Massimo MSU 500 won't start

[Turkey 20k]

Strange problem.  My Massimo is getting fuel, fire, compression.  Injector is working.  Okay if I pop the injector off of the intake, the engine will run till the fuel that was injected in the cylinder is gone. Maybe a few seconds.  When I reinstall the injector it won't start.   Please help.  Valve or timing issue.  Thanks.  PS -  Also if I remove the intake valve cover and turn the key the fuel mist blows out.  What is the cause of this?  Thanks for any help.

[Ben1098]

The P.S. has me thinking......you mention "Fuel mist" out of the valve rocker cover.  All you should is basically NOTHING at crank speed.  Any vapors blown out are from blow by (past the rings) into the crankcase.  IF you are OVER FUELING and wetting down the cylinder walls (that is, washing off the oil coating) you will have blow by.  Oil coating helps seal the rings.  That is why an engine that has set (dried out) and low compression is given a shot of WD-40 or any light oil to seal the rings.

This leads to the next thought.....If over fueling, the raw gas will "drain" into the crankcase and dilute the motor oil.  Check motor oil level.....too high?....too thin?.....wipe on tissue and sniff the oil....Gassy smell?....will light off with a burn test (soak up some oil on a paper towel and see how fast it starts to burn).  Oil basically won't.  Diesel will start slowly but take off.  Gassy oil....if you value the hair on body parts...hold at a distance with long needle pliers!!!!  Gassy diluted motor oil will add to the fuel/air mixture via the breather tube.  Similar to a turbo seal failure on a diesel......RUNAWAY even after the injector pump shut down...very bad ending!  Drain oil and replace filter....won't get it all (always some oil remains that cannot drain) but will dilute the gas.  BONUS:  Pulling the vent tube will clean up a mystery RICH run be it carb or FI (everything is correct BUT) after the motor warms up and cooks off the gasoline----sorta like an EGR Evap system.

Slop fuel never lights off or barely runs depending on the degree of "slop".  You state pulling the injector, the engine runs until it runs out of fuel.  ARE you leaving the injector hole OPEN.  This will allow lots of fresh air into the cylinder and will light off a rich mixture and then die because no more fuel is injected.  ASSUME the ECM is sending the correct pulse width to the injector for now.  Injector can hang and "piss" instead of spray.  The key is the 14.7/1 air fuel mixture.  Too RICH.....runs heavy and then dies at idle.  May start to run, but as the leftover UNburned charge gets richer-----labors-----pukes.  Too Lean......no start....fuel is there but cannot lite off.....then as it builds up, you get a pop only to be to lean again.....repeats the cycle.....THIS IS HELL ON THE STARTER AND REDUCTION GEARS.  This also load the oil with gasoline (unburned).  Again the fuel correct, look for a restriction in the air intake (not enough air).....common causes....CRITTERS...mouse house....full of acorns....rag pulled in for a nest, and so on.  EASY TEST:  Remove the air intake plumbing at the throttle body.  Plenty of air now.  If runs, check out the air box/plumbing.  IF NO RUN....next section.

Too much fuel:  Time to test the ECM/injector system.  ANY BAD input signal to the ECM will make the fuel delivery too much or too little.  Pull spark plug.  Read the insulator tip color.  Just right is a light TAN color.  Very WHITE...blistered LEAN.  RICH has a BLACK, SOOTY, shiny black/wet black (carbon is fuel soaked).  If really black, they might fire outside to the engine block BUT "blowout" under compression even at idle.  If not too bad, they might run at idle but when sputter and die when a heavy  demand on the ignition system (acceleration) is applied....drop in a new plug for testing to just to reduce the possible list of  problems.  Pull the connector to the fuel pump (under the pass seat).  This is the fuel pump power (from ECM) and fuel level signal.  No guessing if you found the right fuse/relay.  This will stop the fuel delivery (40 PSI) to injector.  Injector will still get pulses.  You will shoot a short burst of starter fluid into the air box (plumbing reattached and filter OK).  The motor should lite off and run until it is out of fuel.  Repeat.  Repeat.  If works every time, give a double burst when running to "sustain" the run. Repeat.  If this works, you have the ECM/input signals to ponder.  This gets deep for most.  Coolant temp sensor....open circuit RICH.  Thinks it is at the SOUTH POLE -40 C.  Like a choke for carb.  Throttle position sensor.....wrong fuel mix to match the air thru the butterfly valve.  MAP sensor/ambient air temp....measures engine load....wrong signal rich and lean.  O2 sensor....signal to tell if RICH or LEAN.  Has heater circuit to get it up to operating temp.  Heaters open (toaster that does not toast).  Throw in smashed wires, critters that live the taste of plastic insulation on wires, stick run thru harness, heater shorted to SHARP edged heat shield above the exhaust.  More common failures are the MAP/IAT (intake air parameters) and O2 sensor.

