quick question on checking CIS pressures...any risk of flooding the cylinders?

[bpu699]

Plan to do this weekend, weather permitting. I have the workshop manual, read the threads, and watched you tube videos.

Here is what I don't understand.

If you hook up the guages between the fuel distributor and the WUR, remove the plug to the metering plate (so the pumps run), remove the plug to the WUR (so its cold), and the turn the key to measure...

Won't the engine flood???

The pumps are running, so there is pressure to the fuel injectors, right?

In the videos, the guys check the cold pressure, then the system pressure, then the warm pressure. The pumps are running for 10 minutes or so...

Is that right?

What am I missing here? I don't want to hydrolock the motor.

Bo

[RarlyL8]

As long as you do not depress the air meter plate the injectors will not fire. Best to put a battery charged on if running the pumps to get true values at 13V

[bpu699]

Thanks. Thats very helpful! I figured that had to be the case but wanted to make sure.

What confused me was that I thought depressing the metering plate, OR disconnecting the hookup to the metring plate both make the pumps run. I though the down stream result was the same (IE. Fuel flows everywhere it was supposed to).

Bo

[dos531]

Originally Posted by bpu699

Thanks. Thats very helpful! I figured that had to be the case but wanted to make sure.

What confused me was that I thought depressing the metering plate, OR disconnecting the hookup to the metring plate both make the pumps run. I though the down stream result was the same (IE. Fuel flows everywhere it was supposed to).

Bo

The pumps run to provide the fuel pressure, but that pressure is not released to the injectors unless the air meter is depressed.

[JFairman]

The best way for you to understand it is simple.
Using two 14mm or 9/16" open end wrenches use one to hold the injector from turning and the other to loosen the injector line.. remove an injector line from an easy to reach injector and do your test.

CIS injectors shouldn't open or even dribble until something like 35 psi is put to them and no fuel should come out of the injector line until the metering plate is pushed down a little. If it does something is wrong.
You'll never really understand it until you do it yourself and watch what happens.

[peterpullin]

i broke my 91 3.3 this way. fuel head was bad and fluted one cylinder. cranking lead to a bent rod and defective cam and rockers. fuel head was not totaly shot. had some hot start issues. preasure test was fine, preasure after shut down fine for 30 minutes. and this little bit fuel that found its wrong way was enough. so next time i try, i will crank w/o ignition after this test. in my case it fired up and locked then. much $...

[bpu699]

Originally Posted by peterpullin

i broke my 91 3.3 this way. fuel head was bad and fluted one cylinder. cranking lead to a bent rod and defective cam and rockers. fuel head was not totaly shot. had some hot start issues. preasure test was fine, preasure after shut down fine for 30 minutes. and this little bit fuel that found its wrong way was enough. so next time i try, i will crank w/o ignition after this test. in my case it fired up and locked then. much $...

Thanks for the warning. I will spin the motor by hand before firing up.

Bo