Z150TXRZ HPDI problem in water

[ospreyengineer]

I have a 150 HPDI that will work just fine on the rabbit ears but will only run for 10 minutes in the water before stalling out. I am thinking its the water pump, but maybe I am wrong. Any ideas? Rodbolt would love to hear from you.

 

[rodbolt]

Re: Z150TXRZ HPDI problem in water

a bad water pump may cause an overheat but usually not a stall.
if it stalls due to overheat its most likly junk.
the only reason an overheat would cause a stall on tht engine is the pistons expanded so much they stuck to the cylinder walls.
first step is test the alarm.
pull the emergency stop lanyard and crank the engine, alarm should sound.
second step is test the compression.
after that your most likly going to be fighting a fuel system problem.
when was the last low pressure pump replacement? the last VST cleaning?
the last time the medium pressure inline filter was changed?
but if it hasnt been done in a few years it may also be time for water pump main,t-stat maint and poppit valve maint.
ign system issues were uncommon on that engine however we did have the odd injector driver failure.
when it stalls, is it still at idle or throttling up?
really need a bit more information.
when was the last time it ran ok?

 

[ospreyengineer]

Re: Z150TXRZ HPDI problem in water

Alarm does sound when i pull the lanyard, I just ran it yesterday on the ears for 30 minutes and everything was fine, but last time it was in the water it was running at idle and it just stalled out and wouldnt start again till the next day when i tried it. The day befor that I had it on the water crusing at mid speed and it just stopped and didntstart again so seatow and $600 dollars got me back in. I had replaced fuel water seperator with raycor, and new yamaha fuel filter element thats kind of like the fuel water seperator in the motor, also replaced spark plugs with the same NGK's (quarter turn after hand tight), a new bulb, and ran seafoam the day before the seatow incident. however, i have yet to replace the inline filter or clean the filter in the silver tank (VST???)or the low pressure filter. It ran fine on the ears just yesterday with me engaging the motor in gear and resting at idle for a good hour. I hope i have given enough information.

 

[ospreyengineer]

Re: Z150TXRZ HPDI problem in water

Also when i pump the bulb it never gets hard or full but i can see the gas come into the fuel water seperator on the motor, but as fast as it comes in it seems to never get full only staying at about very bottom of the filter element. If i keep pumping the gas comes out of the exhaust through the prop however this was without the engine running.

 

[rodbolt]

Re: Z150TXRZ HPDI problem in water

fuel leaking from the exhust when pumping the primer simply indicates a blown lift pump diaphram or on HPDI it can also indicate a stuck VST float or a bad VST needle valve assy and the vent is venting raw fuel into #5 intake track and running out the exhaust port. check the lift pumps and the VST vent line carefully nd correct any deficiencies.

then catch up on ALL the maint.
if you cut the band clamp holding the medium presure inline filter on you MUST replace it with the proper clmp.
DO NOT use an automotive style worm clamp and if another backyardigan has already done so carefully inspect the hose and if its not cut up use the correct clamp on reassembly.
how do you know you used the correct plugs?
and I can already tell you they are not properly tightend by your description.

just cause they was in there when ya tookem out dont mean the last backyadign did it right.
trust me.
this stuff aint hard and far from rocket science but a thourough understanding of what HPDI is and how it works as well as some electronics and EFI background is mandtory or you will find how fst that motor can smoke a piston.