You got a lot of checks to get down to where the problem is. 

BTW, the ECM is a DELPHI MT05 small engine unit capable of a twin (2 inputs for the two cylinders individual O2 sensors).  Check out web page for specs, pin outs for both the Grey and Black connector (PDF format)....magnitudes better than the "manual" supplied when first built.  Only covers the electrical engine management with a generic diagram of the analog input(s) and the outputs like fuel pump, ign coil, etc  CHOW.

 

 

[Turkey 20k]

5 hours ago, Ben1098 said:

The P.S. has me thinking......you mention "Fuel mist" out of the valve rocker cover.  All you should is basically NOTHING at crank speed.  Any vapors blown out are from blow by (past the rings) into the crankcase.  IF you are OVER FUELING and wetting down the cylinder walls (that is, washing off the oil coating) you will have blow by.  Oil coating helps seal the rings.  That is why an engine that has set (dried out) and low compression is given a shot of WD-40 or any light oil to seal the rings.

This leads to the next thought.....If over fueling, the raw gas will "drain" into the crankcase and dilute the motor oil.  Check motor oil level.....too high?....too thin?.....wipe on tissue and sniff the oil....Gassy smell?....will light off with a burn test (soak up some oil on a paper towel and see how fast it starts to burn).  Oil basically won't.  Diesel will start slowly but take off.  Gassy oil....if you value the hair on body parts...hold at a distance with long needle pliers!!!!  Gassy diluted motor oil will add to the fuel/air mixture via the breather tube.  Similar to a turbo seal failure on a diesel......RUNAWAY even after the injector pump shut down...very bad ending!  Drain oil and replace filter....won't get it all (always some oil remains that cannot drain) but will dilute the gas.  BONUS:  Pulling the vent tube will clean up a mystery RICH run be it carb or FI (everything is correct BUT) after the motor warms up and cooks off the gasoline----sorta like an EGR Evap system.

Slop fuel never lights off or barely runs depending on the degree of "slop".  You state pulling the injector, the engine runs until it runs out of fuel.  ARE you leaving the injector hole OPEN.  This will allow lots of fresh air into the cylinder and will light off a rich mixture and then die because no more fuel is injected.  ASSUME the ECM is sending the correct pulse width to the injector for now.  Injector can hang and "piss" instead of spray.  The key is the 14.7/1 air fuel mixture.  Too RICH.....runs heavy and then dies at idle.  May start to run, but as the leftover UNburned charge gets richer-----labors-----pukes.  Too Lean......no start....fuel is there but cannot lite off.....then as it builds up, you get a pop only to be to lean again.....repeats the cycle.....THIS IS HELL ON THE STARTER AND REDUCTION GEARS.  This also load the oil with gasoline (unburned).  Again the fuel correct, look for a restriction in the air intake (not enough air).....common causes....CRITTERS...mouse house....full of acorns....rag pulled in for a nest, and so on.  EASY TEST:  Remove the air intake plumbing at the throttle body.  Plenty of air now.  If runs, check out the air box/plumbing.  IF NO RUN....next section.

