Kubota/Universal Diesel Problem

[Rawson30Spartan]

I have a Rawson 30 with a Kubota D850 3 cylinder diesel. I purchased the boat recently. I am having trouble keeping the engine running. The motor will start and run really well for about 20 mins and then it seems to starve for fuel and cut out. The fuel looks good and clean. There seems to be plenty of fuel pressure coming through the injectors. The filter looks brand new and seems to be completely clean. I'm stumped. Also, the engine only has around 200-300 hours on it.

This is my first boat and I'm excited to get it out on the water. Thanks for any insight.

[Kokanee]

Start by changing your fuel filters. If that doesn't fix the problem then I'd say it is air in the fuel


With diesel engines, 90% of problems such as this is the result of air being sucked into fuel lines or the fuel filters. Check all fuel lines & clamps; check your water separator fuel filters, especially the o-rings in the top & bottom. Sometimes the old o-ring is not removed when changing filters and adding a second one allows air to be drawn in.


One way of tracking down the source of air is to temporarily install a section of clear hose and check for small air bubbles. The leak is somewhere upstream of wherever you see the air. Work your way through the system methodically and you will find the source of air intrusion.

[GordMay]

Greetings and welcome aboard the CF, Rawson30Spartan.

[sailormed]

Had the same with my Yanmar. Changing filters was not the solution. On the end of the fuel pickup line in the tank a mesh filter was mounted. Bacteria present in the tank slowly accumulated on the mesh when the engine is running and after a certain time formed a layer starving the engine of fuel. When the engine stops the layer of bacteria disintegrates and the fuel supply is restored. Hope this helps finding a solution.

[Seail]

I had the same problem with that exact engine and it took me months to figure out. Turned out there was gas added to the diesel (about 4 gallons in a 18 gallon tank). It would run about 20 minutes then die.


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[JayH]

Could be a plugged fuel tank vent. Does the tank take a breath if you open it after the engine dies?

[Rawson30Spartan]

Originally Posted by JayH

Could be a plugged fuel tank vent. Does the tank take a breath if you open it after the engine dies?

I checked the vent before and it definitely wasn't plugged or clogged.

[Rawson30Spartan]

Originally Posted by Seail

I had the same problem with that exact engine and it took me months to figure out. Turned out there was gas added to the diesel (about 4 gallons in a 18 gallon tank). It would run about 20 minutes then die.

How did you find out there was gas in the diesel? How would I check?

[DeepFrz]

Check your fuel line from the bottom of the pickup tube to your filters. Make sure that there is no screen filter on the pickup tube. If there is remove it and get rid of it. Check the bottom of the tank for build up of crud that could block your line. Check that the fuel line is clear and in good shape with no kinks.

[Snore]

Had this problem on my boat.

Engine ran 20 and cut out. I bled the fuel system, restarted and it all repeated again.

Before you go too deep take the filler cap off and run the engine at the dock. If this solves the problem, the vent line off the tank is either pinched or blocked.

Eliminate the easy stuff first...


..

[Stu Jackson]

That is more often known as the M25.

Here is a link to tons of info on your engine

Diesel Engine - C34

Good luck.

[Charlie]

check the hose ends for leaks. I once had the hose clamp wear a hole in the hose. I cut off the end of the hose and replaced the clamp with an awab type clamp. much better clamps btw.

[Seail]

Funny story I took the injection pump to the repair center and he ask me if I soaked it in gas. He could smell it but I couldn't. I got a two gallon can of fresh diesel and rerouted the pickup to it and it ran good. The marina that pumped the gas into my tank pumped the bad diesel out and replaced it with good (for free) and àll was fine.

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[GordMay]

Originally Posted by Rawson30Spartan

How did you find out there was gas in the diesel? How would I check?

Tests for Identifying Fuel Adulteration (pg 3) ➥ http://meerutup.tripod.com/diesel.pdf

[shakey doug]

Your model Kubota comes with no less 3 different types of fuel lift pumps if it is not a sealed unit check internal mesh screen filter.
Get a non- smoker to do smell test at the fuel filler or put a small in vessel and light, it if petrol is present it will ignite very easy in comparison to raw diesel.