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hoyabear's Avatar
Join Date: Feb 2008
Location: Seekonk, MA
Posts: 142
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WUR problems???

Hi all,

So the car is finally running and now I'm experiencing some issues I haven't seen with it before (perhaps because it is cold out?). When I start the car from cold, I let it warm up and drive off with no problems at all. If I then turn the car off after driving it, let it cool down a bit and then try to start it back up it will sometimes start and then cut out abruptly. It will then be really tough to start after that until it magically decides to start up again, and then it is usually fine after that. I am mystified as there seems to be no correlation between measured engine temp, time let cool down, etc, and the car behaving this way.

As a side note, the car also runs really really rich for like a minute after it is started to like 6 minutes after it is started, then it tapers back a bit (as it warms up). All in all, I think the car runs a bit too much on the rich side (something I am going to address as soon as I can get to it).

Any thoughts on what is causing the car to cut out? Is this soemthing that will go away once there is a better tune on the fuel delivery system? Should I be looking for leaking hoses somewhere? I would say that of all the things on this car, I understand the CIS system the least. Thanks - Jon
'86 930: 3.4 Andial build, Web GT2 Evo cams, Carrillo rods, ported/polished heads, MSD 6530, B&B headers/exh + intercooler, K27HF, 1 bar spring, Tial wastegate, Andial FE, Lindsey Fuchs. Back in black!!!
Past:997S cab; '88 930; '86 951; C5 Vette; 4th Gen Z28; 3rd Gen Trans Am GTA; '71 Z28
Old 11-25-2009, 09:30 AM
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bcoats's Avatar
Join Date: Feb 2005
Location: Seattle, WA
Posts: 463
Hey Jon, I had similar intermittent issue like your and turned out to be my ignition system. For what it's worth, mine runs pretty rich as well still with the new ignition system and a Brian Leask WUR. . .then really smoothes out, and CO set at 4%, good luck in sorting it out, you have a nice car by the way
1979 911 RS clone hotrod
1983 930 turbo-sold, will be missed
1992 964 C2 Coupe-regrettably sold
1980 911 SC Weissach-regrettably sold
1975 911S-sold but not forgotten
Old 11-25-2009, 09:37 AM
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wjfk32's Avatar
Join Date: May 2008
Posts: 1,257

Could be a number of things. I had a similar issue. I finally got around to change the fuel accumulator...Mine was original with the engine. Quick fix maybe,I would chk the plugs, maybe fouled..Clean them. Put some MMO-4ounces to 10 gallons..Doesn't cost much. Then do some nice top-end runs..Hopefully this works.

Old 11-25-2009, 09:58 AM
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mark houghton's Avatar
Join Date: Jul 2008
Location: Central Washington State
Posts: 3,776
The abrupt cut-out after starting back up from hot tells me it isn't the WUR. The abruptness says it's either the fuel suddenly cutting off or the ignition. Since it seems to be heat related, perhaps your funky yellow overboost fuel shutoff relay is doing the chicken after getting heat soaked.

Need a little more diagnostic info. The next time it does this (won't start up after a short cool down), immediately go back and see if the pumps can be made to run by pulling the connector at the back of the fuel head. If you can't force them to run in this fashion, then one of three things come to mind: the yellow relay, the oveboost pressure switch, or the fuses/wires to the fuel pumps at the fuse block are of poor connection.

And while you're back there, see if you have any spark at the coil (may need someone to crank it over for you as you stick your finger into the coil...just kidding of course). Your CDI may be going south on you.
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.

Last edited by mark houghton; 11-25-2009 at 10:10 AM..
Old 11-25-2009, 10:00 AM
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JBL930's Avatar
Join Date: May 2006
Location: UK
Posts: 1,172
The pig rich time after you start the car when you know it's already warm was my biggest bug with the CIS system! I used to hate the fact that you would stop for fuel, fill the tank, get back in the car and it would be so rich it wouldn't even come on boost!! AAArrrrggggghhhh!!!!
It's the bimetalic spring in the WUR cooling down too quickly and lowering control pressure, i think maybe when they are old they cool down way quicker than when they were new, so the fuel system thinks the engine is stone cold even though the engine was only shut off minutes before.
I'm not sure if this is the same with all other CIS 930's, but it really used to boil my piss with mine!!! Speak to Brian Leask about getting yours rebuilt and made adjustable.

I'm with mark on the cut off, could be a dodgy relay or overboost switch. If not then it could point to your accumulator, or leaky injector. Find a garage with CIS pressure test gauges and they'll tell you
87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
Old 540 BMW, XB12S Modified, for being a total hooligan
Old 11-25-2009, 10:45 AM
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