1999 225 Mercury Optimax very weird problem, any help would be greatly appreciated!!

[Bowhunter/Ranger519vs]

Ok I will try to explain to the best of my ability on here...
So coils 2, 4 and 6 located on my left bank are tested they fire once and than lose power , I than hear a beep just like when you turn the key on. It doesn’t throw any codes on the computer. Coils 1,3 and 5 located on the right bank work just fine. If I switch all the coils from the left bank to the right and all the right to the left same result... left coils fire one and get the beep like when you turn key on, and right works fine... I hope your understanding what I’m saying up to this point, this is where it gets weird... now if I keep coils 2,4 and 6 plugged into the left bank wires and just screw them into the right bank they test fine with no problem. I don’t understand why they won’t test fine when screwed into left bank but work perfectly screwed into the right bank.. reminding you that I’m using the left bank wires the entire time, if that makes sense to you... blowing my mind! Any ideas or advice would be greatly appreciated!! Thanks
P.s I changed the ecm and it does the same thing..
sn- OG802957

[Savage]

Describe the Testing process better....."fire once then lose power" what is "power"????

What does "working fine" mean?? Motor running??

What is the MAIN problem that started all this "testing"??

[Bowhunter/Ranger519vs]

Was running my boat, everything seemed fine. Let off it to avoid some debris, when I got back on it the motor started to break up or misfire and turned off.. it start up up no problem but once I hit 1200 rpms it would break up again and stall by 1800 rpms. So I brought the boat home and my mechanic came over. First, he tested the coils to see if they were firing correctly. Right bank tested and fired perfectly, when the left was tested, let’s say he started with coil 2 all coils on the left bank fired sporadically. So we put the left bank coils on the right bank and the right onto the left and retested on the computer. Same result. At that point he tested everything leading to the coil to eliminate any possible reasons this could be happening. Everything tested good the way it was supposed too. No matter what we did the right bank would test fine and the left bank all coils would fire sporadically. So than we decided just to see what would happen to take coil 4 off the left bank (keeping it plugged into coil 4 wiring) and screw on the right bank where coil 3 should be and than tested coil 4. It tested perfect fired strong and the correct way, unscrewed it from right bank put it back on the left in coil 4’s spot tested the problem came back ( when coil 2 and six were plugged in they would all fire sporadically, when unplugged coil 4 would fire once on the testing board and than you would hear a single beep like when you turn your boat key on. Again, it was not throwing codes on the computer during this. I know it’s a lot, but trying to tell you exactly what happen. At no point in time during this testing was the motor running. And what I meant by working fine is that when tested it fired strong and correctly on the testing board plugged into the coils.
so the weird thing is that the right bank always works no issues, even if you take a coil off the left bank and continue to use the left bank wires, but just screw it into the right bank it works without a problem. Left bank won’t ...

[Savage]

HOW are the coils being "tested"????? Motor running? Timing light? CDS? spark tester?? Volt meter?

[Bowhunter/Ranger519vs]

6 coils spark tester, testing 1 coil at a time with the motor off. Running the test through his computer software... used a volt meter to check all the voltage (all good) etc... spent 8 hours yesterday testing pretty much everything you could imagine... couldn’t figure it out...

[lpugh]

Sounds like you saying if the coils are mounted in place with there fasteners that you get a single spark at key on, then none
Coils 1,3 and 5 grounds are common black wires that are connected together, find them and be sure they are grounded
2,4 and 6 a re common and separately grounded
Also be sure the coil plate is grounded, don't just look at them clean the connection and consider running a redundant ground from the coil plate to the negative battery cable where it attaches to the motor
Don't recall the specific layout on this motor, Maybe Don, Savage or Joe will add to this, I am a automotive guy, they have the daily experience I don't have

[Rip Bass]

As above,check the grounds. They are one common factor.

[Bowhunter/Ranger519vs]

All grounds were checked and we put a new grounds on coils 2,4 and 6. Still didn’t change the results. Is there one ground for the coil plate? If so, if the ground was bad wouldn’t that affect the right bank as well? I know the left bank and right bank are both grounded to the plate, is there another ground that I’m forgetting about?

