Valleypro

Hi everyone, I'm looking for some help, I've got a late 1988 2.7 944 that's been sitting a while, and it will only run with the DME relay jumped, I've tried 2 other DME relays and it still doesn't run, is there anything else I can try ? Thanks!

Gage

A 2.7 in 88?
You'll need to test the signal and grounds (the small pins) to the DME relay socket. The socket connectors can also be problematic.

walfreyydo

The old analog relays, can be problematic, even "new" ones. The fact it runs with the relay jumpered makes me suspect whatever other relays you have are likely bad.

Recommend testing those two other relays (guide on how to do that is here) to confirm if they are actually good (dont assume).

Ultimately, it is my personal belief that all 944 owners should upgrade to a solid state DME relay, such as the ones offered by F9Tech.

Valleypro

Thanks, I'll try and take a look.

Valleypro

Thanks for sharing that, I've took the original one, resoldered everything but no change.

Valleypro

Oh and yes, 1988 2.7, registered in November 1988.

Gage

I suspect it is an 89 model year. This will be indicated on the emissions label (assuming a north american car) located on the underside of the hood.
The registration or manufacture date do not determine the model year.

Valleypro

it's a UK RHD car.

931guru

I'm guessing that you are missing the ground at pin 85b, which is provided by pin 20 on the ECU only if the engine is running over 200 rpm. This is a safety feature, designed to shut down the power to the fuel pump in case of a collision (and a possible resulting fire).

peanut

yes it does sound like it could be a missing ground ........or possibly a missing 12v to pin 86 of the DME relay that is supplied when the ignition is switched on.
Fitting a DME relay bypass would effectively bypass both a faulty or missing ground at pin 85 and/or a faulty or missing 12v+ at pin 86 when the ignition is switched on.
The bypass feeds a permanent 12V+ to the ECU from pin 30 of the DME relay ...which is always live.

I would first check with a multimeter set to resistance and check that there is continuity between DME relay pin 85 and chassis ground .
( It will be the ground point MPlll ...on the inside of the front wheel arch from memory )

Pin 85 is the permanent ground for the first coil of the DME relay.
The first DME relay switch is activated when the ignition switch is turned on and 12v+ is fed to from the ignition switch to pin 86 through the DME relay coil and back to ground from pin 85 This switches the permanent 12v+ sitting at pin 30 through to the ECU( DME ) thus powering the ECU...(.I prefer to use ECU rather than DME as it eliminates any confusion between the DME and the DME relay due to typos etc)