Diesel engine slow to fire

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Ammonite

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My Beta 20hp used to fire instantly - a few seconds preheat and away it would go. I've just replaced the fuel tank and all the fuel lines and now from cold you need two or three ten second bursts before it fires on one or two cylinders followed by the third and then it runs faultlessly. I'm guessing l've introduced a small air or fuel leak some where although as the engine is below the height of the tank I'm a bit puzzled how the air is getting in or why the lost fuel isn't being replaced from the tank by gravity - or can't it get past the lift or injector pump when the engine isn't running. If that's the case I assume the problem is in the leak back piping allowing fuel to drain away from the injectors? Where do you think I should start my search? Many thanks
 
when you say "runs faultlessly" does that mean you have run the engine under load for a reasonably long time, since replacing the tank and lines ? Say 30 minutes ?

Trying to see what operational constraints might have been introduced.
 
sarabande said:
when you say "runs faultlessly" does that mean you have run the engine under load for a reasonably long time, since replacing the tank and lines ? Say 30 minutes ?

Trying to see what operational constraints might have been introduced.
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About 3 hours at 5 - 6 knots. Once you manage to start it, it will restart immediately, it's only when you leave it a few hours the problem returns. Perhaps there is a problem with the preheat? It's just that I haven't touched this and it was working last year.
 
chaktoura said:
About 3 hours at 5 - 6 knots. Once you manage to start it, it will restart immediately, it's only when you leave it a few hours the problem returns. Perhaps there is a problem with the preheat? It's just that I haven't touched this and it was working last year.
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Definitely check the pre heat

Check that there is power onto the glowplugs when there should be

Check each glowplug. Each should be a low resistance. I usually check them with an old car headlight bulb on a couple of leads.
 
Thanks guys, I'll take a look. I'd automatically assumed it was fuel / air related given the tank replacement
 
I'm going to check the preheat as suggested but it would be good to have a plan B. With this in mind could a diesel theoretically run without any noticeable ill effects once started even with the smallist of air leaks, which would then migrate to the high points in the fuel circuit when left for a few hours, one of which is obviously the injectors? The fuel line currently runs down hill from the tank via the primary filter to the lift pump, then uphill to the fuel filter and injectors, then downhill via the leak back to a level just below the base of the tank and then back uphill to the fuel return in the top of the tank.
 
What's the state of the battery and wiring my starting problems after every other possibility was exhaustively explored was down to a slightly knackered battery and a dodgy link.
 
chaktoura said:
I'm going to check the preheat as suggested but it would be good to have a plan B. With this in mind could a diesel theoretically run without any noticeable ill effects once started even with the smallist of air leaks, which would then migrate to the high points in the fuel circuit when left for a few hours, one of which is obviously the injectors? The fuel line currently runs down hill from the tank via the primary filter to the lift pump, then uphill to the fuel filter and injectors, then downhill via the leak back to a level just below the base of the tank and then back uphill to the fuel return in the top of the tank.
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In my 35HP BetaMarine, air gathered in the fuel filter on the engine and got no further. The engine just stopped and refused to do anything until I removed the air by bleeding. My problem was actually blockage of the fuel uplift pipe inside the tank due to ****, with air being drawn in at loose connections by the negative pressure generated by the fuel lift pump. Once I tightened them all the engine just refused to do anything whatsoever!
It ran quite happily after I cleaned out the tank.

EDIT:
Why not get a can of diesel and a length of rubber hose and attach that to the engine in place of your new tank? If it runs well investigate your new tank etc...
EDITEDIT:
If you do this make sure the fuel tank isn't over full. Remember that some of the fuel drawn from the can will end up in the tank!
 
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Vara said:
What's the state of the battery and wiring my starting problems after every other possibility was exhaustively explored was down to a slightly knackered battery and a dodgy link.
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Batteries are in really good nick and turn the engine over very quickly so I don't think that's the problem this time around. Thanks for the suggestion though
 
Last year my Beta 16 became very difficult to start after having been left for some time. Once started it would be fine to restart within 24hrs. Finally solved it by simply tightening the fine fuel filter on the engine. Air was seeping in when left but no sign of fuel leaking. When craned in recently is started first turn after six months.
 
chaktoura said:
Batteries are in really good nick and turn the engine over very quickly so I don't think that's the problem this time around. Thanks for the suggestion though
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You have mentioned most things and its surprising how many miss the obvious (including me) which is the 'starter motor', have you had it long?

I also had starting problems last year, did everything, tried most things, no good, then reluctently took the starter motor off and got it tested, had it reconditioned for £80, engine starts everytime now.

Your never to old to learn :)

Mike
 
Just in case any one is interested the problem was a small air leak in the primary filter. A dab of heldite, bled the filter again and problem gone. Not you usual air leak symptom but the engine now starts instantly again
 
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chaktoura said:
I'm guessing l've introduced a small air or fuel leak some where although as the engine is below the height of the tank I'm a bit puzzled how the air is getting in or why the lost fuel isn't being replaced from the tank by gravity - or can't it get past the lift or injector pump when the engine isn't running.
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As your engine is below your tank any leak (that would allow air into fuel) would manifest itself as a fuel leak. Having said that, it sure sounds like a priming issue (your repeated starts effectively self priming the engine until the first cylinder fires, the remaining cylinders following the first one) BUT, your setup (engine lower then fuel tank) would preclude that from occurring.

UNLESS, your fuel line goes a lot higher then your tank! In that case you might generate a priming issue with an air leak allowing some of the fuel to siphon back into the tank.

Considering the weather I would definitely look at the preheater plugs!
 
chaktoura said:
Just in case any one is interested the problem was a small air leak in the primary filter. A damp of heldite, bled the filter again and problem gone. Not you usual air leak symptom but the engine now starts instantly again
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Am interested but what is " A damp of heldite". Where was the leak, what sort of primary filter and how did you fix the leak?
 
TonyS said:
Am interested but what is " A damp of heldite". Where was the leak, what sort of primary filter and how did you fix the leak?
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Sorry Tony - lousy auto correct. I meant a dab of heldite - a sealing paste that is diesel resistant unlike PTFE tape. It's a CAV filter similar to this one and it was the unused port 3 that was weeping. I removed the fitting put heldite on the thread and then bled the filter again - job done

http://ckdboats.blogspot.co.uk/2012/10/lucas-cav-diesel-filter-mistake.html
 
chaktoura said:
Sorry Tony - lousy auto correct. I meant a dab of heldite - a sealing paste that is diesel resistant unlike PTFE tape. It's a CAV filter similar to this one and it was the unused port 3 that was weeping. I removed the fitting put heldite on the thread and then bled the filter again - job done

http://ckdboats.blogspot.co.uk/2012/10/lucas-cav-diesel-filter-mistake.html
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Just read the thread I borrowed the photo from. Mine is piped left to right (2 to 4 or could be 1 to 4, I need to check) but I've now found several posts which say go with the arrows and others that say go against them. What's the definitive answer? I haven't been able to locate a manual yet - well at least one that makes any sense. Can someone please annotate the photo! Thanks
 
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