| View previous topic :: View next topic |
| Author |
Message |
Piper
Joined: 11 Feb 2010
Posts: 24
Location: Falkirk, Scotland
|
 Posted: Thu Feb 11, 2010 6:52 pm Post subject: 924 N/A troubles |
 |
|
Hi all,
I'm a new member on here, but have been lurking as a guest for a while now just using the search facility! The time has now come that I need to ask a few questions that don't seem to be covered by previous posts.
I have a UK spec 1980 924, which I have been trying to sort out running issues for a while. I bought a CIS tester from JC Whitney and have set up the hot and cold control pressures which has made an improvement but the following problems still remain.
Firstly,
With the valve on the CIS tester open it fails the pressure build up test by a long way, but passes when its shut. This would explain the difficult hot starting i guess, but I'm not sure where the problem lies. The WUR seems to be in good condition as I've had it in bits, so could it be the pressure reduction valve in the metering head? How would I know?
Secondly, it still doesnt run right. Cold Idle is slightly too low (700 rpm) altough the Aux air valve does seem to work, just maybe not open enough when cold? I have 2 of them though and they both behave the same.
Hot idle is lumpy, sometimes it will run too lean and almost cut out, then suddenly idle ok at 950rpm. There are no vacuum leaks as far as I can tell. I'm suspecting metering head problems. but am open to other suggestions. I don't want to just buy new parts randomly - a very expensive excercise on a cheap car.
I also can't get the car to idle properly if the CO is set to anywhere less than 2.0%, which is fine for out MOT test - the limit is 4.5% but should really be less that 1.0%
I am looking to buy James Webers book, solving CIS problems, but as I work away from home I won't be able to look at it for another 3 weeks.
So any ideas guys? I'm not adverse to stripping down the metering head if its likely causing problems, but if I know for sure buying a new part will cure a problem I don't mind either. I don't mind spending money on the car, just not wasting it!
Cheers,
John |
|
| Back to top |
|
 |
rkn
Joined: 01 Apr 2007
Posts: 176
Location: Copenhagen
|
| Posted: Thu Feb 11, 2010 8:10 pm Post subject: |
|
|
Hi and welcome! Of course you may have issues with the metering arm / pressure regulator, but FWIW, a lot of my control pressure issues were solved by replacing the wur with a new one. I also refused to do so at first because I had two used units which looked pristine inside, resistance measurements were fine etc, so I assumed the wur was not the problem. Still made a world of difference when I finally got a new one.
It is expensive but this is one CIS component that I would just replace for peace of mind.
I got mine at porscheshop UK
_________________
1980 924NA ROW |
|
| Back to top |
|
|
Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
|
| Posted: Thu Feb 11, 2010 8:17 pm Post subject: Re: 924 N/A troubles |
|
|
| Piper wrote: | | With the valve on the CIS tester open it fails the pressure build up test by a long way, but passes when its shut. |
A too low pressure with the valve opened means that fuel is flowing too freely through the control pressure circuit. When control pressure is low, the fuel metering rod inside the fuel distributor is allowed to move further - this results in a richer A:F mix. Good news is that there are apparently no blockages involving the fuel distributors' fixed orifices  or the lines to-fro the WUR, and no apparent need to disassemble the fuel distributor. -But, it looks like you do actually have a WUR problem.. They can cause problems A: by restricting fuel flow too much (restricting movement of the fuel metering rod, resulting in a too-lean mix, and a too-high reading with the CIS testers' valve opened (too-high control pressure)), or B: by allowing too much fuel to pass (which results in an overly-rich mix, and a too-low CIS gauge reading with the valve opened (too-low control pressure)).
_________________
"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
|
| Back to top |
|
|
rkn
Joined: 01 Apr 2007
Posts: 176
Location: Copenhagen
|
| Posted: Thu Feb 11, 2010 9:31 pm Post subject: |
|
|
I like this diagram - it gives a nice view of what smoothie explains
_________________
1980 924NA ROW |
|
| Back to top |
|
|
Piper
Joined: 11 Feb 2010
Posts: 24
Location: Falkirk, Scotland
|
| Posted: Thu Feb 11, 2010 10:02 pm Post subject: |
|
|
Cheers for the response guys,
Smoothie, I think I was unclear of the test I was meaning. It was the residual pressure test after the engine is turned off. Must be no less that 26psi after 10 mins, mine was 22. With the valve shut however it held about 35psi with no real drop after 30 mins.
The WUR control pressures seem to be stable and within spec now that I have adjusted them.
If it looks like the WUR is causng my troubles i'll get a new one. I just thought that with the lumpy idle and the leak back it could be the metering unit too?
John |
|
| Back to top |
|
|
Duncan
Joined: 04 Nov 2002
Posts: 425
Location: Delft, The Netherlands
|
| Posted: Thu Feb 11, 2010 10:57 pm Post subject: |
|
|
Hi,
I have a hot-start , loss of residual pressure problem too. And have replaced almost all of the components of the CIS. I recently spoke to a company in the UK that rebuilds CIS fuel dizzies and WURs and he told me the magnetic valve is a major suspect in the hot-start problem, as they tend to get leaky.
I refer to the hot-start valve installed post 1979.
They rebuild my fuel dizzy too, maybe should have asked first 
I just bought a new one from Porsche, but have to install it yet.
Duncan
_________________
1983 NA Alpineweiss since 2001
Peugeot 205 Generation |
|
| Back to top |
|
|
9XX Girl!
Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England
|
| Posted: Thu Feb 11, 2010 11:46 pm Post subject: |
|
|
| Duncan wrote: | | ... I recently spoke to a company in the UK that rebuilds CIS fuel dizzies and WURs and he told me the magnetic valve is a major suspect in the hot-start problem, as they tend to get leaky. |
Thats handy to know. How do you fancy posting their details as I (and others here in the UK) may need their services one day 
In my experience Porsche are extremely helpful with both suppling parts and giving free technical advice here in the UK, and... sometimes they are cheaper than after market patten parts. I have the email address of the parts department (Parts Advisor = chris.raddan@porscheexeter.co.uk) and the service engineers from my local Porsche dealer in Exeter http://www.porsche.com/all/uk/?exeter (100 miles away) and they are always happy to give free advice. I usually give them a ping and say "i can get such and such a part for this price, can you beat it?" They usually give me a yes or no!
Also, the AA (Automobile Association) have offered me breakdown insurance to cover up to £500 of parts and labour per year. I.E. If i break down they will take my car to a garage of my choice (yes even a Porsche Dealer) and pay for the parts and labour up to the value of £500 and they will do this up to 5 times per year. This insurance would cost me £70 per year for my 924! http://www.theaa.com/breakdowncover/brc_info.html the down side is "Keep the car serviced in line with the manufacturers' recommendations. Servicing must be completed by a suitable garage business". Handy to know for when i get old though.
_________________
924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY |
|
| Back to top |
|
|
Duncan
Joined: 04 Nov 2002
Posts: 425
Location: Delft, The Netherlands
|
| Posted: Fri Feb 12, 2010 12:01 am Post subject: |
|
|
I bought a new WUR through Porscheshop, but this firm actually rebuilds them. Porscheshop just tosses the (wrong) part in a box and marks up the price.
This is the firm:
http://www.kmipetrolinjection.co.uk/
I also noticed that in your book the magnetic valve is not discussed.
_________________
1983 NA Alpineweiss since 2001
Peugeot 205 Generation |
|
| Back to top |
|
|
9XX Girl!
Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England
|
| Posted: Fri Feb 12, 2010 12:06 am Post subject: |
|
|
| Duncan wrote: | | I also noticed that in your book the magnetic valve is not discussed. |
Thanks Dude... hmmm.... i know! thats what intrigued me. And thats a Bosch publication!
_________________
924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY |
|
| Back to top |
|
|
Duncan
Joined: 04 Nov 2002
Posts: 425
Location: Delft, The Netherlands
|
| Posted: Fri Feb 12, 2010 12:10 am Post subject: |
|
|
OK the book says: 2nd Edition 1978, so thats why this post 1979 upgrade is not discussed....
_________________
1983 NA Alpineweiss since 2001
Peugeot 205 Generation |
|
| Back to top |
|
|
Duncan
Joined: 04 Nov 2002
Posts: 425
Location: Delft, The Netherlands
|
| Posted: Fri Feb 12, 2010 12:20 am Post subject: |
|
|
The 2000 version does not discuss it either.. 
_________________
1983 NA Alpineweiss since 2001
Peugeot 205 Generation |
|
| Back to top |
|
|
rkn
Joined: 01 Apr 2007
Posts: 176
Location: Copenhagen
|
| Posted: Fri Feb 12, 2010 12:48 am Post subject: |
|
|
just to be sure - it is this valve you mean, yes?
This is interesting (at least to me  ) Most of us have struggled with hot start I guess. There was an attempt at a comprehensive diagnosis regimen , but I don't think this valve has ever been a prime suspect??
Is controlled by coolant temperature?
_________________
1980 924NA ROW |
|
| Back to top |
|
|
Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
|
| Posted: Fri Feb 12, 2010 1:13 am Post subject: |
|
|
| Piper wrote: | | It was the residual pressure test after the engine is turned off. Must be no less that 26psi after 10 mins, mine was 22. With the valve shut however it held about 35psi with no real drop after 30 mins. |
Good to know - this isolates the leak to somewhere in the control pressure circuit.. -So everything else (injectors, CSV, fuel pump check valve, accumulator, etc. are ok. Pretty sure your year would have the "push-up valve" that was added to the fuel pressure regulator for later years. It's located at the fuel return of the fuel distributor. A few cheap little parts (small o-rings of the correct fuel resistant material) will probably eliminate the leak.
_________________
"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
|
| Back to top |
|
|
Duncan
Joined: 04 Nov 2002
Posts: 425
Location: Delft, The Netherlands
|
| Posted: Fri Feb 12, 2010 1:23 am Post subject: |
|
|
| rkn wrote: | just to be sure - it is this valve you mean, yes?
This is interesting (at least to me ) Most of us have struggled with hot start I guess. There was an attempt at a comprehensive diagnosis regimen , but I don't think this valve has ever been a prime suspect??
Is controlled by coolant temperature? |
Yes it is controlled by a thermoswitch. The 1985 car has two of the magnetic valves like in the drawing, earlier cars have only one.
@Smoothie. Do you think a leaky magneto valve can contribute to the hot start problem?
_________________
1983 NA Alpineweiss since 2001
Peugeot 205 Generation |
|
| Back to top |
|
|
Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
|
| Posted: Fri Feb 12, 2010 11:44 am Post subject: |
|
|
| Duncan wrote: | | Do you think a leaky magneto valve can contribute to the hot start problem? |
I do not know (not familiar with the part).
-But, I'd be willing to guess that hollow bolt #9 in the above parts diagram attaches to the WUR..? -Then solenoid #2 opens/closes fuel flow from the fuel distributor to the WUR.. Then yes, if that's leaky, and the push-up valve at the fuel pressure regulator is either leaky or non-existent, yes the magneto valve can be part of the problem. (You were referring to solenoid #2 as "magneto valve", correct?)
_________________
"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
