Volvo D2 Diesels - Fuel Starvation

[rickfant]

I've a pair of Volvo D2-40's in my Leopard 40 catamaran. We see fuel starvation when the fuel tanks drop below half; and have heard this has been occuring on other boats with these engines.

We suspect that the engine driven fuel pumps on these engines are weak and wondered if other's with the D2 series had seen any fuel starvation issues. Fuel starvation in our case results in surging engine RPM's and an inability to run the engines much beyond idle.

[never monday]

Do you have an onboard generator? is it feed from both tanks?

[Alan Wheeler]

Good point Pat.
Heres a few other questions to help us and you.
How far below pump level is mid tank level??
Do you have good fuel line size, filter size. These move more diesel in a circuit system than the older engine systems did.
Are filters clean
Does the return line go to tank or to filter??
Have you verified the issue is not a case of air being drawn into a line via a faulty fitting.
Have you verified the pump is actually working correctly

[seafox]

I have the same motor and no problems such as that.

[rickfant]

Thanks for all the replies to this thread. To answer some questions:
- the installations, lines, etc. have been checked by multiple machanics and no leaks or blockages found. Tanks, Racors and on-engine fuel filters all cleaned and replaced multiple times. Note - the the problem is happening on both engines and they are completely independant systems.
- the tank fuel supply is in the sump of the fuel tank, right to the bottom. The fuel return ends halfway down the tank and goes directly from the engine to the tank (no filter).
- I have an onboard generator - it pulls fuel from the starboard tank only via an electric lift pump pushed thru a racor. no problems with generator.
- I've been in touch with other Leopard owners, they report similar issues, R&C just started using Volvo with the saildrive (previously yanmar)

I'm concluding that the combination of tank, lines and filters may be too much for the on-engine fuel pump when the tank get's below half; and I'm looking to R&C to give me a solution. So far, they have been responsive.

The reason for this post is to see if other D2 engine owners where having problems. So far, in this post and other communications, nobody except for Leopard owners has reported a problem.

I'll update on what is the solution.

[never monday]

What is the diameter of the fuel line?

[rickfant]

The fuel lines are 3/8 interior diameter (for some reason nothing written on the outside of the hose) - I think plenty big enough for the job.

The lastest from the factory (R&C) is this; The fuel return fitting into the tank only goes down to about half way - the factory and Volvo think that when the fuel return fitting is uncovered (tanks half empty) that air is getting sucked back into the system causing the starvation. The factory have instructed owners to get the return fuel line moved to the manual pump tank fitting (which goes all the way to the bottom of the tank). So you swap the hose(s) on the manual pump and the fuel return and all should work fine.

While this may work (so far it has for me); this seems like the on-engine fuel pump is weak and barely moves fuel thru the system and this is a work-around for now. At some point someboday (robertson & caine or volvo) has to figure out why the pump would allow air back into the system.

Anyway - that's the official line. If I get anything more, I'll post it.

[DeepFrz]

I would suspect that when the fuel level drops below the outlet for the return fuel that you start getting "frothing" of the fuel, which then causes the fuel feed line to pick up air bubbles.

[robbie_d]

Rick I have had problmes with my ECV control on my D2 40 in my 2006 Bavaria 42 but not this yet although I almost never let the tank drop past half full to avoid condensation problems. However I will check this out. I looked at the fuel output on my pump when my engine didn't first start and thought it weak..about a spurt of an ounce every 3 seconds when cranking..but when running it should be more than enough to run the engine.

[rickfant]

Thanks for the posts.

The Volvo D2-40's in my Leopard 40 continue to have RPM surge issues; yes - both of them. If we run the engines at cruise power for 30 minutes or so (2,000 to 2,500 rpm) and the tanks are half-full or lower we get RPM drop and recovery. It's repeatable and replicable.

I've had three Volvo dealers look at the problem; T&C, PR and now St. Lucia. They have all given good service and really tried to understand and fix the problem. In a recent sea trial - the dealer mounted an external fuel tank for the stdb engine on deck and the engine ran fine. Which has me pretty much convinced it's a tank or installation problem that's effecting both sides.

The manufacturer - Robertson & Caine (R&C) - installed electric boost pumps just prior to the Racor and they expected this to solve the problem, but no luck. I'm relatively sure it's a fuel tank or installation problem that's letting air get into the fuel feed lines; tank sloshing or frothing or fuel pickup problems. I'm working now with R&C to get this fixed, but they continue to tell me it's not a tank issue.

My overall experience with Volvo dealers is good; but I must admit that these engines seem finicky and want a perfect installation to operate smoothly.

[robbie_d]

Rick,
I read but didn't see but I assume they replaced the pumps at least once?
Also, from what I have read on the Volvo site the EVC system( that little black box on the side of the engine) can affect the way the engine runs based on several different sensors including fuel guage readings.

I have to agree the Volvo dealers so far have been great.

[Alan Wheeler]

Pat, I would have liked to have seen what you posted :-)
In my opinion, 3/8" line is far too small, especially if it is several feet in length. You need to increase the line size as these systems require a high volume flow with little restriction. 1/2" would be accepatable, but I strongly recommend the next size up from that even. You have to realise it is not just the line that is the restriction. But the fittings themselves create a restriction far smaller then the line size. You will have a small diameter fitting on the end of every single component fitted, each adding up the over all effort required to move the fuel.

[never monday]

3/8" is fine, I have IPS 500 and 600's running 1/2" here and they don't skip a beat.

The boost pump is on the wrong side of the Racor, and he's probably pulling a vacuum in the tank causing fuel starvation..

THIS IS NOT A VOLVO PROBLEM. IT'S A BOAT BUILDER PROBLEM.

[Alan Wheeler]

Arrr, I didn't catch what side the pump was on. That makes perfect sense. If so many have looked at this installation, why hasn't someone picked that issue up??

[cal40john]

Originally Posted by never monday

3/8" is fine, I have IPS 500 and 600's running 1/2" here and they don't skip a beat.

The boost pump is on the wrong side of the Racor, and he's probably pulling a vacuum in the tank causing fuel starvation..

THIS IS NOT A VOLVO PROBLEM. IT'S A BOAT BUILDER PROBLEM.

I don't understand, I'd like to learn more about this.
Why would there be a vacuum in the tank? It seems to me that whether you push or pull on the filter, you would get the same back pressure and therefore the same flow. I would think that only a restriction in the tank vent would cause vacuum in the tank.
I looked at the Racor site and it said their filters can be on the vacuum or pressure side, as long as you don't exceed their pressure spec (5-30 psi depending on models I looked at.). They do recommend the filter be on the vacuum side though. My reasoning is that it was to minimize the amount of fuel system components under pressure, to reduce the risk of spraying hot fuel in the engine compartment in case of a leak.

If anything, it seems to me having the filter on the vacuum side increases the chances of getting air in the fuel, at the expense of the safety issue above.

What have I missed or am ignorant of?

That said, my filter is on the vacuum side of my boost pump, since it is the recommendation.

John