Hot start up problems (yes another topic! sorry!)

[peanut]

ORIGINAL: Outrun944

It's not the DME relay

The problem is neither you or your spanner man understand exactly how the Bosch fuel injection and engine management system works . I do. If you ignore advice because you think it isn't relevant how are you going to determine which advice is sound ?

You need to follow a proper sequential system of checking and testing otherwise you can cause more problems than you solve by fiddling in the dark and changing components randomly.

If you were closer I'd pop over and take a look but you are unfortunately at the other end of the country. My advice would be to take the car to a Bosch specialist in fuel injection and engine management systems . It will be cheaper in the long run believe me.

 

[Outrun944]

Hi Peanut, don't worry I'm not personally ignoring your advice - I researched on the forum and the most common answer I thought I found was knackered DME relay, so I ordered one and told them to replace it - for £15 its a no brainer and if it wasn't that at least I have a spare - this was before I posted this topic, because I wasn't 100% convinced nor was he this was the issue, but at 10 minutes to 6pm we put the order in anyway.

I'm waiting a call back from the garage now.

 

[peanut]

Don't worry a spare DME relay is always useful its just that you cannot trust it is working properly . Even new ones are known to regularly fail.

it would be very helpful if we could hear the car starting up and on idle and with the revs rising slowly and then blipping the throttle. You can tell more from the sound of the engine than most folk realise. You could use your cellfone to video it if you haven't got a camcorder.

Verbal descriptions are very limiting when you are trying to diagnose a problem from hundreds of miles away.

Before you had this problem did you run the petrol tank low at any point ?
Had you recently filled up ? or put the car through a car wash ? or repaired, serviced or replaced anything on the car ?

Just trying to build up a bit of a picture of the history of this .

 

[Outrun944]

Thank you for all your help and advice so far.

Firstly, here's a bit more detailed description for you - again - it's over the phone with my mechanic so not ideal. I apologise.

Starts from cold, but within seconds up to 1min runs lumpy - it will get worse then eventually will stall
Starting from hot it does fire up - but you keep using throttle to keep it going, but symptons are a lot worse
(again, sorry from what people having been asking on here that's not majorly helpful)

* Fuel Pressure Regulator - run at 2.5 Bar -
It's at 2.1bar which he thinks should be fine and enough

* AFM - test wires, plugs, sockets to AFM and temp sensor
Yes - a few months ago we had the AFM to bits and cleaned it up and hes had another look to check. Wires, plugs and sockets checked.
Temperature sensor has been replaced yesterday.

* Idle control valve
Hard to get to place place, but what they've tried to do is take it out the equation - squeezing pipe into it ie you doing the work of the valve - and this makes no difference

* Throttle valve plate sticking? Clean it (where the oil breather pipe feeds into the throttle body)
Yep - they cleanded this a few months ago (when looking for oil leaks) - checked again and it is still clean

* Vacuum system leaks - but clean the earths
* pull off the vac pipe and smell for petrol
Yep no leaks, monitored manifold pressure constant - 15 to 20mgs mercury
No smell of petrol ...
Pressure increases to 3bar if they clamp it down
Bypassed earths by using jump leads off to their own earths - no difference

* DME Relay bypass - worth checking because even replacing you may never know if that was playing up. On the base of the DME relay socket the terminals are numbered . You need to connect terminals 30, 87 and 87b together . This will
power the ECU ,injectors, ignition amplifier and fuel pump which you should hear pumping continuously.Be careful because terminal 30 is always live even with the ignition off .
They will try this monday
> Did the DME relay smell of burning?
No, DME relay looked fine, no cracks on solders etc

* Crank sensors - they get hot, while car is stationary heatsoak affects them & they only pick up an intermittent signal, causing what appears to be a low idle speed
* Wiring (connectors near oil cap) and earths
* Throttle position switch

For these three something they haven't tested as yet but want to next however they want to be sure of the correct voltages in and out and resistances
Am I correct in thinking I will find this in the workshop manuals Vol1-engine.pdf and Vol4-electrical.pdf?

