Polaris RZR Forum - RZR Forums.net banner

41 - 57 of 57 Posts

·
Registered
Joined
·
429 Posts
Also mine is bleeding off After an hour of sitting there it's down to 25. Is that normal ?


Sent from my iPad using RZRForums.net mobile app
 

·
Registered
Joined
·
7,253 Posts
Discussion Starter #42
For the pre-2010 machines the fuel pressure at the injectors, per Spec, is to be 39 +/- 3 psi.

If you pump isn't getting within that range, the pump is probably beginning to fail.

I designed the test set up because my machine wasn't performing that well.

Hooked up the test set up and the pressure only got to 16 . New pump and got to 39, right on the button.

The other quick test is, listen as you turn the key on - do you hear the pump "whine" as it comes up on pressure? No - that's a very good sign the pump is failing.

Pressure bleeding off after it sits for an hour. Not a problem. With that kind of pressure its going to bleed of through the pump.

Pirate
 

·
Registered
Joined
·
587 Posts
Awesome write up, I will be using your information to test the pump pressure on my 09 800.

Only question is this, we all know its near impossible to work under the bed without a removable plate or taking it right off, so could I do this right at the top of the fuel tank right there under the passenger seat?

How difficult would it be to separate the line up at the top of the tank, I havent looked to closely at mine yet.
 

·
Registered
Joined
·
4,934 Posts
Awesome write up, I will be using your information to test the pump pressure on my 09 800.

Only question is this, we all know its near impossible to work under the bed without a removable plate or taking it right off, so could I do this right at the top of the fuel tank right there under the passenger seat?

How difficult would it be to separate the line up at the top of the tank, I havent looked to closely at mine yet.
There's a clip disconnect on that end as well.
I don't remember if you have to remove the panel behind the seats.

I think you may be able to access the fuel rail without taking the bed off.

It's worth a shot.
 

·
Registered
Joined
·
587 Posts
Awesome write up, I will be using your information to test the pump pressure on my 09 800.

Only question is this, we all know its near impossible to work under the bed without a removable plate or taking it right off, so could I do this right at the top of the fuel tank right there under the passenger seat?

How difficult would it be to separate the line up at the top of the tank, I havent looked to closely at mine yet.
There's a clip disconnect on that end as well.
I don't remember if you have to remove the panel behind the seats.

I think you may be able to access the fuel rail without taking the bed off.

It's worth a shot.
Okay, thanks. I'll see if I can figure it out LOL. Pretty sure its my pump but might as well be sure before I replace it eh :pint:
 

·
Registered
Joined
·
7,253 Posts
Discussion Starter #46
You can get to the end of the fuel rail, with the bed on, by taking the right rear tire off.

You'll have to twist your self around a bit to be able to see along the left side of the valve cover, Then its probably a bit tough to tight a clamp to hold the test kit hose on the fuel rail.

Do yourself a favor and get a UTV Inc. bed plate...and excellent investment!

Pirate
 

·
Registered
Joined
·
587 Posts
You can get to the end of the fuel rail, with the bed on, by taking the right rear tire off.

You'll have to twist your self around a bit to be able to see along the left side of the valve cover, Then its probably a bit tough to tight a clamp to hold the test kit hose on the fuel rail.

Do yourself a favor and get a UTV Inc. bed plate...and excellent investment!

Pirate
I'll see what I can do, I'm a big boy, getting twisted up in tight spots is a tough one for this guy LOL.

As for the bed thing, I wasnt away anyone made one and I've had one on the back burner for a few years now (ever since I pulled the bed off my machine a few years ago) but just havent gotten around to it yet.
 

·
Registered
Joined
·
7,253 Posts
Discussion Starter #48
Clifford,

I tried to help a friend with an XP900 check the fuel pressure.

I'm afraid I think the answer is no.

There is a clip fitting on the fuel rail, but it is the connection of the fuel line to the fuel rail at the injectors.

Beyond the injectors, there is a pressure regulator with a return line to the fuel tank.

This being said, I thing the place to test XP fuel pumps is at the fuel tank. I think that readings there would be representative of what the pressure is at the fuel rail.

I didn't get a chance to figure out if the pressure regulator makes it difficult to determine if the pump is beginning to fail...only that is has.

