concor

I have a 928s euro auto 1984. The one with LH-Jetronic and dual rotors.

For the last 2 weeks my 928 has been collecting dust. I was on a trip with MG cars and we were driving like maniacs all day. After a 30 minute break we drove home quietly and the engine suddenly kept quitting on the highway. Luckily it restarted too, and under a second. After two emergency stops however it would quit almost immediately and we had to call for help.

Here is the video: http://picasaweb.google.com/concor32...eat=directlink (click View HQ Video)


There are a couple photo's in that album too of the engine and CE panel.

The last three things I did:
- recharged battery, was dead because of mute radio. Voltage is good again.
- put in a new fresh air blower relay
- flasher relay plastic popped off, put it back on.

Things I tried by now:
- exchanged relays VIII (electronic ignition), XVI (LH-Jetronic) and XVII (Fuel pump) with similar relays on the CE panel
- cleaned fuse 13 (fuel pump) and visually inspected power connection 10 on CE panel
- wiggled the key to see if any lights go out
- cleaned battery terminals, including the little wire on the + terminal
- cleaned battery ground and put a start cable between - terminal and chassis. Als compared voltage + and - against voltage + and chassis, which was the same.
- installed new distributor caps and rotors and cleaned wire plugs on that side
- installed new fuel filter
- cleaned all grounds of test point 1 on 28-53 of the LH-Jetronic troubleshooting part of WM. Cleaned CE Panel grounds and some more grounds in the engine bay.
- checked 14 pin connector at the hot post in the engine bay front right for broken pins
- reseated brain connectors in CE panel, plug on temperature sensor II, plug on fuel injectors and two connectors on ignition control unit at front left

I was about to remove the airbox, but figured I might be overlooking something. Something I hadn't thought about. After all, I still consider myself a big car-noob

EDIT: FIXED FIXED FIXED!! See post below.

John Speake

Unplug the MAF to force into limp home mode, the car should start easily and idle reasonably without cutting out.

concor

Hi John, thanks for the answer. I just took off the airbox and unplugged the MAF. It acts a little differently I believe, but it still cuts out. You still see the tach suddenly dropping every couple seconds together with the engine cutting out.

Then I pulled Temperature Sensor II at the front and it wouldn't start at all.

Put it back in, no start. Hit full throttle and it started. After that no start anymore, neither with full throttle.

Put the MAF back in, no start, neither with full throttle.

I did smell gas at a certain point.

So pulling the different sensors made it cut out completely. It doesn't want to start now anymore Hopefully it is just flooded and needs to dry a couple hours.

John Speake

I am pretty sure all you've done is to flood it. But on the other hand if it now fails to start it will be easier to find the problem :-)

From your video, it looks like the tach drops very quickly when the cutout happens. This is more obvious when you gave it some revs.

That suggests the crank sensor, EZF, EZK relay or the rpm feed from EZ-F pin 16 to LH pin 1 is suspect.

concor

Whoops. After I pulled the MAF sensor I thought, let's reseat the crank sensor now I'm at it. I actually didn't pushed it back on hard enough. Once that is back on it starts again. But still with or without the MAF connected it has the hickups.

Thanks a lot for the new tips John, very helpful. I do have to look up what it means what you just said, but that's no problem. I'll look into it tomorrow or the day after. Thanks again.

My brother came to help and we pulled a spark plug. It was black. We tested it and it still sparked about a centimeter from a ground. So that 12mm spark seems to be there.
My brother tried to look if it would stop sparking when the engine cuts out, but he said it was very hard to see because it does not spark that often. It did spark less often when the engine turned slower.

Mrmerlin

I would check the timing marks of the dual distributors they should both have the rotors lining up at their respective hash marks, it fhey dont line up when the engine is at TDC then the timing belt for the distributor may have jumped or broken

concor

One thing I find peculiar. My fuel consumption meter on the dashboard says zero liter/100km. Shouldn't that be 5 or 10 at least when it idles or runs at 2000 rpm?

I made another video, notice the fuel meter at 0. The volt meter jumps occasionally too: http://picasaweb.google.com/lh/photo...eat=directlink


Hi MrMerlin, glad to see you again. Yes, my car has problems now and then I had a look at the rotors and they line up with the marks after I set one rotor to it's mark by turning the crank.

Hi John, I think I am quite lucky that you are helping me. I realize that there are probably very little 928 experts in the world! I tried to test your tips today:
- Crank sensor. 0.98 K ohms which is good according to the manual (0.6-1.6 k ohms). Tested from pin 7 to 19 on EZF. I also jerked the wires and plug and no change in the ohms.
- EZF. I checked the voltage on pin 25 to 12. It's the same as the battery. Do you perhaps know a better test?
- EZK relay. Not sure I have that. I did exchange VIII (electronic ignition) and XVI (LH-Jetronic) with other ones on the ce panel.
- rpm feed, EZF pin 16 to LH pin 1. It makes contact. I am not sure how to test it more thoroughly.

