MX 6.2L MPI No Spark
 

Trying to figure out a no spark condition on a 2001 6.2lx. I’ve checked the power input to the coil, and I have 12.5v. I get this when checking power wire while connected to coil, in reference to engine block ground. If I check for power in reference to the negative wire going to coil, I don’t get it. Not sure where the ground for the coil comes from as I don’t have a wiring manual. I’ve swapped coils and no change. Also swapped coil to distributor wire, no change. Can someone tell me what triggers the ground on the coil?

Is this motor able to be plugged into a scanner where you can see live data? First thing I'd do is see if it shows cranking rpm coming from the crank sensor. I'm assuming being a 6.2 it's fuel injected with no distributor? The ecm won't fire the coils if it cannot see a minimum cranking rpm & cylinder firing position.

What's your serial number?

0m046275

negative. Has typical distributor setup

Merc’s 6.2 of that genre (sp?) is a conventional 23* sbc with 377cid’s.

I have heard if the 6.2mx and 6.2MPI but not 6.2lx. I don’t get out much. :)

Either way, does your 6.2 have the ‘crab cap’ distributor system as pictured ?


https://cimg2.ibsrv.net/gimg/www.off...883d83017c.gif

oh, no kidding. Yours is the few with the Thunderbolt V distributor ?

See:
https://www.mercruiserparts.com/mx-6...03-thru-0m2999

Have you gone thru the thunderbolt dist no spark flow chart ?

no, standard distributor. Correction, it’s a MX 6.2l MPI .

no, I need a service manual. Trying to search the correct manual to purchase now.

https://cimg2.ibsrv.net/gimg/www.off...f6d73a9c1.jpeg

Thanks. I don’t have a spark gap tester, but can try the initial steps.

Don’t need that per say. Regular spark tester (glass bulb type) or spare plug put in a ignt wire and ground strap grounded to engine.

The negative for the coil comes from block ground, not negative terminal on coil. Neg side of coil is what the ECM grounds to cause the coil to fire and also is where the Tach receives signal. Disconnect the gray wire on the Tach to make sure the Tach is not shorting out

TBV but will not be able to use the troubleshooting flow chart due to TBV module is not used.
Disconnect the wires from the module inside the dizzy. Measure ohms between the 2 terminals and see if its greater then 100 ohms. If less then 100 replace pickup

Your wiring diagram
https://cimg8.ibsrv.net/gimg/www.off...24c1d56277.jpg

thanks for the tip

thanks. I’ll check this out tonight. I have a new wire set, cap and rotor, coil, and ignition module coming. Everything looked ugly, so I’m putting new in. But I’m going to look at module tonight to verify that is the problem.

Any help with which manual applies to my engine? Trying to find one on EBay. Thanks

Spark
 

Is there any other reason why the system wouldn’t trigger the ground for the coil? Only thing I did was change the sea water pump since this engine ran last. Crazy how one day it runs fine, next day won’t even start.

Nope. Not at all.

And thank your stars it did that vs while out on the water. :thumbs

On the later mpi’s there is a crank sensor and it is near lower left of timing chain cover which is just over the sea water pump.

later mpi’s, meaning not this engine? Or this one has it?

No 24
Your motor is during the change over time. After yours they went to HVS dizzy and crank sensor

x 2 :thumbs (HVS is the ‘crab cap’d distributor)

gotcha

looks like #24 covers 5.0 and 5.7L, not seeing 6.2 as part of that.

Ignition module
 

Where are you guys usually running the ground ring terminal to on the new module? Old module doesn’t have the ground.

Tach
 

Also, where does the “grey” tach wire interface? I didn’t see that on the coil. Just a power and a ground in the coil.

What ever is close by. Maybe the ECM bracket, relay or other. Then there is also maybe the 10 pin engine plug screws that hold the plug. Need to clean the paint off

There is a engine to MPI harness connector which changes the gray tach to a white wire going to the coil. With a carb you could just remove it off the coil, but MPI need to take it off the back of the Tach

I did have the gauge cluster pulled forward, so I may want to check that.

Okay, now going somewhere. What where you doing in there ? A wire hooked back up wrong (especially tach) or pulled off can cause a no start.

I go right to main ground stud back of engine.
Just a personal preference. No fooling around there. :)

I was getting a picture of the port voltage gauge so I could get a replacement. Didn’t do anything other than that. But I’ll double check to see if there are any obvious issues with the Tach wiring. If the tach wire did become disconnected, which I doubt, why would that create a no start issue? Wouldn’t it just make the tach inop?

Thanks

Correct, If disconnected and not grounding out, Tach is inop and not the cause of no start

copy that, thanks

Pulled the module tonight. Didn’t have power coming out of module per flow chart. Ohmed out the sensor, it was open. New sensor is also open though. Installed new module, cap/rotor, and coil. Fired right up. Btw, I see the Stbd engine has already had the module replaced with the new version.

thanks for the help guys.

Okay, cool. :thumbs