[lpugh]

All grounds were checked and we put a new grounds on coils 2,4 and 6. Still didn’t change the results. Is there one ground for the coil plate? If so, if the ground was bad wouldn’t that affect the right bank as well? I know the left bank and right bank are both grounded to the plate, is there another ground that I’m forgetting about?

Not always, Right bank and left banks have their own separate ground circuits. I would recommend a voltage drop test on the ground ckt. Volt meter connected to the black wire at the coils and the ground test lead connected to the battery ground where it is attached to the motor, check this drop while the motor is being cranked. Any reading on the meter is undesirable voltage drop, up to one volt would probably not be a problem
Grounds can cause some really strange issues.
Might be wise to also drop test ecm power and grounds as well
Report back please

[Bowhunter/Ranger519vs]

Checked all the grounds and power.. all checked out.... even put a new ecm on it. My mechanic says he hasn’t ever seen anything like it in 30 years.... probably going to be something stupid when we find what is causing the problem.. At this point he has 12 hours into testing and troubleshooting anything he thought could possibly be causing it. I was hoping that possible somebody on her happened to have the same problem at some point and could point us in the correct direction.... my mechanic doesn’t want to just start throwing parts at it...

[Bowhunter/Ranger519vs]

Another weird thing is that the block pressure read 15.42 when motor was not running. Wasn’t sure if this was a default reading or something to be concerned about. Have no idea what would cause block pressure when motor isn’t running???

[EuropeanAM]

You stated you put all new grounds on the Port (2-4-6) coils. The grounds are part of the WIRING HARNESS, correct?

[Bowhunter/Ranger519vs]

Yes, all three have a ground that are connected together and grounded on the plate. The grounds tested fine, but we changed the connector anyway just to make sure. There is no physical damage when looking at the ground wires, they all look great...

[Bowhunter/Ranger519vs]

What I’m trying to say is that if I unplug coils 2 and 4, than I test coil six it will spark once and beep like I turned the key off and on. If I have coils 2 , 4 and 6 plugged in and test coil six. They will all fire sporadically and than beep like I turned the key off and on. Now if I unscrew coil 6 and keep it plugged into the coil 6 wiring but mount it on the right bank and test it. It completes the test perfectly.

[Bowhunter/Ranger519vs]

Sorry if I’m being confusing, trying my best.. I appreciate you guys trying to help me...

[lpugh]

Checked all the grounds and power.. all checked out.... even put a new ecm on it. My mechanic says he hasn’t ever seen anything like it in 30 years.... probably going to be something stupid when we find what is causing the problem.. At this point he has 12 hours into testing and troubleshooting anything he thought could possibly be causing it. I was hoping that possible somebody on her happened to have the same problem at some point and could point us in the correct direction.... my mechanic doesn’t want to just start throwing parts at it...

If you did not perform a voltage drop test as described, they have not been checked! How do you know that the coil plate is properly grounded?

[lpugh]

Another weird thing is that the block pressure read 15.42 when motor was not running. Wasn’t sure if this was a default reading or something to be concerned about. Have no idea what would cause block pressure when motor isn’t running???

Do you mean water pressure?

[Bowhunter/Ranger519vs]

Good question, I will ask him that. We couldn’t get the motor to run well enough to perform any tests while it was running... just talked to him we did run a drop test and everything was fine.

[Bowhunter/Ranger519vs]

On his computer it said block pressure... when I looked it up I saw posts that said block pressure or water pressure.. so I think so...

[EuropeanAM]

Block pressure should be (essentially) ZERO with engine OFF.

Unclear from all of the above unhooking, rehooking, moving, unbolting and swapping exactly what methodical "test" is determining there is no spark to a cylinder.

Unplugging coils can result in EST Faults.

If you clip a timing light on each plug wire, one at a time, do you get a steady flashing pattern?

I suspect there may be something else going on (possibly not even ignition related).