525 fuel issues
06-02-2012, 07:22 PM
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525 fuel issues
I have a 525efi in an Eliminator. Ran fine last year with no issues. I performed the normal service in the fall and replaced the fuel water separator. It ran fine for 10 hours this season. Today my fuel pressure gauge has ADD - its all over the place. It will pull 40 psi at idle but when you put a load on it then the fuel pressure goes crazy.
Thoughts? Did I get bad gas? Fuel pump going out? I heard there is a secondary fuel filter but haven't confirmed.
Thoughts? Did I get bad gas? Fuel pump going out? I heard there is a secondary fuel filter but haven't confirmed.
Last edited by rsscoggins; 06-03-2012 at 10:49 AM.
06-03-2012, 12:05 PM
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So looking at the parts diagrams, there are a number of points of failure:
I am going to replace the Fuel water separator as that is a no brainer at a cost under $10
How do I check/test the other items? The mechanical pump and the regulator are $100 each but the electric pump is over $200. I dont want to just start swapping parts.
I suspect it is the regulator but don't know how to confirm that.
- Mechanical fuel pump
- Fuel water separator
- Fuel pressure regulator
- Electric fuel pump assembly
I am going to replace the Fuel water separator as that is a no brainer at a cost under $10
How do I check/test the other items? The mechanical pump and the regulator are $100 each but the electric pump is over $200. I dont want to just start swapping parts.
I suspect it is the regulator but don't know how to confirm that.
06-03-2012, 05:55 PM
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I believe HP525efi's have a fuel pressure sensor on the fuel rail under the plenum and it reads tot eh ECM whcih should be showing a code for low fuel pressure.
You can also hook a fuel pressure guage up to the schrader valve on the fuel rail under the plenum and test fuel pressure under load.
what is the fuel pressure underway at full throttle for example. Fuel pressure at idel is usually about 41-43 psi and should stay above 41 or so PSI under full load.
There are two fuel pumps, one is a mechanical lift pump on the top of the raw water pump and the other is a high pressure pump in the cool fuel unit under the front of the engine in front of the pan. The sefcondary fuel filter is at the left rear top of the engine where the fuel line from the coolfuel goes up to the injector fuel rail connection.
The is a fuel pressure regulator in the cool fuel unit also that can go bad.
Good Luck, hope you find your gremlin quickly.
Best Regards,
Ray @ Raylar
You can also hook a fuel pressure guage up to the schrader valve on the fuel rail under the plenum and test fuel pressure under load.
what is the fuel pressure underway at full throttle for example. Fuel pressure at idel is usually about 41-43 psi and should stay above 41 or so PSI under full load.
There are two fuel pumps, one is a mechanical lift pump on the top of the raw water pump and the other is a high pressure pump in the cool fuel unit under the front of the engine in front of the pan. The sefcondary fuel filter is at the left rear top of the engine where the fuel line from the coolfuel goes up to the injector fuel rail connection.
The is a fuel pressure regulator in the cool fuel unit also that can go bad.
Good Luck, hope you find your gremlin quickly.
Best Regards,
Ray @ Raylar
06-03-2012, 10:57 PM
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I believe HP525efi's have a fuel pressure sensor on the fuel rail under the plenum and it reads tot eh ECM whcih should be showing a code for low fuel pressure.
You can also hook a fuel pressure guage up to the schrader valve on the fuel rail under the plenum and test fuel pressure under load.
what is the fuel pressure underway at full throttle for example. Fuel pressure at idel is usually about 41-43 psi and should stay above 41 or so PSI under full load.
There are two fuel pumps, one is a mechanical lift pump on the top of the raw water pump and the other is a high pressure pump in the cool fuel unit under the front of the engine in front of the pan. The sefcondary fuel filter is at the left rear top of the engine where the fuel line from the coolfuel goes up to the injector fuel rail connection.
The is a fuel pressure regulator in the cool fuel unit also that can go bad.
Good Luck, hope you find your gremlin quickly.
Best Regards,
Ray @ Raylar
You can also hook a fuel pressure guage up to the schrader valve on the fuel rail under the plenum and test fuel pressure under load.
what is the fuel pressure underway at full throttle for example. Fuel pressure at idel is usually about 41-43 psi and should stay above 41 or so PSI under full load.
There are two fuel pumps, one is a mechanical lift pump on the top of the raw water pump and the other is a high pressure pump in the cool fuel unit under the front of the engine in front of the pan. The sefcondary fuel filter is at the left rear top of the engine where the fuel line from the coolfuel goes up to the injector fuel rail connection.
The is a fuel pressure regulator in the cool fuel unit also that can go bad.
Good Luck, hope you find your gremlin quickly.
Best Regards,
Ray @ Raylar
I was on the boat today as I had to take it back to the marina from the mooring buoy at the house. It ran fine although I didn't run it hard for fear of damaging anything.
