Ongoing engine woes - latest theory

[Cardo]

So I still haven't managed to sort out the problems with my Beta 35. The symptoms are that once the fuel tank is run down to below around half a tank, the engine will reasonably often splutter and sometimes (though rarely) actually stop, requiring running the starter for a few seconds to get the engine to fire back up, where it will splutter a bit before running fine again. Rinse and repeat.

I'm pretty confident the problem is air bubbles getting into the fuel pipe, and I'm also pretty confident this is happening at the CAV filter. For information, the CAV filter is located so the top of the filter unit is pretty much in line with the top of the fuel tank. Once there is half a tank of juice left, the fuel level is below the filter level.
In addition to the engine fuel pipe, we also have our Eberspacher fuel pipe coming off the CAV filter. The Eber is connected on the starboard side of the filter whilst the engine is on the port side.

Some of you may recall my posts about Eber problems. Essentially, what I have seen happening is when the Eber is not running, the fuel in the thin transparent Eber pipe drops back down towards the filter. This would suggest air is getting into the pipe at the Eber end somewhere. When the fuel is low, the Eber often takes a few attempts to start as I presume it has to suck through all the air in the pipe before the fuel reaches the unit.

My theory is when the Eber is not running, and the fuel tank level is below that of the filter, air bubbles are being sucked into the filter from the Eber fuel pipe and occasionally being sucked into the engine pipe. My theory is reinforced by the fact the symptoms occur more frequently when the boat is heeled to starboard, causing any bubbles from the Eber pipe to rise with gravity towards the engine fuel pickup.

1) Is this theory sound?

2) When the Eber is not running, should it be allowing the fuel to drop back down or does this suggest a problematic leak of air somewhere at the Eber end?

3) If the fuel shouldn't drop, can I try sorting this by putting some Vaseline around the pipe connections? I've already tried tightening them.

4) Should I simply cut my losses and disconnect the Eber from the CAV filter and subsequently have it plumbed into the tank direct?

5) If I should disconnect the Eber, what type of bolt do I need to fill the hole on the filter? The filter is a Delphi 296 with 7111-296 written below it.

As always, any advice is greatly appreciated!

 

[nimbusgb]

I'd support getting the eber fuel pipe out of the equation. Block it off at the cav filter and try again.

 

[Cardo]

I'd support getting the eber fuel pipe out of the equation. Block it off at the cav filter and try again.

Can you suggest what I use to block it off? As it stands, I don't have the correct bolt to replace the fuel pickup bolt in there. Is there anything in a "standard" toolbag that would do the job of sealing the pickup and not make things worse?

 

[Marsupial]

So I still haven't managed to sort out the problems with my Beta 35. The symptoms are that once the fuel tank is run down to below around half a tank, the engine will reasonably often splutter and sometimes (though rarely) actually stop, requiring running the starter for a few seconds to get the engine to fire back up, where it will splutter a bit before running fine again. Rinse and repeat.

I'm pretty confident the problem is air bubbles getting into the fuel pipe, and I'm also pretty confident this is happening at the CAV filter. For information, the CAV filter is located so the top of the filter unit is pretty much in line with the top of the fuel tank. Once there is half a tank of juice left, the fuel level is below the filter level.
In addition to the engine fuel pipe, we also have our Eberspacher fuel pipe coming off the CAV filter. The Eber is connected on the starboard side of the filter whilst the engine is on the port side.

Some of you may recall my posts about Eber problems. Essentially, what I have seen happening is when the Eber is not running, the fuel in the thin transparent Eber pipe drops back down towards the filter. This would suggest air is getting into the pipe at the Eber end somewhere. When the fuel is low, the Eber often takes a few attempts to start as I presume it has to suck through all the air in the pipe before the fuel reaches the unit.

My theory is when the Eber is not running, and the fuel tank level is below that of the filter, air bubbles are being sucked into the filter from the Eber fuel pipe and occasionally being sucked into the engine pipe. My theory is reinforced by the fact the symptoms occur more frequently when the boat is heeled to starboard, causing any bubbles from the Eber pipe to rise with gravity towards the engine fuel pickup.

1) Is this theory sound?

2) When the Eber is not running, should it be allowing the fuel to drop back down or does this suggest a problematic leak of air somewhere at the Eber end?