Just thoughts,

Pirate
 

·
Registered
Joined
·
57 Posts
I'm not an not an engineer in fluid dynamics and certainly not an expert on RZR fuel systems.
But I tend to think that a regulator, whether gas, liquid, or voltage, is supposed to regulate!
I would expect a regulator set at 39 psi would have a supply of greater than 39 psi.
The regulator would then allow pressures of 39 lbs of less to go to the injectors. Any pressure over 39 would open the internal valve and slow the excess to be bled off back to the tank through the fuel return line.
To maintain pressures of 39 psi during full throttle, the pump would have to be capable of higher pressures. I would expect a flow of fuel returning to the tank with engine off or at idle, meaning that you would have a minimum of 39 psi and the regulator is regulating!
If you have a weak pump as the injectors open, the pressure would drop.
Trying to reason through this.
My 08. 800 Boggs down about 30 mph up hill and is getting worse. Just replaced tank and pump with aftermarket parts about 300 miles ago.
I'm going to build an inline gauge set up to monitor the pressure under load. I will let you know what I find out.
Clint
 

·
Registered
Joined
·
4,934 Posts
I'm not an not an engineer in fluid dynamics and certainly not an expert on RZR fuel systems.
But I tend to think that a regulator, whether gas, liquid, or voltage, is supposed to regulate!
I would expect a regulator set at 39 psi would have a supply of greater than 39 psi.
The regulator would then allow pressures of 39 lbs of less to go to the injectors. Any pressure over 39 would open the internal valve and slow the excess to be bled off back to the tank through the fuel return line.
To maintain pressures of 39 psi during full throttle, the pump would have to be capable of higher pressures. I would expect a flow of fuel returning to the tank with engine off or at idle, meaning that you would have a minimum of 39 psi and the regulator is regulating!
If you have a weak pump as the injectors open, the pressure would drop.
Trying to reason through this.
My 08. 800 Boggs down about 30 mph up hill and is getting worse. Just replaced tank and pump with aftermarket parts about 300 miles ago.
I'm going to build an inline gauge set up to monitor the pressure under load. I will let you know what I find out.
Clint
If it's only under load have you checked out your clutches
 

·
Registered
Joined
·
7,253 Posts
Discussion Starter #51
Clint,

Bear in mind that the injectors are the "pressure regulating" point in the RZR fuel injection system.

If the pressure is a lot higher than the rated, 39+/- 3 psi then the electric injectors might not be able to overcome the pressure and open the injector.

If the pressure is low, failing pump, then the injector is not able to provide enough fuel while its open.

Installing a gauge is probably not necessary. If the pressure at idle and when you step on the gas while in "N" and you get the 39+/-3 psi...the pump is doing its job and providing the injectors with sufficient fuel.

What exactly the ECU does to injector "open time" due to load, isn't a function of fuel rail pressure.

You're having problems...have you checked the fuel pump pressure again after the work you've done and the 300 miles since? That's where I would start.

There have been tales of new fuel pumps that were not good. Did you use an Airtex E-8335? That's the aftermarket pump that fits and works.

Thoughts?

Pirate
 

·
Registered
Joined
·
57 Posts
Thanks Stuart, I had a shop install the pump and tank. It was an E 8335. They said the pressure was correct. My machine had 1200 miles when I got. It now has 3600. When the new pump was first installed it was the quickest it had ever been. On my last trip to Windrock, the third day I noticed a loss of power on the long uphill pull on G2. Speed was around 25 - 30 and rpm were 4500 - 4800.
I replaced the air filter and found a big crack (exhaust leak) in the exhaust manifold.
I have a new exhaust.
My biggest problem is my machine is currently 2 hours away. I have a friends shop and 450 acres to test ride on. I'm building my pressure tester and will take it up there Thursday.
I'll let you know what I find.
Clint
 

·
Registered
Joined
·
7,253 Posts
Discussion Starter #53
Clint,

I'll be interested to hear what you find.

If you find the pump is failing, or you're going to take it out for inspection...then would be a good time to consider a Trail Tank 9 gallon fuel tank.

I put one in my 09 RZR 800 this past Winter....very nice to have the extra fuel capacity for long days!

Just a thought,

Pirate
 

·
Registered
Joined
·
57 Posts
I have a Trail Tank. I had a slow leak on my oem tank so when the pump toasted last summer I had both replaced.
I love it! I can go to from Windrock Park to Caryville Flats and play all day and get back to camp without having to carry extra gas.
Clint
 

·
Registered
Joined
·
242 Posts
Will this work with a 900xp?
 

·
Registered
Joined
·
265 Posts
So I know this is an old thread... But I thought I would provide some feedback as I made the mentioned fuel tester and tried 1/4" ID hose... Way too tight of a fit. Use 3/8" fuel line instead and a hose clamp.

I also was curious if 2011 year and up models are supposed to be 39 psi or 45? My manual says 45 +/- 2 psi, which would be right around 43-47 psi. I am only getting 39psi when running and it takes a bit to get there. From a cold start turning key on I get around 32psi maybe. I think my pump is on it's way out, but want to confirm.

Thanks!
 

·
Registered
Joined
·
265 Posts
Went to polaris and bought a new pump, installed it and I am getting 45psi now. So 2011+ should be 45psi like the manual stated.
 
41 - 57 of 57 Posts
Top