Perkins M30 Fuel Supply Issues

[challenger]

Before all this started, I had no problems with this engine for at least 500 hours.
My engine was shutting off frequently and I discovered massive debris in one of the in-line fuel filters that turned out to be a custom one located right after the supply fuel line. After removing that filter and replacing the one at the water/fuel separator the engine ran for about 4 hours without trouble. Then it all started again, would run for a few seconds then shut off. After replacing the remaining fuel filter (screw on) and removing another add-on in-line filter located just above the fuel line supply pump, the engine just wouldn't start at all.
I then decided to run a clear vinyl line direct from the fuel tank to the supply side of the water/fuel separator (supply) so I could see the fuel coming from the tank. This allowed the engine to start and run for about 10-20 seconds before shutting off. I did the same for the return line and now the engine runs ok without shutting off, though it will only idle high at about 1200 rpm. I do see small bubbles in the return line but no bubbles in the supply line.
Could the fuel lines be dirty/clogged such that the engine wouldn't run? Has anyone removed and cleaned their fuel lines?
Could the fuel pump be going bad (about 3psi on the supply side)?

Thanks in advance for any thoughts.

 

[Davidasailor26]

My guess is that the original problem was diesel bug in the bottom of the tank getting picked up by the lines and clogging the filters repeatedly. The initial problems keeping the engine running after changing the hose were probably residual air in the lines from that change, which eventually was mostly bled out letting the engine run longer. You may still have a bit of air in the system or you may have a leak in one of the hoses before the pump allowing it to pull air in.

I’d check all of the hoses and connections, then put the test hose in a Jerry can of clean diesel. From there you can start to narrow down where the trouble might be.

 

[dlochner]

Some boat builders put screens on the fuel intake line to act as a pre-filter. Remove the pickup line from the tank and remove the screen if it is there. Also check to see that the line is clear.

If there is an inspection port for the tank, open it up and take a look at the inside of the tank, it should be clean and clear with no black goo at the bottom. If there is, the tank needs to be cleaned.

If you follow @Davidasailor26's advice, once removed replace the fuel lines with new. All hoses age and in recent years there have been improvements in diesel fuel hoses. Do use a CG approved hose. Also, if there are any copper fuel lines, remove them and replace with USCG approved hose. Some of the diesel additives react with the copper forming a crystal that can clog hoses and filter and erode fuel injectors.

 

[jssailem]

My guess is that the original problem was diesel bug in the bottom of the tank getting picked up by the lines and clogging the filters repeatedly.

When trying to solve a fuel issue one needs to think system. Start at one end (what you put in - clean fuel - and what is already there - fuel with water/diesel “bugs”). You can empty the tank and clean it or you can treat the tank and filter (dead bug) debris.

BAD FUEL can spoil your day

Here we are in the middle of winter beginning to plan our next sailing season. Maybe we are new to using a boat with an inboard engine. Some of us have years of mechanical experience so we know. Some are facing the idea of being alone in the water with a dead engine for the first time. We...

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My engine was shutting off frequently and I discovered massive debris in one of the in-line fuel filters that turned out to be a custom one located right after the supply fuel line. After removing that filter and replacing the one at the water/fuel separator the engine ran for about 4 hours without trouble. Then it all started again,

Your engine runs based on 3 basic needs:

1. Clean fuel. No air or debris in the fuel line
2. Unobstructed air supply (sucked in through the air intake)
3. Compression

The 4 hour run suggests you accomplished the demands for that period.

Then the problem started again. The first suspect would be the fuel. There was still debris in the system

After replacing the remaining fuel filter (screw on) and removing another add-on in-line filter located just above the fuel line supply pump, the engine just wouldn't start at all.

You installed clean filters, but by opening the fuel lines air was introduced into the fuel lines. The engine will not start with air in the fuel line. You need to bleed the system so that fuel (under pressure and in the correct volume (just fuel no air bubbles) gets sprayed into the cylinders.

I do see small bubbles in the return line but no bubbles in the supply line.

The lines from the tank to the first pump are (the vacuum side) sucking fuel. If there is not a tight seal at all of the connections, then there will be air sucked into the system.

From the first pump to the injectors and then through the return lines to the tank, the fuel is under pressure, and no air is sucked in. Only fuel is sprayed out if the lines are not tightly connected.

1. Could the fuel lines be dirty/clogged such that the engine wouldn't run?
   1. Yes. It is possible. There is (sometimes) a screen on the supply tube in the tank. It clogs and fuel (or not enough fuel) is not sucked out of the tank.
2. Has anyone removed and cleaned their fuel lines?
   1. Yes. I removed each of the lines, using compressed air to ensure they were clear of obstructions. I found a gob of snot-like substance at the fitting of my filter. My boat's fuel lines were old and lacked proper maintenance from the previous owner. Once cleaned, the engine ran without faltering.
3. Could the fuel pump be going bad (about 3psi on the supply side)?
   1. It's not impossible, but it's not likely the culprit because the engine did run for 4 hours. I would focus on the fuel side and see if you can ensure you are supplying clean fuel from the tank to the engine.

 

[challenger]

Update: There were two main culprits.
1. I replaced the fuel pump and even with some air leak somewhere the engine would run well. Fuel pressure increased from about 3 psi to between 5-6 psi.
2. I then replaced the washers/cap lip seal on the water/fuel separator just before the pump and that eliminated all of the air in the fuel lines whereby the engine ran very nicely, no sloppy hesitation and idling well.
3. Both of the fuel filters were replaced in the process and the fuel lines were removed/blown out and looked good so reinstalled.

During this process I had also rebuilt the transmission so if anyone wants help with that just reach out.

Lastly, the analog tach with the stem that comes out of the engine broke and I'm planning on going with a non-contact sensor on the alternator. However, there's a small oil leak in the old analog thru-connector. Does anyone know if that's a standard npt thread that I could simply get a plug for?

I really appreciate all of the comments and that this is an active group!

-Robert