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Old 24-06-2024, 02:35   #1
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Engine stall when fuel tank level is low

We started cruising 2 years ago on our Swift33 sailboat.
At the end of last year our engine began having trouble starting but only in very specific conditions.

It would always start from the first try but after a couple of days of rest with an almost empty fuel tank it would stall again.
After a couple of tries it would keep running and would then happily do so for hours or at full revs.

Our fuel tank is in the keel and when itís less than 1/3 full the fuel needs to be pulled up by an additional meter or so.
 Iím guessing that the mechanical lift pump on the engine doesnít cope with the additional lift.

I already tried changing filters and also changed the pump both didnít make a difference.

Of course the easiest would be to keep the fuel tank full but whatís the point of having 300l of diesel when we can only use 200 of those Ö.

So Iím wondering if it would work to add a small electric lift pump to the fuel line to help when the level of the tank get low.

Would one of these do ? (I have one laying around).
https://www.amazon.com/dp/B00L8IHM9K...hlbWF0aWM&th=1
And would it work to only run it when the tank is low and let the mechanical pump do itís job the rest of the time.
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Old 24-06-2024, 08:56   #2
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Re: Engine stall when fuel tank level is low

did you check for slight blockage? blow back the other way.
remember when the pump is inline and off, then the mechanical has to suck through it causing more resistance.
it doesn’t look great quality, some constant running rated pumps cost much more.
is there a leak so small that the fuel can run out of the pipes when motor off
just a few thoughts
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Old 24-06-2024, 10:27   #3
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Re: Engine stall when fuel tank level is low

Quote:
And would it work to only run it when the tank is low and let the mechanical pump do its job the rest of the time.
Add a **low pressure** electric fuel pump that comes on when your panel is activated. This should solve the issue and make bleeding an easier chore.
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Old 24-06-2024, 10:41   #4
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Re: Engine stall when fuel tank level is low

Quote:
Originally Posted by iGrf View Post
We started cruising 2 years ago on our Swift33 sailboat.
At the end of last year our engine began having trouble starting but only in very specific conditions.

It would always start from the first try but after a couple of days of rest with an almost empty fuel tank it would stall again.
After a couple of tries it would keep running and would then happily do so for hours or at full revs.

Our fuel tank is in the keel and when it’s less than 1/3 full the fuel needs to be pulled up by an additional meter or so.
 I’m guessing that the mechanical lift pump on the engine doesn’t cope with the additional lift.

I already tried changing filters and also changed the pump both didn’t make a difference.

Of course the easiest would be to keep the fuel tank full but what’s the point of having 300l of diesel when we can only use 200 of those ….

So I’m wondering if it would work to add a small electric lift pump to the fuel line to help when the level of the tank get low.

Would one of these do ? (I have one laying around).
https://www.amazon.com/dp/B00L8IHM9K...hlbWF0aWM&th=1
And would it work to only run it when the tank is low and let the mechanical pump do it’s job the rest of the time.
Yes it will work. I've just used a small $25 one from NAPA auto parts, but the Walbro is said to be a high quality pump. I like it to be before the filters, so the pump is pushing through the filters not trying to pull out of them.

Whichever you get just make sure it's rated for Diesel. Most will pass fuel when not activated.
Are you sure you dont have debris in your tank plugging the pickup tube screen? That can cause intermittent stoppage.
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Old 24-06-2024, 10:45   #5
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Re: Engine stall when fuel tank level is low

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Originally Posted by iGrf View Post



So Iím wondering if it would work to add a small electric lift pump to the fuel line to help when the level of the tank get low.

Yes, assisting the mechanical lift pump could definitely help. But while you mention replacing filters, you don't mention replacing/checking fuel lines and vents.

Personally, I would get a vacuum gauge and properly check the tank, all fuel lines, and ventilation before installing the electric pump.
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Old 24-06-2024, 10:49   #6
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Re: Engine stall when fuel tank level is low

If you plan to keep and use the mechanical lift pump then I would just go with a low powered electric pump and run it all the time. Too much flow is not an issue. Diesel are designed to flow more than needed to the injector pump and return the excess anyways.

