Odd engine behaviour - cause?

[Cardo]

I've been having some niggles with my Eberspacher ( http://www.ybw.com/forums/showthrea...the-problem&highlight=beta+struggles+to+start ) and the problem in this thread has recurred seemingly at random. Then I had a lightbulb moment and I wonder whether this could be the issue...

I currently have a fair bit of fuel in the tank, more than half a tank I reckon, however the CAV filter is above the current fuel level. The engine obviously takes its fuel from the CAV filter, however the Eberspacher also takes its fuel from the CAV filter.
Is it possible that if I try to start the Eber with the fuel level as it is, it's likely to draw fuel from the pipe leading to the engine instead of pulling fuel up from the tank and this is what's causing the engine to play up?

I thought of this after the engine had been running absolutely fine, I then tried to start the Eber and then when I subsequently tried to start the engine the following day it went back to the symptoms in my OP.

Is the Eber upsetting my engine? Or is it something else?

 

[Trundlebug]

I've been having some niggles with my Eberspacher ( http://www.ybw.com/forums/showthrea...the-problem&highlight=beta+struggles+to+start ) and the problem in this thread has recurred seemingly at random. Then I had a lightbulb moment and I wonder whether this could be the issue...

I currently have a fair bit of fuel in the tank, more than half a tank I reckon, however the CAV filter is above the current fuel level. The engine obviously takes its fuel from the CAV filter, however the Eberspacher also takes its fuel from the CAV filter.
Is it possible that if I try to start the Eber with the fuel level as it is, it's likely to draw fuel from the pipe leading to the engine instead of pulling fuel up from the tank and this is what's causing the engine to play up?

I thought of this after the engine had been running absolutely fine, I then tried to start the Eber and then when I subsequently tried to start the engine the following day it went back to the symptoms in my OP.

Is the Eber upsetting my engine? Or is it something else?

The (relatively) tiny amount of fuel used by the Ebersplutter is very unlikely to starve the main engine of fuel. Unless the Eber has recently had work done and that's where the air could have got in, I would look elsewhere.
Sometimes fuel lines just get a little air bubble or air lock in one part of a pipe which allow the engine to start, run but not achieve full revs / power or behave similarly to the way you have described.

When you have serviced the engine and changed all the filters etc, bleed it through properly all the way through, including at the injectors and then reassess.

 

[robmcg]

I've been having some niggles with my Eberspacher ( http://www.ybw.com/forums/showthrea...the-problem&highlight=beta+struggles+to+start ) and the problem in this thread has recurred seemingly at random. Then I had a lightbulb moment and I wonder whether this could be the issue...

I currently have a fair bit of fuel in the tank, more than half a tank I reckon, however the CAV filter is above the current fuel level. The engine obviously takes its fuel from the CAV filter, however the Eberspacher also takes its fuel from the CAV filter.
Is it possible that if I try to start the Eber with the fuel level as it is, it's likely to draw fuel from the pipe leading to the engine instead of pulling fuel up from the tank and this is what's causing the engine to play up?

I thought of this after the engine had been running absolutely fine, I then tried to start the Eber and then when I subsequently tried to start the engine the following day it went back to the symptoms in my OP.

Is the Eber upsetting my engine? Or is it something else?

Sounds like a likely suspect! Your Eber should have an independent supply from the tank via its own in line fuel filter. The line to the eber will become pressurized at the expense of the engine fuel supply line - do they call it a hydraulic lock????? Reroute the eber supply from the tank and then cross your fingers!!

 

[vyv_cox]

Sounds like a likely suspect! Your Eber should have an independent supply from the tank via its own in line fuel filter. The line to the eber will become pressurized at the expense of the engine fuel supply line - do they call it a hydraulic lock????? Reroute the eber supply from the tank and then cross your fingers!!

Both the Eber and engine fuel pumps are positive displacement ones with suction and discharge valves, so suction from one will not cause fuel to flow back from the other. In the case of a big truck there might be enough flow through the engine pump to invert the valves in the Eber pump and draw air through but this is not going to happen the other way around. As I think I wrote further up, or maybe on Cardo's other thread, there are thousands of boats with the Eber supply taken from the filter, or from the line past it (e.g. mine). Both the engine and the heater work perfectly, both together if necessary.

 

[robmcg]

Both the Eber and engine fuel pumps are positive displacement ones with suction and discharge valves, so suction from one will not cause fuel to flow back from the other. In the case of a big truck there might be enough flow through the engine pump to invert the valves in the Eber pump and draw air through but this is not going to happen the other way around. As I think I wrote further up, or maybe on Cardo's other thread, there are thousands of boats with the Eber supply taken from the filter, or from the line past it (e.g. mine). Both the engine and the heater work perfectly, both together if necessary.

Being not technically minded, I think you know more about this than me I did discuss this with an eber installer several years ago who said he would not take the supply from the engine fuel filter or fuel supply line and eber installation instructions do not favour this way of doing it either. They say "The diagram illustrates a typical installation using a fuel standpipe, which is the preferred method for the fuel take off. This minimises any problems caused by over pressuring, fuel starvation and air leaks that can occur if
connected to an engine fuel line." Just wondering if the fuel starvation can occur in the engine fuel line, downwind of the fuel pump? Again, caveat being I am no expert so it was just a general wondering

 

[vyv_cox]

Being not technically minded, I think you know more about this than me I did discuss this with an eber installer several years ago who said he would not take the supply from the engine fuel filter or fuel supply line and eber installation instructions do not favour this way of doing it either. They say "The diagram illustrates a typical installation using a fuel standpipe, which is the preferred method for the fuel take off. This minimises any problems caused by over pressuring, fuel starvation and air leaks that can occur if
connected to an engine fuel line." Just wondering if the fuel starvation can occur in the engine fuel line, downwind of the fuel pump? Again, caveat being I am no expert so it was just a general wondering

I believe these are general instructions for installation, not specific to small boat engines. I guess that if you were a professional installer of Eberspachers in trucks, which is by far their biggest market, then you would follow the instructions to the letter.

The fact remains that it is far more convenient to draw the fuel from the filter in many yachts, especially ones that are not new, and this is what happens in a large number of cases. The flow of fuel to the Eberspacher is minute by comparison with what flows to the engine, ruling out engine fuel starvation. I guess that in the case of a fuel tank in the keel there might be an issue of starvation of the Eberspacher but in my case, where the tank is well above the filter, this is definitely not the case.

 

[robmcg]

It was a quote from the Airtronic D2, D4, D5 Marine Heater – installation guide - which is probably the same as the guide for installing in trucks I didn't know that it was so common to draw fuel from the filter on yachts or I should say I wish I had known it was possible as it would have solved a different issue on our previous boat!! All 3 boats I have had with diesel heating have all had a separate dedicated supply from the tank. Useful to know otherwise for the future - but alas I don't think I have helped the OP !