150 HPDI Voltage Too High

[J-absher]

Im still chasing down issues on a Z150TXRB. Idles fine, gets on plane ok and has decent midrange but, it bogs down at 4000 rpms. Everything about it acts like fuel starvation so I’ve been through the entire fuel system on boat and engine. All filters and screens replaced, 2 new diaphragm pumps, electric pump, lines and injectors cleaned. Also cleaned the o2 sensor which needed it badly. Little better but still no top end. 45-50 psi at vst and 723 psi give or take at rail measured with yds. No current codes. While monitoring the engine on the computer I noticed the voltage was around 13 at idle but jumped well over 16 with throttle. The yds lit up red on the voltage line after it crossed 16. I’ve seen regulators fail on other engines and cause low voltage or no charging issues but never had one fail and cause an over voltage issue. Has anyone ran into this on an HPDI? Is the regulator/rectifier the only thing that can cause this? All input and help is appreciated...

[J-absher]

I’ve searched the service manual and can’t find anything about a high voltage issue. The regulator/rectifier section covers low voltage and charging issues but doesn’t mention high voltage. Do you guys think just swapping the regulator/rectifier will get this back into spec?

[fairdeal]

I have not heard of the voltage value reported by the ECM to YDIS being 'wrong'

but if you measure voltage, with a meter at the battery terminals, >15
that 'should not be'
and is definitely and solely the fault of the r/ r

would 16 volts to the ECM "cause it to make the engine run bad at high rpms?"
doubt that-

[J-absher]

Thanks for the reply. I checked the voltage at the battery with a voltmeter and it’s definitely over 16 with throttle. Volt meter matched yds. I don’t know if this is related to the running issues or not but definitely something I want to address before firing the engine again. I’ve changed a laundry list of parts on this motor this year already, definitely don’t want to add an ecu to that list. I’m going to order a new R/R from SIM today. I was hoping the ecu might be reading a high voltage and cutting rpm to protect itself. This is my first Yamaha so I have a lot to learn about it. Trying hard to make sure it’s 100% before fall fishing kicks off.

[fairdeal]

so the r/r is definitely NFG

if replacing that also solves the running problem - let us know!

[99yam40]

OP were the fuel pressure readings at WOT/ where the limited RPM was happening?

have you sent off the injectors to have them tested and cleaned?
need to make sure they are flow tested and spray pattern checked

Have you checked the part prices here instead or at least compared to other places

[J-absher]

I will definitely check out the parts here. The injectors have been cleaned and tested. Was actually testing the new injectors when this was noticed. The fuel pressure readings have been measured at idle and running. Some fluctuations but no drastic drops. After I seen the voltage spike I’ve stopped and shut everything down. I don’t want to chance hurting any of my other electronics on the boat or motor. I’m assuming that if it measures over 16 volts on yds and at the battery that it’s also sending that high voltage through the boats electric panel and to my electronics. I’m afraid that could get very expensive fast if it surges and the fuses don’t catch it in time.

[J-absher]

I do apologize, I had read about SIM in several posts and incorrectly made the assumption that the 2 were connected. My mistake.

[99yam40]

what I was getting at is you need to know the pressures when the motor is having the problem.
if the pressures are not staying in spec when it starts bogging down, that will tell you where a problem is

[J-absher]

When tested before the injectors the vst held around 45psi and the high pressure was around 723psi. This was after changing all screens and filters and also changing the electric pump (I found the one in it wasn’t the correct one when I changed the vst filter. It didn’t fit and was forced together). So I then checked the exhaust tuner for restriction or damage and checked injectors. I pulled plugs and looked in each cylinder while firing the injectors from yds. Found #5 injector was definitely not clouding the cylinder as well as the others. So those have now been cleaned and reinstalled but I haven’t been able to do a true water test yet because this voltage issue showed up. Hopefully with a new regulator and the injectors it’ll finally come alive. I rarely run wot. Usually cruise around 3500-4000 when fishing but I want to make sure this motor is healthy when it goes back to the water. Thank you for the input and keep the suggestions coming. It’s much appreciated.

[99yam40]

so, it sounds like you have not checked pressures when the motor is bogging down at 4000.
need to do that when you get the RR replaced .
should be able to at least have the lap top hooked up to watch HP while running hard.
motor not being able to get to WOT mean it has problems that need looking into

[boscoe99]

Carefully clean and reattach the R/R ground wire ring terminal. The point of the block that it grounds to as well.

[J-absher]

I will definitely do that. Thanks. I need to go through and clean all the grounds and connectors. I had problems with connecting the yds cable. Kept getting a communication error. I thought it was an issue with comm port or cable. Turned out that the connector pins on the engine had slight corrosion coating on em. Scratched them good with a blade and it started working perfectly. I would imagine if that one had issues then they all need to be cleaned. I’ll do that while I have it apart.

[J-absher]

Problem solved. Did a 15 mile run early this morning after replacing the regulator. After a good warm up it got on plane smooth, good midrange and no surging on top end. The voltage held around 14 and the surging went away so fingers crossed it’s running good for now.

[boscoe99]

Problem solved. Did a 15 mile run early this morning after replacing the regulator. After a good warm up it got on plane smooth, good midrange and no surging on top end. The voltage held around 14 and the surging went away so fingers crossed it’s running good for now.

What do you think fixed the problem?