Too much fuel:  Time to test the ECM/injector system.  ANY BAD input signal to the ECM will make the fuel delivery too much or too little.  Pull spark plug.  Read the insulator tip color.  Just right is a light TAN color.  Very WHITE...blistered LEAN.  RICH has a BLACK, SOOTY, shiny black/wet black (carbon is fuel soaked).  If really black, they might fire outside to the engine block BUT "blowout" under compression even at idle.  If not too bad, they might run at idle but when sputter and die when a heavy  demand on the ignition system (acceleration) is applied....drop in a new plug for testing to just to reduce the possible list of  problems.  Pull the connector to the fuel pump (under the pass seat).  This is the fuel pump power (from ECM) and fuel level signal.  No guessing if you found the right fuse/relay.  This will stop the fuel delivery (40 PSI) to injector.  Injector will still get pulses.  You will shoot a short burst of starter fluid into the air box (plumbing reattached and filter OK).  The motor should lite off and run until it is out of fuel.  Repeat.  Repeat.  If works every time, give a double burst when running to "sustain" the run. Repeat.  If this works, you have the ECM/input signals to ponder.  This gets deep for most.  Coolant temp sensor....open circuit RICH.  Thinks it is at the SOUTH POLE -40 C.  Like a choke for carb.  Throttle position sensor.....wrong fuel mix to match the air thru the butterfly valve.  MAP sensor/ambient air temp....measures engine load....wrong signal rich and lean.  O2 sensor....signal to tell if RICH or LEAN.  Has heater circuit to get it up to operating temp.  Heaters open (toaster that does not toast).  Throw in smashed wires, critters that live the taste of plastic insulation on wires, stick run thru harness, heater shorted to SHARP edged heat shield above the exhaust.  More common failures are the MAP/IAT (intake air parameters) and O2 sensor.

You got a lot of checks to get down to where the problem is. 

BTW, the ECM is a DELPHI MT05 small engine unit capable of a twin (2 inputs for the two cylinders individual O2 sensors).  Check out web page for specs, pin outs for both the Grey and Black connector (PDF format)....magnitudes better than the "manual" supplied when first built.  Only covers the electrical engine management with a generic diagram of the analog input(s) and the outputs like fuel pump, ign coil, etc  CHOW.

 

 

Thanks for all the information. I will try to step through this. I'll let you know. Thank you 👍

[Turkey 20k]

On 4/22/2023 at 2:12 AM, Ben1098 said:

The P.S. has me thinking......you mention "Fuel mist" out of the valve rocker cover.  All you should is basically NOTHING at crank speed.  Any vapors blown out are from blow by (past the rings) into the crankcase.  IF you are OVER FUELING and wetting down the cylinder walls (that is, washing off the oil coating) you will have blow by.  Oil coating helps seal the rings.  That is why an engine that has set (dried out) and low compression is given a shot of WD-40 or any light oil to seal the rings.

This leads to the next thought.....If over fueling, the raw gas will "drain" into the crankcase and dilute the motor oil.  Check motor oil level.....too high?....too thin?.....wipe on tissue and sniff the oil....Gassy smell?....will light off with a burn test (soak up some oil on a paper towel and see how fast it starts to burn).  Oil basically won't.  Diesel will start slowly but take off.  Gassy oil....if you value the hair on body parts...hold at a distance with long needle pliers!!!!  Gassy diluted motor oil will add to the fuel/air mixture via the breather tube.  Similar to a turbo seal failure on a diesel......RUNAWAY even after the injector pump shut down...very bad ending!  Drain oil and replace filter....won't get it all (always some oil remains that cannot drain) but will dilute the gas.  BONUS:  Pulling the vent tube will clean up a mystery RICH run be it carb or FI (everything is correct BUT) after the motor warms up and cooks off the gasoline----sorta like an EGR Evap system.

