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Bad cold start after rebuilt??

Hi guys
Finished a complete rebuilt and now the car is super rich when started but ok after
What could have caused this?
Did not do anything to the fuel head just replaced the gas filter.
Thanks
Erick
Old 05-20-2014, 04:25 AM
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Crotchety Old Bastard
 
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Did it run rich before you replaced the gas filter? Can you check the pressures?
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 05-20-2014, 04:46 AM
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first off thanks for all the help ,
car had and still has Andial I/C,1bar boost , K27-7200

car ran great before the rebuilt. the only different thing from the original engine is
SC cams set at 1.7 and new fuel filter.

here are 3 pictures
1- BL sheet that came with the WUR
2-cold pressure 1.15bar @15C
3-warm pressure 3.65 bar

can the cold pressure lose adjustment over winter? never touched it.
where should I set all this?
Thanks
Erick


Last edited by ertech; 05-20-2014 at 08:45 AM..
Old 05-20-2014, 08:35 AM
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is the cold start valve connected wrong?
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Old 05-20-2014, 10:19 AM
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Cold start valve?where is that?
Thanks
Old 05-20-2014, 10:35 AM
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Are you sure both fuel pump relays are plugged in and working? The rear pump relay powers the bimetalic spring thermostat heater elements in the CIS mechanical cold start gadgets. The control pressure regulator/WUR and the throttle body air bypass valve.
You didn't say it's idling high too so that's probably not it. Maybe the plug on the WUR needs to be cleaned, plugged in, or just wiggled.

The cold start injector is in the intake manifold under the throttle body and it usually only squirts when it below 50 out while the starter motor is engaged.
Old 05-20-2014, 10:46 AM
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what dos the WUR plug have to do with it?
as the engine heats up the pressure goes up so the plug is working. once the WUR hot it runs well. only problem is cold start
thanks
Old 05-20-2014, 10:56 AM
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Then tune it by ear with a cold motor while the gauge ball valve is set to read control pressure.
Put the little tool Brian gave you to raise cold start control pressure during cold starts on the WUR and disconnect the electrical plug from the WUR so it stays in cold start mode.
Start the motor and quickly turn the little allen head clockwise that draws the cold start adjustment slug in the WUR upwards to raise cold start pressure and stop when it runs smooth and isn't too rich and you can blip the throttle without it hicupping or hesitating from being too lean.
You have about 20 -30 seconds to do that after a stone cold start before the combustion chambers and pistons get hot and want a leaner mixture to run right.

Do the same thing again after it completely cools off overnight.
If you have experience you can tune CIS beautifully by ear if it isn't too far off just like a carburater.

Last edited by JFairman; 05-20-2014 at 11:42 AM..
Old 05-20-2014, 11:40 AM
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Ok will try
Does the CO screw affect pressure at all?
Old 05-20-2014, 11:58 AM
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Quote:
Originally Posted by ertech View Post
Ok will try
Does the CO screw affect pressure at all?
no.
Old 05-20-2014, 12:07 PM
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Can I set cold pressure with wur unplugged engine off key on?
Thanks
Old 05-20-2014, 01:06 PM
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If the fuel pumps are running, yes.
Old 05-20-2014, 02:48 PM
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Raised the cold pressure to 1.7 and now the warm pressure is also at 1.7 ? Does the warm pressure go down when the cold is raised?
I don't get it why is my car so rich post rebuilt?
I thinks since I must of had a vacuum leak the car was richened to compensate
What should I raise warm pressure to?
Thanks
Old 05-21-2014, 07:29 AM
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Your specs are listed in the BL manual. If ccp and wcp are the same I would verify the WUR is getting power.
Old 05-21-2014, 08:20 AM
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There was air in the system I am such a dork
All ok now
Old 05-21-2014, 09:31 AM
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Should cold pressure be stable?
Every morning I check it is different? And does it make a difference in pressure if engine is running or just the pumps by disconnecting the plug?
Thanks
Old 05-23-2014, 10:50 AM
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