Oh no, not another CIS cold start issue !!!

Deschodt · 04:02 AM

Well, yes, but really just a quick check before I farm it out... (out of time, no proper fuel pressure tools, no desire to just throw parts at it without certainty)

It's my 83 SC... When cold, it starts on the first attempt but idles very low and lumpy - 300/400 rpm. If you so much as touch the gas pedal while it does that, it'll stall on you and/or backfire/pop at you in the process....

If you wait it out 1 minute or 2, you can now press the gas and actually get revs, and you are fine for the rest of the trip and immediate restarts... until you leave it alone for a few hours, and the cycle starts again... It's not a huge problem but it means warming it up at 6AM pointing at my neighbor's window, it's rude !

I'm thinking WUR, lean mixture when cold, or a vacuum leak (but not noticeable when warm?). Since I'm going to farm it out, and could not find obvious air leaks, I was going to try screwing with the mixture by making it a bit richer (3mm allen between boot and fuel distrib, 1/5 turn clockwise right?) and see if it helped.

If not, and if it's the WUR, can I expect the shop to fix that thing or to bill be for a new one ? They seem pretty pricey ! Other than, that, the car already has a pop off valve so the airbox is fine, and it's become gradually worse over the last month...

T77911S · 08-04-2009, 03:54 AM

the aux air reg (AAR) should be bringing the idle up if everything else is ok.
it is located on the right side of the motor between runners 5 and 6. it should be open when cold.
you made it sound like you just installed the popoff valve. if it has backfired before the install, you could have blown the air box.
investing in some gauges and checking the pressure yourself may be th eway to go. you will have the gages and if the pressures are bad, you acn change the WUR yourself and you have the gages for less than the shop labor.

Deschodt · 08-04-2009, 04:06 AM

It's had a pop off valve since 95 ! I hear you about the gauges, but truly, between work/commute/a 2 year old kid/house projects/other old cars, I need to draw the line somewhere... Learning CIS is just not in the cards right now, I have my 912 apart all over the garage ;-) I'll try the mixture thing first - just hoping for confirmation there - and then farm it out, was just curious as to the worst case (WUR) and if that was a repair ($$) or exchange ($$$)...

Halm · 08-04-2009, 04:19 AM

A rebuilt WUR from Special T will set you back about $370.

Paulporsche · 01:20 PM

Have the shop tell you what the fuel and control pressures are and either post them or check them against the chart from Bosch or Bentley's. Remember, the ccp varies w/ the ambient temp.

Fuel Injection Corp in CA will rebuild your WUR for about $175.

Provided your bimetal arm is working (and it sounds like it is) you may simply need to have the cold cp plug knocked slightly in so that your cold cp is lower.

One more thing--I found a hole emerging in the metal vac pipe that goes to the AAR & AAV on my engine recently. It was around toward the firewall, near the oil light sender and the oil cooler housing.

ianc · 08-04-2009, 10:26 AM

Don't screw with the mixture Greg. It will be affected across the board, so while it may help the cold start behavior, once it warms up it will be running too rich.

It is probably the WUR, so the options are to buy a rebuilt, or modify yours to make it adjustable. Search here for threads on making it adjustable; it's a fairly simple procedure that you could pay a machine shop to do for you for much less than the cost of a new one.

Unfortunately, you'd still need the gauges to set the CCP correctly after making it adjustable. However, modifying the WUR and buying the gauges will still cost less than rebuilding your old WUR...

Doesn't sound like it's a hugely pressing problem. Cold starts in FLA are less of a problem than, say, in ME or NH, and you've still got other cars to drive until you get it taken care of?

Deschodt · 08-04-2009, 11:04 AM

Quote:

Originally Posted by ianc

Doesn't sound like it's a hugely pressing problem. Cold starts in FLA are less of a problem than, say, in ME or NH, and you've still got other cars to drive until you get it taken care of?

Cold is relative. I mean the engine has not been operated for a few hours.
It's just that I'm rude to my poor neighbor a 6AM when I go to work, that loud Flat 6 couging and sputtering for a few minutes befor eI can get on my way ;-)

And yes, it's hot here. I effing HATE florida in august ! And september....;-)

psalt · 08-04-2009, 11:42 AM

Hello Greg,

If your engine is original, try this test. When the engine is warm, disconnect and plug the grey vacuum retard hose from the back of the distributor. Rest the idle speed to 950 rpm with the large by pass screw on the throttle body. If your cold start problem goes away the next day, you do not have a WUR or mixture problem.