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Author Topic: HW3 Marine Engine - Bleeding problems  (Read 252 times)

RobAJacobs

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HW3 Marine Engine - Bleeding problems
« on: June 13, 2019, 04:01:20 PM »
My Engine is a HW3 (Eng no 253, Manufactured in 1969.
It is installed in mr Roberts 32' Ketch Motor Sailor.
I have the fuel tank above the engine and the fuel is fed by gravity only.
I turn off the fuel.  If the engine is not started for a period I need to bleed the 3 pumps to get full power to the engine.
If I dont bleed the pumps the engine will start but will not deliver full power.  Once I bleed the pump the full power of the engine is achieved.
Does any one in the forum have this issue, How can I solve the problem.?

LowGear

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Re: HW3 Marine Engine - Bleeding problems
« Reply #1 on: June 13, 2019, 06:50:49 PM »
No expertise here except a second pair of eyes.  I'd look to see if one of the injectors (pumps?) was the loan offender and consistently causing the problem.
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BruceM

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Re: HW3 Marine Engine - Bleeding problems
« Reply #2 on: June 13, 2019, 07:43:28 PM »
Here's my thoughts-
That's an odd problem.  Loss of power in diesels while still starting and running normally is typically fuel starvation, and clogged lines/filters from microbes, etc., are the usual culprit. 

Bleeding restoring full power is either circumstantial, having restored adequate flow by flushing or points to the loss of one cylinder by air leakage into that IP cylinder.  You can find out which cylinder isn't firing by loosening the high pressure lines to the injectors one at a time.  Normally a skilled operator familiar with the engine would notice the loss of a cylinder in a 3 cylinder diesel.

glort

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Re: HW3 Marine Engine - Bleeding problems
« Reply #3 on: June 14, 2019, 03:09:04 AM »

My suggestion would be you have a leak somewhere, either in the fuel lines or in the pump. Sounds like a trapped air bubble which will allow some but niot enough fuel to go through.
Air has to be getting in somewhere and often leaks are air leaks not fuel leaks. Seen a lot of vehicles with this problem.

If you have soft lines and a filter from the tank to the IP replace them to start including new quality clamps.
there were a batch of the CAV filters some years back that had a problem with the top bolt leaking due to poorly cut seats the washer sat on.  a quick spin with a countersink fixed that. I never used it so did as I did with all fittings and used a sealant on them. My go to is PVC pipe cement.  If the area is clean it seals perfectly but isn't hard to remove from metal if you have to .

Once you have isolated fuel feed leaks, see how you go.  Not sure of the IP on those is fed from the sump but if it is and the oil level is rising, it's the pump.  A seal or diaphragm has gone inside. If it's not oil fed, the fuel has to be going somewhere so clean around the area and check for drips.

You can clean around any unions with brake cleaner and then give a good coat of the PVC cement or whatever else is out there in sealants.  If you have metal fuel lines, Check for cracks or pinholes.

BruceM

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Re: HW3 Marine Engine - Bleeding problems
« Reply #4 on: June 14, 2019, 03:29:38 AM »
"Sounds like a trapped air bubble which will allow some but niot enough fuel to go through.
Air has to be getting in somewhere and often leaks are air leaks not fuel leaks. Seen a lot of vehicles with this problem. "

Good one, Glort.  This would be at filters and such, where there is a riser in the fuel path.

glort

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Re: HW3 Marine Engine - Bleeding problems
« Reply #5 on: June 14, 2019, 04:46:21 AM »

The air leaks happen when the fuel is being pulled from a tank like in a vehicle.  In the veg circles where the problems could be increased through the thicker oil, the solution was often to put a pump at the tank to push the fuel and exclude the air. The merc pumps like on your car would pull a golf ball through a garden hose so anything not perfectly sealed was prone to air leaks.   Often the irony was air would get in but people couldn't find  any leaks where the oil got out. Obviously different density's of the materials but showed how hard some of these leaks could be to track down. The one with the CAV fuel filters had people scratching their heads for a long time till a friend of mine found and solved the issue for everyone.  Never did like those filters anyway!

