Apparently you swapped the FUEL injector (only) in Post#1?Originally Posted by ChrisCarsonMarine
Apparently you swapped the FUEL injector (only) in Post#1?
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
bmac101960 Many 2 stroke techs have vary rarely if ever heard the various intake sounds that a four stroke will make with various valve train problems, what you described along you test results makes me inclined to think this very well may be a bent rod (piston not rising all the way to the top). I would think to get a 30 psi drop from this cylinder the piston would be coming up short around .080 to .120. Which would also mean port timing has been changed by the same amount, ports would be open sooner and close later, this would have the same effect as advancing cam timing a great deal on four stroke motor as well as lot more overlap which would cause reversion on that cylinder!
I get what Chris is saying about the direct injectors though I would think that would also show up in the leak down test.
It might be a useful test to check compression with the direct injector disconnected before relocating it just because it would be quick and easy and it passed leakdown
Chris's method of leak down test is exactly the way I do them as well
Just thinking out as I am ASE master tech as well, I am not a Outboard tech, I count on guys like Don and Chris to reinforce my thinking on the Mercs
Please keep us informed, I am really currios about this one
Last edited by lpugh; 11-02-2019 at 10:38 PM.
Thank You Leon Pugh
Lpugh,your theory of a bent rod is applicable for some motors,but in this case not so much.The bottom of the cylinder is closed except for the rod slot,and the piston travels to almost the bottom of the semi-closed cylinder,with only around .030 clearance.For the rod to be shortened enough to lower the compression I’m pretty sure the piston would bottom out at the Cyl base,Chris
Thank Chris, I was not aware of that design feature
Thank You Leon Pugh
Don, Chris, and Leon. Thank you ALL very much!! I am very happyto report that I checked the compression in #3 with the direct injector disconnected as advised and to my surprise got 90 psi on the gauge!! Don, I did NOT change the direct injector when I changed the fuel injector in my first post (had no idea it existed) All of the help you guys gave me has saved me a LOT of money and time!! Can the direct injector be cleaned/repaired? Am I better off getting a new one?
What is the cost to have ALL injectors and fuel rails serviced? Obviously this would be a good investment! This boat and motor are new to me and I'm unaware of its maintenance history.
Keep in mind this does not absoluty mean it is a bad injector, keep in mind if the injector control side wire is shorted to ground it could hold the injector open at the wrong time or always open, even a ecm could cause this to happen, might be wise to swap it to another hole as Chris mentioned as that would narrow it further to injector or control problem. I would think if electrical it would set a fault
Thank You Leon Pugh
We service and test direct and fuel injectors,as well as the rails,regulators and vst.Give a call to discuss,305-394-3354,Chris
It's pretty likely that the #3 DI is done. They can be cleaned, but they cannot be "repaired" (cleaning and testing is wise- but in my experience, the odds of that DI recovering by cleaning it are not good).Don, Chris, and Leon. Thank you ALL very much!! I am very happy
What is the cost to have ALL injectors and fuel rails serviced? Obviously this would be a good investment! This boat and motor are new to me and I'm unaware of its maintenance history.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Thank You. I will switch out #3 with #1 as advised to rule out electrical and confirm stuck injector.
Better inspect the internals of your air compressor!!
I have switched #1 and #3 direct injectors. Soaked the cylinder end of each injector in Power Tune prior to re-installing. I now have 90 psi compression in both cylinders with the direct injectors connected to electrical harness. It is idling good at this time on all cylinders. It will be a few days before in can take the boat out and put it under a load.
Is the best way to check the compressor to pull off the end cap and head assembly. Will an oil prime need to be done after inspecting the compressor?
1. Yes
2. Yes I would.
Reply With Quote