Universal M-18 Troubles

[vincentshine]

All,

My 1985 Universal M-18 is being a pain. After purging all old fuel, changing all filters, new fuel pump she is dying after running seemingly well for 30-45 minutes. I bleed the fuel line at the bleeder screw. It appears some air escapes, restart, and runs well for another 30-40 mins. Then repeat.

I can not figure out one - if air is the problem and two - where the air is coming from. When I bleed it at the bleeder screw some air comes out before a constant flow of diesel. I have my theories:

1. The gaskets on the bleeder screw are shot from over tightening and are now drawing in air.
2. There is a gap on a hose somewhere introducing before the fuel pump.

Pretty perplexing. Any thoughts welcome

Vincent

 

[Loren Beach]

Funny you should ask..............

As it happens....
this morning our engine installer/ship wright came out to our boat to trouble shoot a small vacuum leak that showed up after running for less than 30 minutes.
Knowing that we had installed a new Racor 500 and plumbed in the former electric lift pump in a different location we suspected a small leak around a fitting.
He brought his smallest air compressor, long hose and an adapter for out tank fitting.
The procedure was to remove the vent hose from the tank, connected up an adapter for the compressor, and run the compressor at about 2# max.
This put some pressure on all the fittings throat the fuel system. After about 5 minutes we found a minuscule fuel leak at a hose clamp and could hear a faint hiss around the top of the new filter housing.
Some tightening was done.
Engine started and ran fine.
Tomorrow we will test run it for a while again; and then plan a day out testing it under way.

So, for a pesky air ("vacuum") leak, a bit of pressure is a fast way to find it.

 

[vincentshine]

Loren Beach,

I love this forum. If nothing else it fills me with optimism.

So let me play this back. you pressurized the fuel system through the fuel tank vent. And listened for any leaks. Was there fuel in the tank and system at that point? would like to avoid a full extraction. Then are you looking for actual fuel leaking somewhere? How much pressure do you think was used?

Thanks!!

As it happens....
this morning our engine installer/ship wright came out to our boat to trouble shoot a small vacuum leak that showed up after running for less than 30 minutes.
Knowing that we had installed a new Racor 500 and plumbed in the former electric lift pump in a different location we suspected a small leak around a fitting.
He brought his smallest air compressor, long hose and an adapter for out tank fitting.
The procedure was to remove the vent hose from the tank, connected up an adapter for the compressor, and run the compressor at about 2# max.
This put some pressure on all the fittings throat the fuel system. After about 5 minutes we found a minuscule fuel leak at a hose clamp and could hear a faint hiss around the top of the new filter housing.
Some tightening was done.
Engine started and ran fine.
Tomorrow we will test run it for a while again; and then plan a day out testing it under way.

So, for a pesky air ("vacuum") leak, a bit of pressure is a fast way to find it.

 

[Loren Beach]

"victory thru air power"

Loren Beach,

I love this forum. If nothing else it fills me with optimism.

So let me play this back. you pressurized the fuel system through the fuel tank vent. And listened for any leaks. Was there fuel in the tank and system at that point? would like to avoid a full extraction. Then are you looking for actual fuel leaking somewhere? How much pressure do you think was used?

Thanks!!

Even better, if the advice that produced the optimism is bad, I am a very long way away from your wrath!

This test used 2# pressure maximum. I recall that our tank was pressure tested to 3# when built, so it should not be harmed. It is not really about how much pressure -- one pound would likely be enough -- but the applying a gently push against the fittings throughout the fuel system.
It then took several minutes of careful listening and watching to find some seeps. A spray bottle with some soap solution would have been even faster.

Our tank is down to about a quarter full, and is soon to be filled for the season. More fuel should not be a factor either way.

 

[supersailor]

Adding to Loren's little list, I found a small crack on the inside of my Racor filter in the aluminum . No bubbles going in. Bubbles coming out. The engine would run awhile then quit. When I posted the finding, several others posted that they, too had filter leaks. If I had a older Racor (10+ years) I would replace it.

 

[vincentshine]

Adding to Loren's little list, I found a small crack on the inside of my Racor filter in the aluminum . No bubbles going in. Bubbles coming out. The engine would run awhile then quit. When I posted the finding, several others posted that they, too had filter leaks. If I had a older Racor (10+ years) I would replace it.

All good suggestions. I will check the Racor. My new idea is the tank vent is blocked, though for not allowing air to replace the volume removed.

I will be busy this Saturday - but remain optimistic.

Vincent

 

[Emerald]

With the caveat of there are many Racor models out there, a friend had a similar problem with a split in a nylon plug on his Racor filter. This plug was slotted, so you could unscrew it. Not an obvious failure, but it was allowing air into the wrong places.

 

[supersailor]

I also had a vent blockage. It was discernable by only being able to put a gallon and a half in the tank when it was empty. The fuel then spurted out the filler neck. The problem was a plugged vent filter screen. Easy fix but extremely frustrating. Happened within a month of purchasing the boat. The PO replaced everything except the vent fitting.

 

[Alan Gomes]

As it happens....
this morning our engine installer/ship wright came out to our boat to trouble shoot a small vacuum leak that showed up after running for less than 30 minutes.
Knowing that we had installed a new Racor 500 and plumbed in the former electric lift pump in a different location we suspected a small leak around a fitting.
He brought his smallest air compressor, long hose and an adapter for out tank fitting.
The procedure was to remove the vent hose from the tank, connected up an adapter for the compressor, and run the compressor at about 2# max.
This put some pressure on all the fittings throat the fuel system. After about 5 minutes we found a minuscule fuel leak at a hose clamp and could hear a faint hiss around the top of the new filter housing.
Some tightening was done.
Engine started and ran fine.
Tomorrow we will test run it for a while again; and then plan a day out testing it under way.

So, for a pesky air ("vacuum") leak, a bit of pressure is a fast way to find it.

This is one of those helpful pieces of advice that I store away in OneNote for a rainy day!

 

[Christian Williams]

Original equipment 200-series Racor filter assemblies are often worn out, cracked, or leaking air.

See if the fuel line will reach to fit directly on the fuel pump, which is often right next to the Racor.

If the engine runs with the primary filter bypassed, the problem is the filter.

Replace with a 500-series if possible. physically larger unit, but the filters are cheaper and easier to install than the screw-in type.

 

[bgary]

If the engine runs with the primary filter bypassed, the problem is the filter.

How long does it take to determine that the engine runs? In other words, does it take 5 minutes for the fuel (and/or air) in the line to cause a hiccup, or an hour...?

And, it is idle-at-the-slip sufficient load, or does the engine need to be run under load to show an issue?

 

[Frank Langer]

When I had a tiny air leak in the fuel pump, my universal engine would run at cruising speed for about 20 minutes, then falter and slowly stall. I could bleed the air out at the bled screws and run another 20 minutes. The only way I could diagnose it was to run a fuel line to the fuel pump, then from the fuel pump into a pail of diesel fuel watching for tiny pinhead size bubbles, almost invisible.
Frank

 

[Christian Williams]

My anecdote: with an invisible crack in the series-200 body, the engine would start and then fade after 30 seconds.

A boat mechanic, without seeing the boat, instantly dignosed air in the fuel line and confidently blamed the old Racor primary filter.

It is his absolute confidence I'm passing on, for what it's worth. (He is Peter Franzen of The Boatyard in MDR).