Troubleshooting diesel fuel systems with an outboard squeeze bulb

[donradcliffe]

I just finished a successful search for a fuel problem in a Santa Cruz 70 I was delivering with a Yanmar 4JH4-TE. The symptoms were that the engine died when throttling back to an idle, and was a bit hard to restart. It also had a problem holding an rpm setting. I was pretty sure that it was a fuel problem, either a partial blockage or air in-leakage. Finding the location of a blockage or air in-leakage can be difficult, so I thought I would share my method.

The history of the boat was that the original fuel line had not been replaced when the engine was moved further forward--they just spliced in a section on the engine end. The hose, the splice, the shutoff valve missing its handle, and the pickup tube were all suspect, as was sediment in the fuel tank. In addition, the fuel filters had been changed a week before, which seemed to help for a few days, but the problem reoccurred with a vengeance on an overnight delivery to San Francisco. The boat was raced down to Santa Barbara, where they experienced more engine trouble with the engine after the race. My next delivery was 215 miles back up the coast with the engine, so I needed to get the issue sorted.

First, I purchased an outboard fuel squeeze bulb with 3/8" ends, and some clear 3/8 in vinyl tubing (at home depot for $0.50/ft vs West Marine at $3.00) and some hose clamps for the tubing. I attached a 3 ft length of the tubing to the output of the bulb (see photo).

Step one was to remove the fuel line from the input to the primary spin on Racor filter and fix it to the squeeze bulb. I pumped with the bulb into a clear plastic drink bottle. Once I cleared the air out of the bulb by holding it vertical, I got good flow with no bubbles in my vinyl hose, and clean fuel in the bottle. This test eliminated a whole lot of suspects upstream of the filter.

The next step was to replace the input line on the primary filter and remove the input line on the secondary filter and fix it to the bulb. I got good flow (no plugged primary), but no matter how many times I tried to clear the air out of the bulb, I got tiny bubbles in the vinyl hose, indicating air was leaking into the Racor.

I then dismounted the Racor, removed the filter element and started looking. What I found was shown in the second photo--the surface which was supposed to seal with the spin on filter element was missing paint in spots and corroded. I replaced the Racor housing, bled at the secondary filter, and the engine ran like new for 27 hours.

[Sos]

Very helpful thanks

[Jim Cate]

good one, Don! All those years in Mexico and the SP were worthwhile... taught you some useful techniques .

Jim

[Snore]

Thanks! I would have wagered that the Racor gasket would have compensated for the thickness of the missing paint.

[donradcliffe]

Its my suspicion that the gasket couldn't seal the corners where the paint remained. Its about a 100 micron square step.

If I was in the bush, I would have taken my random orbital sander with 220 grit and smoothed out the housing. However, it was a half million dollar boat and West Marine was at the head of the dock.

The owner is very happy, because his 'professional' mechanic did not find and fix the problem.

[Gaia]

Good stuff. This why I like CF. TX for thinking and posting.

Jim

[Scubaseas]

Kudos on building then following an excellent logic tree.

[jhulmer]

I use the bulb to pump fuel from the tank to the racor after a filter change and to check the fuel in the bottom of the sump. But never thought of the clear hose.



That is a great idea! thanks for sharing.



Jim

[bobnlesley]

...use the bulb to pump fuel from the tank to check the fuel in the bottom of the sump...

We do this too - the small/clear tube entwined with a length of coat-hanger wire slides easily through the dipstick hole and 'tap's when it hits bottom.
Additionally we have another bulb permanently plumbed into our fuel supply line a few inches after the filter/water separator; it does nothing whilst the engine's running but is a godsend for re-priming/bleeding the system after any problem or a filter change compared to doing so using the standard Yanmar mechanical lift-pump on the side of the engine.

[deblen]

Originally Posted by bobnlesley

...use the bulb to pump fuel from the tank to check the fuel in the bottom of the sump...

We do this too - the small/clear tube entwined with a length of coat-hanger wire slides easily through the dipstick hole and 'tap's when it hits bottom.
Additionally we have another bulb permanently plumbed into our fuel supply line a few inches after the filter/water separator; it does nothing whilst the engine's running but is a godsend for re-priming/bleeding the system after any problem or a filter change compared to doing so using the standard Yanmar mechanical lift-pump on the side of the engine.

I too have a 3/8" replacement bulb plumbed permanently for the same purposes. I worry a bit about it. A while ago,there was a story going around that the o/b primer bulbs may "rot" when used with diesel fuel. Mine has been in service for 5 yrs & seems ok. Any comments? / Len

[bobnlesley]

Originally Posted by deblen

...story going around that the o/b primer bulbs may "rot" when used with diesel fuel. Mine has been in service for 5 yrs & seems ok. Any comments? / Len

I'd not heard that warning, ours has only been in for about 2.5 years, but I'll keep an eye on it; we have a couple of spare bulbs or a double ended barb coupling so we can get it out of the system fairly quickly/easily if needs be.

[Wotname]

Originally Posted by deblen

I too have a 3/8" replacement bulb plumbed permanently for the same purposes. I worry a bit about it. A while ago,there was a story going around that the o/b primer bulbs may "rot" when used with diesel fuel. Mine has been in service for 5 yrs & seems ok. Any comments? / Len

Yep, I have heard the same caution. I have spoken to a guy who says he has seen in some boats and cautioned me to only use a "quality" bulb and steer away from the cheapest ones in the shop.

I'm not sure how one determines what is a "quality" bulb but I simply chose one that looked more robust and had a higher price tag.

It was still working well after three years of service at which point the boat was sold.

[jhulmer]

Make sure to get one that is rated for diesel.
https://www.amazon.com/CarBole-Rubbe...-1-spons&psc=1

[JeffOnTheBoat]

could one of you with the bulb plumbed in for priming the filters give me a bit more detail on how I would do this. I have hose from the tank going through valves to dual raycor filters then on to the engine filter and engine. It sounds like the bulb is placed on the engine side of the filters, but it seems like it would make more sense to put it on the fuel tank side of the filter. Then to prime, close the valve to the engine open the air relief on the filter and pump fuel into the filter to prime it. Is this correct?
Thanks

[deblen]

Originally Posted by JeffOnTheBoat

could one of you with the bulb plumbed in for priming the filters give me a bit more detail on how I would do this. I have hose from the tank going through valves to dual raycor filters then on to the engine filter and engine. It sounds like the bulb is placed on the engine side of the filters, but it seems like it would make more sense to put it on the fuel tank side of the filter. Then to prime, close the valve to the engine open the air relief on the filter and pump fuel into the filter to prime it. Is this correct?
Thanks

I put mine between the tank outlet shut-off and the primary filter.
I wanted to be able to fill & slightly pressurize the filters right to the mechanical lift pump,after a filter change & before starting the engine.
This seems to eliminate air problems for me.


Putting it on the engine side of filters would probably work fine also./ Len