87 944 turbo no start, have slight tach bounce

[WHLSUP]

I have a 944 Turbo that will not start. I have tach bounce while cranking, just off bottom of the gauge. I have tried a new DME relay, installed both new hall effect sensors due to harness plugs deteriorated and crumbled when testing with scope. new sensors have good scope reading clear down tot the DME harness plug. I do have fuel at the rail during initial cranking, but no spark. I can generate spark with key on by grounding coil momentarily.

Any help would be greatly appreciated.

[mytrplseven]

I hope you didn't buy URO DME relays and expect success. They're crap and strong probability that they'll fail right out of the box.

[DannoXYZ]

Is your distributor rotor aimed in correct direction? Are both screws tight?

[WHLSUP]

I forgot to mention that I did also try the DME relay bypass, The results were no different than with relay installed. I have fuel pressure, no spark at the coil. The tach is slightly bouncing during cranking. The cap and rotor are good, bolted in properly.

thanks

[kdjones2000]

Do you have injector pulse? You say you have tach bounce, so pull the injector rail and look if injectors are squirting fuel.

If you have injector pulse and no spark, then your computer (DME or KLR) is bad.

You can bypass the KLR out of the circuit if you follow the DME Test Plan. That should narrow it down to one or the other.

[WHLSUP]

Thank you for that path to check. I do have pulse with noide light at the injector rail. I followed the DME test plan to test 14 and the scope does not show a square wave, but rather a constant voltage with no drop to ground while cranking, see video and picture. So at this point I am going to make the determination that the DME is at fault. Can anyone point me to where I can send in for repair?

Thanks for all the help with this.

[kdjones2000]

Bypass the KLR first. It can cause issues that you think are DME related, even though the Test Plan pretty clearly states that it's likely the DME.

One other thing you can try is to pull apart the DME and look for cold solder joints, especially in the spark control circuit area.

There are documents out on the interweb that can help you find that location on the boards. You may have some fried output resistors or transistors.

Regarding testing/refurbishing: I know that 944 Online does that, but there are others out there as well.

Good luck...

[WHLSUP]

I didnt see the bypass details in the DME test plan. Do you know which test or how to bypass the KLR?

Thanks

[kdjones2000]

Connect #9 to #16 with a jumper:

https://rennlist.com/forums/944-turbo-and-turbo-s-forum/441254-klr-bypass.html

[WHLSUP]

BINGO! we have ignition. With the KLR bypassed it starts and runs. Now to find either the known problem with the KLR or send in for repairs...

kdjones2000 thanks for your guidance with my problem, you were invaluable!

[kdjones2000]

The bill is in the mail

Glad you have it running, just don't go on boost without your KLR in the loop or bad things will happen.

I would just get a new-to-you one. If you have special chips in yours, just swap them out.

[soxnail]

You would reckon I could find schematics for the KLR, its 35 year old tech....But no.
Any way as I occasionally post if any one has any source or knowledge of where I might acquire them I would really like to, so trouble shooting would be a tad easier.
Thanks.
Sox
Ps. I pull this post out every few years, may get lucky one of these days

[kdjones2000]

I thought I had them, but it looks like I only have schematics for the DME.

[UROParts]

Originally Posted by mytrplseven

I hope you didn't buy URO DME relays and expect success.

Hi everyone, quick FYI: as of March 2018, URO discontinued its second-generation DME relay and released a completely-redesigned third-gen unit. The new relay utilizes strong through-hole component mounting using Surface Mount Technology (SMT) "pick-and-place" robotics in a clean room environment for consistent assembly quality, along with modern modular-design mechanical relays for long-term reliability. We'd be happy to provide one of the new units to anyone who had one of our DME relay 993 615 227 01 fail in the past, just contact us with your purchase details (send a private message here or email "sales @ uro parts . com", remove spaces) and we'll get you one of the updated units.

Here's what Rennlist member "steeley90" had to say about our new relay:
"The parts arrived at my work and I swiftly made my way to the car park to try one out. I wish I had a dash cam that had captured my face when the car started first time with the new relay installed. I'm absolutely ecstatic. I cannot value these new relays high enough. I've tried every other option of relay including Porsche OEM and none worked. It's still a luxury for me to get in the car and not have to pop the bonnet. One I'm sure I won't get tired of for a long time. Thanks ever so much to the guys at URO, you've made this 944 owner the happiest guy!"

[kdjones2000]

Ummm, the resistors shown in your 3rd Gen part are still through-hole technology, not SMT.

I assume that the improvement is the solid-state relay as compared to the mechanical relays in your 2nd Gen part.

[UROParts]

^ Thanks for pointing out the lack of clarity, edited the post to better explain how the new URO relay uses both technologies.

Through-hole mounting is stronger and preferred for military and aerospace applications, plus our factory is using SMT robots to place the components on the circuit board, which is far more accurate and consistent than the hand assembly used by our competitors (and quite likely OEM). The relays are still mechanical, but they are modern self-contained modular units that are higher-quality and more consistent than older OE-style relays.

Here's a good video showing this type of assembly (skip ahead to 0:53): https://www.youtube.com/watch?v=2sm_qdeconI

[soxnail]

The new relay appears to be a Song Chuan 905-1AH-C which is not a solid state, but has a coil and contacts in it ?

[UROParts]

Originally Posted by soxnail

not a solid state, but has a coil and contacts in it ?

Correct, the relays are mechanical.