potent951turbo

Alright I am trying to get an 87' 944na to start. I am getting signal from the reference sensors because the tach is bouncing and I am getting fire to the plugs. The car will start and run for a split second if you spray a little starter fluid into the throttle body, so once again it confirms that I am getting spark. I am not hearing the fuel pump come on when I turn the power on. I switched out the fuel pump with another pump that I had and am still not getting anything out of them. I switched out all ingnition relays with known good ones and still nothing. The fuel pump fuse is fine. Is there anything else I can check that I am missing?

PorscheDoc

Have you tried jumpering the DME relay in the fuse box? 3 wires to the big slots tied together with a wire nut. That will turn the fuel pump on instantly. Don't leave it in there for too long, because the pump will run continuously.

potent951turbo

Edit- The fuel pump will come on if you jump pins 30,87, and 87b. I have switched the relay with a known good one but nothing changes.

potent951turbo

Alright I just checked to see if the pump was okay off the car by running some wires to it off a battery and it came on just fine in my hand...... any ideas?

quinnfiske

Check the fuse. It has it's own fuse.

potent951turbo

Fuse has been checked and is okay.

PorscheDoc

So the car will run with the ports jumped?

potent951turbo

No, the car will not start with the jumper in place. The only time it will start is if I spray a little starter fluid into the trottle body, it fires right up and then dies. I also just finished cleaning the grounds on the back of the bell housing, with no difference. I also pulled the injector plugs and I am getting voltage to them.

82-T/A

I have this EXACT same problem on an 84/944. It will run so long as I run a wire from the pump directly to the battery. But otherwise it's not running. I too have checked the fused AND swapped out the DME relay with a brand new one from 944Online.

Same symptoms.

SoCal Driver

Fuel pump runs when the engine is being cranked. The signal to the starter is split off to the DME, the DME closes the contacts for the fuel pump. You should hear the fuel pump run for about a half second after you stop cranking. If it's not running at the stop of cranking but is running when you jumper the DME relay socket then either the DME relay is bad or the DME is bad.

As you report the engine will not start even with the Y jumper in the DME socket and the fuel pump is running with this jumper, I would suspect the DME and/or the fuel pressure regulator. The DME has a few large transistors that fire the injectors and the coil. These tend to loosen in the PC board and require resoldering. The FPR will go bad and over pressure the fuel rail causing the pintals in the injectors to be held closed. Unplugging one of the four injectors seems to provide more current to the other three which will force the pintals open against the pressure.

potent951turbo

If the DME is bad, would the engine still be able to fire and run for a split second when I spray starter fluid into the throttle body?

StoogeMoe

I think SoCal is on the right track. If a running fuel pump still doesn't make it start, then it's most likely your fuel pressure regulator. Check the pressure at the end of the rail to verify.

tomrc

How about the ignition switch?

potent951turbo

Alright I started out this morning by pulling a fuel injector plug and seeing if that helped, it did nothing. After that I switched the fuel pressure regulator with another one I had and now the car acts like it wants to start. Before it just turned over, but now I am getting firing/sputtering. I tried cleaning out the distributor cap/rotor but that didn't change anything. I also tried putting the jumper in to run the fuel pump but that didn't help either. I think the puzzle is almost together I am just missing one piece to get it to fire up. Keep the ideas coming.......

quinnfiske

Clogged fuel filter? There is a check valve in the fuel pump inlet. Maybe that is stuck closed.