4.3lt mpi mercruiser burnt out fuel pump

[idomeneus5]

I have a 2006 4.3ltr mpi mercruiser. Just had its 20 hour service done by an approved mechanic in the area we were holidaying. Engine performance after the service was lousy, but put I it down to a damaged prop & poor weight dist. Subsequent inspection revealed no prop damage, performance continued to worsen and revs decreased.My usual mechanic advised that when the fuel filter is changed, the new filter must be filled with fuel prior to fitting it on the engine, to avoid sucking in air and burning out pump. He said it is a known problem, but I cant find anything on "the net". Engine has been fixed under warranty, but does his explanation sound "SUSPO" ?. Wouldn't a similar thing occur if /forums/images/graemlins/confused.gif(god forbid, but it can happen) we were to run out of fuel ?. Any ideas ?

 

[spannerman]

He's not wrong, the electric pumps on fuel injection systems are designed to deliver fuel under pressure around 30-40 psi. Due to the design of the rotors they don't suck very well, also the fuel is what cools and lubricates them, so prolonged dry running won't do them any good.
So we always fill the fuel filter so that they don't have to pull fuel very far before they are primed.
It wouldn't happen if you ran out od fuel because as soon as the fuel pressure fell the engine would stop.
Its trying to pull fuel all the way from the tank to fill up the filter before it gets to the pump thats bad for them.

 

[alan006]

I'd love someone to tell me why Mercruiser changed from the mechanical fuel pump to the electric fuel pump. I agree with Spannerman the electric pumps don't like priming the system, a friend of mine put a fuel bulb in the circuit so if it did run dry then all he had to do was squeeze the bulb a few times ( like priming an outboard). The trouble is if there was an accident would that alteration be criticised by a surveyor?

 

[alan006]

I can reply to my own question as I've just asked an engineer. He told me with fuel injection you need fuel pressure straight away. The mechanical system was fine for carbs but is not suitable for fuel injection systems.

 

[idomeneus5]

Alan. I actually did that (installed a primer bulb) on my old boat, It had a merc 165, with mechanical pump. It tended to get the occasional vapour lock whilst the boat was on the trailer during the hot summers we get here, but I initially did this after a pump failure at sea. I jury rigged an o/board fuel hose into the line between tank and carby, and just gently kept squeezing to get home, (took a bit of practice) but it wasn't too far. Peter.

 

[Latestarter1]

Hey guy's just wait a minute.

This is a BIG deal. We are mixing up gas engines and diesels here but certain rules still apply. If the engine has a mechanical lift pump it is perfectly OK to pre fill the filter. Better still is fitting s squeeze bulb in the line is pretty common just about everywhere except the UK.

Running out of fuel is bad seamanship but it does happen, a squeeze bulb in the line gets your fuel system bled real easy.

However if you have a common rail fuel system with an electric pump NEVER pre-fill the fuel filter. The electric pump is there for a reason. I have no experience of Volvo, they are no where near as big in the U.S as here. We were Cummins, Deere and Yanmar dealers. I do now that the Volvo D4/D6 shares the same Bosch CP3 fuel system with Cummins and is similar to the set up on Deere.

Please note; It is an absolute requirement on a common rail fuel system when changing the fuel filter that the new filter is NOT pre-filled with fuel. The risk of contamination is huge. The correct procedure is to remove the protective film immediately before fitting the filter and screw on empty. Switch on ignition a and listen for the pump to run. When the pump stops running crank the motor until it fires. It is as simple as that.

Common rail fuel systems are incredibly sensitive to dirt, if guy's out there are servicing these motors pre filling fuel filters on common rail engines then seeing failures they are 90% responsible for any fuel system issues they create. A spec of crud just a little larger than 10 microns can take out an injector.

I suspect the talk about Volvo D4/6 failures and fuel quality is vapour, more likely down to the the servicing procedure. Just another thought, if the guy commissioning the motor at the builders is doing it the way he has always done it and pre filling filter from the plastic container he keeps for the purpose in the corner of the workshop. A new engine could have the seeds of damage sown before you take delivery.

Fuel in the U.S is junk so we got our act together in time for common rail. If red neck farmers can be made to get religion about keeping fuel clean on common rail engines where is the marine industry?

Now I am on a rant I had better finish but just a question for the Volvo techs here. Cummins has an feature in the ECM called the 'Unintended fueling algorithm' which watches out for an injector failure caused by dirt and starting to 'hose'. You get a warning and have time to shut the engine down before the injector washes the lube oil off the bore and wrecks that pot. Deere has something similar. The tech wizards at Volvo need to take a look at what the completion is doing and do some network education.

 

[spannerman]

Lateboater sorry but you are talking out of the back of your manifold!
Your comments about the D4 & D6 are in your own words 'vapour' as it is an ongoing problem with 32 motors failed here in Norway, we had a D6 fail last week at 100 hrs and are waiting for a new lump from Volvo. Bosch are now in on the carpet to try and get to the bottom of these failures.
Its nothing to do with servicing procedures when an engine fails before it gets to its first service!
I am the service manager for a Volvo workshop and am familiar with Volvo procedures and there is a mandatory checklist without which you have no warranty when commissioning a new boat and Volvos have a primer and bleed nipple on the fuel filter so its not neccessary to prefill the filter, you just pump until the air is gone then close the nipple pump some more and then crank it a couple of times and she will start.
There are no electric fuel pumps on these engines as the lift pump is built into the high pressure pump that supplies the rail.
I guess we are the opposite, Volvo and Mercruiser and Yanmar are big here in that order, with a few Cummins on the bigger boats.
John Deere is just a tractor to us.

 

[Latestarter1]

Spannerman,

Forums are normally a place to share information for mutual benefit. Rudeness has no place when trying disseminate information however I will leave it there.

Having served my time in the Merchant Navy and at least having a Chief Engineers ticket back around 1970 and having been in the marine industry around the world I am pretty comfortable with what are my limitations.

Worked way back with NOGVA in Norway doing development of Cummins B engine very low temperature operation in fishing boats and I developed a high regard for Norwegian engineers I worked with being both professional and courteous.

I declared my credentials as having little knowledge of the Volvo D4/D6 product I made the comparison with the fuel system of the Cummins QSB which is identical.

My major concern was your comment;
'So we always fill the fuel filter so that they don't have to pull fuel very far before they are primed'

This led me quite wrongly to conclude that you were practicing this procedure on the common rail engines you supported. Likewise any owner tempted to perform their own servicing may misconstrue your advice and pre-fill filters of a common rail motor.

Having been dealer principal I am well aware of manufacturers new engine commissioning procedures. Also being at the helm of a dealership during the recent Yanmar LP valve drop disaster and working closely with the U.S. distributor in resolution of the problem, I have to say that if I had found out that my service manager was giving his own completely un-databased personal opinions on the product problem on a website at the time I would have fired him.

I have run the numbers and there are over 300,000 Bosch CP3 pumps operating in Europe, other than dirty fuel this is a mature and robust system operating with many different engine manufacturers.

On a positive note perhaps if you took the concept of the 'Unintended fueling algorithm' which would have a major impact in limiting the damage caused by injector hosing to your Volvo distributor he may see you in a more constructive light.