Additionally they have also don an engine compression check and all is fine.

Also, before I bought the car (2 years ago now) the owner told me the ECU had been replaced with an after market product - he didn't know much about it but apparently there was startup issues previously and one was related to the immobiliser and alarm which has been disconnected.

 

[Outrun944]

ORIGINAL: peanut
it would be very helpful if we could hear the car starting up and on idle and with the revs rising slowly and then blipping the throttle. You can tell more from the sound of the engine than most folk realise. You could use your cellfone to video it if you haven't got a camcorder.

I think I'll take my camcorder in on Monday morning when I take in workshop manual / volltage and resistance stuff if I find the correct things

ORIGINAL: peanut
Before you had this problem did you run the petrol tank low at any point ?
Had you recently filled up ? or put the car through a car wash ? or repaired, serviced or replaced anything on the car ?
Just trying to build up a bit of a picture of the history of this .

The petrol gauage has always been a bit off! On a full tank it sits below the "1" and it can get down to empty and no petrol warning light, but by then I've always gone and topped up - usually putting about 35-45litres in so there must be a fair amount left.

As for servicing / replacement ... ummm wow there's a huge amount been done. I think I need go through everything and build up in a summary a full service history, I think I will do this later this afternoon if I have time, or tomorrow and post this somewhere.
Last major work was a few months ago fixing various oil leaks on the engine which turned into quite an epic thing, and also AFM refurb, distributer cap, rotor arm.

 

[peanut]

thats an excellent report well done.

I take it we are talking about an early 944 here yes ? pre oval dash model?

I believe the early cars had an extra fuel injector for cold starting wheras later cars get a fuel enrichment controlled by the ECU and engine temperature sensor. Check for a leaky or constant running cold start injector and try disconnecting the electrical connector to it and see what happens.

Is the car running over-rich ? You may have a leaky injector ...A quick test is to disconnect the electrical connector to one of the injectors. If the engine runs a little better it could suggest leaky injector/s . It won't run well on 3x injectors but if you have an over-rich mixture the running and idle should improve a bit.

Fuel pressure is a bit low which could cause some injector problems.

If the problem exists at part open throttle as well as on idle then the idle control valve is not the fault although it may not be functioning correctly. it only has any effect at idle where it feeds a small amount of air to the inlet when the throttle valve is completly closed.

 

[Outrun944]

Hi Peanut - thank you! And a quick reply.... Yes this is a square dash - year is 1985, but class as 1984. It's had an engine swap at some point to an earlier year (1983 I believe)
I've forwarded on your above reply to my mechanic.

 

[Outrun944]

I noticed no-ones commented on the fact this all started with the alternator dieing, 'a right nasty mess inside' was the description.

What's the connection here? Any ideas?

Thanks guys!

 

[peanut]

impossible to say .... Are you saying that the car ran perfectly before the alternator expired ?

if that is the case then I have misunderstood entirely sorry.


My guess now...... is that the ECU may have been damaged by a surge from the alternator. The regulator should limit the maximum voltage to around 14.4v but if the regulator failed the voltage could have soared and fried some of the ECU circuitry.

The only practical way you can test the ECU is by substituting a known good one from a pre 1985 944

 

[Outrun944]

ORIGINAL: peanut
impossible to say .... Are you saying that the car ran perfectly before the alternator expired ?

Car seemed fine yea! Had a lovely hour long - relatively spirited - run up to Birmingham, with a fair amount of weight in the boot and seemed good.

ORIGINAL: peanut
My guess now...... is that the ECU may have been damaged by a surge from the alternator. The regulator should limit the maximum voltage to around 14.4v but if the regulator failed the voltage could have soared and fried some of the ECU circuitry.

