Plz help!! 03 Z150TXRB, no spark cyl 6

[refimike]

I have a 2003 z150 txrd with 300 and some odd hours on it.

I have no spark in cylinder 6 when checked with inline tester as well as by physically looking at the plug. It is new as the day I put it in.

I have done the following:
Fuel system completely done from tank to VST and all other filters/lines up to hp basket filters all new. (Needed done anyway) Also just got back all injectors from brucato, flow tested and cleaned and 1 was replaced so fuel system is completely good. Yds also shows all good fuel pressure as does physical pressure gauge on mid pressure Schraeder valve checks out as well. I'm 100 percent confident that fuel is not the issue at this point.

On elec side, I have tried 3 separate spark plugs, I have new coil, wire and boot on suspect cylinder, and have swapped others just to make sure one of the new items wasn't faulty. Still never any sign of spark on both inline tester and spark plug is always clean pure white and wet with fuel. Zero sign of ignition.

I've also replaced the neutral/shift position switch.

Yds software also shows cyl 6 is firing even when it isn't.

No other codes have shown and no history of any other codes.

With key in on position I have verified 12v to all the coil packs so the harness is good.

I don't have the harness to check peak voltage at the pulsar coil but I believe that's the next link in the chain and since I've already dumped so much on this thing I figure why not another couple hundred....
Was planning to order one unless you
you all have any other ideas or if you think I'm barking up the wrong tree.

Lastly, compression is pretty even across the board. With an expensive tester I get 115 on cyl 5 and 6 and 120 on the rest. The cheap one I have shows 105 and 110 respectively.

Anyways, I have occasionally gotten spark on this cylinder but it's been a while since I last did. I can't find anyone that's willing to work on it and being as there is no sign of catastrophic failure happening I'd really like to try and get it running right.

Please help....

[99yam40]

I thought all z motors did not fire all plugs under some conditions.
under what conditions are you testing for spark?
and what about the other plugs under the same conditions?

[refimike]

It's an hpdi. Does not fire cyl 2 and 3 when in idle. All six should fire when cranking and should also fire when in forward gear. No matter the condition, never spark on cyl 6.

Always testing while boat is in the water as well. It's on a lift.

No spark regardless of rpm, neutral or in gear and only ever cylinder 6 that never fires.

[99yam40]

if it has 12 v then I would chase what opens and closes the negative side to cause spark.
bad connection or wire maybe?
hope it is not the ECU

[refimike]

Andy from over at SIM seemed to suggest the same. Looks like I need to check black brown wire from the coil harness to pin 58 on the ecu.

Will update shortly.

[boscoe99]

If no spark why in the world all of the time and expense of messing with the fuel system?

Knowing that the neutral position switch does not affect spark on the number six coil, why was the switch replaced?

Do you have the service manual that tells how to check the pulser coils? You don't have to have the test harness to check the pulser coils for output.

If the pulser coil outputs voltage then test the connection and the wire from the #6 pulser coil to the ECU. If the wiring to the ECU is good then test the ECU for its output to the #6 coil. Also inspect the ECU input and output pins to the affected wires.

[refimike]

Great questions boscoe. The motor was new to me in that I recently bought the boat and I was daily certain that the fuel system had never been properly cared for when I noticed that there wasn't even a paper filter inside the bowl under the cowl. At that point I figured better to be safe than sorry and just replaced all the filters and having not had a paper filter was concerned injectors could have been pretty dirty. Turned out to be a good idea because 2 injectors were lean and one was still lean after cleaning so that one got replaced but the rest were cleaned and adjusted. Fuel Lines were replaced due to 1 line having collapsed so I figured best to do them all if 1 was collapsed which also hinted at ethanol being used. I use rec-90 now but didn't really know the history so I figured it was better safe than sorry to go through the fuel system since these motors are known to hate unclean fuel.

If this torrential rain for ever stops today I plan to test the continuity of that wire. My service manual does not go into detail on how to test it correct output from the ECU. Whatever manual I have it does not seem to be very detailed. Came with my yds software I bought on the bay. If you or anyone else could point me in the right direction to get a better one any advice would be appreciated.

[boscoe99]

[boscoe99]

[boscoe99]

[refimike]

Well, I am very happy to report it was indeed a corroded wire from the ECU to neg side of coil. Boat starts and runs like a top now. THANK YOU so much for your help! I never would have found this on my own.

Now, unfortunately, I'm all of sudden unable to keep the boat in gear at anything above an idle. So I guess Ill be starting a new thread for this issue. Seems like maybe misaligned shift linkage. I did just have the lower replaced. Ughhh

[refimike]

It was a spun prop. Not sure how that happened as I have little hours on it and hit nothing but all is well that ends well. Thanks again for your help everyone.

[99yam40]

did you get the proper lower unit and prop?
what kind of hub was it?
seems like I remember reading some motors needed special lower units that helped keep prop hubs cooled with a stream of water, or the hubs would fail
but I do not remember which motors those were.
maybe on bass boats or boats with jack plates that run with motor high

[TownsendsFJR1300]

seems like I remember reading some motors needed special lower units that helped keep prop hubs cooled with a stream of water, or the hubs would fail
but I do not remember which motors those were.
maybe on bass boats or boats with jack plates that run with motor high

https://www.yamahaoutboardparts.com/...-on-lower-unit