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WUR removal problem - fuel

 
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SecaBlue  



Joined: 16 Sep 2022
Posts: 37
Location: Sweden

PostPosted: Tue Jul 16, 2024 6:28 am    Post subject: WUR removal problem - fuel Reply with quote

Hi, I've been struggling getting my '84 924 starting and running properly, but thought I would start a new thread for a very specific issue that puzzles me.

I feel I need to remove my WUR to get the cold start idle sorted. Reading other threads and watching every YT video about it, seems straight forward.

So, I didn't drive the car for 48+ hours, parked on flat surface, disconnected the battery, put a big rag under the WUR to catch any small parts or fuel, and started removal...

After a little anti-seize spray and careful encouragement, the top fuel line bolt came loose for the first time in 40yrs, and easily removed. No fuel coming out. Moved on to the lower fuel line bolt, came loose too, and immediately started to flow with fuel. Thought ok, as some of the info I read says it will leak a little. I kept on unscrewing, and soon the big rag under was soaked, and the fuel was dripping fast under the car. I thought this was excessive, so quickly tightened it up again. I imagine it was easily a couple of hundred millilitres - enough to completely soak the rag and pool under the car.

So where do I go from here? Is that much fuel draining from the WUR return line normal?... as I never read anywhere or saw on any removal video so much fuel leaking constantly. I assume the fuel distributor was draining, but should it? Is it a symptom of a clogged/dirty WUR internals if when I reconnected the lower fuel line bolt, no fuel at all leaked from the top bolt hole that was still open - as I was under the impression that when cold, there should be an open path for fuel to travel either way inside the WUR.

I want to get the WUR cleaned asap, so any advice is helpful Thanks!
_________________
1984 924 manual.
1993 928GTS Auto.
1990 944S2 manual (sold).
1987 928S4 Auto (sold).
2001 996 Turbo (sold).
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morghen  



Joined: 21 Jan 2005
Posts: 8947
Location: Romania

PostPosted: Tue Jul 16, 2024 4:45 pm    Post subject: Reply with quote

Usually the mesh in the WUR ports clogs up and you get less fuel flow trough it. You can try to find a shop that specializes in restoring the WUR and send it there. I heard(a few years ago) of such a thing in UK, about 500gpb for the WUR, or i know a shop in Italy, similar pricing, but you have to send every k-jet component so that they clean and balance them together.
Total you will likely be under 1k for the repair and calibration.

I think your k-jet has multiple failures, i suspect the WUR is pretty dead and the fuel distributor has some sort of internal failure as well.

I think i still have a rebuilt WUR and a good known to work fuel distributor, let me know if you want them.

If you want to forget about these complicated stories and have a reliable car, have a look on my website and send me an email.
The originality is kept very well and my EFI system will be a legal and homologated product in EU by the end of this summer.
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SecaBlue  



Joined: 16 Sep 2022
Posts: 37
Location: Sweden

PostPosted: Tue Jul 16, 2024 8:08 pm    Post subject: Reply with quote

I don't think I WUR is "dead", as the car runs really well when warm. The WUR has 12v going to it, and it has the right resistance as per factory spec.

If I get it off, I can give it a clean with a friend's ultrasonic cleaner. And I don't want to fit an EFI kit to a museum quality 924. The value is in its originality.

So back on topic... why so much fuel dumping out of the WUR return line when I remove it? Is another seal upstream failing allowing it to flow freely? Is there a way I can mitigate the flow?
_________________
1984 924 manual.
1993 928GTS Auto.
1990 944S2 manual (sold).
1987 928S4 Auto (sold).
2001 996 Turbo (sold).
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1384
Location: Washington DC area

PostPosted: Wed Jul 17, 2024 1:42 am    Post subject: Reply with quote

Possibly a full fuel tank with the fuel level higher than the level of the WUR. I've jacked up the nose of the car and left the rear on the ground to avoid the siphon effect while working on my fuel system.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car
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SecaBlue  



Joined: 16 Sep 2022
Posts: 37
Location: Sweden

PostPosted: Wed Jul 17, 2024 3:42 am    Post subject: Reply with quote

Fifty50Plus wrote:
Possibly a full fuel tank with the fuel level higher than the level of the WUR. I've jacked up the nose of the car and left the rear on the ground to avoid the siphon effect while working on my fuel system.

Aha... my fuel tank at 2/3 full may be causing this then? I didn't think the fuel tank was higher than the fuel manifold, but then I have never measured it
_________________
1984 924 manual.
1993 928GTS Auto.
1990 944S2 manual (sold).
1987 928S4 Auto (sold).
2001 996 Turbo (sold).
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SecaBlue  



Joined: 16 Sep 2022
Posts: 37
Location: Sweden

PostPosted: Sat Jul 20, 2024 7:22 am    Post subject: Reply with quote

Drove the car a bit. Apparently half full tank is still too full. 🫤
_________________
1984 924 manual.
1993 928GTS Auto.
1990 944S2 manual (sold).
1987 928S4 Auto (sold).
2001 996 Turbo (sold).
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SecaBlue  



Joined: 16 Sep 2022
Posts: 37
Location: Sweden

PostPosted: Fri Jul 26, 2024 4:35 am    Post subject: Reply with quote

Drove the car even more... even fuel tank at 1/3 full is too full. Fuel running freely from WUR return line as soon as I crack it.

