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doug60
Joined: 24 Jan 2012
Posts: 11
Location: england
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 Posted: Fri Feb 03, 2012 4:37 am Post subject: Haynes manual on testing control pressure |
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I'm a bit confused on what i have read in the haynes manual on testing control pressure when the engine is hot, the WUR ( control pressure reg)
will now be closed for this test, so surely it should give you a control pressure reading of 65 to 75psi not what they state 49 to 67 psi surely it is just the same test as for system pressure ( page 77 ) ?? The car is a 924 1984.
Thanks for any info |
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Khal
Joined: 26 Sep 2003
Posts: 4872
Location: Sunny and lovely interior BC, Canada
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bruce76-924
Joined: 22 Feb 2007
Posts: 105
Location: Bradford, England
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| Posted: Fri Feb 03, 2012 5:06 am Post subject: |
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Hi,
System and control pressure are 2 different things, do not confuse them. Remember that they are tested differently. The control pressure regulator ( warm up regulator) never fully closes. What are the problems with the car?
Bruce.
_________________
1976 924 LHD, full cage, semi tube chassis, 951 brakes, lightweight 951 body panels.
1.8t engine conversion with Holset turbo and 6 speed Audi gearbox. |
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doug60
Joined: 24 Jan 2012
Posts: 11
Location: england
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| Posted: Sat Feb 04, 2012 4:11 am Post subject: reply |
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[quote="bruce76-924"]Hi,
System and control pressure are 2 different things, do not confuse them. Remember that they are tested differently. The control pressure regulator ( warm up regulator) never fully closes. What are the problems with the car?
Bruce.[/quote]
Hi Bruce, Thanks for the reply. I thought that the WUR completely closed when the car was warmed up, i get it now !! The car is jerky when i first start off, and very slightly jerky in the 2000-3000 rpm band after that all is fine. the tickover fine etc
Thanks DB |
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ptheskil
Joined: 03 Aug 2004
Posts: 128
Location: Essex, UK
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| Posted: Sat Feb 04, 2012 8:56 pm Post subject: |
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I have absolutely no evidence for this statement whatsoever (!) but I suspect that many (the majority) of running problems with older K-jetronic systems are due to the WUR? It seems to be susceptible to deterioration/blocking. I suspect as well that many POs have tinkered with the idle mixture when warm to get the engine running sort of OK leading to poor (lean) running when cold and lean mixture at the higher air flows.
The only way to put this right is to check/set system and control pressures hot and cold before you adjust anything else. Once you have put that right then you will probably have to undo previous adjustments. A proper fuel pressure test is the only way to go.
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1981 931 series2 Euro spec |
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bruce76-924
Joined: 22 Feb 2007
Posts: 105
Location: Bradford, England
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| Posted: Sat Feb 04, 2012 10:09 pm Post subject: |
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| ptheskil wrote: | I have absolutely no evidence for this statement whatsoever (!) but I suspect that many (the majority) of running problems with older K-jetronic systems are due to the WUR? It seems to be susceptible to deterioration/blocking. I suspect as well that many POs have tinkered with the idle mixture when warm to get the engine running sort of OK leading to poor (lean) running when cold and lean mixture at the higher air flows.
The only way to put this right is to check/set system and control pressures hot and cold before you adjust anything else. Once you have put that right then you will probably have to undo previous adjustments. A proper fuel
pressure test is the only way to go. |
It is also susceptible to being fiddled with in the ignorance that you can adjust it to get more power. It can be adjusted but you need to know the pressures it is then set at. Many control pressure regulators ( WUR) have been messed about with by people who don't know what they are doing and just following "Internet experts"! Beg, borrow, steal or even buy the correct gauge and get the system set to the factory specs. Don't forget the basics though, plugs, leads, cap, rotor and filters.
Bruce.
_________________
1976 924 LHD, full cage, semi tube chassis, 951 brakes, lightweight 951 body panels.
1.8t engine conversion with Holset turbo and 6 speed Audi gearbox. |
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dpw928
Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055
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| Posted: Sun Feb 05, 2012 12:36 am Post subject: |
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| bruce76-924 wrote: | | ptheskil wrote: | I have absolutely no evidence for this statement whatsoever (!) but I suspect that many (the majority) of running problems with older K-jetronic systems are due to the WUR? It seems to be susceptible to deterioration/blocking. I suspect as well that many POs have tinkered with the idle mixture when warm to get the engine running sort of OK leading to poor (lean) running when cold and lean mixture at the higher air flows.
The only way to put this right is to check/set system and control pressures hot and cold before you adjust anything else. Once you have put that right then you will probably have to undo previous adjustments. A proper fuel
pressure test is the only way to go. |
It is also susceptible to being fiddled with in the ignorance that you can adjust it to get more power. It can be adjusted but you need to know the pressures it is then set at. Many control pressure regulators ( WUR) have been messed about with by people who don't know what they are doing and just following "Internet experts"! Beg, borrow, steal or even buy the correct gauge and get the system set to the factory specs. Don't forget the basics though, plugs, leads, cap, rotor and filters.
Bruce. |
Agreed. The warm up regulator adjusts control pressure based upon the ambient temp through the bimetal plate that changes the valve adjustment. If the control pressure is correct at one temp, it should be correct at all temps unless the laws of physics have changed. Since the engine seems to be running correctly when warm, other areas as suggested by Bruce should be checked. Also the AAV could cause poor cold running if it is stuck closed.
Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Sun Feb 05, 2012 3:14 am Post subject: |
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| dpw928 wrote: | | If the control pressure is correct at one temp, it should be correct at all temps unless the laws of physics have changed. |
Disagree.
| ptheskil wrote: | | I suspect that many (the majority) of running problems with older K-jetronic systems are due to the WUR? |
WUR plays a role, so to do dirt (from cheap fuel without sufficient detergent) and vaccuum leaks.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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