Volvo Penta 4.3L won't accelerate

[mjs22]

Posted earlier about setting ignition timing. I changed the cap, rotor, plugs and set the timing using volvo part to set initial timing to 0-1° BTDC.<br /><br />Took out for a ride. Would not go above 35 mph at first (will usually run up to 54 mph)and accelerated there slowly. Then after about 10 minutes the engine ran even rougher and would not go above above idle. Had to idle back in. In neutral I can get the engine to rev up but not under load. <br /><br />I checked the coil according to a GMC repair manual I have and it checked out okay for expected resistance when not connected.<br /><br />What else can I do? The old plugs were carbon black indicating to me weak spark or rich fuel mixture. Do I need a carb rebuild?<br /><br />Earlier in spring I had a water in gas issue so I drained the tank and fuel water separator and solved that. It ran great all summer but I know the carb has some deposits because early on I had something breaking loose and clogging a jet every now and then. Could I have an internal clog or stuck float?<br /><br />Any help would be great.<br />Thanks.

 

[navigator336]

Re: Volvo Penta 4.3L won't accelerate

Sure sounds like carburetion to me. The fuel/air mixture is too rich. If it's smoking (black smoke)at idle, the power valve (or acceleration needle)may be stuck open or deteriorated. If it's not smoking at idle, check the air bleeds for the main circuit. These feed the emulsifying tubes with air to pre-mix the fuel prior to the venturi. In the last year, I've had these blocked on a marine in-board, a small outboard, and a motorcycle carb. For a good reference document on the air bleeds go to:<br /> www.grapeaperacing.GrapeApeRacing/tech/carbbasics.cfm.

 

[navigator336]

Re: Volvo Penta 4.3L won't accelerate

I forgot to ask about your ignition timing. Does the manual say to set it at 0-1 BTDC? That seems awfully retarded to me. What type of distributor do you have? Many HEI systems require a timing shunt to set the advance correctly.

 

[mjs22]

Re: Volvo Penta 4.3L won't accelerate

I used the volvo part 885163-3 to shunt the ignition and set the initial timing. A service bulliten from Marine Mechanic<br /> http://marinemechanic.com/volvo/sb-34-2-5.htm <br />claims the ignition timing should be 0 or 1 ° BTDC depending on which model I choose (mine is a 1996 volvo penta 4.3 L PNCS. I do have EST so I think this set the timing correctly. Thanks a bunch for the info on the carb. I will check it out.

 

[mjs22]

Re: Volvo Penta 4.3L won't accelerate

navigator336 your link to the carb basics does not seem to work. Is it correct?

 

[navigator336]

Re: Volvo Penta 4.3L won't accelerate

Sorry about the link. It is:<br /><br />www.grapeaperacing.com/GrapeApeRacing/tech/carbbasics.cfm

 

[loadnet]

Re: Volvo Penta 4.3L won't accelerate

If it was running lean I would expect you'd hear a slight multiple popping sounds from the carb and an occasional weak backfire at WOT.<br /><br />I also would think the plugs would be clean.. not all carbon up? because weak spark can melt plugs they get so hot.<br /><br />Sounds like..<br /><br />- weak spark<br />- bad fuel<br />- or good spark - but at the wrong time.