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Diesel feed pipe


Rob-M

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Just spent best part of a day with RCR trying to work out why our engine was cutting out with air in the system.  Fortunately fuel boat Mountbatten went past and we got him to fill the tank and issue has gone away. So the consensus is that there is a hole in the feed pipe in the tank as everything else had been ruled out by testing from a separate container of diesel.

I had 90 litres of fuel put in to what I think is around a 150 litre tank.  How big a job is it going to be to get a replacement pipe put in the tank?

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More likely that a tiny air leak in the top union of the feed pipe prevents the pipe lifting fuel unless the tank is more full.

I have in the past managed to fit a new suction pipe into  a tank by drilling and tapping 1/2" BSP near the top, fitting a pre bent dip tube in a drilled out 1/2" male X 5/16" compression fitting. I try to get the bottom of the tube close to the tank bottom but hard up against the tank side to stop it vibrating.

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How old is the flexi into the fuel pump? I had a leak at the crimped fitting that allowed sucked air into the pipealong with fuel. Over a period the air travelled back up the pipe to airlock the feed. The internal rubber degrades and allows a capillary action to develop. On the suction side, this does not show as a leak. If you undo the pump connection and the spigot turns in the hose, replace it. A full tank will reduce the suction from the pump and provide a positive head to the engineso the symptom disappears. In this case, you may notice weeping from the crimp.

Edited by Ex Brummie
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The pump is electric, putting the feed pipe in to a container of diesel fed through fine. For now I will keep the tank topped up until back at base and then get my usual mechanic to have a look.

The RCR guy checked every connection and pipe and was happy with them all 

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8 minutes ago, Rob-M said:

The pump is electric, putting the feed pipe in to a container of diesel fed through fine. For now I will keep the tank topped up until back at base and then get my usual mechanic to have a look.

The RCR guy checked every connection and pipe and was happy with them all 

Please inform us of the resolution as we get asked this time after time and we all would like to know what caused it.

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11 minutes ago, Rob-M said:

The pump is electric, putting the feed pipe in to a container of diesel fed through fine. For now I will keep the tank topped up until back at base and then get my usual mechanic to have a look.

The RCR guy checked every connection and pipe and was happy with them all 

The effort to suck from a can would be much less than a half empty tank.....unless you could rig up a pipe to simulate the height/length of the feed pipe in the main tank

 

Just for info Id take any trouble shooting done by an RCR employee....I struggle to use the term engineer or even spanner monkey.....with a lot of scepticism.....

Edited by frangar
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4 minutes ago, frangar said:

The effort to suck from a can would be much less than a half empty tank.....unless you could rig up a pipe to simulate the height/length of the feed pipe in the main tank

 

Just for info Id take any trouble shooting done by an RCR employee....I struggle to use the term engineer or even spanner monkey.....with a lot of scepticism.....

And salt in large pinches.

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18 minutes ago, dmr said:

Is this a new problem or a long term thing?  Did it come on suddenly or develop over time?

 

................Dave

A new problem that suddenly started after boating from Great Haywood to Ellesmere on the Llangollen so we had done 5 days boating plus the engine was serviced before we left.  All has been fine for the last 6 years and I've used more than 90 litres of diesel between fillings regularly.

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Just now, Rob-M said:

A new problem that suddenly started after boating from Great Haywood to Ellesmere on the Llangollen so we had done 5 days boating plus the engine was serviced before we left.  All has been fine for the last 6 years and I've used more than 90 litres of diesel between fillings regularly.

I think Id be looking to swap the fuel pump next or has that been done?

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5 minutes ago, frangar said:

I think Id be looking to swap the fuel pump next or has that been done?

No that hasn't been done, the focus was on the feed from the tank. I think I will discuss with my usual mechanic and see if he can do something to test the pump.  I also thought that filling the tank may just be masking the issue by having a greater weight of fuel.

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Just now, Rob-M said:

No that hasn't been done, the focus was on the feed from the tank. I think I will discuss with my usual mechanic and see if he can do something to test the pump.  I also thought that filling the tank may just be masking the issue by having a greater weight of fuel.

When I was working on new builds some boats were the very devil to get fuel from the tank unless the tank was over 3/4 full...this varied even with shells from the same builder....so the pump does have to work quite hard.....one other thing to check is that the airway on the breather is free with no obstructions to the tank...tank vacuum can cause all sorts of odd issues.

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7 minutes ago, frangar said:

When I was working on new builds some boats were the very devil to get fuel from the tank unless the tank was over 3/4 full...this varied even with shells from the same builder....so the pump does have to work quite hard.....one other thing to check is that the airway on the breather is free with no obstructions to the tank...tank vacuum can cause all sorts of odd issues.

RCR guy did check the breather so he can have a tick for that one.

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37 minutes ago, frangar said:

I think Id be looking to swap the fuel pump next or has that been done?

 

Standard fuel pump test:

 

Thumb over inlet connection and get someone to turn the ignition on for maybe 30 seconds. Turn ign. off and keep thumb over inlet. The pump should hold vacuum for at least 30 seconds. Any less indicates a faulty pump.

 

Do the same for the outlet but this time it should hold pressure.

 

In a workshop situation one would normally use a vacuum/pressure gauge rather than a thumb.

Edited by Tony Brooks
  • Greenie 1
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When I first launched Harnser I had a similar problem, I was actually sucking air in to the primary filter when it had to suck the diesel from the bottom of the tank all te way to the engine room. I cured it by moving the filter to near the diesel tank so lots less restriction on the suction side.

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  • 2 months later...
On 03/07/2021 at 17:22, Tracy D'arth said:

Please inform us of the resolution as we get asked this time after time and we all would like to know what caused it.

 

On 03/07/2021 at 18:00, frangar said:

I think Id be looking to swap the fuel pump next or has that been done?

Just to update on this, we had a new fuel pump fitted by the mechanic who looks after our engine and so far having been out cruising for a bit all seems fine. I've not let the fuel tank get extremely low yet which will be the test to do once I've got a spare can of diesel for an emergency top up.

  • Greenie 1
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2 minutes ago, Rob-M said:

 

Just to update on this, we had a new fuel pump fitted by the mechanic who looks after our engine and so far having been out cruising for a bit all seems fine. I've not let the fuel tank get extremely low yet which will be the test to do once I've got a spare can of diesel for an emergency top up.

Fingers crossed that’s sorted it! Thanks for the update…always useful for those that have given advice and others that might have similar issues. 

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