Well that's what has been in the back of my mind but I don't know enough about the engine electrics to make that assumption.
I was leaving Birmingham for an hour run back to Nottingham, and shortly after pulling off I noticed the battery warning light was on... I had really no choice at the time but to carry on and hope for the best, so I guess there's a good hour window for damage to have been caused. Meh.

ORIGINAL: peanut
The only practical way you can test the ECU is by substituting a known good one from a pre 1985 944

Balls. That's going to be tough to do and find.... []

 

[JamesO]

ORIGINAL: peanut

thats an excellent report well done.

I take it we are talking about an early 944 here yes ? pre oval dash model?

I believe the early cars had an extra fuel injector for cold starting wheras later cars get a fuel enrichment controlled by the ECU and engine temperature sensor.

No 944 ever had an extra fuel injector.
Fuel enrichment is controlled by the temp sensor at the front of the engine as you say, they do however give a different resistance between models and its not unheard of to fit the wrong one. IIRC the workshop manual has the resistance/temperature tables.

 

[Outrun944]

ORIGINAL: JamesO
Fuel enrichment is controlled by the temp sensor at the front of the engine as you say, they do however give a different resistance between models and its not unheard of to fit the wrong one. IIRC the workshop manual has the resistance/temperature tables.

Now that is interesting, the mechanic said they had sent the wrong temp sensor out twice to them - third time lucky - but maybe it might be the wrong one still. I'll have to query them further, but that might be helpful cheers. I can see why further now they're so kean for me to get the right resistance and voltage figures here to them.

 

[JamesO]

Either way as Peanut said, if it was fine before the alternator went pop, chances are something got fried in the ECU.

 

[peanut]

ORIGINAL: JamesO

No 944 ever had an extra fuel injector.
Fuel enrichment is controlled by the temp sensor at the front of the engine as you say,

I read somewhere that the early cars were fitted with a cold start valve (like some of the 924 were) having never owned an early 944 I am not familiar with the minor differences .Thanks for putting me right about that .

Even so it is the ECU that controls fuel enrichment not the engine temperature switch (ETS). The ETS simply supplies a resistance value to the ECU which is converted to voltage. Dependant on the engine temperature The ECU is pre-programmed to enrich the fuel supply when the engine is cold but it is the ECU chip that determine the program used.

If the temp switch isn't working the ECU uses a fuel map determined by other sensory imput otherwise it uses a standard fuel 'map ' which is effectively a 'limp home mode'

Disconnecting the ETS might make it a little difficult to start and run rough when cold but once the engine has warmed up a the car should run perfectly normally . If the ETS is faulty and still connected it could cause the ECU to provide fuel enrichment to a warm engine which cause over-fuelling but that is easy to spot.

 

[Outrun944]

Garage is currenly doing tests on voltage/resistance everywhere, as per the service manual.

Funnily enough when I first spoke to them this morning before I said anything they were thinking it's an ECU fault.

OK so delving into the cars service history beyond what I've done in the last 2 years I find stuff that is related....

August 2002
* Fault finding diagnostic testing on engine running fault
* Checking all engine electrics wiring & relays
* Replace DME control relay
* Checking temperature sensors & airflowmeter
* Checking fuel injectors & fuel system pressures
* Checking all earth points
* Sending engine management control ECU for testing

- nothing else done here apart from the crank sensors replaced, but interesting the oldest piece of service history I have relates to engine running faults

February 2003
* Reports 'engine over heating and hard to start when hot' but appears no work was specifically done here

December 2003
* Engine wiring loom replaced

June 2004
* "Problem with intermittent non start relating to poor connections on engine. Speed/Position Sensor, by pass connector plug and join redirect. Battery drain caused by replacement wiring harness connected to permanent live feed rather than ignition supply, change to correct position. Intermittent fault with aerial"

July 2004
* Check engine management system, send ECU for specialist repair and repair broken connections
- they note that the above work in June they did ECU testing, and they have replace the ECU with a second hand one here.

