CIS System Pressure Question (930/68)
 

After the 1st round of adjusting the Cold Control Pressure via the plug on the WUR, my 930 still had a bit of cold start crankiness.

The 1st round of WUR/CCP adjustment was made on a cooled down with fans etc for about 20-30 minutes, but not absolutely cold (ie left over night) engine.

An infrared thermometer indicated 30 degrees C and we adjusted the CCP to 2.6 Bar based on 30 deg C temp reading and the Warm Control Pressure was around 4 Bar.

The next morning, it was around 65 degrees when I went to start her.

She started better, but some of the familiar bogging and popping was back again.

Warmed up she ran well, except for an occasional exhaust backfire/pop shifting between 1st & 2nd.

I decided to check out the WUR CCP on a dead cold car. Engine/Outside temp was 25C.

CCP at 25C was approximately 1.7Bar so I adjusted the CCP to the workshop manual values and now have the following:

Cold Control Pressure @ 25C - 2.3Bar
Warm Control Pressure (at 5 minutes w/ 12Volts to WUR) - 3.9Bar

The only pressure that seemed "off" was the system pressure which was about 6.35-6.4 bar (should be 6.75 Bar).

I noticed the pressure gauge would hiccup between 6.3 and 6.4 Bar every 10-20 seconds or so (not sure if this is normal)

Should I be concerned about the System Test Pressure of 6.35-6.4 Bar v. the 6.75 Bar specified by the manual?

Thanks!

PS. We just changed the fuel filter about a week ago.

Set your cold start CP on the WUR by the seat of the pants.
I have the CIS gauges and know how to use them but I don't use them to set cold start CP unless everything else in the fuel system is new and or working like it should. Instead I set it to where the car starts right up and runs perfect while cold. On my car the cold pressure is a little lower than the stock specs for it to do that.
As an example, my cold start AFR is around 11:1 and goes up to around 14.2:1 after a couple minutes running.

If your car still coughs or hiccups back through the intake when you give it the gas right after starting it cold and you know it's not misfiring because it's way too rich then you have to tap that plug in a little farther.
Thing is if you tap it in too far you have to take the WUR all apart to tap it back out from the inside unless you have made the WUR adjustable to draw it back out with the adjustment stud or bolt, and nut.
Or send it out to someone like Brian Leask to have it made adjustable.

Raising system pressure might help if it's too low, but I've seen cars run fine with it a little below spec.
Unscrew the system fuel pressure regulator on the side of the CIS unit and be careful not to loose any of the parts while removing it.
It's the one that sticks out toward the passenger side of the car. It's 90 degrees to the return line port and it's a 16mm wrench size.
You'll need to add another tiny shim under the spring to raise system pressure. Finding one will be difficult unless you know the right sources but you may be able to find a tiny super thin washer that will work. Or make a shim from shim stock.