3) If the fuel shouldn't drop, can I try sorting this by putting some Vaseline around the pipe connections? I've already tried tightening them.

4) Should I simply cut my losses and disconnect the Eber from the CAV filter and subsequently have it plumbed into the tank direct?

5) If I should disconnect the Eber, what type of bolt do I need to fill the hole on the filter? The filter is a Delphi 296 with 7111-296 written below it.

As always, any advice is greatly appreciated!

As and old grey haired engineer I would suggest one pipe one job, but the modern cheapskate ideas don't accord with this, BUT that is the first thing I would do - have separate tank dip tube for each appliance. Yes I know there are lots of installations like yours but it's shoddy work, it makes fault tracing more difficult as you are now finding.

Next it seems possible that when the fuel tank is half empty the fuel lift pump is having to do more work, it could then as you suggest suck air from the ebber pipe, very very common in my old very humble opinion and experience or the lift pump itself could have a fault that only manifests when its under stress. OR you have both problems again very likely and another reason to make another hole in the fuel tank.

The problem is fuel supply aggravated by a poor installation I believe.

 

[Bosun Higgs]

So I still haven't managed to sort out the problems with my Beta 35. The symptoms are that once the fuel tank is run down to below around half a tank, the engine will reasonably often splutter and sometimes (though rarely) actually stop, requiring running the starter for a few seconds to get the engine to fire back up, where it will splutter a bit before running fine again. Rinse and repeat.

I'm pretty confident the problem is air bubbles getting into the fuel pipe, and I'm also pretty confident this is happening at the CAV filter. For information, the CAV filter is located so the top of the filter unit is pretty much in line with the top of the fuel tank. Once there is half a tank of juice left, the fuel level is below the filter level.
In addition to the engine fuel pipe, we also have our Eberspacher fuel pipe coming off the CAV filter. The Eber is connected on the starboard side of the filter whilst the engine is on the port side.

Some of you may recall my posts about Eber problems. Essentially, what I have seen happening is when the Eber is not running, the fuel in the thin transparent Eber pipe drops back down towards the filter. This would suggest air is getting into the pipe at the Eber end somewhere. When the fuel is low, the Eber often takes a few attempts to start as I presume it has to suck through all the air in the pipe before the fuel reaches the unit.

My theory is when the Eber is not running, and the fuel tank level is below that of the filter, air bubbles are being sucked into the filter from the Eber fuel pipe and occasionally being sucked into the engine pipe. My theory is reinforced by the fact the symptoms occur more frequently when the boat is heeled to starboard, causing any bubbles from the Eber pipe to rise with gravity towards the engine fuel pickup.

1) Is this theory sound? Seems very sound from the symptoms you describe

2) When the Eber is not running, should it be allowing the fuel to drop back down or does this suggest a problematic leak of air somewhere at the Eber end? Letting air in means the Eber will not start as it should so that is wrong. But its also wrong to connect the eber in that way - it should have its own connection fdirect to the tank.
3) If the fuel shouldn't drop, can I try sorting this by putting some Vaseline around the pipe connections? I've already tried tightening them. Why vaseline - OK its soluble in diesel but if its on an air leak it will get sucked in and not work. .. I have in the past used insulating tape to cover a suspect joint temporarily to see if indeed it was the source of an air leak but not vaseline

4) Should I simply cut my losses and disconnect the Eber from the CAV filter and subsequently have it plumbed into the tank direct? Yes but first check your theory by disconnecting the eber feed and blanking it off. See if that cures the problem.

5) If I should disconnect the Eber, what type of bolt do I need to fill the hole on the filter? The filter is a Delphi 296 with 7111-296 written below it. God knows, I dont. Get the box of bolts you have in the garage and toddle along to see which one fits.

As always, any advice is greatly appreciated!

**********

 

[Heckler]

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IIRC the bolt size is 1/2" UNF
Stu

 

[nimbusgb]

The thin clear nylon hose on my Eber is connected to the pump with a short section of rubber hose. Disconnect at the pump and plug with something suitable temporarily? Keep the hose full of fuel so you can see if air's getting in.

 

[earlybird]

AFAIK, some 296 filter housings have 14mm x 1.5mm female thread. A standard, but not common metric size.You'll have to check yours.

