JonScot91928S4

Hi Everyone, I'm new here. I am from Scotland and have a 1991 928S4 which I've owned for the last 4 years. It's the 3rd I've had, great cars, very reliable.
Here's the problem. I use the car regularly and normally it's totally fine.

I put it away in my garge after a 150 mile round trip and it was totally fine.
Left it there for the last 8 days.
Now it will not start at all. At first I thought it was just a flat battery, or a low battery, so I disconnected the battery and recharged it overnight.

Now when I turn the key first I get a ticking noise from under the bonnet, which can be traced to a vibration on the fuel injection rails, so I think is one or more of the injectors firing. It's a harsh tap tap tap type noise, hard to locate exactly but can be felt in the fuel rails. On first turn of the key, but not to the crank position, it does this endlessly, but if I either crank or turn off the key it stops and the tapp tap won't restart until so time has passed( 5mins or so ). THe car tries to fire, but and nearly does, but then sounds like it hasn't any pertrol.

I removed a plug from each side, as I thought maybe I initially had a flooding problem, but both are dry as a bone, so thought maybe no fuel. So decided to check the fuel by disconnecting one pipe at the front of the engine and running fuel pump, this produces fuel. I can run the fuel pump as it's relay case pulls off If I close the contacts it runs the pump.

It seems like a lack of fuel, but could it be somehing else and what might be causing this endless tap tap tap noise.

Given that the car has been sitting for days, what componet could jsut fail like that ??

Any ideas greatly appreciated.

Kevin in Atlanta

The clicking injectors typically indicate a failed injection brain.

JonScot91928S4

What I can't understand is the car was / seemed entirely fine then it wasn't!
Is there any other way to diagnose this, would they tick if they were'nt getting any fuel ?

tammons

I think I remeber having a battery that had a bad cell that did that a while back.

I would replece the battery first or at least have it tested.

John Speake

Jon,
It sounds as though your LH ECU has failed. They can do this without warning. Please check the FAQs on my website. http://www.jdsporsche.com/23fiecu.html

Regards

JonScot91928S4

Thanks for the info. It does sound like it's the ECU.
I'd like to try swapping out the relays first, just in case but thereafter I'll give you a call to arange what to do with the ECU.

I seem to recall when I bought this car that it had been chipped in some way, so what will happen with that ?

Could your diagnostics tester for the 928 confirm this problem is the ECU ?

Also when I charged the battery I disconnected it before I started by doing both the Ground and then the Live, in that order and reconnected in reverse order, after charging. Is that the correct way to go at it with the 928 ?

The clicking only started AFTER the battery was reconnected prior to that it wouldn't start, but i don't recall the clicking.

If I fit a new ECU does anythign else have to be done to the car to make it run properly again or does the ECU just take care of it all ?

algie928s4

Where in Scotland are you?
I'm in Dunfermline, Fife and a mate in East Lothian, both with S4's,if your close we could do a brain swap to clarify.
You haven't done a jump start recently? (the brains don't like it)

Tails

John,
There are many reasons why the vehicle won't start.

Ignition problem/s
Battery problem or battery connection problem
Fuel problem, fuel pump or brain problem

If your car is an automatic (91 S4 usually are as the GT is a 5 speed manual) then it could be the Isolating Switch on the Auto that only allows the engine to start in Neutral or Park position, this may need to be reset.
Plus there could be other problems, difficult to say from a distance.

However, from your description your problem could be the battery.

You say a harsh ticking noise, it sounds like the starter motor solenoid may not be holding in due to low voltage from the battery. Bad battery or dirty terminals on the battery or starter motor or other connections.

Does the ticking noise strart when the key is in the engine 'run' position or is it when the key is pushed over into the start position?

Is the engine rotating on the starter motor?

If it is what is the voltage shown in the Voltmeter in the instrument cluster. If the voltage is too low then the ignition system may not get sufficient EMF to get a spark at the plugs.

You need to do some logical fault finding and reporting of the symptons.

If its in the run position and you trace the ticking to the fuel injectors it could be the BRAIN? However you need to run some more checks as it could also be the fuel pump.

Have you checked whether you have fuel pump pressure in the fuel rail?

You can see from the above we need a better description of the fault. so as to assist.

Regards,
Tails 1990 928 S4 Auto

chaadster

On first turn of the key, but not to the crank position, it does this endlessly, but if I either crank or turn off the key it stops and the tapp tap won't restart until so time has passed( 5mins or so ).

THe car tries to fire, but and nearly does, but then sounds like it hasn't any pertrol.

