, sorry about that. I usually step away for a while when I get frustrated. Your wiring appears correct (your pin numbers are opposite of factory numbering, but accounting for that, it looks good to me).

Does your tach still bounce like in the video when you crank the motor? It shouldn't do that, so it's trying to tell you something.

Have you checked the DME and KLR for solder joint cracks? See:

https://rennlist.com/forums/924-931-...ed-w-pics.html

Do you have a factory alarm and, if so, have you bypassed it?

Have you bypassed the KLR to make sure it's not killing the ignition signal?

Are you sure the gap for the speed and reference sensors are set right?

EJZero1

Pin extraction was pretty easy. I used a tiny screwdriver like the ones used to repair eyeglasses. Slid it up in the slot next to the pin socket to depress the "barb" and the pins lifted right out.

The most challenging part of the installation was getting the harness through the boot in the firewall.

Tach still bounces, but not as dramatically as the video I posted. Consistently bounces up to,about 750 while cranking now.

You mention my pins being opposite of factory. Are you referencing my attempt at identifying the pins on the sensor plugs?

Shortly after I bought the car I about 5 years ago it had an intermittent stall issue. Resoldered some of the suspect points and it had been running flawlessly since then til this issue. That issue was no where near as symptomatic as this one.

No factory alarm.

Haven't tried bypassing the KLR yet, but it's on the do-list I'm already putting together for tomorrow. Also,going to run some Clarks Harage diagnostics in an attempt to rule out a failing ignition switch.

You mention sensor gap as well. Wouldn't that have prevented the multiple successful starts last weekend? The only thing I did between the no-start condition and the multiple successful starts was swap connections, then swap them back again.

Gonna get some sleep and reattack tomorrow.

Thanks again for the inputs. I wanna track this gremlin down and beat its ***.

Tom M'Guinn

Agreed, if it works intermittently, then it's "probably" not the gap.

You just listed pin 1 as 3 and pin 3 as 1, compared to the factory manual, but looks like the wires all go to the right places...

Normally the tach just twitches a little. Makes me wonder about the DME ignition driver. Do you have access to a known-good DME? That transistor can burn out... Bypassing the KLR will at least help rule the KLR out.

If you previously found bad solder joints, it increases the odds of there being more bad solder joints I'd say. Have you looked recently?