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carrpet

930 WUR low and static fuel pressure issue ! Help !!

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Hi there
I have created a problem of my own making !
I started the day with a hard cold starting / high cold pressure problem which was clearly WUR related. I was getting 20psi at 7.5C. Engine ran fine apart from hard starting with a warm pressure of 53psi.
Pulled out the WUR, knocked in the small plug about 1mm.
Connected the WUR up again, made some mods to the simplify the fuel pipework where I have a tee piece to accommodate by AEM pressure sensor, and now all I get is about 6-7 psi which is static with the fuel pumps running ie. no apparent pressure increase as the bimetallic strip heater kicks in, but when I turn them off the pressure gauge jumps to about 20-25psi depending upon how long I ran the pumps for. I checked that there are 12 volts for the heater element and the resistance of the heater element is 25 ohms.
I can't believe this is down to a 1mm depression of the cold pressure plug ?
I haven't yet checked the system pressure.
Any ideas as to what may be going on or what I may have unwittingly done and how to get out of the mess ?
Peter

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Hi Peter,  

It’s odd that your WUR went out of whack as I recall you had all your pressures in spec a few weeks ago. It makes me think something else was causing the problem. In any event, knocking the pin in 1mm seems an awful lot so may well give you far too rich a mixture and possibly cause damage. 

What mods have you done to your fuel lines?  I’m not quite understanding.

I’d reverse all the changes you made and start again. Remove the mod to your lines and inspect the WUR for damage and roughly set the pin where it was (think you’ll need to push the pin out from inside). Measure all pressures, inc system, and go from there. Obviously you’ll need to  then set the WUR up again. 

Cheers 

David 

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Hi David,

Thanks for your response
First of all I continued to have an intermittent cold start problem.
While my warm pressure was right on specification my cold pressure was always right at the high end limit.
I figured from all of the discussion on a range of forums on WUR related cold start problems, that I really ought to be at the mid to bottom end of the Cold Pressure specification if I was experiencing Cold Start problems. I also noticed that every time I cold started the car after breaking into the fuel lines, the car started first time, perfectly. This reinforced my view that I needed to be at the bottom end of the range.
So to lower the CP I pushed in the plug but clearly too far. I hadn't realised how sensitive that CP plug position is and I dropped out the end of the working range. I have now made the CP plug adjustable and have extracted it to its original position, then adjusted the plug position to give a CP of 11psi at 7 degrees centigrade with both pumps running, the WUR heater plug disconnected and the airflow switch plug off.
Started first time and ran perfectly as I might have expected, the real test is tomorrow morning. Warm pressure solid at 53psi.
What freaked me out was that with the plug pushed in by 1mm I was getting no increase in pressure at all due to the bimetallic strip bending and therefore no warm pressure !
All is great now but I did have a minor panic. I got down to it this morning put the CP plug back in its original position then set the cold pressure in-situ by adjusting the plug position. Panic over !
The fuel line mods were to tidy up the connection of my AEM pressure sensor which had previously long unnecessary pipe runs with lots of fittings. That is now fixed with proper hydraulic swivel fittings.
Cheers
Peter

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