engine stalled after 2 min. of idling
 

Hi, guys.
i've 1987 924s, which was parked for about 7 years.
I was running a lettle rough with high rpms (about 1100 or so), the car was shaking. Idled for more than 10 minutes.
I replaced the engine mounts. and... and started the car - was idling rather rough (shaking, too) for a minute or two and then rpms dropped and the engine stalled. tried to restart (with or without gas pedal pressed) - doesn't start.
all fuses are ok.
Is it fuel pump? its relay (where is it?)
I'm searching internet for a solution.....but will need your input!!!!!
Thanks in advance.

update:
I tapped on DME and all relays below dash, cleaned 2 plugs (CB) by oil filler cap. restated the engine and it RUNS! RPMS are high - 1000.

If it was me (and it was) I'd drain the old fuel and refuel with fresh fuel and filter (Varnish and moisture in the tank would contaminate the injectors). Pull the fuel rail, jumper the DME relay pin 87B to 30 to pressurize the fuel system, use a 9v battery, touch the two leads to each injector pin momentarily to observe the spray pattern (ensure you have a jar or clear cup underneath). If they aren't clearly a cone pattern, rebuild the injector. Good luck.

Thanks for your advice.
the fuel filter is new, I installed it before the engine was running the first time (after I bought the car).
Previous owner filled the tank before sale, but with the old fuel (maybe) and old filter.
do clogged injectors contribute to shaking (somewhat rough idling) and/or high idle (1000 rpms)?

If your car sat for 7 years, I guarantee that the tank had gasoline varnish, rust deposits and possibly heavy tar deposits in the sump, unless the fuel was completely drained before the car was stored (unlikely).

The fuel filter only filters fuel from the pump discharge to the injector rails, not fuel going into the pump, so any trash in the tank sump gets pulled into the pump and can jam, slow down or stop the pump or keep it from providing the 36 psi required for the Bosh FI system. This is possible if you didn't drain the tank, unscrew the tank filter screen and check for trash. Did you remove and check the sump filter screen?

Dirty fuel is the enemy of a fuel injection system and after 7 years of sitting, you are bound to have dirty fuel. I had to drop the tank on my '84 and get it professionally cleaned and coated after a 7 year hiatus. Also had to get the injectors cleaned and flow tested. No sign of fuel trouble since and car starts and runs great!

update.
The fuel is drained, screen from sump is removed and cleaned. After all gas evaporated, I found some SAND on the tank's bottom. Vacuumed it all and wiped the bottom of tank with a rag and alcohol thru fuel level sender opening. Then, I used manual pump to wash the inside of tank (with alcohol/water mixture and also flushed it directly into the sump opening (from the tank).
Now the metal is clean. Sump also seems to be clean (observed from the same fuel level sender hole). All dried and ready for fresh gas.
Observation - the fuel pump's body is bright green. Could it be original (factory)?

If you're unsure of the age of the fuel pump, put a fuel gauge on the fuel rail and do the system check per Clark's garage. When I've had old fuel issues like yours I usually run through the entire system from the tank to the injectors and everything else in between. An injector spray check will indicate if more work is necessary there. A lot of us send our injectors to Witch Hunter (sp) in Duval Washington for rebuild and documentation. It runs about $100 to do them all and it's worth the investment.

Here's another update:
After cleaning gas tank and putting fresh gas, car started fine - again with high idle (1000).
Let it warm up, shut it off. came back in an hour - won't start - only cranks.
hm. I check the ignition - spark is present. After cranking - no fuel smell from the cylinders - therefore - no fuel pumped. Check relay (fuel pump/DME - left top second on the relay board) - it looks like new - all contacts are in excellent shape.
check voltage at fule pump terminals - no viltage while cranking the engine.
connected outside elect. source to the pump directly - engine starts fine.
Checked (rather feelt with my hand) relay - it clicks once when key at position #2 and once more when cranking.
checked all fuses - none is burnt.
Conclusion - there is no voltage at fuel pump.
I think I need a wiring diagram and lots of advice from you, guys.
Thanks in advance.

