4.3L EFI Merc I/O, Have fuel and spark, won't start.

Jughead

Member
Hello,

Here is a little history of my motor and I hope somebody will be able to help.

This summer I got salt water in my fuel tank through my tank vent. It filled the water separating fuel filter and ran through my motor stalling it out.
I drained the tank and refilled with good gas.

Now my motor cranks over but will not fire. It is getting fuel as evident by viewing fuel spraying in the throttle body. I pulled a spark plug, it had some rust on it and it is getting spark (although it is orange? should it be blue or white?).
Will not start.

Please if anybody has any ideas where to start that would sure help. Thanks a lot!
 
I would start with a compression check and go from there.
 
It could still have fouled gas in the line between the tank and the motor. if saltwater stayed in there too long it can cause a bunch off problems like fuel pump, injectors, etc. Like previously mentioned compression, then spark, fuel, air, timing, then call a mechanic if that doesnt pan out.
 
Problem with salt or salt water is that in liquid form it conducts electricity (ie you you would lose your spark as soon as your plugs flooded). As soon as it dries it acts as an insulator (ie any residue left on your plugs will insulate your spark). I would be inclined to pull all your plugs and clean them or replace them. Then while your plugs are out I would put a small shot of oil in each cylinder so any dried salt or material can be carried out your exhaust.
 
I hear you. Once water gets past all filters and into your injection system, its a pain in the butt to resolve. You probably will need to remove all spark plugs and crank engine over with0out them in there. This should displace most of the water. Clean and possibly heat spark plugs before reinstalling them. You may have to do this more than once. Good luck.
 
when your take plugs out put a little gas down the hole motors need three things air fuel and spark
I wouldnt be puting any fuel down the spark plug holes, If he should happen to dump too much he could get a hydraulic situation or cylinder wall washdown, its EFI let the injectors do the dumping, plus theres not much room on these 4.3's to get anything down the plug holes and you'd probably end up spilling it into the bilge,
he did mention orange spark, it should be nice and bright blue, orange is weak and probably the reason for no start, when your checking for spark make sure that spark plug is grounded nice and tight against clean steel on the engine it should be nice and blue,
the concern here is that the engine ingested enough water to stall it out, that is because water does not compress and the engine actually hydrauliced and may have bent connecting rods, best advice above is to start with a compression test and make sure it is all even, if there are any really low ones I would not fire that engine, if a rod breaks it will usually come out the side of the block.
don't mean to sound so negative, just warning of what can happen when water enters an engine.
 
I wouldnt be puting any fuel down the spark plug holes, If he should happen to dump too much he could get a hydraulic situation or cylinder wall washdown, its EFI let the injectors do the dumping, plus theres not much room on these 4.3's to get anything down the plug holes and you'd probably end up spilling it into the bilge,
he did mention orange spark, it should be nice and bright blue, orange is weak and probably the reason for no start, when your checking for spark make sure that spark plug is grounded nice and tight against clean steel on the engine it should be nice and blue,
the concern here is that the engine ingested enough water to stall it out, that is because water does not compress and the engine actually hydrauliced and may have bent connecting rods, best advice above is to start with a compression test and make sure it is all even, if there are any really low ones I would not fire that engine, if a rod breaks it will usually come out the side of the block.
don't mean to sound so negative, just warning of what can happen when water enters an engine.
Another bit of bad news is that injectors and water do not get along and some of your injectors might be damaged. Sorry.
 
Thanks everybody.

I'm going to tackle it this weekend.
Going to start with plugs and distributor and go from there.
 
check the compression while you got the plugs out, its ways easier to do it now and adds piece of mind!
 
If you get too much fuel and a mixture of water in the combustion chamber that can cause rod damage and thus the need to do a compression test, but only after you drain and completely dry everything out. Afterwards change the spark plugs and go from there. When you tried to start the motor, did you hear anything?
 
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