So decided to check the fuel by disconnecting one pipe at the front of the engine and running fuel pump, this produces fuel. I can run the fuel pump as it's relay case pulls off If I close the contacts it runs the pump.

John Speake

Hello Jon,
If the LH ECU has failed, then the diagnostics will not work.

If you can borrow an LH ECU from Algie to confirm the problem, that would be excellent. Or I can check it out on my test jig.

A low battery/poor battery connection/faulty ground will usually give a repetitive clicking form the relay panel in the passenger foot well. But you sound sure that the clicking is from the fuel rail - this is a sure sign of LH failure.

Performance chips don't cause these kind of symptoms. You were pefectly correct with disconnecting the battery to charge it.

A rebuit ECU would plug straight in without problems. If you want to discuss on the 'phone, PM me, or mail to my website.

Regards

JonScot91928S4

Algie thanks for your posting. I'm in Edinburgh.

I haven't done a jump start and generally this car has always started first time every time. Only once in the winter it failed on the street after I started, in the freezing cold, it moved it literally 20 feet and stopped it, was a bad move. The thing flooded and wouldn't start for days! At that time I changed the battery for a new one, changed all the plugs and all was well since them.

THe only other very vague symptom has been that very very occassionally in the last year it has demonstrated a dip in idle speed, when sitting at lights, almost like it was thinking of dying, but didn't. THis has happen very occassionally and not consistently. Also some days it feels like it performs better than others, but I often put this down to me rather than the car !

When I took the plugs out yesterday, I took out the 2nd plug from the front of the engine on each side. Both were dry as a bone, even after a load of cranking. The passenger side( right side if you face the car, its RHD UK Car ) was light brown/beige/white-ish, the driver side was black and sooty. I haven't checked the other as yet.

JonScot91928S4

Unfortunately the ticking/tapping can be felt on the fuel rail, on the valve( thing with the vacumn pipe on the front of the engine, and almost anywhere else that's attached to the fuel pipes. It does sound very pronounced in the centre of the engine under the large intake housing ( if that's it's name ! ). Is there anythign under there that could cause this or are we heading for the inevitable diagnosis of "brain death"!

John Speake

I am afraid it is bad news.....all the stymptoms you describe are typical of "brain death".

JonScot91928S4

Tonight swapped round the relays, although they all seem to work fine, they are mostly originals, so I might replace these anyway. TOnights symptoms are :-

1) Turn key to the run postion but not to crank. Various clunks from th erear of the car, Short tap tap tap from injectors at the front and clicks from the LH and Electronic Ignition Relays, car tries to start but it doesn't hold.
2) Turn key to run postiion, again, all the noised but NO tap tap, crank it and it doesn't try to fire.
3) Turn key off, and repeat, now I get a motorised noise from the rear, which isn't the fuel pump. It seems to iccur every now and then, every few cycles of the key routine, have no idea what it is.
4) Turn key to run, this time get the whine from the rear followed by the tap tap and we nearly start on crank.

This whine from the rear and other clunks from the rear seem to be timed/intermittent, so anyone know what that's all about ?

Tried keeping the fuel pump running and trying the proceedure. Each time the Tap Tap occurred we nearly started on cranking, few times even was running momentarily.

Atfer a while the battery isn't happy so had to stop to recharge.
The battery gauge started the session readin gabout 13.5 and finished reading 10.5

My battery charge has a battery condition meter, bu tit seems unable to decide if the battery is good or not. After a full 18 hous on the charger the charger reckons the battery is 75% ok and just into the green 100% range. THat said th ebattery starts out strong and then fades away over time, as you 'd expect I guess.

I sure it is "brain dead" but I can't get over the fact it was fine one minute, then unused then dead !!!

Jim bailey - 928 International

The motorized noise might be your PSD limited slip pump pumping left rear fender... The fuel pump only runs briefly while the starter motor is cranking but as a test you can open a 141 951 253 B relay like for the horn and wedge the contact points together then insert into the fuel pump relay spot (top row tenth from the left ) and with the key switch on the fuel pump will run all the time BUT DO NOT DO THIS FOR LONG you can FLOOD the engine with fuel. Being a 1991 you have the odd clear relay (ignition monitoring) on the outside of the LH brain box. This is what checks exhaust temperature on cylinder 3 and 7 and if there is a low reading assumes the ignition has failed and it shuts off the injection to the 4 cylinders which are fired by one coil (two on each bank). Since it has the ability to shut down 1/2 of the injection alternatively it can also shut down ALL the injection.