I pulled a couple of plugs and they look as normal and do not show a lean condition. I found the secondary fuel filter up close the back of the intake so I will be changing that as well.
I am going to put a gauge on the intake schrader valve and see what it tells me - I would hope that my in dash gauge is simply bad but the coughing and hesitation that I had yesterday does not give me much hope that it isn't something else.
I am also going to put gas in the other tank and see if the same behavior is exhibited.
Why oh why did they put that regulator and other pump under the motor - not exactly the easiest to get to in a cramped engine compartment.
06-04-2012, 02:15 AM
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I believe HP525efi's have a fuel pressure sensor on the fuel rail under the plenum and it reads tot eh ECM whcih should be showing a code for low fuel pressure.
You can also hook a fuel pressure guage up to the schrader valve on the fuel rail under the plenum and test fuel pressure under load.
what is the fuel pressure underway at full throttle for example. Fuel pressure at idel is usually about 41-43 psi and should stay above 41 or so PSI under full load.
There are two fuel pumps, one is a mechanical lift pump on the top of the raw water pump and the other is a high pressure pump in the cool fuel unit under the front of the engine in front of the pan. The sefcondary fuel filter is at the left rear top of the engine where the fuel line from the coolfuel goes up to the injector fuel rail connection.
The is a fuel pressure regulator in the cool fuel unit also that can go bad.
Good Luck, hope you find your gremlin quickly.
Best Regards,
Ray @ Raylar
You can also hook a fuel pressure guage up to the schrader valve on the fuel rail under the plenum and test fuel pressure under load.
what is the fuel pressure underway at full throttle for example. Fuel pressure at idel is usually about 41-43 psi and should stay above 41 or so PSI under full load.
There are two fuel pumps, one is a mechanical lift pump on the top of the raw water pump and the other is a high pressure pump in the cool fuel unit under the front of the engine in front of the pan. The sefcondary fuel filter is at the left rear top of the engine where the fuel line from the coolfuel goes up to the injector fuel rail connection.
The is a fuel pressure regulator in the cool fuel unit also that can go bad.
Good Luck, hope you find your gremlin quickly.
Best Regards,
Ray @ Raylar
06-04-2012, 11:42 AM
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The question I have is does that stainless line carry fuel? I would assume it would but want to confirm before I break that seal if I need to remove or replace the gauge.
Last edited by rsscoggins; 06-04-2012 at 11:46 AM.
06-04-2012, 01:02 PM
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I just went through similar problems with my 575sci's, but only on one side
http://www.offshoreonly.com/forums/g...e-3000rpm.html
After replacing the fuel pump I still had the same problem. I pumped my tanks dry to start the year, turned out I was still getting water out of the tank. The water would max the seperator and when it made its way into the fuel system my gauge would lose accuracy and engine would run terrible. Change a separator and run good for a while, then gauge would jump and I would have issues again.
Water is gone now, problem solved.
Not saying this is your problem, but you might want to take a fuel sample and check.
Maybe someone smarter than me can explain why gas mixed with water reads higher on a pressure gauge than good clean gas?
http://www.offshoreonly.com/forums/g...e-3000rpm.html
After replacing the fuel pump I still had the same problem. I pumped my tanks dry to start the year, turned out I was still getting water out of the tank. The water would max the seperator and when it made its way into the fuel system my gauge would lose accuracy and engine would run terrible. Change a separator and run good for a while, then gauge would jump and I would have issues again.
Water is gone now, problem solved.
Not saying this is your problem, but you might want to take a fuel sample and check.
Maybe someone smarter than me can explain why gas mixed with water reads higher on a pressure gauge than good clean gas?
06-04-2012, 02:11 PM
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I just went through similar problems with my 575sci's, but only on one side
http://www.offshoreonly.com/forums/g...e-3000rpm.html
After replacing the fuel pump I still had the same problem. I pumped my tanks dry to start the year, turned out I was still getting water out of the tank. The water would max the seperator and when it made its way into the fuel system my gauge would lose accuracy and engine would run terrible. Change a separator and run good for a while, then gauge would jump and I would have issues again.
Water is gone now, problem solved.
Not saying this is your problem, but you might want to take a fuel sample and check.
Maybe someone smarter than me can explain why gas mixed with water reads higher on a pressure gauge than good clean gas?
http://www.offshoreonly.com/forums/g...e-3000rpm.html
After replacing the fuel pump I still had the same problem. I pumped my tanks dry to start the year, turned out I was still getting water out of the tank. The water would max the seperator and when it made its way into the fuel system my gauge would lose accuracy and engine would run terrible. Change a separator and run good for a while, then gauge would jump and I would have issues again.
Water is gone now, problem solved.
Not saying this is your problem, but you might want to take a fuel sample and check.
Maybe someone smarter than me can explain why gas mixed with water reads higher on a pressure gauge than good clean gas?
Last edited by rsscoggins; 06-04-2012 at 02:25 PM.
