I do not.

try cycling switch without turning motor over and see if there is a change . i think you are on the right track with the fuel pump

I replaced both of my mechanical pumps last year for maintenance, original with wasted oil in them. Ran fine for 1 hr then 1 engine started to lug and was really hard to start and keep running. Then it wouldn't start at all. Turns out my brand new Merc mechanical fuel pump had almost zero pressure when tested after we got back in. Installed another brand new one and problem fixed.

@HyFive578: sounds like it could be a "hot soak flood" condition. This is caused when the fuel pressure is fine but some or all of the fuel injectors are just dirty enough to let fuel seep into the cylinders when sitting for a while (say 20-60 minutes) with fuel pressure, causing a flood condition. The flood condition is of course cleared with extended cranking.

Had this on an 87 Corvette MPI engine, and it was cured by GM replacing the (presumably) faulty injectors under warranty. However, it can also be caused by fuel contaminants leaving residue on your injectors so that they don't close and seal perfectly. A good fuel injector cleaning procedure may cure things. IIRC this can be a pressurized can of cleaner that you attach to the Schraeder valve on the fuel rails while cranking.

The old engine ran and started fine with the new fuel pump. The problem didn't start until the engine was re-assembled with the new long block.

I think you may be on to something here. The need to crank the engine over and over again before it starts reminds me of a flooded engine. When the engine was torn down, my shop sent the injectors out to be serviced. I wonder if they were maybe damaged in that process or when they were re-installed in the rail. Pushing the throttle forward a little when cranking the engine helps it to start; any significance to that?

This problem is intermittent, so taking off the intake and checking the injectors every time this happens really isn't practical, is there something I can check right at the time when the engine fails to start to see if this is the issue?

I can't promise this will work, but a trick I used on EFI engines that I suspected were loading the motors is to pull the air intake tubing, open the throttle blade all the way and take a good long sniff. If I smelled raw fuel than I had a good idea my fuel pressure bleed off was going into the motor. Perhaps pulling the flame arrestor and taking a sniff might lead you somewhere? I would also measure fuel pressure and see how long it takes to bleed down after shutting the motor down compared to the other two motors.

Absolutely, pushing the throttles open would be allowing more air into the engine to help lean out the overly rich condition.

Think of holding a carbd engine gas pedal down half way or more when its flooded to get it to start.

Time to check fuel pressure and see how fast/slow it bleeds off compared to one of the good engines.

Thank you guys!! How do I check the fuel pressure?

There is a test valve on the fuel rail under the intake plenum. Looks almost like a valve stem on a tire. I have to double check but I think 41-43 psi at idle is the spec.