Porsche Enthusiasts Club Forum

After a great morning out karting at Buckmore Park in Chatham my 944 decided to ruin the day by refusing to start.

Mark at JMG was very helpful on the phone, but we still couldn't get it running. It turns over but won't fire. Here's what we tried:

Changed DME relay
Hotwired the 3 large terminals of the DME socket
Dismantled the relay and verified that one circuit closes when the ignition is switched on, and the other circuit switches when attempting to start.

However the tach does not move at all, and the fuel pump doesn't appear to be running. Mark suspects it's the fuel pump or one of the crank sensors.

With that rough diagnosis, even the RAC technician decided he couldn't help. So I'm being towed home. I hope to try to fix this at home instead of paying a garage as it will be a useful lesson! So, any ideas what to do next?

Try swapping the plugs over on the crank sensors & see if the tacho bounces, that was what confirmed i had a faulty sensor. Good fun trying to get it out if it is faulty, not much room down there to get at it!

Check the fuel pump fuse before you do anything else!

Crank sensors or connections or DME itself. Easiest way is substitution. Getting the old sensors out can be a complete pain.

Does seem like crank sensors

if you run 12v direct to the pump it will confirm its functionality, I would suggest removing it first, pretty easy job. Euro car parts do a genuine bosch pump for about £100.

Sounds like crank sensors to me

I'd agree with it being crank sensors or DME itself.

I could lend a crank sensor from mine if that is any use?

Thanks for all the ideas and support. I'm going to start with the easy things (fuel pump fuse) then move on to testing sensors and wires. I shouldn't need any spare parts until I know what's wrong. Even Mark at JMG said that getting the crank sensors out is a pig, and they often break, so I won't be trying to remove those unless I know they are at fault.

Fuel pump fuses always get hot on 924s and series one 944s. Its in the second (horizontal) fuse box under the near side dash. Its about the third one from the back and red, from memory.

As has been said here in the past pull the wiring connector off one injector, if it starts and runs on 3 cylinders look to the FPR.

Update: I checked the fuel pump fuse, and it's fine. Cleaned the connections just in case, still fine. Does the fuse come before or after the relay?



Is there some way that it would start on 3 but not on 4 then?

Yes. Google "Clarks Garage" and follow the procedures there.

I should know this with nearly 1000 posts