Help, Yamaha 150 HPDI, engine surging

[Bob Gale]

Help, RODBOLT or anyone
My 2001 150 HPDI Yamaha model Z150TXRZ, starts and idles ok, when I bring it up to around 2000 it starts surging violently as if running out of fuel. Here's what I have done so far. I have checked the VST tank and electric motor, all spotless, I put a Gauge on the test port and it shows a constant 50 psi at all times. I removed the filter/strainer between the VST and the mech pump and installed a short piece of clear plastic to observe if any air is flowing. It shows only solid fuel at all times. Using the Yam diag SW, it shows fuel pressure of 750 psi and 5 MPa (I don't know what the MPa is?) when running ok. As it starts breaking up the fuel pressure drops to about 13 psi and the other drops to 1 MPa. Am I facing replacement of the dreaded $1000 mech pump. Is there any thing else I should check. I was told it should run with the belt off up to about 2000 rpm?? If the pump, is there any way to clean or try to gt it working?

 

[Bamby]

Re: Help, Yamaha 150 HPDI, engine surging

I had simular thing happen to my Honda. Was acting exactly like yours. Mine had a obstruction in the fuel line. More spicificly in the conn. from fuel line to motor. I would remove line at internal fuel filter and see if you can get good fuel flow there. If not check up line for a obstruction in fuel line.

 

[zzzzz]

Re: Help, Yamaha 150 HPDI, engine surging

use a portable 6 gallon tank to isolate the boat from the motor...may be a restriction somewhere in the boats fuel system...very common problem is the anti-siphon valve at the top of the fuel pickup tube on top the fuel tank...they get sticky or the spring inside gets weak

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Hi, thanks for the reply. I have checked all that, even using a remote tank, etc, but keep the ideas coming.

 

[rodbolt]

Re: Help, Yamaha 150 HPDI, engine surging

ok, 50 psi out of the VST when its breaking up with a loss of high pressure fuel
means the vst pump and fuel level is doing its thing.
have you ever replaced the meduim pressure fuel filter?
its located on the top of the VST and is between the VST outlet and the high pressure pump inlet.
yes there are some screens in the high pressure pump, no ,yamaha SAYS they cannot be cleaned.
all I can say about that.
but try replacing that filter, DO NOT use a standard hose clamp.
the correct clip MUST be used at reassembly I dont care if it does cost 9 dollars.
you can use a CV boot clamp crimper to correctly install the fuel line clip.
stand by that filter is about 80 dollars.
but its next inline to the high pressure pump inlet and if its clogged the high pressure falls and the engine goes into RPM reduction.

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Hi, thanks for the reply. Here is what I did regarding that filter. Just for testing I removed it and put a short piece of clear plastic hose in it's place, so I could make sure no air was intruding. The engine had the same exact problem and the hose, though bulging under the strain, shows no air just solid fuel. Yes I'll remove it and put the filter back in, will also take your advice on the proper clamp. Note, even though the engine is a 2001, it only has 154 hours on it. If you think the mech pump is the only thing left I'm prepared to take it down and try cleaning it. Worst case, I found a used one from a blown engine, with a guarantee for $500, or worst, worst a new one for about $1000. Oh, I also plugged the gas hose to the tank directly into a vacuum Gauge to be sure the 2 low pressure pumps were sucking properly. The Gauge showed a 7 psi vacuum.

 

[rodbolt]

Re: Help, Yamaha 150 HPDI, engine surging

now you have most likly introduced crap in the high pressure pump. why could you not simply replace the filter?
7"hg is way way to much.
4"Hg is max at the lower lift pump inlet.
why ask a pro when you solidly aint gonna take the advice ?

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Sorry, I did that before I asked you. It only ran for about 2 minutes at the dock. Have a new filter in place now. Nothing has changed. What can make the 2 vacuum pumps have to much vacuum? Remember the gauge was not connected in a T with the line, but directly to the line in place of the gas tank. Would that give it a higher reading then a T connection.

 

[rodbolt]

Re: Help, Yamaha 150 HPDI, engine surging

start by Ting your vacum gauge into the system between the engine mounted filter and the lift pump, at WOT the system should show more than about 1"Hg and less than 4"Hg. if more than 4" start moving the T back until vacum falls into range. then you have found the restriction.
have you checked for anycodes with the winky blinky or the laptop?
that would be a good place to start, usually low pressure on the fuel rail just makes it run funny.

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

I'll do the pressure check as you described. What is WOT and is Hg the same as PSI? The laptop diagnostic code section shows normal for all sensors both when running OK and when surging. What is different is the 2 "Fuel pressure" readings. The 5.0 shows 5.07 MPa (what is MPa?) and the 725 shows 734 psi when running OK. Both readings drop drastically when breaking up to .09 MPa and 13.32 psi. The only other thing I notice in the readings is the "Fuel Injection Duration" is at 1 ms when OK and at 8.7 ms when breaking up. The rpms at the time where 1425 & 1325. The O2 was reading .23 v when OK and .11 v when breaking up. The electric pump shows 50 psi at all times with a gauge.

