Dan, thanks for the suggestion and info on the fuel pump relay. I went back through Bentley and it references only the DME Relay regarding the fuel system but it could certainly be an omission. I did visually check all of the relays noting that the pins on all are discolored and probably all should be replaced. I'll stop by the dealership on the way to the office today and try a new relay in position 1 as you suggest. I suspect it may be a couple of days before they are able to get to it.

All, let's be real clear. The 84-89 3.2 Carrera does not have a separate fuel pump relay. The DME relay is what controls the fuel pump through fuse #3 (25A). The DME relay is actually two relays in one housing. The first stage controls Term. 15 (hot with ignition switch in RUN or START) and the second stage controls the fuel pump and the O2 sensor heater circuit.

There sure could be some aftermarket installations of an additional relay. But none of the circuit diagrams in the work shop manuals show a separate relay for the fuel pump.

A simple check is to measure voltage at fuse #3 (25A) while cranking. You should see +12V while cranking on either side of the fuse.

You can also jumper a +12 source to fuse #3 (25A) and you should hear the fuel pump coming on.

Ingo

Simple test for Motronic ML 1.3 units .http://forums.pelicanparts.com/uploa...1288020666.jpg

Nice list. This will help diagnosing issues with the DME harness and the sensors. There are a couple of additions/corrections I suggest:

Rename the "fuel pump relay" to "DME relay"to avoid confusion since pin 20 powers the second stage of the DME relay with the DME acting as a low-side switch.

Connecting the injectors to full battery voltage by grounding pin 14 or pin 15 is not really a good thing to do for extended periods of time. You should include a warning like this: "Don't connect these pins to GND for more than a second to avoid damage to the injectors and/or flooding of the engine" The 3.2 injectors are low-impedance. The DME uses a peak&hold driver to control the current. This is to avoid overheating and damage to the injectors and the driver circuit.

The AFM diagnostics in this table seems to imply the use of a break-out box since the AFM is powered by the DME. Most unfortunately don't have access to one. So they will have to test the DME harness with the DME not connected. When measuring at the 55-pin connector the AFM acts like (almost) like a potentiometer and an NTC. Unfortunately, for a proper diagnosis of the AFM you need to provide power (+5V) to pin 9 and then you can measure the signal at pin 7 while actuating the flap. You should see something between 0.2V to 4.5V (with +5V power). If you use a 9V block battery the signal is larger (0.5V - 8.1V).

Ingo

Good points Ingo .we will correct the list .

Ingo, thanks for the clarification on the fuel pump relay or lack thereof issue. I actually received your response this AM after attempting the relay swap - which obviusly did not work.

Drum roll...........................

Just got the call from the Dealership. Preliminary diagnosis of no-start situation is bad reference sensor (replaced with Bosch OEM 5/09) AND adjustment of the Speed Sensor (also replaced 5/09) as diagnostic readings were off suggesting adjustment vs replacement.

Lots of good technical information contributed to this thread that should be helpful to others.

Thanks!SmileWavy

Reference sensor replaced and I'm back on the road to close out this thread!

Thanks SmileWavy

Called that in post #11. the more my car breaks, the better im getting at this "Carrera Diagnosis" thing :) Glad to hear your back on the road

You did call it! I would not have suspected the failure of an OEM Bosch Sensor after only 18 mos. It was one of the BMW ones ($50 vs $150) but I have not heard about any problems with them here. Dealership charged $202 for the part + 4.5 hours total labor (diagnosis and replacement) :eek:...... BUT I'M BACK ON THE ROAD!!!! :) and they did give me a free loaner while the car was in the shop.

Great that you're on the road again! For my own mental database, I wish I understood how the sensors wouldn't allow start up when unjumped.... but allow start up, when jumped. Anybody?

The sensors are essentially little coils wrapped around a magnetic core. Read here for more detailed information. This setup generates a small AC voltage when you chance the reluctance by having the toothed part of the flywheel (metal) moving by in close proximity. The gap between the sensor and the passing teeth of the flywheel is critical since the amplitude of the AC varies with the square of the distance. In other words if you double the gap the amplitude decreases to 1/4 of the previous value.

Too close and the flywheel makes contact - bad.
Too far and the signal is too weak to properly work.

The static test alone is not sufficient to issue a clean bill of health. It only measures the DC resistance of the coil. But if salt and years of use have deformed the sensor housing or if the gap is wrong or if the shielding is compromised or if the magnetisation is reduced the output can be far from optimal. This is why you need an oscilloscope to properly measre the sensor output while cranking.

Ingo

excuse my ignorance, but as the owner of a newly acquired 85 3.2, where is/are the troublesome sensors located? should I carry spares? thanks Bill K

I'm going out to Harbor Freight to purchase an oscilloscope first thing tomorrow. :confused:

Bill K, those sensors are located side-by-side on the motor near the flywheel. Carrying spares is probably not advised, they are kinda expensive and a bit of a PITA to replace.

are they accessible or visible from the engine compartment or the underside? thanks Bill K

They are located in the 2 o'clock position in this photo and are accessable underneath between the engine bulkhead and the rear engine tin. Working space is tight particularly using jack stands vs a lift.

http://forums.pelicanparts.com/uploa...1288293195.jpg

more info here if interested:

http://forums.pelicanparts.com/porsche-911-technical-forum/442105-any-good-tricks-removing-speed-reference-sensors-mounting-bracket.html

you could probably get away with something like this as a low-cost scope: Search eBay for item #160415866721 if the link doesn't come through.....

ARM Nano Portable Oscilloscopes / USB Handheld - eBay (item 160415866721 end time Nov-16-10 07:49:19 PST)

ingo