concor

Help rennlisters, help! Share me your wisdom please.

(my car is a 928S 1984 Euro auto)

I left home driving slowly and after about 5 minutes the engine stopped in front of a roundabout. The guy behind me was quite calm and after a bunch of restarts I managed to keep it running while giving it some gas. I ended up parking it in front of a church where there was lots of parking space.

The engine would start but would hardly keep running. Only if I gave some extra gas it would keep running, but very badly. In this video I start it twice, the second time with some gas:
What I tried on the parking place:
- I turned the fuse of the fuel delivery pump and switched out the relay of the fuel delivery pump. I hear the pump running normally when the car runs.
- I switched out the relays of the Electronic Ignintion, Starter Relay and LH-Jetronic
- I cleaned the contact points under the two distributor caps
- I reseated the two big connectors to the computer next to the fuse panel
- Added 5 liters of fuel just in case

Does this type of engine behaviour seem familiar to anyone? Does anyone know what could be causing this? Thank you in advance.

Mrmerlin

has the MAF ever been rebuilt?
what was the last thing you fixed?
It looks like its running out of fuel,
did you jack the car up before the running issue?
Have you done a ground cleaning and battery terminal cleaning?,
did you use deoxit 100 on the fuel pump fuse blades?
has the car been washed before this issue started?

concor

Hi MrMerlin, thank you for the quick reply. That's a lot of questions, allow me to copy-paste them:

has the MAF ever been rebuilt? No, never.
what was the last thing you fixed? The headlights, the relay was bad.
It looks like its running out of fuel, did you jack the car up before the running issue? The last time I jacked it up was over a year ago.
Have you done a ground cleaning and battery terminal cleaning?, No
did you use deoxit 100 on the fuel pump fuse blades? No
has the car been washed before this issue started? No, it's been in the garage for weeks.

It was running perfectly fine for a couple of years before this issue.

Mrmerlin

if you have a tester MAF swap it in.
Otherwise consider getting your MAF rebuilt. NOTE do this after you do the electrical cleaning.

How long ago did you touch the headlight relay.

Clean the battery terminals and ground points ,
also do the grounds at the back of the engine V and /or the right side cam tower.
Order some deoxit100 amazon has it, use it on your elex connections

hacker-pschorr

Is that a twin distributor EuroS?

I'd make sure the small belt didn't break, could be running on 4 cylinders.

Mrmerlin

good idea on the dizzy belt

concor

Oh sorry, yes the little belt on the twin distributors did not brake. I tried to push the rotors when I was cleaning inside them. It did broke before, about 5 years ago It made the car shake a lot, its different now. Less shaking.

Randy V

Did you pray?

That sometimes works with these cars.

concor

Small update, I got the car back in my garage. It worked good for a little bit when I started it at the church. Engine sounded great, idle was fine too. But after a couple bends after I drove of it was back to running badly. When it runs bad its putting out some grey or black smoke too. Must have lost the divine influence.

Jfrahm

It could be a blown fuel pressure regulator diaphragm allowing gas into the vacuum line and thus into the engine. It could also be an ECU temp sender issue causing the car to run very very rich or similar ECU problem.

If gas comes out of the FPR vacuum barb that's a problem, careful of fire if you investigate this.

You can take a look at the spark plugs, and then if you get it running again and it acts up check them again to see if they are wet.

Mrmerlin

pull the vacuum lines off the dampers and fuel pressure regulator as Joel has suggested smell for fuel,
if you find wet or smell.
then replace all three of these parts.
NOTE the damper goes at the front center of the engine,
It looks just like the fuel pressure regulator.
FPR goes to the right rear fuel rail,

the other damper is on the left side rear fuel rail while seated in the car.

NOTE with the miles its probably time for an intake refresh

the flyin' scotsman

its running very similar to when the MAF went bad on my S4.......did you try a known good loaner MAF as suggested?

concor

Hi guys, little update. After 2 months in the garage I started the car again and it worked fine! Although the idle was quite low at around 500 rpm and sounded a bit rough. I let it idle for about 15 minutes. Then I drove off the driveway turning right while idling and it stalled. However, it did survive a 20 minute drive after that.

Today I think I found the culprit and it looks like Mr Merlin was right again! As usual! You deserve that name. It seems that the battery ground point was very corroded. I added a picture below.
About 3 months ago it has been outside in the rain for a long time. Water gets into the boot. It gets wet under the boot carpet and around the battery terminal and in the spare tire compartment. It must have dried up after 3 months in the garage.

After cleaning the battery terminal, I drove for about 30 minutes and all was fine. Idle was a bit higher at 600 and the engine sounded better. At 2000+ rpm the engine buzzed perfectly, like a vacuum cleaner.

I am planning to clean all the ground points soon.

I should have checked the car for issues earlier, have been feeling quite miserable about the situation for 2 months! Merlin, thanks again! Other guys thank you too! It's great to get free advice from fellow 928 owners. And let me state this again; this forum rocks!

Mrmerlin

get some DC 111 and put it around the lock cylinder grommet and the wiper rubber shaft seals i n the hatch this will reduce the water leaks if you have a spoiler i would get some 3M strip caulk and put some around each screw for the spoiler to reseal them

Randy V

Stan, no DeOxit recommendation?

Seriously?