I cracked one of the injector lines at the top of the fuel distributor, and the fuel sat level with the hole but nothing ran out. I then cracked the fuel line on the side of the FD that feeds the WUR, and a lot of fuel ran freely out.

I can't imagine a 1/3 tank is higher than that??? I think next I need to find a hill to park on, as this fuel flowing issue was not expected. Just want to get my WUR off! 😛
_________________
1984 924 manual.
1993 928GTS Auto.
1990 944S2 manual (sold).
1987 928S4 Auto (sold).
2001 996 Turbo (sold).
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Raize  



Joined: 18 Sep 2013
Posts: 236
Location: Scotland

PostPosted: Fri Jul 26, 2024 7:27 pm    Post subject: Reply with quote

SecaBlue wrote:
Drove the car even more... even fuel tank at 1/3 full is too full. Fuel running freely from WUR return line as soon as I crack it.

I cracked one of the injector lines at the top of the fuel distributor, and the fuel sat level with the hole but nothing ran out. I then cracked the fuel line on the side of the FD that feeds the WUR, and a lot of fuel ran freely out.

I can't imagine a 1/3 tank is higher than that??? I think next I need to find a hill to park on, as this fuel flowing issue was not expected. Just want to get my WUR off! 😛


The line that feeds the WUR is not on the side of the FD it is on the top, between the four injector ports. The WUR return line is on the side (brazed to the fitting for the main return line) and drains directly to tank.

A small fuel spill is normal when removing WUR, try to catch in a container rather than on a rag, it's not as much as you probably think, gas just has virtually zero viscosity so it flows everywhere rather than staying in one place like water would.

There should not be any siphoning with a 1/3 full tank.

There should never be an "open path" through the WUR unless some pressure is applied, even when cold.

If you just have cold starting / running problems then you're definitely looking in the right place, you can add the cold mixture adjustment screw mod once it's off but bear in mind the adjustment is super sensitive so you will 100% need a k-jet pressure tester to set it. A wideband sensor in the exhaust is also very useful.

The book values are also not necessarily what will work, my 924 runs extremely rich to the point of not starting if using the book values for control pressure.
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SecaBlue  



Joined: 16 Sep 2022
Posts: 37
Location: Sweden

PostPosted: Wed Jul 31, 2024 5:47 am    Post subject: Reply with quote

Raize wrote:
SecaBlue wrote:
Drove the car even more... even fuel tank at 1/3 full is too full. Fuel running freely from WUR return line as soon as I crack it.

I cracked one of the injector lines at the top of the fuel distributor, and the fuel sat level with the hole but nothing ran out. I then cracked the fuel line on the side of the FD that feeds the WUR, and a lot of fuel ran freely out.

I can't imagine a 1/3 tank is higher than that??? I think next I need to find a hill to park on, as this fuel flowing issue was not expected. Just want to get my WUR off! 😛


The line that feeds the WUR is not on the side of the FD it is on the top, between the four injector ports. The WUR return line is on the side (brazed to the fitting for the main return line) and drains directly to tank.

A small fuel spill is normal when removing WUR, try to catch in a container rather than on a rag, it's not as much as you probably think, gas just has virtually zero viscosity so it flows everywhere rather than staying in one place like water would.

There should not be any siphoning with a 1/3 full tank.

There should never be an "open path" through the WUR unless some pressure is applied, even when cold.

If you just have cold starting / running problems then you're definitely looking in the right place, you can add the cold mixture adjustment screw mod once it's off but bear in mind the adjustment is super sensitive so you will 100% need a k-jet pressure tester to set it. A wideband sensor in the exhaust is also very useful.

The book values are also not necessarily what will work, my 924 runs extremely rich to the point of not starting if using the book values for control pressure.


Soooo rookie mistake on my part. I never thought the fuel tank would be under so much pressure that it would push the fuel through. My neighbour suggested opening the fuel tank cap - fuel stopped running out of WUR return line instantly.

Yeah yeah... laugh all you want hehe but I really didn't think of it.

Back on subject, WUR removed, opened and cleaned with ultrasonic bath for 30 mins, and other parts cleaned with brake cleaner. All looked good inside with no dirt. Guess the gauze filter could have been blocked more than I could see.

Back on car, broke one of the banjo bolts. Ran to a parts shop to buy replacements of the broken M8 and an additional M10 with new crash brass washes. Back on the car and no leaks from the fittings.

Will try a proper cold start tomorrow with fuel in the complete system.

Thanks for your help!
_________________
1984 924 manual.
1993 928GTS Auto.
1990 944S2 manual (sold).
1987 928S4 Auto (sold).
2001 996 Turbo (sold).
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