Have you checked your ignition switch, the white nylon switch terminal right behind the ignition lock cylinder? They are famous for cracks opening up in the case or the rotating part becoming so worn over the years that the contacts don't always touch. Pelican has them for $11.00 here.

https://www.pelicanparts.com/catalog/SuperCat/944M/POR_944M_ELSWCH_pg5.htm#item19

It could be that your fuel pump is getting power when the switch is in the start position, but not when it rotates back to the run position, due to the crack or slop in the operation of the switch. Replacement is an easy job; just remove the dash trim around the key and you can see the switch. Unplug the electrical plug, remove it and install the new switch. Clarks garage has a write-up and good pictures to go with it.

That may not be your problem but it does happen. My case split open enough that the rotor inside was very loose and sloppy.
Good luck!

Edit: Sorry, but I forgot that steering wheel and lock cylinder removal is necessary in order to access the switch. It's been a few years since I did this and I was doing a lot of things at the same time. Still a doable job; it will just take longer.

Spring44,
Fuel pump doesn't get power in any key position.

Do you have tach bounce while cranking?

Yes, tach niddle bounces.

update:
I checked speed and positioning sensors neart top/back of engine.
resistance in both (i think terminals 8/23 and 25/26 (left and center pins)) are withing specs (950-ish ohms).
I look at the actual sensors and their bracket - look fine/not damaged), except "front" bolt rotates - stripped thread (it's finger-tight).
What's next? To check connectors at fuse #2 (16 amp) and wires behind relay board???
check ground wire points?

Yet another update:
I checked continuity for the fuel pump from positive battery terminal to the fuel pump - the "line" is continuous.
so. the spark exists, the pump doesn't get electricity (under normal conditions).
the only way to run the engine is to connect a separate power source directly to the fuel pump.
I suspect an onboard computer (DME) to be faulty.
Looks like my DME is remanufactured unit from programainc.
Had anybody opened the DME to inspect the internals?
This remanufactured DME is out of warranty, off course.
OR... did I miss anything in attempt to troubleshoot my problem?
Any thoughts?

http://forums.pelicanparts.com/uploa...1587175112.jpg

Update:
DME soldering points didn't show any deterioration. I re-soldered points at mosfets (at two vertical alum. plates).
re-installed DME - problem persists - the engine cranks, but doesn't run.

Sounds like a ground loop issue...

Very common on German made cars especially Porsche and BMW.

Run a 8ga. ground wire from Batt (-) terminal, back to ground harness point located within 2-3 inches of Flywheel Pickup sensors near firewall (top).

use Digital mm to measure resistance between those points should read (0.001) or less on lowest ohm setting.

Keep me posted, Later...

Make a "Y" connector to jump out your DME relay. Install it in place of that relay (only one way to do this, so you can't mess it up).

You should hear your fuel pump running, and have power to your DME computer.

Oh, and your car should start and run...

If that doesn't happen, you have some fundamental power delivery issues to either the DME relay or your DME computer.

If it runs, then you are missing some signal out of the DME to the second loop of the DME relay. The first loop sends a signal from the speed/reference sensors to the DME to tell it that you are cranking. The DME needs to recognize this (tach bounce), and then energize the second relay in the DME relay, which powers the fuel pump.

Something in there is amiss...

Thanks, Guru944 and kdjones2000,
The ground point on bell housing is hard to reach. I only looked at it yesterday and saw that ring terminal was put up-side-down and wasn't fully touching bell housing. If that ring terminal is copper, then it will corrode against magnesium or alum.
I will run test per guru944 and kdjones2000 tonight and will post the results.
Thanks.

update:
resistance is 0.6 Ohm (MM setting 200 Ohms).
Ground point on bell housing is cleaned.
Fuel relay is replaced with a new one.
the engine started!
Thank you, guys, for your help.