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Old 14-10-2018, 20:07   #1
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Diesel engine won't start after changing fuel line

I'm new to working on diesel engines (all engines in fact) and have just replaced a section of the fuel line that was split on mt 25' Compass with a Kubota diesel engine. the section of fuel line was between the fuel pump and the motor. After replacing the line the engine ran for about 1-2 minutes then topped. I thought it might be lack of fuel so filled the tank with fresh diesel and tried several times turning her over with no luck (I primed for about 5-10 secs before each try).

Would this be due to there being air in the line after replacement? My only other thought is that I somehow messed with the fuel pump wiring when connecting the new line to it and it might not be pumping.

Any assistance would be appreciated.
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Old 14-10-2018, 20:13   #2
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Re: Diesel engine won't start after changing fuel line

Sounds like you need to bleed the air from the lines.
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Old 14-10-2018, 20:16   #3
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Re: Diesel engine won't start after changing fuel line

You have air in the lines that need to be bled. Also be careful about over cranking as you will back-fill the engine with cooling water. Shut through hull go engine if you’ve crank excessively already and just open IMMEDIATELY.
I am not familiar with your engine however bleeding is not hard and something you should know how to do..... god learning moment! Sure here are manuals available.

Good luck
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Old 14-10-2018, 20:19   #4
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Re: Diesel engine won't start after changing fuel line

Thanks Paul L and NYSail... I'm back on dry land and readng up now :-)
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Old 15-10-2018, 08:46   #5
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Re: Diesel engine won't start after changing fuel line

Just did the same on my Beta (Kubota) engine last week. It took a lot of bleeding as the new hoses had air trapped where they were bent or coiled a bit. We bled through the bleed screw successfully but then the engine still wouldn't run for long. So, we then pumped the primary filter (Racor) for quite a while and the engine eventually started better. When engine really started running, did a few extra pumps on primary filter, then screwed it down. Engine is now running well.
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Old 15-10-2018, 08:58   #6
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Re: Diesel engine won't start after changing fuel line

Bleed the system
Start from tank and follow along bleeding at each point (ie loosening bolt or joint until fuel is present then close and move to next point filter - injection pump - finally loosen each injector until fuel is present, then re tighten , one at a time Done engine should start immediately
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Old 15-10-2018, 09:29   #7
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Re: Diesel engine won't start after changing fuel line

This is a perfect time to learn how to bleed your lines and a big lesson in why you don't want to run your fuel tank dry...
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Old 15-10-2018, 09:38   #8
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Re: Diesel engine won't start after changing fuel line

Will someone please design a diesel that does not require bleeding?
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Old 15-10-2018, 09:45   #9
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Re: Diesel engine won't start after changing fuel line

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Originally Posted by sailingfarmer View Post
Will someone please design a diesel that does not require bleeding?

The same problem can exist with a petrol engine. Air in the fuel line of any liquid fueled engine can prevent it from starting, but for some reason bleeding a diesel engine is more of a misery.
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Old 15-10-2018, 09:51   #10
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Re: Diesel engine won't start after changing fuel line

Kubota engines have a priming lever to manually operate the mechanical fuel pump. It is a pain to use it but better than cranking the engine to bleed it.

Another alternative is to add an outboard motor priming pump (squeeze bulb) to your fuel system between the tank and the first filter. It works much faster and easier. One caveat it that your marine surveyor and insurance company might not like it because they are not rated for diesel fuel.

I have had one installed since 2002 - when I installed my Beta Marine 50. It works great for bleeding after changing the Racor or on engine fuel filters.
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Old 15-10-2018, 09:52   #11
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Re: Diesel engine won't start after changing fuel line

I, too, agree that there is still air in the lines. The one place that many folks miss, until pointed out is that there is often 2 bleed points on the injector pump. Get the instructions from the engine manufacturer and follow them. It often takes repeated attempts ro ride a diesel of all of the air. Until it starts, keep the raw water seacock closed to prevent back-filling of the exhaust system, thus the cylinders.
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Old 15-10-2018, 09:52   #12
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Re: Diesel engine won't start after changing fuel line

Diesel engines are designed to make owners swear and curse when they need to bleedan engine... the future designer of a NON-BLEEDING Diesel Engine will make a fortune... maybe some sort of fuel compressor that rids the lines automatically of air....?
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Old 15-10-2018, 10:44   #13
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Re: Diesel engine won't start after changing fuel line

Direct injected fuel systems are self bleeding. These are individual unit injectors operated off the eng. camshaft and rocker arm. Example GM 53 , 71 and 92 series. Cat 3116 3126 and there are lots more but i think you get the drift. What you have is a fuel nozzle. The pressure is built up in the inj. pump. Air compresses then the fuel nozzle does not open and the air remains.
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Old 15-10-2018, 10:52   #14
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Re: Diesel engine won't start after changing fuel line

There have been various recommendations about bleeding a diesel engine in these replies. All well and good, but some simply do NOT apply to YOUR engine.

The ONLY bleeding technique YOU need to know is what is required for YOUR engine.

For example, on my M25 Kubota/Universal, there is a knurled knob on the injector pump that is very easy to hand loosen while the electric fuel pump is running to bleed the engine. NO touching of the injectors is ever required.

The later versions of this M25 engine, the M35, is self bleeding.

Notice, I carefully said "On MY engine." I didn't say "No Kubota engine ever require touching the injectors." I don't know that for a fact, so I don't say it.

Yanmars are different engines and require different techniques.

Find out what is required for your engine and do that. Doesn't matter what anyone else does, does it?

Look up Maine Sail's "Hall of Fail" post on his website and learn why manual fuel bulbs are a bad, bad, bad idea. I don't know why people with Yanmars just don't install fuel pumps and make their lives a lot easier, but we see it here all the time, and on other boating forums.

Good luck.
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Old 15-10-2018, 10:56   #15
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Re: Diesel engine won't start after changing fuel line

Quote:
Originally Posted by OZ-Sailor View Post
>>>>>>>>>>
>>>>>>>>>>>>>>
with a Kubota diesel engine.>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>

Which specific Kubota engine?
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