 

[nigelmercier]

Split a piece of plastic or copper pipe into two C sections. Clamp to hose with mole grips.

 

[GrahamM376]

If you have the standard filter head with 2 x IN & 2 x OUT and are only using 1 x IN you already have a blanking plug which can be removed as a sample. Find a local diesel/injector service centre and they will no doubt have some lying around.

 

[ribrage]

I had a similar problem to this on a pacific 22 rib we had in africa, the problem was tracked to the central bolt holding the CAV filter assembly together, although the washer was fitted to the top of the bolt, the small o ring under it had not been changed for some time and slowly allowed air into the system , its an easy thing to replace and its often over looked on servicing as everyone concentrates on the large o rings and not spilling fuel everywhere....... worth a look.

 

[nimbusgb]

I had a similar problem to this on a pacific 22 rib we had in africa, the problem was tracked to the central bolt holding the CAV filter assembly together, although the washer was fitted to the top of the bolt, the small o ring under it had not been changed for some time and slowly allowed air into the system , its an easy thing to replace and its often over looked on servicing as everyone concentrates on the large o rings and not spilling fuel everywhere....... worth a look.

Or distorted through over tightening ....... good idea!

 

[geem]

I am not a fan of the CAV filter. They can be troublesome with air leaks. We swapped our CAV filter unit for a seperate glass settlement bowl then a spin on filter unit. These are like an oil filter housing and very easy to change filters in a hurry. no seals to fit and little to go wrong. Remove the eberspacher from the filter and install seperate tank pick up pipe.

 

[Otter]

As said, check whether metric or imperial, we had the metric one, ASAP supplied imperial plug. My fault not there's. Simple to block the Eber in extremis, get some mole grips and clamp the clear tube, you may damage it but its cheap to replace and right now you're fault finding. Replace the Eber tube with a pickup into the tank.

 

[Cardo]

So, we stopped a short while ago to take on some fuel (sadly, the pump was out of order, and the next one is 50km further along. We'll be on fumes!) and I took the opportunity to take the Eber pipe off the CAV outlet and sealed it up with a load of insulating tape. Not a permanent solution but I'm hoping it should hold for now.

We've now been motoring for the better part of an hour and not a single hiccup (I did bleed the engine again after my tinkering). I have touched wood, as it'll likely die once I post this!

 

[savageseadog]

There's a filter in the pump and it's effectively a non return valve as well. Correct thing to block it off though to narrow the problems down. There's a lot to be said for having a stop cock on the filter outlets, easier maintenance and problem eliminator and safer from leaks.

 

[Cardo]

There's a filter in the pump and it's effectively a non return valve as well. Correct thing to block it off though to narrow the problems down. There's a lot to be said for having a stop cock on the filter outlets, easier maintenance and problem eliminator and safer from leaks.

I would've expected there to be a non-return valve on the Eber pump, but seeing how quickly the fuel drops back down the pipe when the Eber is stopped it either isn't working or there is one helluva air leak in the joint between the pipe and the pump!

 

[vyv_cox]

I would've expected there to be a non-return valve on the Eber pump, but seeing how quickly the fuel drops back down the pipe when the Eber is stopped it either isn't working or there is one helluva air leak in the joint between the pipe and the pump!

Any pump that goes tick-tick-tick is a positive displacement one and will almost certainly have suction and discharge valves. Sounds like your may have ceased working.

 

[ianj99]

Just fit a non return valve in the pipe to the Eber so the engine cannot suck air from it rather than fuel from the filter.

 

[Cardo]

After blocking off the Eber take off, the engine ran fine for an hour or so before it started getting upset after hitting some bumpy stuff. I delved back into the engine compartment and had a look at the bottom of the CAV filter. I found loads of big air bubbles caught at the top of the glass bowl part that would occasionally break free and rise up when the boat bounced around!

After we topped up the fuel tank, I gave the CAV filter a good shake to get all the bubbles to rise. I then tried to bleed it using the bolt right at the top of the filter however this appears to be above the top of the fuel tank and therefore it was no help whatsoever! I long old bleed at the engine fuel filter seemed to do the trick. We've been motoring for 7 hours today with not a single hiccup. Let's hope it stays this way when the tank runs down!