111 01 dme vs. 121 05 dme

[blk924s]

Can i swap out the dme from my 88 924s (944 618 121 05) for an early 944 dme (944 618 111 01) i have on hand? This is just to check and see if my dme is failing to tell my injectors to fire; I would purchase a used 121 05 if the dme is the problem.
thanks,
-Gabe

[924Sman]

I believe you can if you use the AFM also.


Dal

[944 Ecology]

If and only if you have the early AFM.

The 05 DME boxes are fairly rare.

[SoCal Driver]

The difference in the AFS (they are not meters but sensors) are minor if you want to get your car started. May not perform very well but should start and run a bit.

What is missing is the proper wiring to the idle control valve. In the early 944's this is a heated spring that slowly closes the valve blade. It's power comes off of the fuel pump circuit.

In the later 944's (your 924S included) the valve is acutally active -- the DME opens and closes it according to the rpm/speed sensor feed back.

It's better to buy a noid light for the bosch injectors than to swap out the DME.

[blk924s]

Ive tested the injectors with a noid, got no signal, so I replaced the reference sensor, and tried the 111 01 dme and still have no signal, but i didnt know about the AFM. Anyhoo, Im going to check the water temp sensor in the head for corrosion; I believe those are nessesary for injector signals also, and then look for the right dme. Thanks guys.

[944 Ecology]

You said that you replaced the reference sensor. Do you understand that you need inputs from both the reference sensor and the speed sensor (same part in two different locations) in order to get spark and injection?

[SoCal Driver]

I've just gone over all of your posts. In one you indicate that you have spark. If so you should also have the injectors firing as the reference sensor triggers both. However the DME triggers the spark independent of the injectors.

I think you need to go back and start over with a structured testing procedure.

[blk924s]

I'm sorry I forgot to mention I also replaced the speed sensor. Socal- I do have spark for sure, so what would that narrow it down to?

[SoCal Driver]

Spark and the noid light indicates no injection pulse. Check the resistance on both sensors. The new one first as this will give you a base for the speed sensor (one closest to the fire wall).

Reconnect the sensors behind the engine then pull the plug and check from pins #25 and 26 for the reference sensor and pins #8 and 27 for the speed sensor. This will eliminate any question about the sensors.

As to why both DME's will not fire the injectors I would look for a break in the injector harness. There are splices where the wires split off to the injectors. You can feel them through the sleeve around the sensor connection area. Check each injector connector for voltage with the key on too.