Procedure for testing bleed line check valves

[hkeiner]

My shop manual contains a page describing the way to test the bleed line check valves with the motor at idle on the water (see pic below). Basically I want to make sure that the check valves are not stuck open or stuck closed. Doing this test with the motor in the water is not nearly as convenient at doing the test with the motor idling on muffs in my driveway. I am a few hours away from the lake and it is a pain to do such a test while tied to a dock. My questions are these

a) Is the test valid (i.e. are the pressure readings on the fuel pressure gauge still valid) if I do the test with the motor idling on muffs rather than in the water?

b) Are there other ways to test the check valves with the boat out of the water, perhaps with the motor turned off?

 

[Faztbullet]

Re: Procedure for testing bleed line check valves

To answer you questionsA) No (B) Yes and no.. You can test valves while engine is on hose, use a 12" piece of bleed line to fitting, with engine running the fuel should be a mist or spray from hose, if it dribbles out or is soild fuel check valve is sticking or partily blocked. Symptoms of bad valves are: loading up at idle, little extra smoke and stumbling when accelerating

 

[hkeiner]

Re: Procedure for testing bleed line check valves

To answer you questionsA) No

Just curious....Why would the fuel pressure gauge test with the motor idleing on muffs not work OK?

I am asking because with my limited experience with bleed lines and check valves, counting on my judgement and observations is not as reliable as checking things to spec with a gauge. I generally prefer to do troubleshooting with gauges and meters when it is practical and applicable.

 

[j_martin]

Re: Procedure for testing bleed line check valves

The old timer at the outboard shop taught me to do it this way.
Attach a line to the bleed valve
attach a syringe (20 cc or so) to the hose
You should be able to gently withdraw the plunger, but not push it in. You're feeling for the check valve action.

ttttthhhhaaaatttts it folks.
John

 

[Faztbullet]

Re: Procedure for testing bleed line check valves

Crankcase pressure will be lower because of no backpressure on engine, guage reading will be lower indicating a problem when there may not be one. I use the syringe trick to clean check valves, you can get a good one from CO-OP.

 

[hkeiner]

Re: Procedure for testing bleed line check valves

Thanks for explaining the reason why the gauge test would not work on muffs. It prevented me from probably diagnosing a problem with the check valves when one may not actually exist.

I am going to first try the "syringe" method and see what happens. I guess that if a check valve is solidly stuck closed or solidly stuck open, it would be apparent when using the syringe.

I am also going to try the "watch for mist/spray with motor idleing on muffs" method to see what happens. I guess if nothing comes out of the bleed line at all or if lots of fuel/oil run out of the end of the line, the check valve is suspect.

Thanks for the great advice guys! I searched this forum and did not find much about testing bleed line check valves.