86 Turbo fuel pump wires both show ground.

[Richey]

I'd suggest bypassing the KLR to see if you are losing the spark on its way through, but that wouldn't explain the fuel pump not powering up. Since you have no power to the fuel pump and no spark, you never know, but I doubt the issue is the coil per se. Seems like something upstream -- DME relay, alarm, key switch, etc. I'll mull it a bit.

Can you point me in a direction to do this? Google's algorithm thinks I want to know about Kawasaki KLRs and ignoring "Porsche 944 KLR bypass".

[Tom]

Basic instructions are here:

viewtopic.php?t=4092&start=20#p45777

But I can't think of any way it would help with a fuel pump not getting power...

[dr bob]

<<....>>

Can someone point me to the current flow diagrams for the 951? It would allow me a more specific diagnostic support path. I'm a diagrams/meter/test diagnostician. Always learning!

The schematics represent 9 or 10 fold-out pages in the factory manual. I'll see about scanning them to a pdf and uploading here.

Tom -- Shirley Someone has posted a set on a website somewhere. Does anyone have contact info for member Shirley Someone? Or a current link to that Somewhere website? Somewhere.com isn't the one.

[Richey]

So I just watched a video that shows doing the alarm bypass with the module plugged into the car. When I looked at Clark's Garage it shows jumping 1&4 and 7&8 but says nothing about the module being plugged in at the same time.

Then I found this video that shows the same jumpers but with the module plugged in.

Does it matter if the module is plugged in or not?

My attempt at the alarm bypass was with the module unplugged.

[dr bob]

Some searching brought me to the Clark's Garage site https://www.clarks-garage.com/shop-manual/fuel-05.htm with a detail of the DME relay itself. Two relays integrated into one case. The relay internal diagram suggests the following:

First contact enables the second when it gets closed by power from ignition key circuit 15 to relay pin 86, with ground to relay pin 85. The first contact supplies power from socket from pin 30 (always hot from battery) to the DME plus the injectors via the socket terminal for relay pin 87.

When the DME detects the engine is turning, it grounds the socket terminal for pin 85b. Assuming that the first contact is closed, power from 30 is supplied to relay pin 87b, with the socket connection supplying battery voltage to the fuel pump plus the heater in the exhaust gas oxygen sensor.

----

Early AFM-equipped 928 cars use a similar relay. The emergency travelling spares kit for those cars has a 3-legged jumper wire with a toggle switch in the middle. Two legs connect to one side of the switch, the third to the other side of the switch. Each wire has a standard male spade connector. The single-wire connection goes to the socket for pin 30, while the the other two tied together go to 87 and 87b socket connections. Close the switch and you have power to injectors, the DME itself, the fuel pump, and the heater for the exhaust oxygen sensor.

Use care with the jumper as a diagnostic tool. It will run the pump and power the injectors, and if there are any other issues with starting that can risk filling cylinders with fuel if the engine isn't actually cranking or running. So use it to rule out a failing DME relay, but not as anything more than a limp-home 'crutch' if a failing relay otherwise strands you somewhere that isn't your own garage. Accidentally leaving the switch closed will also drain the battery in short order if the engine isn't running.

[Richey]

So 30 should always have 12+
86 should only have 12+ when the key is on.

87 and 87b should get 12+ when the key is in the start/run position.

Should 85 and 85b always have ground or only when the DME provides a ground when the car is starting/running?

[Richey]

So following harnesses I found this. I don't think it's the current issue but it's something I'm going have to address very soon. I found a harness kit from Lindsey Racing I'm going to use for this. I think I'll make this harness repair before looking to pick up a second DME to test.

The only reason I don't think at this moment it's causing my issue is that at the DME harness I'm getting about 980-990Ohms on both sensors. I'm also getting the expected voltage on each test.

I used this video as my guide.


I did manage to get the relay bypass to work tonight and get the fuel pump to fire off. Maybe my made up harness wasn't in there well enough.

It will probably be a week or two before I get the harness replacement and get it swapped out. I'll update this once I do the next steps.

Thanks for the help guys.

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Screenshot 2025-09-16 at 8.58.25 PM.png (5.91 MiB) Viewed 432 times

[dr bob]

So 30 should always have 12+

Correct!

86 should only have 12+ when the key is on.

Correct!

87 and 87b should get 12+ when the key is in the start/run position.

Not quite --

87 gets 12+ only when the key is on.

87b gets 12+ when the DME detects the engine is spinning.

Should 85 and 85b always have ground or only when the DME provides a ground when the car is starting/running?

85 is ALWAYS ground.

85b gets pulled towards ground by the DME when it detects the engine is spinning. Cranking or running will do it.

This is a failure/protection function, so the fuel supply is shut off if the engine stops while key is on. Like after the crash, when we don't want the fuel pump feeding a fire, and we might be too dazed and confused to turn the key off. Or we get out of the crashed/burning car and forget to turn the key off. I'm sure there are several other common scenarios where the function helps.


The linked narrative from Clark's Garage reminds us that the heater for the exhaust gas sensor is also connected to the fuel pump part of the DME relay. If you are troubleshooting pump connections and continuity with a meter, unplug the oxygen sensor before testing.

[Richey]

I got around to changing the connectors and still crank no start. I also replaced the DME relay and that didn't help either. I also know my reference sensor and speed sensors are good as they test fine with a multi meter and they put out voltage in the correct range when turning over the starter.

At this point what else is there to test/replace? The car cranks over freely but there is never even the slightest attempt at starting. It might be the DME but I really have not found any good suggestions on how to test the DME other than just swap it out against another one. I don't have a second DME to test with so I'm kind of at a dead in.

Any suggestions on how to test the DME short of just buying another one?

[Tom]

I got around to changing the connectors and still crank no start. I also replaced the DME relay and that didn't help either. I also know my reference sensor and speed sensors are good as they test fine with a multi meter and they put out voltage in the correct range when turning over the starter.

At this point what else is there to test/replace? The car cranks over freely but there is never even the slightest attempt at starting. It might be the DME but I really have not found any good suggestions on how to test the DME other than just swap it out against another one. I don't have a second DME to test with so I'm kind of at a dead in.

Any suggestions on how to test the DME short of just buying another one?

Did you just put new connectors on the old wires or install patch harnesses like LR and 944 online sell?

If you want to send me your DME, I'll toss it in my car and see if it fires up...