Yamaha VZ150TLRZ 2 Coils not firing

[doughboy1]

On the advice of 99yam40 senior chief, I check my coils and spark plugs using an induction light. Two of the coils, 1 on the port side (top plug) and 1 on the stern side (middle plug), did not light the induction light. I change the plugs to plugs that were firing with the same results. My initial question concerned losing power when turning left. I did not check the pressure of the fuel flow; however, I was able to verify the filters, plugs, and I changed the fuel hoses. I am trying to understand why two coils going bad would cause the engine to lose power on a left turn. The engine appeared to be running rough at idle with the muffs on the engine.

 

[99yam40]

Re: Yamaha VZ150TLRZ 2 Coils not firing

Why did you start a new thread? Did you read the top thread about how to get the best results to your question?
You should just keep replying to the original, giving what you have found.

How and when did you verify spark to all the cylinders, was it at idle?

I believe the HPDI motors drop 2 cylinders while in neutral.

Do a forum search on HPDI motors and read up on the systems, troubleshooting, and maintenance. If you do not have a Yamaha service manual for your motor, get yourself one. It will pay for itself many times over and save you and us lots of time

 

[doughboy1]

Re: Yamaha VZ150TLRZ 2 Coils not firing

Thank you for the help. I have ordered the Seloc manuals from iboats. The manuals should be here this week. I had read where some of the hpdi engines dropped 2 at idle. The coils were checked at idle. I will swap the coils around to check if that is the case.

 

[rodbolt]

Re: Yamaha VZ150TLRZ 2 Coils not firing

buy new coils and retest.
then you will have 2 spare coils.
either you are running the test in nuetral and the system is working as designed or your nuetral position switch is broken.
the ECU is doing what its been commanded to do.
at idle on the muffs that motor sounds blown up.
go chase your fuel problem. most likly the VST filter and the medium pressure inline filter.
that engine shuts down #2 and #3 cylinders in nuetral,will shut down two more cylinders if you attempt to rev it past 1800 RPM in nuetral.

 

[doughboy1]

Re: Yamaha VZ150TLRZ 2 Coils not firing

rodbolt
I changed the medium filter and cleaned the VST electric motor filter. The VST tank was very clean, no ring in the bowl nor was the filter dirty. I can change the low pressure fuel pumps or buy a vacuum pump and check the low pressure pumps.
The engine is still bogging down on a left turn. The engine starts easy, runs great, idles good (900) and does great until the engine is turned for a left turn. It does not matter what rpm the engine will bogg down. The boat did better with what I have done but it is still acting out. I am at an impass with limited tools (meters, pressure gauges, vacuum gauges) and experience. I am willing to continue troubleshooting and replacing parts but as you stated I need a plan.
The Yamaha dealer in my area (Morristown, Tn) is a 5 star dealer. As you stated in one of your post, you have the knowledge and tools to troubleshoot the problem.

 

[doughboy1]

Re: Yamaha VZ150TLRZ 2 Coils not firing

The coils were fine, the filters were fine and the problem was a left turn. After several months of troubleshooting and replacing fuel parts, I took the boat to a Yamaha mechanic and explained that it stopped on left turns. He smiled and said I can fix it. He took the boat for a run up the lake, had his equipment on the engine and made a left turn. The engine quit just as I had told him. After a little troubleshooting, he found a broken red wire in the main wiring harness. He replaced the wiring harness and the boat is doing great. Thanks for all your help.