No spark

[porschedavid]

1984 Porsche 911 3.2 carrera
Tried to start it today ,turns over but no spark.Put new in DME RELAY.Still no spark.last time it was started was 4 months ago and it was fine ,no problems.Any ideas guys.

[Joe Bob]

Check the fuse for the DME power. If still using the torpedo style fuses they can corrode at the tips. Either replace it or spin it.

Then locate the relay, slowly turn the key. You should hear a click or feel it if your hand is on it. No click, then your DME is not getting power.

[porschedavid]

HI
Thanks
Do you know which fuse is for dme relay

[Joe Bob]

My ride is a conversion so my fuse box is not likely the same. Pull the cover off the fuse panel, inside the cover should give you location. But see if you have power to the relay....no clickee no workee....

[porschedavid]

Got click when turn key .still no spark

[mysocal911]

The Pelican Parts Forum is your friend. Read here;
911 3.2 No-Start Troubleshooting

[gomezoneill]

Originally Posted by Joe Bob

My ride is a conversion so my fuse box is not likely the same. Pull the cover off the fuse panel, inside the cover should give you location. But see if you have power to the relay....no clickee no workee....

You're a very helpful guy on the PP website buy your avatar is extremely annoying.

[Hnichols]

If there's someone in your area with a 3.2 you can eliminate alot of troubleshooting by installing your DME (the DME itself, not the relay) in his car: if it doesn't start, then it's the soldering on the ignition circuit of your DME. Then you can send it off to Sal on this site and he'll fix it up like new for a very reasonable fee.

[cabmandone]

DME relay controls fuel. Speed and Reference sensors along with DME, coil and distributor deal with spark.

[porschedavid]

Does the DME Relay control spark at spark plug.

[gomezoneill]

Replace the position and reference sensors first. Like the poster said before me.

[cabmandone]

Originally Posted by porschedavid

Does the DME Relay control spark at spark plug.

The DME, not the DME relay, controls spark. The DME relay pretty much only controls your fuel pump. The DME (or the ECU... or Motronic... whatever) under the driver's seat gets signal from the Speed and Reference sensor. The speed and reference sensors let the DME know the engine is spinning. The DME sends a signal to the DME relay closing the relay coil which closes the contacts sending power to the fuel pump. The Speed and Reference sensors deal with spark as do the coil, distributor and the DME itself. The DME relay has nothing really to do with spark as I understand.

[mysocal911]

Originally Posted by cabmando

The DME, not the DME relay, controls spark. The DME relay pretty much only controls your fuel pump. The DME (or the ECU... or Motronic... whatever) under the driver's seat gets signal from the Speed and Reference sensor. The speed and reference sensors let the DME know the engine is spinning. The DME sends a signal to the DME relay closing the relay coil which closes the contacts sending power to the fuel pump. The Speed and Reference sensors deal with spark as do the coil, distributor and the DME itself. The DME relay has nothing really to do with spark as I understand.

But it does! The DME relay provides 12 volts to the; DME ECM, the injectors, and the idle valve. Without a good DME relay, no spark!

Note: The relay also runs the fuel pump, based on a signal from the DME ECM.

[cabmandone]

Originally Posted by mysocal911

But it does! The DME relay provides 12 volts to the; DME ECM, the injectors, and the idle valve. Without a good DME relay, no spark!

Note: The relay also runs the fuel pump, based on a signal from the DME ECM.

I'm not saying you're wrong... but I had a bad dme relay and still had spark. No fuel... but had spark.

The second part I mentioned in another comment. That's why I'd start looking at speed and reference sensors if I have a no spark situation.

[cabmandone]

Btw, does the car by chance have an alarm system?

Also, an easy way to tell if you're getting power from the ECU is to see if your idle air control valve is vibrating. If it's vibrating you've got power to and through the ECU (again DME... Motronic... whatever) under the seat.

[mysocal911]

Originally Posted by cabmando

I'm not saying you're wrong... but I had a bad dme relay and still had spark. No fuel... but had spark.

The second part I mentioned in another comment. That's why I'd start looking at speed and reference sensors if I have a no spark situation.

There're two stages to the DME relay;

Stage 1 - Ignition switch to alarm module to DME relay - this sends #30 power to DME ECM, injectors, & idle valve
Stage 2 - DME ECM activates this stage to run the fuel pump, when ref & RPM signals occur

[porschedavid]

Hi Again
Put another DME RELAY in ,Still no spark or fuel getting to plugs.
idle air control valve is vibrating.
Coil as 12 volts both sides.

[porschedavid]

Hi Again
Put another DME RELAY in ,Still no spark or fuel getting to plugs.
idle air control valve is vibrating.
Coil as 12 volts both sides.
Also when trying to start the rev counter needle does not bounce.

[cabmandone]

Originally Posted by mysocal911

But it does! The DME relay provides 12 volts to the; DME ECM, the injectors, and the idle valve. Without a good DME relay, no spark!

Note: The relay also runs the fuel pump, based on a signal from the DME ECM.

Originally Posted by mysocal911

There're two stages to the DME relay;

Stage 1 - Ignition switch to alarm module to DME relay - this sends #30 power to DME ECM, injectors, & idle valve
Stage 2 - DME ECM activates this stage to run the fuel pump, when ref & RPM signals occur

I'm aware of how the dme relay works. You said without a good one you get no spark. Without a good one you get no power to the ECU which means you get nothing coming from the ECU so you get no injector pulse, no signal to the IACV etc. You get more than just no spark. He'll know in a second if his DME relay is working on that part of the relay by seeing if the IACV is vibrating. Since he said it is in the post above, I'd move to speed and reference sensors.

I was probably a bit short in what I wrote from a technical standpoint but then again so were you. So how about we try to help the guy get his car running rather than argue about what the DME relay does or doesn't do?
__________________________________________________ ___________________________________________

To the OP:
Here's what John Walker suggests in another thread. It's not a "perfect" test of the Speed and Reference sensor but it should give you a ballpark idea

Originally Posted by john walker's workshop

ohm the two black plugs to the reference and speed sensors. around 1000 ohm between two of the 3 terminals on each plug.

Word of caution: If testing and removing both at the same time, mark so you know which goes where. If you plug them in wrong, the engine won't start. Years ago when I installed my engine, someone had put the sensor leads into the wrong plug. No fire.

The reason I say it's not a "perfect" test is, as things warm up, a sensor that tests good cold and lose resistance as it warms up and cause issues. There are threads on here where users swear their sensors are good but when the car gets warm they stop working.

Also, how are you determining no spark? Are you using a spare spark plug connected to a plug wire and having someone crank while you check spark?

One more thing: If you determine the speed and reference sensors are the issue, you can use the BMW sensors that cost less but are the same sensor.
From the host: Part#0-261-210-002-INT

[cabmandone]

Originally Posted by porschedavid

Hi Again
Put another DME RELAY in ,Still no spark or fuel getting to plugs.
idle air control valve is vibrating.
Coil as 12 volts both sides.
Also when trying to start the rev counter needle does not bounce.

Easy test for fuel is to jumper the fuel pump. You can do this at the DME relay or at the fuse panel to make sure it works but I'd still focus on the Speed and Reference sensors because they'll cause your no spark and they're what tell the ECU to signal the DME relay to close and bring on the fuel pump.