 

[rodbolt]

Re: Help, Yamaha 150 HPDI, engine surging

dude
do you know the difference between PSI and Hg"
if not dig up your 3rd grade physical science books.
we gotta get on the same page here.
I can help you but not if you dont grasp 3rd grade math and science.
WOT is Wide Open Throttle at full load.
the rest you need to gooogle.

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Wow, your brutal. Sorry but 3rd grade was 65 years ago for me and I don't remember any more then pressure at sea level was 14.69 PSI or 29.92 Inches of mercury. I took your advice and looked it up, also see my vac Gauge is in Hg. It reads about 2 Hg at around 2300, any more throttle and the engine just dies like no gas. I have a 6 gal clean remote tank with a clear hose hooked right to the onboard fuel filter and can watch the fuel movement. I know it's tough working with an amateur, particle by email, I appreciate your help.

 

[rodbolt]

Re: Help, Yamaha 150 HPDI, engine surging

sorry if I seem brutal
sometimes its the only way to get someones attention.
gasoline can boil at about 60*F at 5"Hg of vacum.
that means its changed from a liquid state to a vapor.
fuel pumps are not desined to move vapors.
if you have 50 PSI on the medium pressure pump at the failure RPM and the High pressure pump shows low pressure you either have a restricted filter or the screens in the HP pump are clogged.
could also be a defective pressure regulator in the HP pump.
I dont mean to be brutal, however if you wish to maintain or repair this rig yourself there are simply certain tools, test equipments and terminologly you must master or you will post about blown pistons.
you simply cannot splatter gun trouble shooting this engine.
its a very precise rig that MUST be maintained or it pops.
the HPDI is very similar in engineering to the Optimax, TLDI and E-TEC.
the fuel used for combustion is placed in the cylinder after the piston has moved up and closed of both the intake air port and the exhaust port.
means we dont have much time to place the proper amount of fuel for the air allowed in by the throttle plates, burn it,ehaust the gasses and do it again.
its all fairly simple, but it does require a bit of study and a lot of skepticism.
trust no one.
2"Hg is acceptable in the suction side of the lift pumps.
all the VST is is a mini gas tank that allows the medium pressure pump a solid liquid tank to pass fuel bubble and vapor free to the High Pressure pump.
from there the rail is pressurized to about 750 PSI and fed to the injectors.
each injector also has a screen that can clog.

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Hello again,
Since you seem to think it may be pointing to the mechanical pump, I think I'll tackle changing it. Also, the filter on the vapor tank to mech pump has been changed. I was a Merc factory trained mechanic in the 50's and have rebuilt many outboards and inboard engines. YES, I KNOW, PREHISTORIC TIMES. Just trying to give you an idea of where I'm at and if you think it's to complex a job for a non factory trained amateur. Is there any thing I should be aware of that only a factory trained pro would know? I will change all the washers, seals and clamps listed as non reusable. I have heard of some success with extracting the 2 small slim filters and cleaning them, any chance?

 

[rodbolt]

Re: Help, Yamaha 150 HPDI, engine surging

while the fuel and ign controls changed a bit from the 50's not much else really has.
your best tool still sits on your neck.
HPDI isnt really that complex just looks intimidating.
the VST is easy, the high pressure pump I really cant say much about other than man made it.
any full radius clamps you cut off need to be replaced with the correct clamp.
just remember to bleed off the fuel pressure before dissconnecting things as 50 PSI fuel spray is nasty and 700 PSI fuel spray isnt funny.
other thn that almost everything on that motor is testable and can be monitored with a multimeter and a service manual. the laptop is nice, the diagnostic test lamp is good but nothing is a subsitute for that tool on your neck.
just as in the 50's its suck,squeeze, bang and blow,.

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Hi, as always, thanks for your reply. Another question. I decided since the 2 Vac pumps are 7 years old to replace them, can't hurt. My question is, while waiting for them to come in I cut open the old med pressure filter (vapor tank to mech pump) and it contained about enough very fine debris to put on the tip of a knife. It looked metallic so I tried a magnet on it and sure enough it was metal filings. Even though the electric pump is putting out a solid 50# at all times is that a sign of failure, or impending doom?

 

[Bob Gale]

Re: Help, Yamaha 150 HPDI, engine surging

Problem solved, I replaced both the HP mech pump, $1000 at Boats.net and the pressure regulator, $200. Boat runs great now. PS replacing them is a really easy job. You can remove the whole assy in a few minuites.