what controls cranking injector pulse width
 

On a MEFI 1 is there anything that controls the cranking injector pulse width besides TP sensor and coolant temp? When its around 7ms it fires right up but when its around 12ms it will not take off. My TP is set to .43 volts at idle and coolant always looks close.

The MEFI 1 is not that smart, and I'm thinking there is something else going on. When motor starts cranking the ECM looks for the Dizzy to start firing before the injectors start. I would look more at spark

I could pull the distributer out and put a new pickup in. But every time i have the computer hooked up it shows engine rpm when cranking.

My comment comes from if there was good spark it should fire up, so long as its not flooding. Don't see 12ms causing it to flood.

Have you tried giving it a very slight bit more throttle?

My MEFI 3 when cold will crank 2 or 3 seconds before firing up. When hot it doesn't even get a full revolution

If we are looking at the same tables, the Crank BPW Multiplier vs TPS is part of the flood clear mode logic. This should be a percentage based multiplier and not a ms term.

I can give you the values from a stock Merc table that work for me if that would help.

Did you wipe out the original tune? Are you starting from scratch? The reason I ask is I have never had to touch or modify this parameter when tuning.

The three parameters I see affecting Cranking BPW are Baro, TPS and Coolant Temp.

There is a threshold value for spark/fuel for engine running in the constants/scalars section. It is my understanding that above this threshold the engine is considered to be running and not use the Crank values stated above. This can come into play as it determines which scalar or constant to use.

It acts like its flooded. I don't think i have tried just cracking the throttle for a long time. usually i try low idle and if it don't go or starts and dies i go to 3/4 throttle where the injectors are shut off according to the computer then if its being stubborn it will almost start but not quite. On normal day with this boat first start - procedure is crank a few seconds stop then second time i hits right off and after warmed up starts right off also.

I have no business trying to change tunes. I mailed it to Ben Bowman and he did it for me. It worked great for a while and even now if it will start it still runs great. Is the barometer sensor the same as the map sensor?

Don't think a M 1 has a clear flood mode, a M 3 does
The barometric air pressure is measured by the MAP

Need some input from Smitty

I don't have my mercruiser book with me but it said about 75 percent throttle and on my laptop key on engine off you can see the running injector pulse width climb until you get to about 3/4 throttle then it goes to zero then after you open the throttle past a certain point the injector pulse width comes back to a lesser value.

MEFI 1 does have a flood clear mode.