Proper use of CIS gauges

[mikemdd]

I would like clarification on the protocol for testing CIS fuel pressure. I have seen different procedures used. Some say that the engine should be running with the gauge hooked up...others say the pressures should be tested with the engine off. Please advise a) which pressure readings should be recorded with the engine running, b) which pressure readings should be recorded with the engine not running, and c) which pressure readings can be taken with the engine running or not running (ie system pressure, cold control pressure, warm control pressure).

Thanks for the clarifications.

Mike
1981 SC
1987 930

[MotoSook]

Your system pressure should be taken with the engine off. For that test you are blocking the pump pressure in the fuel distributor (the pump must be on). Where as the fuel normally flows through the WUR and the WUR controls your pressure.

The residual pressure also is done with the engine off. In this test the gauge is measuring the pressure left in the system, so the valve should be open to allow a flow path to the WUR. Watch the pressure, it should drop then maintain at a low pressure...IIRC it's about 20-30 PSIG.

You could momentarily block the flow to the WUR with the engine on to check system pressure....very momentarily...the system will go lean in that case and the engine may die. Just do it the right way.

With the engine cold, running and valve open, you are checking cold pressure. You can leave it like that and watch the pressure rise as the engine and WUR warms ups. That will then be your warm pressure.

[mikemdd]

Perfect...that is exactly what I was looking for. Your complete explanation is much appreciated.

Mike

[Diesel_mp5]

There is a Book for Ktronic injection on amazon... it is great at going over all the tests avaliable to diagnose youre car... here is a pic....