View Single Post
ischmitz ischmitz is online now
Registered
 
ischmitz's Avatar
 
Join Date: May 2002
Location: Santa Barbara, CA
Posts: 4,821
Garage
Send a message via Skype™ to ischmitz
Your voltage is fine. If the car tunes over there is enough power for the DME to run. If you haven't done this try these things:

Switch the ignition to ON. Then feel the ICV. It needs to vibrate and shudder with a 1 second interval. If that is the case your DME is alive and powered. If not you have an issue with your ignition switch/DME relay, wiring or a bad DME.

Next, have an assistant and check for spark. The easiest is to have an extra spark plug and pull one of the plug wires. Connect it to the extra spark plug, ground it to the engine (metal) and then have the assistant crank. You need to see sparks. Be carefull and use a glove or isolated pliers. While not life-threatening a spark can give you a little jolt.

If you have spark you confirm that your DME is getting the speed signal fine and has most parts working. Also you should at this point smell the tail pipe. You should be able to smell fuel. A more elegant way to test for spark is to have a timing light with magnetic pickup. A good excuse to head to the local auto parts store.

Then test the fuel pump: While an assistant cranks measure the voltage on fuse (3) fuel pump. You need to see +12 volts during cranking. You might want to get an LED test light and check for fuel pulses directly while an assistant cranks. Disconnect one injector and measure.

I believe the jumpering of various parts is not really going to help you here at this point. You already replaced the one part that can be bypassed: The DME relay. Now it is either a bad sensor (speed or reference or both) or something wrong with the DME.

In most cases it is one of the sensors and you won't get spark or fuel. Sometimes you get fuel but not spart at the proper timing pointing to the reference sensor. And if both are fine the DME itself can have a bad ignition stage. Again, you should be able to smell unburned fuel at the tail pipe.

Of course you could also have a blocked fuel filter and the alike. You can crack a banjo fitting and see if fuel spills out while the pump runs. A more elegant way is a fuel pressure gauge.

Good luck, get an assistant and head out to the airport one more time,
Ingo

Ingo
__________________
1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430

I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs
Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!!
How about a NoBadDays DualChip for 964 or '95 993
Old 09-06-2009, 10:47 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #43 (permalink)