Having an electric pump that is off will act as additional head due to the obstruction. You could design it to have a t valve to provide a bypass around the electric pump but I would just keep it simple and wire the pump to run when engine is on. Don't put it before the filters. The water seperator in filter only works if the water is separate. Pumps emulsify everything letting water pass through the filter.
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Old 24-06-2024, 12:06   #7
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Re: Engine stall when fuel tank level is low

Donít overlook a corroded fuel pick up line inside the fuel tank. All tanks have them and they will eventually become brittle, or corrode and break off, inside the tank. When that happens, you can only draw fuel under certain conditions. Pull the sending unit out of the tank and inspect. Easy to do.
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Old 30-06-2024, 02:56   #8
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Re: Engine stall when fuel tank level is low

Thanks for all the replies and suggestions.

- Yes I checked all the lines and connections, there are no leaks and when I open the fuel filter after a couple of days of not running I can hear a little air 'rushing' in, so it still has some 'vacuum' on it.

- the pickup pipe in the fuel tank appears to be fine, I switched the fuel line to a second one that I installed recently for a heater and that doesn't make a difference

- the fuel in the tank is clean, I don't see anything floating around in it and the diesel is transparent. I always strain our fuel through a 'Mr Funnel' before it goes into our tank and add a good biocide to prevent any bacteria growth. So far this has done the trick of keeping our tank clean.

I understand that the electric pump is pretty cheap, but I have one that I use to fill the diesel heater day tank so it's available on board

As a test I put it in line with the mechanical fuel pump and that seems to do the trick.
With the engine off I can see fuel coming from the return line into the tank and the engine doesn't stall after starting.
I tried turning off the electrical pump once the engine runs and the mechanical pump is then able to overcome the additional back-pressure and the engine keeps running.

So next time I'm in a bigger city I'll get a better quality pump and redo my McGyver setup.
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Old 03-07-2024, 00:57   #9
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Re: (update) Engine stall when fuel tank level is low

so it seems like it didn't do the trick.

last night when the wind died down I started the engine (while running the aux lift pump) and it only wanted to idle roughly at around 600rpm.

Only after pushing the manual bleed pump the revs went up and stabilised.
It's been running without a stutter for the last 6 hours but I'm not to keen to shut it down before we are somewhere safe. Luckily Valencia is only a couple more miles and we have pre-booked berth there for a couple of days.

I'll go over the whole system again, one of the things that I didn't look at yet is this manual bleed pump.
When I try to pump it with the engine off it 'pushes' back, like it should when the system is properly bled. But I'm wondering if this manual pump could be the problem ?
Could it get stuck somehow and be the reason that the engine doesn't get any diesel ?
Once it's open and the fuel runs through it wouldn't be an issue anymore and it would match with our symptoms.....

anyone know if these can be serviced / inspected ?
in my workplace manual it only shows how to replace it.

engine is a VP D1-30B
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Old 03-07-2024, 07:56   #10
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Re: (update) Engine stall when fuel tank level is low

Quote:
Originally Posted by iGrf View Post
so it seems like it didn't do the trick.

last night when the wind died down I started the engine (while running the aux lift pump) and it only wanted to idle roughly at around 600rpm.

Only after pushing the manual bleed pump the revs went up and stabilised.
It's been running without a stutter for the last 6 hours but I'm not to keen to shut it down before we are somewhere safe. Luckily Valencia is only a couple more miles and we have pre-booked berth there for a couple of days.

I'll go over the whole system again, one of the things that I didn't look at yet is this manual bleed pump.
When I try to pump it with the engine off it 'pushes' back, like it should when the system is properly bled. But I'm wondering if this manual pump could be the problem ?
Could it get stuck somehow and be the reason that the engine doesn't get any diesel ?
Once it's open and the fuel runs through it wouldn't be an issue anymore and it would match with our symptoms.....

anyone know if these can be serviced / inspected ?
in my workplace manual it only shows how to replace it.

engine is a VP D1-30B
I'm not familiar with your D1 so I'll think generally:

First, I would buy a new quality electric fuel pump. They're not expensive, and you would eliminate the possibility of an inadequate fuel pump.

Next, I wouldn't run the electric fuel pump through the mechanical. Instead, I would split a rubber fuel line bypassing the mechanical lift pump and bleeder and run an electrical pump with a switch.

