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Mercury 6.2 MX hard to start

I have a Merc 6.2 MX engine here at the shop that is hard as hell to get started at it's first initial start up. Engine sometimes pops too. Fuel filters are new, pressure is good, IAC has been replaced etc. Can't figure this one out, any and all help is appreciated!

Randy

Tell us your symptom in detail. Is the engine turns over easy/fast only it doesn't start right away?
Checked the crank sensor [ near the harmonic balancer] wire plugged in properly? Checked the bolt tightness at the 90A fuse block on the starter?

Quote:

Originally Posted by spectras only (Post 3727785)

The engine turns over fine, acts like it is getting no fuel, but it is. Have to open the throttle up and play with it and finally it will crank. Never thought about that crank sensor, I will check that first thing tomorrow. Thanks for replying.

That 90A fuse block gave me havic for about 3 months, mine started but wanted to hiccup, Spectras only lead me to the 90A fuse block, I took mine off cleaned it and tightened it and now no problems, there's also a similar fuse block on the trim motor and it was also loose on my boat.

Quote:

Originally Posted by osur866 (Post 3728285)

Thanks again, will check that too. Appreciate all input.

Quote:

Originally Posted by baja24outlaw (Post 3728533)

Thanks again, will check that too. Appreciate all input.

OK, fuse block is tight and clean, crank sensor plugged in correctly, engine spins over nice and fast, but doesn't want to start. Can hear fuel pump pressure up just like the opposite engine, but when you turn the key she just spins over. ocational hick up and a little back spiting through the throttle body, this is driving me nuts! Could the crank sensor cause this issue, it is original? Acts almost like it's out of time, these engines have never been touched other than oil changes and water pumps impellers.

"Occasional hiccup" , it could well be the crank sensor that you may find at a GM service department cheaper. Too bad you don't have twins to swap them out to see if it's the crank sensor or not. If you have a multimeter, I'd check continuity through the 90A fuseblock, even though it looks clean. Remove the battery cable at the batt post first. You could also, temporarily remove the fuse block and reconnect the cables for a test run. Unplug and re-plug all the connectors that goes to the ECM555 as well ,squirting some contact cleaner into the female connectors.There are some fuses near the ECM to check too.Computer driven engines [ in cars or boats] are voltage sensitive and sometimes a 0.5V drop can cause ignition problems.
I had three Cherokees and the 1990 and later models had this problem with the waterproof crankshaft sensor connector in the back of the engines.All it needed was to spray some contact cleanerin the connector and it was good for another year. Friend worked at a Chrysler dealership as a service manager, told me the horror story that they would replace the distributor charging $$$ to poor customers, finding out it didn't fix the problem. Took the service dep a while to figure it out after hundreds of customers were duped . Same scanario was with the V-6 Ford Probe a friend had. She had the distributor replaced and a charge of around $800,lol.
The small ign coil unit next to the distributor could be at fault as well.

cam sensor . . . this comes up every once in a while with the 08 and up trucks.

Something else you could change pretty cheaply would be the ignition and fuel pump relays I did that also, but in the end it was the fuse block on the engine, I had about a .5voltage drop across the block before I cleaned mine and tightened mine up, afterwards I had only .1 and problem solved, my problem was after it was running underway.
Might also clean and make sure the main round wiring harness is clean and secure on the back of the motor, I cleaned each and every female pin and some where a lil more dirty than I would have thought, also make sure theres a hose clamp around it and it's plugged in tight.

Side note, sure the wires are in the proper firing order??
I once got mine out of wack once while changing plugs I reversed a couple, felt like a winner after I realized what I had done