1985 Porsche 911 Targa Carrera

[junebear58]

The car is running fine but the gas tank is almost empty. I stopped at the gas station to fill up. While waiting inline, I turned off the engine. I turned on the engine again, it won't start. It is cranking but it seam like not enough fuel to start the engine. Pushed the car to the pump and fill up the tank. Started the engine again, iit won't start, only heard the cranking. End up to tow back home. At home, check the DME relay is fine. Car still won't start. I am thinking to remove and test the fuel pump. I am looking for a procedure how to remove the fuel pump. Any suggests to trouble shooting engine won't start issue. Thanks

[Marc Bixen]

Where are you located? Is it raining, or did you just wash the car? 3.2's are very sensitive to moisture if the distributor cap is old. (over 45,000 miles) Pull the cap, check it, dry it, try to start again. If that works, replace the cap. Also, if the DME relay is more than 10 years old, swap it out also.

[pmax]

JB,

How did you conclude the DME relay's fine ?

[Crude Rudy]

Check resistance of speed and reference sensors per the SM in the engine bay - they can go out like a light bulb and your can will not start

[kevbo]

Fuel pump right behind tank underneath. Just need to remove protective shield to.access.

[tratza]

Marc, Thanks for the tip about the distributor cap and moisture. I rarely wash mine but rather use a spray cleaner. But recently I did and after starting it and shutting down the engine would crank but not start. Suspect verified by your post. An hour later tried again and the old girl fired right up. Time to change the cap though. BTW in the past 10 years its only seen rain once.

[twistoffat]

When I hear the tank was nearly empty I keep thinking about dirt getting into the lines

Think you may need to clean the tank and replace the filter

[spoke]

Originally Posted by twistoffat

When I hear the tank was nearly empty I keep thinking about dirt getting into the lines

I agree.

I fill up when the gauge goes to 1/2 tank. My 930 sucks down too much fuel to let it get low.

[85911]

"Check resistance of speed and reference sensors per the SM in the engine bay - they can go out like a light bulb and your can will not start"

What does SM stand for?

[Crude Rudy]

service manual

[911obgyn]

A Bentley manual goes a long way towards keeping the tow trucks at bay.

[proporsche]

when you say the tank was almost empty? Did you see the reserve light on ..or was it on for a while..?

Also check in your engine compartment these 3 plugs if by coincidence one of them is off..

Ivan

[McLovin]

When you turn the car off, you create a bit of a heat sink on engine components, that can make marginal sensors not work right.

My guess is it is one of the three sensors proporsche posted (speed, reference and CHT sensors). Esp. the CHT.

I think the fact that it didn't start after you filled up the gas tank is not related to the no-start.

[McLovin]

I'd also check to make sure your battery connections are tight and clean, esp. the ground cable. And that the battery cable end crimps are solid and clean.

[ischmitz]

To the original poster: it would be nice to have a title that is a little more descriptive. It will give you a lot of more focused answers quicker. That being said there are lots of 3.2 no-start threads here. Do a search and you will be surprised. They mostly fall into one of two categories. 1) "I had the same and it was that...." and 2) a more systematic approach:

The 3.2 engine is controlled by a DME. The two items that are notorious to fail are the DME relay (aka fuel pump relay) and the sensors that tell the DME the flywheel speed and position. Either can fail intermittently and either will cripple the car. The systematic approach is to check for power to the DME (ICV on top of engine vibrates with ignition ON. If not an alarm system or a bad ignition switch could be the issue. Next, the DME relay can temporarily be replaced by a jumper. Some suggest to carry a spare. If either makes the car run you found your issue. Next, it's down to some more diagnostics. The engine needs fuel and spark to run. There are three cases:

1. No fuel
2. No spark
3. No fuel AND no spark

Case 1
Spray starter fluid into the intake. If that makes it catch it's missing fuel (fuel pump, fuel filter, fuel pressure, or worst-case the DME or one of the injectors). It also tells you the FW sensors are good.

Case 2
Checking for spark is done easiest with a timing light or a spare spark plug. If spark is absent now it's either case 2 or case 3. To find out which you need a NOID light (eBay is your friend) or an LED test light and check for fuel signals on the injectors. If you confirm fuel signals are present but only spark is missing this points towards the ignition coil, the distributor or the DME itself. This is a classic failure mode of the DME.

Case 3
If spark and fuel are missing this points towards one of the FW sensors. If one of them is bad both fuel and spark pulses will be missing. The sensors can be ohmed out for a quick check but even if they check out O.K. that way they can still be the culprit. Lot's of cases here. If the sensors are good it could be the DME (sometimes the decoder for the flywheel sensors fails).

The other sensors would cause poor running but not be responsible for a complete non-start. So table that for the time being.

Cheers,
Ingo

[junebear58]

Originally Posted by pmax

JB,

How did you conclude the DME relay's fine ?

I pulled out the DME and tested. I also heard the click when it energized.

[junebear58]

Originally Posted by proporsche

when you say the tank was almost empty? Did you see the reserve light on ..or was it on for a while..?

Also check in your engine compartment these 3 plugs if by coincidence one of them is off..

Ivan

No, the reserve light wasn't on. Will try to test the sensors. Thanks

[darrin]

Originally Posted by junebear58

I pulled out the DME and tested. I also heard the click when it energized.

DME relay failure can be pretty transient and the cold soldier joints that are generally the failure source can work just fine with a high current test but fail when dealing with the real world low current -- I'd recommend picking up a spare and confirming that substituting in the spare doesn't change things

[junebear58]

@proporsche. I found the white plug is broken. Do you know the part number of this plug and how do I order it. Thanks for younhelp

[cabmandone]

FWIW, I bench tested a DME relay once and SWORE it was good..... it ended up being the reason my car wouldn't start. If you don't have one, get a spare... you'll need it at some point.
As I understand it you can hear the relay click but there are solder joints that fail so even if the contact closes, the circuit might be open.