Time and process to replace RPM sensor

[Ski]

Hello all!

I've been working with Ingo Schmitz to troubleshoot crank no-start, and after eliminating fuel filter, fuses, DME, DME relay, and having RPM sensor come back with range of 2800 to 3200 OHM readout, we believe it likely is the sensor causing my issue. So, new sensor is on its way and I'm now working to plan how much time it will take as well as hoping to get some idea of what the high-level process to replace is.

In looking at the engine bay routing, that in and of itself looks to take a fair amount of time to remove old and install new, much more to route sensor to flywheel.

Any help would be greatly appreciated!

Also, want to thank Ingo for testing out my DME and also "coaching" me during troubleshooting process - even while he's in Korea! If you're in need of testing and/or repairing of DME, Ingo's the Dude!

Thanks,
Kevin

[Flat6pac]

No way to make it fun or easy. Do both sensors while there and pull the carrier off because the sensors are frozen in place in the housing.
If you could pull the heat box it would simplify the awkwardness of the job, but most of them have been on too long too.
Bruce

[Ski]

The PO had engine cleaned when top end was done and kept compartment crystal clean as well, so removing heat box is probably very doable. I can see how that will help with making process at a least bit "easier" .

Thanks!

[Ski]

Bruce, forgot to ask about "carrier"?

[911 sc]

Change them both along with the cht sensor mine just crumbled when I touched them car runs way better! Good luck getting the sensors out of the bracket.

[mysocal911]

Hopefully when the DME ECM was tested, the simple DIY 5 minute modification was done to prevent
95% of the 3.2 DME ECM circuit board problems was done - re-soldering 3 pins:



Obviously, it would have been included (no additional charge) as part of the testing charge, right?

[Ski]

Just unpacked RPM sensor. Also, bought second to replace TDC sensor.

As I'm new to using a multimeter, and to ensure I'm testing correctly the sensors still in the car, thought I'd test the new ones to see the correct readings and how they differ from what I perceive are the wrong ones coming from old.

When testing terminals 1 and 2, I get 1.0 which seems to be inline with what I should be getting per parameters taken from another thread below (italics)

When checking 1 and 3, I don't get any reading? I suspect it's because of a setting I'm not properly using on the multimeter, but given it's an auto-ranger, I didn't think I'd need to mess with changing the setting.

Any help would be greatly appreciated. I'm prepping for taking out and replacing old sensors this weekend, but want to make sure I'm replacing truly broken parts!

Thanks!!

between one and three, 100K ohm.
between one and two, 960 ohm.

[ischmitz]

Kevin,

The 100kOhm are not right. The 960 Ohms are the coil inside the sensor. Think of it like a long wire wrapped around a metal core. This is what picks up the teeth or reference mark passing by.

The third pin is connected to the shield in the COAX cable and should read to any of the other pins. If it does the COAX cable is bad and the signals from the internal coil will be compromised.

Let us know how things go with the install.

Ingo

[Ski]

Oh, how I've come to hate DME relays! PO installed a Kaehler in February, barely drove the car in interim before I purchased in April. Turns out after all other tests done, including what PO and I thought was a good spare (original) in glovebox that the PO installed one had gone bad. This I discovered after ordering, but thankfully not installing the RPM and TDC sensors, and after purchasing a relay locally just to make sure I totally eliminated it. Well, I put in the new relay and abracadabra she fired right up!!!

Ingo, thanks for checking in once again. I didn't want to bug you anymore while you were out of town!

I've never liked dealing with electrical components and I still don't. Heading over to parts store to purchase another relay....maybe 2....tomorrow. After that, hitting the road and making her work a little!

[timmy2]

There is someone making a solid state electronic relay for the DME.
Solid state DME Relay conversion ?