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Newbie asking for advice re: Massimo 700 not running


mahnoo51

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Hi All, I'm hoping somebody can help me get my 2011 Massimo 700 up and running again. It's a real workhorse when it's working but lately it's been giving me problems. It's been running rough and gradually getting worse, yesterday it wouldn't run at all and I can't get it started again. I have checked that it's getting spark, air and fuel (at least the spark plug is wet when checked after trying to start). The service manual/owners manual is worse than helpful. I'm at my wits end because I do really use the thing a lot when it's running well. Does anybody have any thoughts or advice?

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  • 1 month later...

TIP: Running the motor for short times will foul the spark plugs.....the ECM is mapping the cold start-up and will have a rich fuel mix....Run long enough to get some heat into the plug to self clean. Repeated short run times can kill the plug.

some T/S tips----you have an apparent rich F/A mixture OR the unburned fuel is wetting down the plug. The problem appeared gradually....start with the air filter. Pull shift and cover...debris on filter and or blocked intake (as in mouse house)...clean and reinstall.

Check for air leaks downstream....a LEAN mixture will not light off BUT can wet down the plug.

The above REPLY was the air vent for the fuel tank....they used be to routed into the intake runner...newer units have the hose elevated behind the pass seat. If removed from intake, PLUG off the connection...dowel pins work good.

Start with new plug or known good unit. Leave the cylinder open for now.

Remove all fuel sources.....to prevent over fueling....pull fuel pump connector---no more pump whirl sound on KEY ON and carefully pull the injector electrical connector...no fuel from residual fuel pressure.

Spin over the motor for 5 seconds. Install the spark plug now.

Spin over again....should not start.

Starter fluid....pop in a 1/2 second burst into the intake and crank. Motor should fire and run for a couple seconds....try again to be sure the only fuel source is the go juice.

Reconnect the fuel pump (no injector yet)....crank...should be a no start. Time for some starter fluid again....runs again and dies (good so far).

Reconnect the injector. Key on (pump pressure build up). should run now.

IF NOT OR RUNS POORLY or LUMPY...fuel system problem, ECM, and or ECM inputs.

Possible problems: Most common in order

BAD E10 fuel....phase separation, older than 3 weeks, moisture droplets. Drain and purge system. Best to get the NON-ethanol fuel as the rubber parts will last longer also.

Fuel pump problem---need around 45 PSI

Blocked injector----will dribble fuel...can pull injector and check spray mist.

O2 sensor failure----pull the connector...if runs better (NO INPUT SIGNAL---thus ECM defaults to a "safe" limp mode).....have also seen the +12v heater problem (too cold to work)...heater OPEN or an intermittent short to frame (like the exhaust sheet metal burr edge).

Harness failure in connector or the butt splices hidden in the trunk.

ECM failure.

Try these tips

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