Yanmar 6LY3-ETP Hard Starting

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Moonzy1

Senior Member
Joined
Feb 20, 2018
Messages
115
Location
United States
Vessel Make
2007 Henriques 35 Express
Port motor starts hard...Meaning it takes more time for it to turn over and run.

Once running, it runs absolutely fine. Just takes about 5-10 seconds for it to start. Stbd motor fires rt up.

Funny thing is it gets worse after its run for several hrs then i turn off and start again after a few hours resting (ususally whe we are drift fishing at night...sun comes up and we start trolling again)

I have replaced all fuel filters 2x's and also completely rebuilt the Racor for that motor.

assuming at this point injector issue?

Anybody expericence this before?

thx
 
For a fairly new motor like yours, I wouldn't expect an injector or a poor compression problem. I would suspect a fuel system problem. Air is leaking into the fuel lines and it takes ten seconds or so of cranking to pull good fuel through. Check all connections, particularly how the Racor was reassembled. If you reassemble it incorrectly, it will leak.


David
 
Last edited:
Sounds like air. A nice trick is to put clear temporary fuel lines at engine supply and engine return. Then watch for bubbles on start and run.
 
Hello David ! Hope you’re well

Racor is good...motors are 1600 hrs
This was a symptom before I rebuilt it and there has been no change. I’m sure I did it correctly

I could certainly check all other connections in the fuel line and make sure all is tight tho.

It may explain heat expansion after s long run and excacerbating the issue
 
Does this still happen if you reverse the starting order? Could be low voltage to the port starter from multiple causes. Start the starboard motor and bring up the voltage to the port battery then start it.
 
Tried that specifically for that reason. To make sure port was getting enough juice.

Batts were loaded tested and good too

Cranking speed seems the same as well
 
It could be a bad valve in the lift pump. Valves are small disks and a spring. One on each side of the diaphragm. Each is a check valve that keeps the fuel from returning toward the tank. If one is bad or has a piece of debris embedded, the fuel is allowed to escape. In cranking cold, some of the pumping effort is wasted. When the engine is hot, and shut down, the expansion of the fuel exposed to heat pushes the fuel back toward the tank. The injector pump is designed to receive fuel under some pressure. If the fuel bleeds back to the tank, on starting, the pump isn't as efficient in producing high pressure fuel until more fuel is supplied by the struggling lift pump.
 
Not a bad theory
My mechanics first inclination was a dirty check ball valve in the racor but I eliminated that

So symptomatically what your saying lines up

How would I check that ?

Maybe time for the experts ?
 
By any chance have you cracked open any of the banjo terminations? I had a similar problem with a 3GM in a sailboat, and it turns out the copper (I think?) washers under and over the fittings don't like being loosened and retightened from bleeding too many times. I was getting a little air in the system, which worked itself out with some cranking.
 
Tomandjeri,
No have not touched anything other than filter replacement an racor rebuild
 
Ski in NC said:
Sounds like air. A nice trick is to put clear temporary fuel lines at engine supply and engine return. Then watch for bubbles on start and run.
Click to expand...

Sorry SKi
I didnt see your post. As usual great advice and good trick. This is something I could test myself.
 
Also check your fuel shut off solenoid. If they are are normally closed the slow starting one may not be opening fully once excited by the current when cold. One of my 6LPA's solenoids failed and it took a lot of tracking down.
That said bleed back from a weak side supply valve as suggested above sounds more likely with the symptoms you describe.
 
If this engine has pre combustion chambers , I would look to see if the pre heat is working (if fitted).

With a Cold engine give a shot of starting fluid and see if she starts and runs instantly.

Do not use starting fluid on a warm engine.
 
Lepke said:
It could be a bad valve in the lift pump. Valves are small disks and a spring. One on each side of the diaphragm. Each is a check valve that keeps the fuel from returning toward the tank. If one is bad or has a piece of debris embedded, the fuel is allowed to escape. In cranking cold, some of the pumping effort is wasted. When the engine is hot, and shut down, the expansion of the fuel exposed to heat pushes the fuel back toward the tank. The injector pump is designed to receive fuel under some pressure. If the fuel bleeds back to the tank, on starting, the pump isn't as efficient in producing high pressure fuel until more fuel is supplied by the struggling lift pump.
Click to expand...

If this was the case,
Could I clamp off the fuel line in front of or behind the razor to temporarily stop the backflow and see if she starts up more easily ?
 
Don't see how that is going to work but you can pressure test the discharge side of the lift pump and vacuum test the suction side of the lift pump.


You could use a helper pump for testing to ensure you have pressure to the injection pump.
 
Mike Negley has many times warned about the Racor check valve causing this type of trouble.
The ball seat must be installed correctly or the check will leak.
There is apparently printing indicating which way is correct. The problem is the printing is easily missed, indistinct, so the seat is installed incorrectly and trouble ensues.

Check it again unless you are ABSOLUTELY positive that did not happen or you may go down a long road.
 
Yes I believe it says “ this side up” def got it rt

Read an article about that

The thing is, this motor started harder than the stbd motor since I bought the boat ( used) ealler this year. This condition has gotten progressively worse over the season. And of it were the racor check ball, why would it start at the dock and then get harder to start after it’s been running a while??

I would think if it was the racor, it would be the same condiotn regardless
 
if the lift pump seal was the issue, and it was allowing fuel to push back to the tank....wouldnt it run rough once started?

Because once started, it runs fine.

still waiting for mechanic to show up...
 
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