Not much since then, from what I gathered the owner SORN'd it for a year and then didn't really drive it much apart from weekend excursions and tinkering with it

November 2009
* Electronic test componest
* Checked spark plugs
* Fuel pressure and supply
* Striop and check for split hoses and air leaks
* Check crank pulses
* Injector pulses
* Ignition erratic trace but out put high
* Try another coil check and adjust air flow meter
* Finally send away ECU for testing and repair/set up
* Send away airflow meter to be checked and tuned to ECU

- charge for new/reconditioned ECU ... turns out it's from here - http://www.atpelectronics.co.uk/c/porsche-944-petrol-ecu


So ummm wow.

ECU replaced 2004 & 2009. And here we are in 2012...

I called up the previous owner (who's a nice chap) to see if they gave any info on why the ECU failed the last time (he owned the car in 2009 onwards), all they said was apparently 'commont fault, ECU's are crap in this era of 944s, to be expected - and worse if the car is left standing for long periods of time'

 

[Outrun944]

I took some video as well, I'll hopefully upload this later somewhere - not pleasant viewing []

 

[Outrun944]

Video uploaded as requested - http://www.youtube.com/watch?v=m77Fp93QSK4

 

[peanut]

excellent video well done.
Mmmm it definitely sounds like its hunting , like it is an over-fueling issue ?

Your mechanic said he could smell excess fuel at the end and when you started it for the final time, it almost sounded to me like the engine was running in reverse ![][] just like Non injected cars sound when they have an over-run issue or the cars ignition timing is seriously retarded

Have you tried starting the car on 3x injectors ? if you are getting an over-fueling or over-enrichment running on 3x cyclinders should improve the running slightly. it will still sound rough obviously but possibly better.

The other thing you could do is check the plugs after the engine dies to see if they are wet with fuel although it would seem as though you can actually smell it.

lastly if you pull off all the little wire clips around each fuel injector then pull off one injector electrical connector at a time whilst its running and see if there is any appreciable difference between cylinders. I'm thinking possible leaky injector.

i know you have checked for vacuum leaks but I'd still recommend you do a smoke test on the vacuum system to be certain. Its easy to rig up something , theres a vid on youtube.
http://youtu.be/FfiQ7qWiG-M

 

[peanut]

one other thing to check is the ignition timing..it sounds completly off on the last few runs. You could connect up a timing light and check the advance when running .
On the earlier cars both the speed and reference sensors are together on the clutch housing . Have you checked that you have them connected the right way round and that both the reference and the speed sensor is working properly ?

 

[JamesO]

ORIGINAL: peanut

ORIGINAL: JamesO

No 944 ever had an extra fuel injector.
Fuel enrichment is controlled by the temp sensor at the front of the engine as you say,

I read somewhere that the early cars were fitted with a cold start valve (like some of the 924 were) having never owned an early 944 I am not familiar with the minor differences .Thanks for putting me right about that .

Even so it is the ECU that controls fuel enrichment not the engine temperature switch (ETS). The ETS simply supplies a resistance value to the ECU which is converted to voltage. Dependant on the engine temperature The ECU is pre-programmed to enrich the fuel supply when the engine is cold but it is the ECU chip that determine the program used.

If the temp switch isn't working the ECU uses a fuel map determined by other sensory imput otherwise it uses a standard fuel 'map ' which is effectively a 'limp home mode'

Disconnecting the ETS might make it a little difficult to start and run rough when cold but once the engine has warmed up a the car should run perfectly normally . If the ETS is faulty and still connected it could cause the ECU to provide fuel enrichment to a warm engine which cause over-fuelling but that is easy to spot.

Well explained, I kept it simple as I was using a phone to type and misworded it a bit, sorry if it seemed blunt.
The most noticable differences between the early and late eight valve cars fuel systems, are the AFM uses different signel voltage 5v rather than 12v IIRC and the idle control valve was changed to a PWM type valve.
I've used bits from early and late systems on my last standalone project and I'm in the process of moving the turbo to full standalone, currently tracing some annoying interferrance.