Slop fuel never lights off or barely runs depending on the degree of "slop".  You state pulling the injector, the engine runs until it runs out of fuel.  ARE you leaving the injector hole OPEN.  This will allow lots of fresh air into the cylinder and will light off a rich mixture and then die because no more fuel is injected.  ASSUME the ECM is sending the correct pulse width to the injector for now.  Injector can hang and "piss" instead of spray.  The key is the 14.7/1 air fuel mixture.  Too RICH.....runs heavy and then dies at idle.  May start to run, but as the leftover UNburned charge gets richer-----labors-----pukes.  Too Lean......no start....fuel is there but cannot lite off.....then as it builds up, you get a pop only to be to lean again.....repeats the cycle.....THIS IS HELL ON THE STARTER AND REDUCTION GEARS.  This also load the oil with gasoline (unburned).  Again the fuel correct, look for a restriction in the air intake (not enough air).....common causes....CRITTERS...mouse house....full of acorns....rag pulled in for a nest, and so on.  EASY TEST:  Remove the air intake plumbing at the throttle body.  Plenty of air now.  If runs, check out the air box/plumbing.  IF NO RUN....next section.

Too much fuel:  Time to test the ECM/injector system.  ANY BAD input signal to the ECM will make the fuel delivery too much or too little.  Pull spark plug.  Read the insulator tip color.  Just right is a light TAN color.  Very WHITE...blistered LEAN.  RICH has a BLACK, SOOTY, shiny black/wet black (carbon is fuel soaked).  If really black, they might fire outside to the engine block BUT "blowout" under compression even at idle.  If not too bad, they might run at idle but when sputter and die when a heavy  demand on the ignition system (acceleration) is applied....drop in a new plug for testing to just to reduce the possible list of  problems.  Pull the connector to the fuel pump (under the pass seat).  This is the fuel pump power (from ECM) and fuel level signal.  No guessing if you found the right fuse/relay.  This will stop the fuel delivery (40 PSI) to injector.  Injector will still get pulses.  You will shoot a short burst of starter fluid into the air box (plumbing reattached and filter OK).  The motor should lite off and run until it is out of fuel.  Repeat.  Repeat.  If works every time, give a double burst when running to "sustain" the run. Repeat.  If this works, you have the ECM/input signals to ponder.  This gets deep for most.  Coolant temp sensor....open circuit RICH.  Thinks it is at the SOUTH POLE -40 C.  Like a choke for carb.  Throttle position sensor.....wrong fuel mix to match the air thru the butterfly valve.  MAP sensor/ambient air temp....measures engine load....wrong signal rich and lean.  O2 sensor....signal to tell if RICH or LEAN.  Has heater circuit to get it up to operating temp.  Heaters open (toaster that does not toast).  Throw in smashed wires, critters that live the taste of plastic insulation on wires, stick run thru harness, heater shorted to SHARP edged heat shield above the exhaust.  More common failures are the MAP/IAT (intake air parameters) and O2 sensor.

You got a lot of checks to get down to where the problem is. 

BTW, the ECM is a DELPHI MT05 small engine unit capable of a twin (2 inputs for the two cylinders individual O2 sensors).  Check out web page for specs, pin outs for both the Grey and Black connector (PDF format)....magnitudes better than the "manual" supplied when first built.  Only covers the electrical engine management with a generic diagram of the analog input(s) and the outputs like fuel pump, ign coil, etc  CHOW.

 

I hope I'm updating this post correctly.   When I disconnected the power wire from fuel pump she fired up and runs smooth till fuel is gone.  It'll keep going for about 20 or so seconds. If I keep shooting carb cleaner it keeps going.  When I reconnect the fuel pump wire it floods the cylinder.   Okay so do you think it's a sensor?  Making progress sir.  What do you think?  Thanks.

 

[Turkey 20k]

On 4/24/2023 at 4:46 PM, Turkey 20k said:

 

Okay after good info which is much appreciated I figured out the problem.  When the starting issue started I replaced the fuel injector with a new one.  The new injector has 4 holes versus two on the original. I didn't think anything of it when I installed it.  Any way it's putting too much fuel in and drowning the spark.  Fortunately I kept the old one. I cleaned it up best I could and reinstalled.  Reconnected the fuel tank wire and now she runs as before. I have ordered a new OEM 2 hole injector and hope to be riding again. Thanks for the advice on where to check.