924Board.org

[John Brown]

Just an observation (again) with a recent experience to back it up.

At least a couple of years back I made the grumpy suggestion that instead of all the scattershot parts replacement and guessing when the pick one (cold start, warm start, cold idle, hot idle, hot start, low speed mism, high speed miss, rough running,...) problems surfaced; just check the fuel pressure. On a CIS fuel system THERE IS NO SUBSTITUTE FOR CHECKING THE SYSTEM AND CONTROL PRESSURE!

Like everyone, we too simply put the LJ project car 931 back together and since it ran, left well enough alone. Yesterday, had reason to check CIS and discovered that the control pressure regulator was completely INOP! Car ran fine! Now, I'm sure we had a lean mixture at power which would eventually melt the pistons, and also that this would have become a problem starting in cold weather (for a street car at least). Point is that the idle adjustments I made upon the initial start up made the motor run fine and completely masked the bad regulator!

Granted, the guage setup list price is between $100 and $185 depending on where you source it. Find a mechanic with the guage and pay them to check the system. It should be a minimum labor charge and the whole thing can be done in 30 min start to finish. They will need to start with a cold motor. So you'll need to leave it overnight or at least for a few hours.

Because the heart of CIS is the hydraulic pressure control of mechanical metering of fuel the importance of proper fuel pressure cannot be overstated.

Have a nice weekend. Since it was not the CIS, I gotta go put a scope on the ignition. See ya!

[924RACR]

BMP Design, a well-known BMW parts place, sells these now regularly for $60:
http://www.bmpdesign.com/bmw/parts/catalog/tools_21.shtml
(scroll down to the K-Jet tester).

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[awilson40]

How right you are. Verifying correct pressures are the first place to begin. The CIS gauges were the first tools I bought.
JC Whitney... $60.

[Paul]

Bought mine from JC also, have been using it for more than a decade with no problems.

[John H]

I've found this site quite useful in tracking down problems with the CIS system

http://www.users.bigpond.com/INTERJECT/KJETRON.HTM

[Joes924]

Thats good reading there about cis enjoyed it,