496HO - Hard starting - Need help!
 

Starboard motor starts hard when cold. 3-5 cranks average to get to fire. After the motor gets warm and it is shut off it take 5-10 cranks to get to fire. Have changed: IAC, plugs, Crank Sensor, Cam Sensor, TPS has right volts, and switch from port side, and still has starting problem. Battery has proper volts. have changed all four solenoids - no change. Fuel/Water separtor is good. Screen is clean.
Have checked it on Merc scan tool - no codes that apply.
Thanks for any help,
Jeff

My suspicion is that it's probably a fuel pressure issue or fuel system issue.
Get a fuel pressure gauge and hook it up to the Schraeder valve and see if with key on, engine running the fuel pressure comes up to 41-43 psi. If it does not come up to that area of pressure it will not allow the injectors to spray properly enough fuel for a good start.

Best Regards,
Ray @ Raylar

496HO Hard Starting
 

Thanks Ray, but I forgot to mention the fuel pressure was checked. It was at 43psi when running. I have a couple of friends that are certified Merc mechanics helping me with it. We have tried most of he common problems but still have not found it.

Jeff

But does the battery/s have proper amps?

Your battery should be a starting battery with 800 CCA or 1000 MCA.

Wouldn't it be safe to assume it isn't a battery voltage / amperage problem if the engine is turning over vigoriously? Now, loose connections to the ignition or fuel pump would be another issue.

try this once put both batts on all start the good motor then try the other ,mine do the same thing if I start the stb. side first it starts slow .if I start prt.side first its ok ,my freind at marine tec in Oh. say,s to check for bad batt switch or corded wire

Fuel pump could be losing prime. Turn the key on/off several times to cycle the fuel pump and see if it starts.

496HO Hard Starting
 

I have tried starting bad motor first or second it does not make a difference. The boat has built in charger that I leave pluged in while on lift. This keeps the batteries charged. When the motor is cold it starts faster if I just turn on key and not let the fuel pump cycle. The fuel pump losing prime was my thought , but I have turned key on and off and it does not make a difference. The only common thing it seems to start cold quicker, but not like the port motor.
Thanks again for all your help.

I would check the fuel pressure regulator, when they go bad they usually start better cold than when warm.

If you advance the throttle a little will the engine then start? If so you may need to turn the idle set screw slightly to open the throttle a little further, which will take some load off of the iac motor. You might check iac counts when idling and see how high they are. They should go way up when first started and then settle back down once the idle stabilizes. Another trick that I do upon starting is cycle the key a couple of times before cranking. This will assure you have solid fuel pressure immediately upon cranking and the engine usually will start faster.

Bob Lloyd
Full Throttle Marine