Author Topic: HW3 Marine Engine - Bleeding problems  (Read 2979 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.

BruceM

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Re: HW3 Marine Engine - Bleeding problems
« Reply #3 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.

oldgoat

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Re: HW3 Marine Engine - Bleeding problems
« Reply #4 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.

BruceM

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Re: HW3 Marine Engine - Bleeding problems
« Reply #5 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 #6 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 #7 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.