2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

[floydff]

Good morning! I friend of mine passed away last year, and I am trying to get his boat running again. It sat for about 8 months with gas station fuel, and then his daughter ran it. BAD! I have emptied the fuel tank, replaced the fuel filter, replaced the VST fuel pump (even though it may not have been bad-mechanic said tank was hot and dangerous) and filter, and even sent the injectors to Witchhunters in Washington to be serviced. But, the engine still has a major problem. When it gets above 2000 rpm, the Yamaha diagnostic program is saying the fuel pressure is dropping from 700 psi down to 300 psi. My mechanic normally works on Mercruisers, and is not a Yamaha expert. He now wants to think the belt-driven high pressure pump is the problem. But, it appears from reading several older posts that the 2 diaphragm pumps are often recommended for replacement. What are the steps to check? What are the differences in the symptoms? Thank you in advance for your assistance!

 

[rodbolt]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

check medium pressure fuel rail while the high pressure is failing,if it mantains 50 psi while hp falls to 300 its either a bad hp pump or the medium pressure inline filter is clogged, if you replace that filte one end is a quick connect the other an oerlieker clamp. you have to cut of that clamp and MUST replace it with a like clamp.
flagship marine in punta gorda FL can repair the HP pump.

 

[floydff]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

My Mechanic said that one pressure went from the mid-700's to the low 300's, while the other pressure went from about 55 to 50. He did see signs of leaking out of the bleed valve (I think) of the upper diaphragm pump, so I have ordered two new pumps and gaskets. I replaced that filter (I think the one you are talking about) when I replaced the pump in the VST tank.

Rodbolt- What is a "oerlieker" clamp? I think the Mechanic said the thing came with tie wraps. I did a Google search, and could not find the item. On one parts website, I did see "clamps" with this part number 90465-11M10-00. Is this what you were referring to?
http://www.boats.net/parts/search/Yamaha/Outboard/2003/Z150TXRB/FUEL 1/parts.html

What are the signs of the pump in the VST tank going bad? I replaced it because my mechanic said that tank enclosure got VERY hot to the touch, which he thought was dangerous. But, I think the pump was still pumping (although the pressure was irratic). Did I possibly waste $1000, since replacing the pump did not fix my problems?

Any other tips or suggestions? I HATE ethanol fuel!!!

Thanks!

 

[floydff]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

Ok- I Googled clamps and found what Rodbolt was talking about- Oetiker clamps.
http://www.newageindustries.com/oetiker.asp

Now, if getting this Yamaha engine running were as easy...UGH!

 

[rodbolt]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

never said I was a master speller
use the correct clamp and a CV boot clamp tool to tighten it.
the part number for the medium inline filter is 60v-24251-01.
most likly wasted your money as you cant touch the pump when its running and yes the tank gets rather warm.
fuel compressed to 625 PSI and whats not used is returned to the vst tank.
no fuel cooler for some reason.
medium pressure pump is cooled by the fuel running through it.
50 PSI is acceptable.
its either the medium pressure filter or the filters in the HP pump.
HP pump filters are not field servicable but flagship marine can do them and test the pump.
only tie wraps used are on the low pressure lift pumps and the VST inlet line.

 

[floydff]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

Well, my mechanic said that he thought there was a leak in one of the diaphragm pumps (I guess that turned out to be true- he said one of them had a hole in it). So, I ordered and had him replace both pumps, since I saw on several posts that is recommended every 3 years ago. I was in Miami when he put it in the water, but I understand it got to 3000-3500 rpm's and then started running LOUSY again. Then, they said it started running bad at even lower rpm's. Can Rodbolt or someone tell me if the only remaining possibility is in the belt-driven fuel pump? Are there any additional tests or gauge measurements that can be done while the computer is hooked up to verify the problem? I'd hate to send this pump off for an expensive repair and then STILL have this problem.

I found a Flagship Marine website, but I did not see where they specifically mentioned working on marine fuel pumps. What should I ask them to do? Replace the filters and ...?

Thanks again for your input!

 

[rodbolt]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

monitor medium pressure rail for 50 PSI while monitoring HP pressure while its failing.
HP can be monitored with a laptop,a diagnostic test lamp or a voltmeter.
pink to black at the fuel pressure sensor must remain 2.8 to 3.4V any time the engine s running.
if the medium 50 psi is there and the 625PSI isnt its either the inline filter or a failing HP pump. its really really very simple.
that engine will run at a reduced speed with the pump belt off.
why doesnt your mechanic simply moitor both fuel rails at the same time and fix it?

 

[floydff]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

Here is the latest information I have from my Mechanic:

i dont think that it is the top pump, the boat ran well for the 1st 10 min or so even at high rpm, then it started deteriorating. the high pressure pump according to the lap top started rapidly jumping pressure between 750 and 200. i am trying to find out if a defective sender will cause a poor running condition.ther low pressure pump on the top had a hole in the diaphram , changing those improved it but did not cure it
---------------
Any thoughts, anybody??

 

[rodbolt]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

either the medium pressure filter is clogged or the HP pump filter are clogged.as long as while it was jumping the medium pressure rail maintained 50 PSI.
defective sender wont affect it.
but its imperative to observe BOTH rail pressures at the failure RPM.

 

[floydff]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

Thanks Rodbolt! I am NOT a boat mechanic, and don't ever to pretend to be one!

I don't think it can be the medium pressure filter, because that was just replaced when the VST tank fuel pump was replaced.

So, I guess it's time to send the HP pump in to have it looked at and its filters replaced. Ugh!

 

[floydff]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

Just to give some insight for future people doing a search for a similar problem:

I did a forum search for recommended mechanics in my area. I also went to the Yamaha site and found the list of their top Master Certified Mechanics. One guy was on both lists. So, I took the boat to him. He said that he encounters this problem pretty frequently. He took off the high pressure pump and flushed it, and its screens, out. That fixed the problem...at least for now. Sometimes, he says they clog back up in a few months. Anyway, before someone goes buying a pump, I'd recommend taking it to someone who can clean the one you've got. As it is, I have a $1000 VST fuel pump that I bought and installed that I probably didn't need to...

 

[rodbolt]

Re: 2003 Yamaha 150 HPDI Fuel pressure dropping at higher RPM's

I too am a Yamaha master tech.
yes I have pulled apart the HP pumps even though there are NO field service parts for most of it.
mostly for the tournament guys thats its go or blow and no one has time.
but I wont and never will reccomend ANYONE to dissasemble that pump.
leaks at 625 PSI wont be pretty, the 3.3L motors run 1150 PSI.