HELP! Mercury 250 EFI won't start, then later runs great. What could it be???

[bluewaterbug123]

Twin Merc 250 EFI's. Stbd engine cranks and cranks but won't start. Port runs fine. Swapped fuel lines, checked fuel bulbs, checked for water in fuel, fuel pump running and fully pressurized, engine appears to be sparking, but won't fire. <br />One hour later, engine fires at the turn of the key and runs great for a 30 mile trip. Next day starts easily and runs great all day. Third morning won't start after dozens of attempts and similar fuel checks. A few hours later engine roars to life on the first try and runs strong for hours. Fourth day sees similar results. There doesn't appear to be any pattern to it starting (not warmer/colder, same battery, same fuel, etc, etc).<br /><br />I'd really like to try to fix this myself before I call the shop. (I'd rather get more familiar with the engines so I'm better equipped if something similar happens again and don't have to limp home on 1 engine). <br /><br />Any thoughts on what it might be? Is there a way to check the ECM's and other stuff on the engine w/a volt meter only (no computer)? <br /><br />Thanks for any help.

 

[Clams Canino]

Re: HELP! Mercury 250 EFI won't start, then later runs great. What could it be??

Re: HELP! Mercury 250 EFI won't start, then later runs great. What could it be??

If you verify the non-starting motor is getting spark at the plugs (easy to do) then you can bet it's probably "something" in the system that controls the fuel movement. Intermittant problems are the worst to find. I assume you've checked for loose connections.<br /><br />Since you are short on diagnostic equipment, you could always try swapping the ECM's between the two motors - see if the problem follows.<br /><br />Perhaps someone with more experience in the EFI V6's can help more - I'm an inline dood.<br /><br />-W