3.2 Carrera no start

[Paul Shepherd]

The car was going fine on its last run and I then got it up on stands to update the AC and rebuild the brakes just as a bit of preventative maintenance as everything was fine. Also put in a new distributor cap and rotor as was looking a bit shabby. Went to start it and strong turnover and fuel pressure at the rails but not a single fire so pulled a plug and no spark. Suspected the distributor cap not being right so checked everything again and all ok. Leads in right place. Pulled the coil lead off the cap and put a plug in the lead and touched earth with the key on run but nothing. I know I need to check the coil and dme but I did notice some wiring that had lost insulation, possibly dislodged when I was putting the AC hose in and wondered if this could be the problem, please see pic, I assume these go to some sensors. Also wondering if these can be done with the engine in the car
thanks

[Coastr]

You didn’t post a pic

[Schulisco]

Picture is missing, as Coastr already mentioned.

Of course the suspected cables and connections have to be checked.

But also the DME/ECU relay controls on a 3.2 Carrera both the fuel pump power as well the power supply of the DME/ECU and therefore the ignition...if this relay fails, the motor will be cranked with no fuel and/or no spark...

https://www.swchips.com/dmerelay.html

Thomas

[Paul Shepherd]

Thanks guys technical issue but pic added now
Thomas fuel pump seems to be working ok

[ant7]

Silly question, but did you try putting your original rotor arm back in ???

Originally Posted by Paul Shepherd

Thanks guys technical issue but pic added now
Thomas fuel pump seems to be working ok

[mikedsilva]

Let us know what happens when you replace the relay under the seat..

[boyt911sc]

Originally Posted by Paul Shepherd

Thanks guys technical issue but pic added now
Thomas fuel pump seems to be working ok

Paul,

What fuel pressure readings are you getting at the fuel rail? With and without vacuum, use numbers instead of “seems to be working OK”. Units such as bar or psi. would give a better picture than using adjectives. Thanks.

Tony

[mysocal911]

Read here; 911 3.2 No-Start Troubleshooting

[wazzz]

Pic shows that sensors have lost their outer insulation. Not an issue, as the inner insulation and shield are still there, but a sign that sensors have lived a long life.

[Mr. Merk]

We had a 3.2 get towed in for no start. Replacing those sensors resolved the issue. You can use the 944 part number and save about half. 944 606 115 00

I had the white one (cylinder head temp) sensor fail on me causing my car to stall while driving.

My opinion is that all three of those and the fuel lines should all be replaced/updated by now on the 3.2s

[Mr. Merk]

Originally Posted by Paul Shepherd

Also wondering if these can be done with the engine in the car
thanks

Yes you can, I did it on a lift for the first time and it took me three hours. There are some DIY guides out there.

[Missed Approach]

Hi Paul- This string helped me immensely for sensor replacement:

no-spark problem finally resolved

Per the write-up, using the BMW sensors 12-14-1-708-619-M14 will also save a bit of cost.

Hope this helps!


Cooking on a Porsche 911- The herb butter made the difference.
https://www.youtube.com/watch?v=FvXBR50rH9E

[911obgyn]

Do you have a bentley manual?
Crank and reference sensors
Head temperature sensor
Use an ohm meter and see if any of those sensors have no continuity.
When you order the sensor get a spare DME relay located under the drivers seat.
Stick it in your glovebox it will come in handy.

[ischmitz]

At this point fuel pressure can build up during cranking. That more or less gives your DME relay a clean bill of health. While it might make sense to carry a spare (they do fail quite a bit) it will not solve this issue.

Next you need to determine if only spark is missing or all DME signals (fuel pulses, spark and tachometer). Some observe the tachometer during cranking which is the third signal that indicates the DME goes into RUN mode when it "sees" flywheel motion with both sensors. Or get an LED test light or a NOID light kit to visualize fuel pulses on the injectors while cranking.

If all three signals are absent it likely points towards the flywheel sensors or in some rare cases a defect inside the DME with the sensor amplifier. Insulation of the FW sensors cracks and ages, humidity gets into the COAX and the signal deteriorates. Time to check them (measure AC voltage during crank, check for shorts or get a cheap oscilloscope to measure their outputs) or straight replace them.

If only spark is missing this points to a failure inside the DME. Either solder joints or the driver or driver conditioning circuit are bad and the DME needs repair.

Keep us posted on findings

[Paul Shepherd]

Thanks for the reply’s I will report back when I get a chance to do some testing in a week or so as I’m heading on holiday for a while

[Mr. Merk]

FYI, we were able to wiggle those three connectors and get the car to start in three separate cases, both with crank sensors and CHT sensor failure. Best to wiggle one at a time to narrow down which one is faulty.

[MAH77]

I had to replace my speed and reference sensors when they failed last fall while driving. It's easier if you take the left rear tire off, you will need some patience to get the allen bolt loose. While you are in there I would definitely replace both. I would also consider replacing the CHT sensor, but that is another PITA. One thing to note is my CHT sensor connector crumbled apart when I touched it lightly (and is currently taped together) so be very careful when you are working back there. Removing your cabin heat fan on the left of the motor will help a lot getting access to the connectors on top of the engine. Also, definitely buy the BMW sensors from Pelican, not the Porsche sensors to save money.

[Cevan]

I just did mine and got two sensors here for $244 shipped.

https://www.***************/pn/0261210005

[Paul Shepherd]

A bit of an update as I had a bit of time before I went away.
To answer a few of the questions
Yes I have changed the DME relay I always have 2 spares so tried both and nothing
There is 12 volts getting to the coil when on run
There is fuel pressure also from cranking so think DME relay is good
Have confirmed no output from coil to distributor lead
Also no signal to injectors as plugged my noid light in to cyl 1

Next thing is to check sensors but I will replace them anyway because the cabling insulation has crumbled off. I am now wondering if I disturbed one of the sensors when I was working under the car doing brakes and AC hoses. I also gave it a good wash so maybe moisture got into the dodgey cables

[mysocal911]

Originally Posted by Paul Shepherd

A bit of an update as I had a bit of time before I went away.
To answer a few of the questions
Yes I have changed the DME relay I always have 2 spares so tried both and nothing
There is 12 volts getting to the coil when on run
There is fuel pressure also from cranking so think DME relay is good
Have confirmed no output from coil to distributor lead
Also no signal to injectors as plugged my noid light in to cyl 1

Next thing is to check sensors but I will replace them anyway because the cabling insulation has crumbled off. I am now wondering if I disturbed one of the sensors when I was working under the car doing brakes and AC hoses. I also gave it a good wash so maybe moisture got into the dodgey cables

Then read the "B" section from the Pelican Forum as posted up-thread (post #8) earlier here; 911 3.2 No-Start Troubleshooting
You can also test the sensors on the DME ECM connector; ref sensor on pins 25 & 26, RPM sensor on pins 8 & 27. It's a five minute effort at the most!