Pumps didn't work for me on my truck. Haven't found one yet with the grunt to push the oil through fast enough when the thing is spooled up and pulling hard. Even the expensive Holley pumps which would flow 1000HP of petrol wouldn't last long on oil. Solution in the end was Bypass most of the OEM Lines after the hard line reached the engine bay, use a Subaru filter and straight into the IP. Removed about 3M of fuel line and a lot of connections and bends.

The thing here with what the Op describes I find the key to be the fuel tank is raised. Normally that would help push the air out or stop it coming in but he says he turns the fuel off.  I forgot to mention to look at the fuel tap as well because if that is leaking air it would allow the level to drop and fill the space with air.  Thing is though, fuel has to be draining somewhere for the level to drop so to me that indicates there is a path out somewhere lower down.

This makes the problem 2 fold to me, a leak down near the engine and possibly one up the top although the air could come in the same lower leak and then try and travel up.  Air bubbles in my experience are weird like that. Rather than travel along and out they can act like a plug or at least a significant restriction as the liquid tries to get around them.
Leaving the fuel on may help but then there is going to be a puddle of it somewhere, not what you want floating around in the bilge.

I replace all the soft line on my vehicle annually.  I know it lasts longer so I do it aircraft style, before it fails.  I have eliminated all I can so there are only a couple of easy to get at its about  30 Cm and 15 Cm so it's not expensive either seeing I use the cheap braided hose. Been using and replacing that some years now and although I always carry spare, never needed it. I do like the clear Braided line because you can see what is in it.... Like air bubbles or crap from the tank.

There can be other things like cracked injector lines which may be a possibility on this engine but still tend to be lesser in my experience than air leaks in the supply lines. Plus with injector lines the spray is often easy to see and the engine NEVER runs right.

One thing with the Mercs though and my Nissan, the pumps are really good at self Bleeding.  You can watch the air go in the pump and often they don't even cough or when they do, they clear up as soon as they get clear fuel flow. The bosch Inlines were awesome Pumps and the Rotary styles weren't far behind.  The bosch pumps are capable of pumping a viscosity of oil that would be impossible to flow down a line because it would be well and truly gelled. One of the reasons I gave away the whole heating the oil waste of time. Only thing that is good for is melting any fats and you only need the oil 40c if that for them to melt out.

oldgoat

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Re: HW3 Marine Engine - Bleeding problems
« Reply #6 on: June 14, 2019, 03:27:42 PM »
I had a twin cylinder lister with gravity fed fuel and turned off the fuel when I had finished and had the same problem. It was leakage past the pump elements. If I didn't run it for 3 weeks I would have to reprime it. If it was used more often it was never a problem.

glort

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Re: HW3 Marine Engine - Bleeding problems
« Reply #7 on: June 15, 2019, 04:54:34 AM »

Where did the leaking fuel end up?

BruceM

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Re: HW3 Marine Engine - Bleeding problems
« Reply #8 on: June 15, 2019, 06:27:38 AM »
Repriming for starting, from fuel supply leaks I've had in spades- a cracked fuel banjo fitting on the IP did it.  What I haven't experienced and I think is a lot more rare is a fuel leak on the supply that causes no problems other than fuel starvation at higher power.

ajaffa1

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Re: HW3 Marine Engine - Bleeding problems
« Reply #9 on: June 15, 2019, 12:12:49 PM »
This maybe a silly question but why do you turn off the fuel? Gravity fed fuel systems will not leak unless you have a major fuel system problem. How long are you leaving this engine stationary? Diesel exposed to air turn into a very nasty sort of varnish that will clog up filters/pumps/injectors.

Some fuel injectors have a 1 micron filter built into them, bleeding the system might allow particles in that filter to flow out restoring full power.

Bob

oldgoat

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Re: HW3 Marine Engine - Bleeding problems
« Reply #10 on: June 15, 2019, 01:09:02 PM »
In the sump but it was only half an eggcup full so I didn't worry. It was due for retirement anyway.