John Speake

Sorry, my typo, I meant EZ-F relay. The document you need is "Test Plan EZ-F igntion and LH Jetronic Injection 84/85/86 " WKD 491 120. I'm not sure if that Euro publication is on Jim Morehouses Tech Info CD set, available from Roger Tyson. I could scan a few pages for you.

That states that EZ-F relay is XVI Try linking pin 30 to 87 on that relay, see if the engine still cuts out.

Somehow you need to monitor these voltages as above when the engine is running and then cutting out as the fault is intermittant.


Any signs of water getting to the LH or EZ-F units ?

John Speake

I've just looked at an early version of Jim's Tech Info CD set and there is a test plan for the EZ-F and LH fro the 85/86 32v US engines. As far as EZ-F is concerned it appears to be identical to the Euro 84-86 version.

If you can't get hold of a copy of the test plan, email me at info(AT)jdsporsche.com and I'll attach a copy to my reply.

concor

Hi John. I just soldered a relais jumper from the pins of a broken relais. I jumped relais XVI EZF and no go. While I was at it, I also jumped the fuel pump relais and the LH relais.

Yes, testing voltage while the engine is running would be the solution. Problem is of course, the engine won't run with connectors disconnected.

No water signs on the LH and EZF boxes.

That'd be very nice, email sent. I had a look if I could find it myself first. I came across some other EZF and LH tests I'm gonna check out:
http://www.electronikrepair.com/page6.html
http://www.electronikrepair.com/page9.html
http://www.nichols.nu/tip816.htm

bernard farquart

My fuel pump failed and gave the very similar symptoms. When it finally left me stranded, I would crank and crank with no start, then it would fire up and run for a few seconds, then die again.

I finally nailed down what was going on by making a six foot double lead with a toggle switch, hooking it to the panel and laying under the tank listening while I turned power off and on to the pump. (tapping the pump got it to spin)

It was very intermittant up to the point of failure, and had done the die-and-restart thing on me for a couple of days leading up to failure.

concor

Hmm, well, I just jumped my fuel pump relais and it sounded pretty happy to me. At least, I heard a constant zooming sound from the fuel pump. I haven't checked my fuel pressure yet, but I did smell gass while trying without the MAF connected and my spark plug was black which means, as I was told, too much fuel. So, I think my fuel pump is okay. Again, I'm no expert.

Dutch 928 fan

Hi Concor, By the looks of your numberplates you're Dutch, so here's an answer from a fellow Dutchman. Hope it helps.

I had similar problems as shown in your videos. The belt driving the alternator had slipped off. The first 100 meters it was fine, but then the engine started cutting out as in your first video. I tried again and then it looked more like the second video as the battery supplied less and less power.
With old cars, like my old triumph TR6, it is possble to drive many kilometers just on the battery. But in modern cars, the loss of power from your alternator will leave you stranded. All kinds of weird symptoms start showing up as the electronics no longer get the right voltage and power supply.
As you said: initially your battery was dead, which can be seen in the first video. I think your battery has died completely, not being able to transfer the current through the electric systems anymore. Change it with a different one (just try one from another car). Then check the output of your alternator with a voltage meter (don't trust the intrument pod's reading, although it does look good in your video).
Hope it starts again.

Leo.
Euro 1984 S2 dual rotor, manual. Hey isn't that the same as your car? Where are you located?

See ya.

concor

Well John, I did the tests that I could perform from your plan. No joy though, everything checked out:

- temp sensor 2 on LH plug terminal 2 and ground and twisted cable (about 3 k-ohms)
- temp sensor 2 on EZF plug terminal 23 and ground and twisted cable (about 3 k-ohms)
- throttle switch EZF terminal 4 - ground gives 1 ohms closed (max 10 ohm) and 0 ohm at open
- throttle switch EZF terminal 17 - ground gives on 2/3 15 ohms (max 10 ohms) and idle 0 ohms
- throttle switch LH terminal 3 - ground gives throttle closed 0,3 ohms (max 10 ohms) and open 0 ohms
- throttle switch LH terminal 12 - ground gives idle 0 ohms and on 2/3 16 ohm (max 10 ohms)

I have no fuel pressure tester, so I pulled the return line and made another video: http://picasaweb.google.com/lh/photo...eat=directlink




There is some sand in the tank though although that was there last year too. I also replaced the fuel filter.




Hi Leo, I'm in Zwolle. I had a look at the alternator. I had to find out where it is located first But it spins happily. The belt is tight too.

Hi Bernard, well my pump sounds nice and the video above looks good to me too. Thanks for your input though.

John Speake

Why did the fuel stop flowing near the end of that video ?