No start - It's the DME, but something is off..

[CanaganD]

For the last week, my car hasn't been able to start. It was getting increasingly harder and harder to start the car. Previously, I had to turn the key to ON for 3 seconds, then all the way to engage the starter. Not doing this will make the car even harder to start. At that point, I'd need to crank it, then shut it off, then crank it again immediately after to get it to start. Sometimes when the engine is hot, this is even harder.

So, now it won't even start. However, just now, being desperate and all, I checked the DME (as a lot of threads point to the DME as the problem most of the time). I held down one of the coils with my finger to run the pump. I could hear it running, then I hop into my car to start it. To my surprise, it started and then sputtered and died after some 2 seconds.

I got my buddy to hold down the relay while i cranked the engine, and the engine came to life immediately. This is after doing almost everything the entire week to get it to start. After the engine started, my buddy can let go of the relay and the engine would continue running. I also watched the relay as the engine is being cranked, it doesn't close. It's only after it's been forced to close (to get the engine running) that it stays closed.

I suspect that there should be something to trigger the fuel pump relay when I turn the key to ON, or even to START. Thing is, I remember hearing the pump go for 2-3 seconds when I used to turn it to the ON position. Now I don't even hear it.

So I really have just two questions:
1.) Is there something, a relay or a switch or a chip, that engages the fuel pump before the engine is started, or even when it's being cranked?

2.) Failing option 1, could I jump the ignition relay power to engage the fuel pump relay? The relays are right next to each other and the ignition relay is on when I turn the key to ON. I guess the question really is: is the fuel pump on all the time when the car is running?

Note: The DME looks to be in excellent condition. I was surprised when I opened it up. The copper on it all looks pretty shiny. In addition, the DME works fine when the car is running. It leads me to suspect that whatever is supposed to give the DME signal before start, is not working.

Thanks so much in advance.

[jmd_forest]

Replace the DME Relay and your problem will probably go away. The way it looks is no indication of operational status. If not, provide some more details back here and someone will almost assuredly try to help.

jmd_forest

[CanaganD]

Well, when the car is running (when I can get it started), the DME seems to work fine. There is no stalling and there is no sputter once it's running. It's getting it started that's the problem. The fuel pump relay doesn't seem to engage until it's running. If it doesn't engage before running, I can't start it.

[jpk]

Do some research on the Bosch Motronic system and you'll find that the symptoms you're describing are due the DME relay not working correctly. Don't make any assumptions about how it works based on how a Toyota or Ford does; turning on the ignition does not make the fuel pump run.
The DME relay is really two seperate relays in one housing. One side provides power to the DME computer when you turn the ignition on. The other side provides power to the fuel pump when the DME provides the signal to close that coil. One of two conditions must be met before the DME powers the fuel pump; either the engine must be cranking (signal from the ignition switch at pin #4) or the engine must be running at 300rpm or higher (based on the pulse signal from the engine speed sensor reading the teeth on the flywheel).

[jmd_forest]

Try cleaning up your battery terminals, alternator terminals, starter terminals, and ground points. Check under the fusebox/relay board for corrosion/corroded wires. From your description, once the alternator starts cranking out the 14+ volts it normally does the problem goes away. The 12V in the battery may not be enough to overcome any corrosion and trigger the relay.....or the relay is going bad and needs more than 12V to operate.

Easiest test...............REPLACE THE RELAY (they're only about $28). If you still have the problem, you'll have the recommended spare DME Relay in your glovebox for when (not if) the relay does go bad.

jmd_forest

[CanaganD]

SOLVED

Went and did some more work on the car today. Previously when I thought that the relays worked after the car started is due to physically actuating the relay. That subtle physical jolt would allow the relay to close on its own and remain closed.

Today, I jumped the connections, bypassing the relay actuation and saw that even when the car was running, the relay did not close. A slight tap to the coil and the relay will close and the car would continue runing.

Conclusion is that the DME relays, more specifically, the one for fuel pump is no longer working reliably. This confirms above poster's suspicion.

At the moment, I've jury rigged the fuel power circuit to a fog light switch. Seems to be fine so far. In fact, seems to start up even better than ever. Course of action now is to get a new DME. Damn this car is taking all my money.

[Lapponia]

CanaganD! Please dismount your DME relay as Dave Boetcher a Pelican member did one or two weeks ago and take some pictures if possible. All Pelicans here are more than intrested to know how the relay contacts look like. Surely it is the pair that supply current to the fuel pump and it is at opposite side of bottom plate with relay flags. Good luck!
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Lapponia 1984 944 na

[scotmick]

I have a similar problem with my 1985/1 944; I bought a new DME Relay. I looked at all the diagrams I could find about its location, but my fuse panels don't match the diagrams. My question is: where the hell is the DME Relay?

Thanks, Don