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Old 09-02-2020, 17:10   #1
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Yanmar 4JH-HTBE fuel pump

1980ís vintage Yanmar 4JH-HTBE. engine has not been run since March last year. I had a fuel tank split, and the engine cut off almost immediately. I known there was a lot of water / biologic whatever / schmeg in the fuel because when I got the boat back to the slip, I drained all the fuel out of the system (or so I thought) and it was funky.
New tanks installed, new lines all the way around, new fluids in engine, etc.
Engine cranks. Good movement on everything that should be moving except for the fuel pump.
Gear driven fuel pump. I know the gear is driving the pump, because i checked the oil fill port on the forward part of the engine, and I could see the gears meshing and turning.
I know I am getting fuel into the pump, and through the pump to the return line, but no fuel to the lines going up to the cylinders. Iíve bled everything the manual says to- but when I try to bleed the injector lines , I get just driblets of fuel at the cylinder end of the injector line.
Is it possible that the lifters / injector bits inside the pump are gummed up? Without having to remove the whole pump from the engine, is there a way to clean the injectors? Or is this starting to get into call a pro territory?
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Old 09-02-2020, 17:19   #2
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Re: Yanmar 4JH-HTBE fuel pump

check the engine stop mechanism first. could be an electric solenoid or a wire/cable going to the back of the injection pump that is somehow stuck in "stop" position
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Old 09-02-2020, 18:16   #3
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Re: Yanmar 4JH-HTBE fuel pump

All you get from the injector lines is just a dribble of fuel, very small amount, but restrict it and it go to very high pressure, just tiny amounts.
Have the injectors serviced, can’t hurt, but unlikely they are all so bad that it won’t run.

Usually a stop solenoid is required en activated to stop fuel so very unlikely it’s stuck in the closed position, but too easy not to check and verify it’s correct.

No matter how bad the fuel was assuming your running a Racor or similar water separator and the factory fuel filter noting should have gotten through.
You did I’m sure change the factory filter?
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Old 09-02-2020, 19:21   #4
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Re: Yanmar 4JH-HTBE fuel pump

A64 Pilot - I changed out all the filters
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Old 09-02-2020, 19:27   #5
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Re: Yanmar 4JH-HTBE fuel pump

If your sure it’s bled and I doubt you really need to bleed the injectors, then maybe it’s time to call in a mechanic.
Unless your comfortable pulling the pump and taking it to an injection shop. Timing is the issue if your comfortable then pull it, if not call a mechanic.
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Old 09-02-2020, 21:29   #6
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Re: Yanmar 4JH-HTBE fuel pump

If the engine was running fine before the tank issue, don't see anything in your description that indicates you should pull either the injection pump, the injectors or the supply pump; seems more likely that you've just not worked enough of the air out of the system to allow the engine to fire and start.

Before disassembling anything major, make sure the starter is spinning the engine quickly enough, and that you've spun the engine enough to get a relatively air-free flow of fuel from the tank to the output side of the injection pump (it must be full, or mostly full, of fuel to operate properly). If you have an electric lift pump, this is pretty easy, if you have a lever on the side of a diaphragm lift pump on the engine, or on a filter housing, not so much.

Persevere, it could take several minutes to get enough solid flow to start the engine.

Make sure you have a fully charged battery, and that the connections at both the battery and the engine are clean and tight.

Don't overheat the starter.
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Old 09-02-2020, 22:25   #7
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Re: Yanmar 4JH-HTBE fuel pump

Its possible that the lift pump is blocked, do you get a good flow of fuel from the bleed point when manually operating the primer?
While exploring this issue, turn off the raw water seacock to avoid overfilling the exhaust.
If you have a stuck plunger in the injector pump there are 3 different results. The first is no fuel at all from the HP outlets. The second is a lot of fuel and an ungoverned runaway and the third is a tiny amount of fuel but no start with the potential of a 3 cyl less immediate runaway.
To avoid the overspeed, take off the boost hose between the turbo and intake manifold and keep a bit of plywood close by while trying for a start. Another tip is to try manually operating the stop lever on the back ( block) side of the injector pump. You should be able to feel some mechanical feedback and possibly see movement of the throttle lever on the front of the pump.
The other way to verify a jammed plunger locking the rack is to remove the 5 screws holding the coverplate on the side of the injector pump and viewing the fuel rack. With the engine stopped , try to gently operate the fuel rack. The little alloy collars should move very very easily ( rotate). The stop and the cold start will also move em if they are all ok. If they donít move, the injector pump is going to the fuel injection technician
Your first step though is to eliminate any possibility of this being a problem with the supply of fuel to the injector pump.
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Old 10-02-2020, 22:55   #8
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Re: Yanmar 4JH-HTBE fuel pump

On my Janmar I had an electrical connection to the fuel filter this has a a float type switch in side the filter , which is water activated , if activated it needs to be reset , or the fuel is cut off . I have since changed the type of filter unit - may help your issue Rgds Garth
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