Mercury vst I’m read to learn

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Thanks to anyone who reads and or responds!

i have a 2006 40hp mercury 4stroke 3cyl that is fuel injected.

i got the motor a few months ago ran fine until one day it started to miss at high rpms. Then the next day stated missing at idle.

i checked the fuel pressure at the Shrader valve on the vst.i got 42psi.

when I put the gauge on some fuel squirted out past the gauge and the motor ran fine for 30sec or so. Then starts missing again. So I started on rebuilding the vst I purchased and install

all filters entire fuel system and waterseperater witch I added
regulator
high pressure fuel pump
and I removed the cooler and found all o rings were bad and since been replaced.

nothing has made a difference in the miss except for relieving pressure from the schader valve on the vst.

thanks for the time you spent to read/understand my troubles

 

[alldodge]

The 42 psi is correct, so my next thought is you have low compression or injectors are leaking

Suggest having your injectors flow tested
http://boatinfo.no/lib/mercury/manuals/30-40_02.html#/166

 

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Thanks for taking a shot at this!
I put a gauge in between the the vst hp line out and the injector manifold. It went from 42 to 40. Still ran the same. I also took a high pressure pump and regulator and bypassed the vst and to my surprise it ran the same. I set the regulator to 50psi and down to 35. The miss remained. It seems that the vst is not the issue. I just don’t understand why it runs well when I vent the vst.

At this point I started to believe I could have a vacuum leak.
So to make sure I didn’t have air leaking into the manifold I took a small bottle of propane and without striking a flame I moved it around the intake manifold hoping to find a increase in rpm.

 

[alldodge]

Click on the link in my first post then go back one page. There is a list of things which can cause poor idle and running. It list things to check which include injectors, crank position sensor, timing, loose ground etc

 

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Thanks I will