Mercruiser 5.0 EFI won't start

[Luv'n Life]

In late December, one of my manifolds started leaking into the engine. Over the winter, I replaced the manifolds and installed rebuilt heads. When completed, I started the engine on ear muffs. After about 15-20 seconds the guy at the marina helping yelled to shut it down because there was no water coming out, so I did. Since that time, I have been unable to get it to start. I have gone back to basics several times rechecking everything. Compression OK, timing rechecked, valve adjusted, new plugs, plug wires. Coil, distributor cap rotor, rechecked firing order. The engine is getting fuel, enough to flood the engine in short order. It sounds like it wants to fire but just won't kick off. The computer has been checked and appears good. The motor is a 2000 with the MEFI 3 computer. If you have any suggestions something else to try, I would greatly appreciate them. My wife says she will send $100 to any one can tell us what will gate it started.

 

[Strecker25]

An easy thing to check and probably not likely, but what is the voltage at the battery when it's trying to crank over? the ECU is sensitive to voltage and my understanding is that if the battery is old/weak/low it may sound like it's cranking good but you won't get ignition. That was my symptoms when one of the batteries was on its way out but the emergency crossover start would immediately fire that engine if the other one was running

 

[SAshton]

Try WOT and hold it until it starts and then back off


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[scoflaw]

compression, fuel and timed spark........which 1 are you missing ?