Volvo Penta 4.3Gi V6 Petrol

[DarrellH]

I would like some advice on a problem I’m having with the port engine.

When the engine is ticking over and the boat is berthed I can rev the engine upto 4 thousand revs with no problem, but when the boat is moving forward and both engines are moving up the revs the port engine seems to lose power when going over 2 thousand revs and the engine seems to spit back, below 2 and the engine runs fine. The fuel/water separator just after the petrol tank has been cleaned and fuel filter has been replaced, which made a difference for a little time and then returned back to the original problem, there is around £200 pounds worth of petrol in the tank and the starboard engine is fine.

Any help or advice were to go next would be welcome

 

[davedpc]

Hi , Welcome to the forum. Its not usual that your post should fall on def ears . Sorry i cant help you but if i bump you back up to the top again then perhaps some kind formalite will answer your query!

 

[DarrellH]

Hi Davidpc,

Thank you, and for the words of encouragement and I appreciate you posting the thread back to the top, you never know.

Thanks

Darrell.

 

[tinkicker0]

Dunno nuthing about VP, however; If the VP is based on the same GM 4.3 V6 lump as a mercruiser, on some carbs there is a small gauze filter fitted behind the fuel inlet union.
This may be blocked if so.

Does the Gi denote fuel injection? If so, back to the drawing board.

 

[spannerman]

I think you should get the fuel pressure checked as if the pump is failing they will rev up in neutral quite happily but not under load.
If thats Ok then its dig deeper i.e. injectors, and plug in to Vodia for a diagnostic check of what the various sensors are saying.

 

[oldsaltoz]

Sounds like fuel starvation.

As you have 2 lumps the same, can you pull the fuel line off the good one close to the carb/s and measure the free flow (engine off) into a container and see how long it takes to run one litre of fuel out.

Then do the same on the sick lump, if the flow is lower, just work your way back to the tank looking for the restriction.

PS. The problem may be in the tank, crud being drawn up into the outlet when a higher flow rate is asked for. Some tanks have a filter in the tank that won't block but will restrict flow.

 

[DarrellH]

Hi,

Thanks for taking your time out and all your responses in pointing me in the right direction, on the advice of one of the magazine experts I attached a separate petrol tank with a fuel injector cleaning additive to the engine with the problem, after running this through for 30 mins I took the boat out. With the boat moving forward the engine did try and with a bit of persuasion rev up to around 3 and half thousand revs. I then disconnected the spare tank and reconnect the main fuel tank and the engine will now rev up to 3 thousand revs. I think that eliminates everything up to the engine.

Any more advice based on this information would be welcome.

Thanks

Darrell

 

[beyondtheblue]

Sounds very similar to what happened to my V/P 5.0Gi last year. It is hard to say without knowing the year of your engine but it is probably TBI (throttle body injection) same as mine. TBI uses two injectors unlike six in full fuel injection.

My problem turned out to be a dirty injector, unfortunately V/P say they are a non serviceable item and I finished up buying two new ones (not cheap) but cured the problem. I have since learned that the injector could have been cleaned using some kind of sonic cleaning method. If this turns out to be your problem I suggest you try cleaning them before forking out for new ones.

This is a link to a cleaning company I spoke to http://www.injectorcleaning.co.uk/

 

[trying]

A misfire / losing power under load may well be an ignition problem rather than a fuel problem. Generally a fuel starvation problem will also be evident (although maybe not quite as obvious) when revving the engine in neutral whereas an ignition fault will be apparent when revving the engine under load.

It would be worth checking the ignition system.

Ref the last post, yes injectors can be ultrasonic cleaned, but i'd still check the ignition sytem through.

 

[DarrellH]

Hi,

Thank you both for your replies, a bit more info Beyondtheblue, the year of the engine is 1997-1998, engine type -4.3GIPBYCCE and looking at the schematic on MarinePartsEurope sounds similar to yours - good to know about the Fuel Injector Cleaning company, the engine will rev up to 3 thousand revs with no misfire and will sit there running with the boat moving with no problems, but Trying, I'm certainly not discounting it and thanks for the information.

Thanks

Darrell

 

[beyondtheblue]

Darrell

Yes it sounds TBI. Its simple to check the injectors, just remove the flame arrestor cover and you will see the injectors working (or not) the picture shows the right hand injector spraying fuel but nothing from the left one. If yours are both working then go down the ignition route . BTW you can briefly swap over the plugs on the injectors to check a wiring fault on the leads.