Yes, I think the mechanical pump/bleed could be caused by a diaphragm issue, causing air to enter the system. Bypassing the mechanical lift pump and bleeder could indicate where the air is entering the system.

I also would consider adding a vacuum gauge at your filter/filters for future help in seeing when fuel filters or system flow is restricted.

Thanks for the update.
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Old 03-07-2024, 08:12   #11
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Re: Engine stall when fuel tank level is low

I looked up the D1 and see that your engine has the mechanical bleed, lift pump, and fuel filter as 1 unit.



This makes it difficult to bypass the system without adding another fuel filter.

I have an electric pump set up as a backup for my system. I can disconnect and separate the fuel line, connect the electric pump, and switch it on. It's meant to get me home or into a safe place if the mechanical were to die. If I were to do the same for your D1, I would add a filter to the setup.
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Old 03-07-2024, 13:03   #12
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Re: Engine stall when fuel tank level is low

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Originally Posted by Glenn.Brooks View Post
Donít overlook a corroded fuel pick up line inside the fuel tank. All tanks have them and they will eventually become brittle, or corrode and break off, inside the tank. When that happens, you can only draw fuel under certain conditions. Pull the sending unit out of the tank and inspect. Easy to do.
Having had a similar problem, this would be easily checked and simpler than some of the options you are considering. Can you just run your engine from a portable diesel fuel source like a jerry can for a test? My situation was that crud in the tank would work its way up the pickup tube and then block it.
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Old 08-07-2024, 09:22   #13
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Re: Engine stall when fuel tank level is low

We also have a Swift 33. We had a very similar problem with fuel. I added a small 12-volt diesel pump and check valves between the tank and the Racor filters. The flow is like this. Line from tank to a tee. From the tee, one line goes to the pump and the other line goes to a check valve. From the pump it goes to a second check valve and on to the second tee. This gives you a bypass around the pump. Underway we use just the engine diaphragm pump. First start, docking, inlets or any congested waterway the electric pump is on. We call it the "boost" pump. We also have 2 fuel filters and a vacuum/pressure gauge between the filters and the engine. If I see the vacuum going up (boost pump off) it's very easy to open the ball valve to the second Racor filter and close the valve to the restricted filter.
I would really like to see some pictures of your boat. Swallow Craft Swift 33's seem to be a very rare bohttps://www.cruisersforum.com/forums/attachment.php?attachmentid=291833&stc=1&d=1720455 717at. We have had ours for 11 years.
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Old 09-07-2024, 00:20   #14
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Re: Engine stall when fuel tank level is low

Quote:
Originally Posted by Glenn.Brooks View Post
Donít overlook a corroded fuel pick up line inside the fuel tank. All tanks have them and they will eventually become brittle, or corrode and break off, inside the tank. When that happens, you can only draw fuel under certain conditions. Pull the sending unit out of the tank and inspect. Easy to do.
That.

Replace the pickup tube and if you have a level gauge, check it, too. If you don't have an inspection plate in your tank top, you should put one.

My 4-107 is very sluggish in starting when it hasn't ran in a few days, or in cold weather, but my cheap charlie Chinese Amazon Prime fuel pump makes a huge difference. The mechanical lift pump sucks fuel through the pump just fine when I shut if off, but it is simple enough to plumb in a bypass if tat were not the case. The electric pump is also quite useful in filling up your fuel filter housing and bleeding off the air in the system after changing the filter. It can also help when bleeding the rest of the fuel system.
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Old 09-07-2024, 06:15   #15
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Re: Engine stall when fuel tank level is low

I purchased an old boat that had a similar issue. Tank lower than the engine. If left sitting for a few hours, it would take forever to start and then would stall almost immediately after starting and then take a few repeat goes before it would run smoothly. The engine has a water separating filter before the primary filter that must have been installed years ago, possibly when the engine was originally put in. Solved the problem when I noticed that outlet of this filter was connected to the tank, and the inlet connected to the engine's fuel pump and replaced the filter and corrected the direction of flow.

Also, if installing an electric self priming pump to help lift the fuel up hill, I reckon don't install it before the filter. Self priming pumps will gunk up quickly if any sludge gets sucked from the tank. They'll still pull fuel quite satisfactorily from the other side of the filter.
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