Air in fuel system-Westerbeke 21a

[lenjag]

This past Saturday, I moored my new/old CD 32, Scrimshaw, at City Island. We had completed a shake down cruise from Robinhood and the boat performed better than I had expected. Of course there are some problems that surface during a shake down and the only serious one is a persistent problem with air blocks in the fuel system. The boat was winterized and commissioned at Robinhood, the engine has 550 hours since a 2003 rebuild and runs fine in all other respects. On the return trip the engine quit a number of times and was serviced by experienced diesel mechanics at Dodsons in Stonington and at Oyster Bay Marine. It still findis some air after 7 to 20 hours of operation. The servicing included checking and or changing fuel lines, fuel pump and filters [all were clean] but really centered on a harder than usual bleeding effort. I would appreciate any help in finding the source of the air.

[Kurt]

You might try plugging the fuel tank vent and then pressurizing the whole fuel system with a bicycle tire pump while you check all the fittings/hoses for an air leak. Use liquid soap on the whole system while watching for bubbles. Crude method but might be effective.

[Wayne Grenier]

whenever you "mess" with a diesel fuel system -do one thing at a time-change one fuel filter-make sure you don't have any airleaks-them move on to the next one-if you change all of your filters and or some of the lines you will now have a very difficult time finding the leaks-
rub motor oil generously on all the filter gaskets-use new crush waters-etc-

[Stan W.]

It was Cape Dory's practice to put a fine mesh screen on the end of the pickup tube which can clog easily if you have any crud in your tank. Many, if not most, diesel mechanics will tell you that if you have two fuel filters you don't really need the screen and just to take it off and throw it away.

[Boyd]

The Westerbeke fuel system is essentially self bleeding in the sense that the system will purge air from the lift pump back to the tank if you simply let the pump run without the engine running. When you turn on the power from the key the pump moves fuel in a circuit that sends fuel to the injector pump with a return to the initial engine filter and the fuel tank, this purges air from the system ahead of the injector pump. Because of this the system will purge air from all parts ahead of the injector pump. Once air gets into injector pump then it has to be manually purged. Usually this is done by cracking open each fitting just ahead of the individual injectors as the engine is cranked.

Most of the system is pressurized and a leak becomes apparent as fuel coming out as opposed to air getting in. What you are looking for is a leak on the suction side of the system. I suspect that the banjo bolt at the lift pump needs new seals. This is where the line comes from the lift pump and connects to the injector pump.

The only problem I have had with my 21a fuel system was at the fitting where the fuel line from the tank mates with the system. This was a standard brass barb to thread fitting which kept working loose. Also the fuel line had hardened and a leak developed. The metal fuel line had also developed a break in the brazed joint where this brass fitting threaded into it, probably caused by over torquing the brass fitting. This manifested itself as fuel leaking out. My engine never shut down like your has.

If the fuel filters are clogged the engine will at first fail to make noload WOT max rpm's of 3200. Like wise it will fail to make its normal WOT speed under load (fuel starved condition). It will eventually "miss" or cutout and finally shut down as the filter becomes increasingly clogged. Generally giving it a few minutes rest and it will restart. I installed a vacuum gauge on the Racor primary and monitor it. When the gauge shows about -3 PSI then its time to change the Racor element. A new filter shows almost 0. The engine will reportedly shut down at -7PSI

Your system should have 3 filters, a good primary such as a Racor, a secondary on the engine in the little metal bowl, and a third inside the body of the lift pump. Attached to the removable cap on the bottom of the lift pump is a magnet that should be cleaned also. Surprisingly despite two filters in series ahead of it the lift pump filter picks up a lot of crud.

If the problem is cured by just resting the engine then I suspect crud and or water in the fuel, or a clogged primary filter as the cause.

Have you cleaned out the fuel tank yet? A crud problem can clog your primary filter in just a few minutes runtime.

I haven't been able to confirm the presence of a screen in my pickup tube but like others have said if you have one get rid of it and monitor the Racor instead.

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.

[Chris Reinke]

Just curious as to how you were able to confirm it is an air block in the system. Boyd has offered a few great ideas to investigate surrounding possible fuel starvation which could present the same symptoms as air leaking into the system.

I had similar symptoms as you have described on my CD330 (Westerbeke M30) where a sludge mass had developed in the bottom of my fuel tank. The engine would run fine and suddenly drop RPM's and only run at low idle or stop. After several minutes she would start-up again and run for what appeared to be a random amount of time before the situation would repeat itself. I worked the problem each time it occurred over several VERY frustrating weekends until I ended up back at the tank. I found the mass after pumping out the tank and inspecting the inside.

[Bill Goldsmith]

I think all the relevant suggestions have been made. My 21a has almost 3000 hours on it and starts and runs like a top. Not sure when the prior owner may have had major service or done a rebuild, but I am keeping it well-maintained and it is extremely reliable.

One unrelated suggestion--has the old-style exhaust manifold (with endcaps and gaskets) been replaced with the new style (sans endcaps and gaskets)? This is an important upgrade that will prevent a major source of failure (coolant leaking into the cylinders). My guess is that if there was a rebuild in 2003, they did this. Westerbeke highly recommends it.

Welcome to the lonely but loyal group of 32 owners on the Board! By the way, I saw and admired Scrimshaw's picture on Yachtworld when it was for sale. What hull number is she?

[Bob L]

lenjag,

As other posters have pointed out, your problem may not be an 'air' problem. You didn't mention the symptoms leading you to this conclusion. What are they? I had a problem on my 21a that Chris had. Turned out it was fibrous material lodged in the angle fitting at the fuel tank.

Bob

[Cathy Monaghan]

It's nice to find another CD32 owner out there. Are you keeping her at Gateway Marina in Dead Horse Cove in Brooklyn? We keep our boat on Raritan Bay too but all the way at the other end.

Everyone has already made some excellent suggestions and have already pointed out that the Westerbeke 21A is self-bleeding.

Have you checked that the fittings for the Racor filter are on really tight. The plunger doo-hickey on the top of the Racor will allow air into the fuel system if it's not tightly screwed down.

Crappy fuel will cause a problem too. We had that problem last year.


Cathy
CD32 Realization, #3
Rahway, NJ
Raritan bay