Fuel Pressure in the XR1200
 
A while back I had an issue with my XR1200 not starting after it had not been ridden for several weeks. When I tried to start the bike, it cranked and cranked, but would not ignite and start.  After checking the bike over, and doing a simple fuel check by disconnecting the gas coupling after cranking it, it appeared that I was not getting any fuel pressure. 
 
I  removed the fuel tank and pump and took a look at the filters and Fuel Regulator.  Nothing was obviously wrong, and at about 12,000 miles the filters were still clean, so I reassembled it and tested it outside of the tank.  The pump functioned, so I put the bike back together, filled the tank, and tried to start it again.  It sucked some air as it re-primed, and fired right up.  Having ridden the bike for another 10,000 miles, all seems normal.  I am not a big fan of opening the fuel tank more often than necessary since the parts, and particularly the connecting hose lose their flexibility over time, and leaving the tank empty, or disassembling to pull everything out in the air, can cause more problems with the fuel system failures than just riding regularly and being sure to park the bike with a full tank of good fuel.  But, in this case, I still was concerned that there might be an underlying problem, like a pinhole in the hose between the pump and fuel filter (item 11 in Figure 1 below)r, or that the fuel regulator might be going bad.  So  with the bike reassembled and a partially refilled fuel tank, I proceeded to check the fuel pressure in the system.   I checked the fuel pressure with a partial tank of fuel, to see whether things looked normal with the internal fuel hose uncovered.

The following is a look at checking the fuel pressure in the XR. 
 
 
The Fuel Pump Assembly
 
 
For perspective, here is a look at the fuel pump assembly (diagram from the HD Service Manual) for the XR1200.  The assembly mounts to a plate in the bottom of the gas tank.  With the tank pulled off the bike, it is easy removed the pump assembly unscrewing the five torx screws in the mounting plate  I would not try to remove the pump assembly without pulling the tank, if only because there is no way to completely drain the gas from the tank and a significant amount of gas will drain out if this is done.  A few minutes more time to do this right, will make this a much safer and quicker job overall.

 

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Figure 1:  Fuel Pump Diagram from HD Service Manual
 

The pump assembly is shown in Figure 1 above.  The assembly includes the Fuel Pump itself (2), the Fuel Regulator (22), the pre-screening filter (8) on the pump, and the fuel filter (25).  The Fuel Pump is capable of maintaining over 62 psi of pressure.  It should hold a minimum of 55 psi.  The Fuel Regulator has a spring valve in it that is set to open at 62 psi.  The pre-screening filter (or fuel sock) and the fuel filter keep garbage out of the pump and the fuel injectors.  HD calls for a service interval of about 25,000 miles for the filters but some riders have found that these need replacing by 10,000 miles due to their local riding conditions.
 
If there is a problem with fuel delivery and the fuel pump is working (the whirr one hears prior to starting when the ignition key and switch are turned on), then the first things to look at are generally the tube (the filter housing hose) that connects the pump body to the Filter Housing (23), and the Fuel Regulator.  The tube from the pump to filter will get pinholes in it with age.  When that happens the bike may appear to run fine with a full tank of gas, but not run well (or start) when the fuel level falls below the height of the hose.  Parking the bike for long periods of time with an empty fuel tank, or removing the pump assembly from the tank excessively, will accelerate the deterioration of this hose.  Alternately, if the Fuel Regulator fails it may constantly bleed gas back to the tank and prevent the fuel pressure from building to its normal 55-62 psi.
 
 
The Fuel Pressure Regulator
 
 
The fuel pressure regulator on the XR1200 is a  common part with other late model Sportsters.  It is small module that plugs into the end of the fuel filter housing and is retained by a spring clip. Fuel pressure in the XR1200 should hold at about 55-62 psi.
 
When I opened up the fuel tank I was in a hurry and didn't take any pictures but the diagram above is pretty good.  Here are a few pictures of the Fuel Regulator itself.  The plastic collar and o-rings position and seal the regulator in the top of the Filter Housing.  As mentioned a spring clip (part 24 in Figure 1 above) holds it in place.

 

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Fuel Pressure Regulator Size
 

The fuel enters and exits the Fuel Regulator on one end.  The flow is rather like the in and out of a fuel filter, except there is a spring loaded metal plate in the regulator that is set to bleed fuel back into the tank to regulate the flow.  When fuel pressure rises above about 62 psi the plate gets pushed back and gas bleeds out the small hole on the opposite end of the regulator to return to the fuel tank.

 

Fuel Regulator
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Bottom

Top
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Fuel Regulator
 

While there is nothing wrong with the design or construction of the HD Fuel Regulator, I have yet to find a plug and play upgrade for this piece.  Without modifying, or removing, the entire pump assembly, it looks like the OEM HD Fuel Regulator design is the only option for the XR1200. 
 
 
Fuel Pressure Test Gauge
 
 
To test the fuel pressure, one disconnects the fuel fitting for the hose from the fuel tank to the fuel injectors, and inserts a test fitting.  A fuel pressure test gauge is then inserted inline between the fuel hose fitting and the tank.

 It is possible to make an adapter for this purpose but the easiest thing for me to do was buy the HD tool (HD-44061) shown below.  A fuel pressure gauge is then connected to the fitting's Schraeder test port.


 

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Test Fitting
 

HD does sell a complete fuel pressure test kit, but far less expensive than the HD fuel pressure gauge was this Actron model that I picked up at an auto parts store.  It is equipped with a bleed valve and hose to vent air out of the test line for the pressure reading.  Any equivalent kit will work.

 

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Pressure Gauge
 

The black button on the side of the gauge fitting is the bleed valve to vent air out of the gauges hose.

 

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Bleed Valve
 


Testing Fuel Pressure
 
 
To test the fuel pressure, one installs the test fitting in the fuel line on the bottom of the left side of the fuel tank.  The coupling is the silver collar on the bottom of the tank in the middle of the cylinders.

 

Fitting on Tank
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Fuel Line

 
Just unsnap the hose to the fuel injectors and snap the test fitting in place.

 

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Installing the Test Fitting
 

Here is the test fitting attached to the engine and the fuel hose snapped into the fitting.  The Schraeder port on the side of the fitting is similar to that on the fuel rails in EFI automobiles and the gauge threads on here.

 

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Test Fitting Installed
 

Once the pressure gauge installed (as in the below figure), the bike is started, the bleed valve pressed a few times to bleed the air out of the gauge's hose, and the pressure reading is observed. 
 
In my case the gauge is reading 60 psi of pressure with about 3/4 gallon of fuel in the tank.  So, not only do my pump and regulator seem to be in spec, but there is no evidence of the tube that connects the two having any pinholes.

 

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Pressure Reading
 

It is important to note that, it is a good idea to put a catch bottle on the bleed tube from the gauge.  I pressed  the valve 3 or 4 times, for a second or so each, to let the air out of the gauge hose.  About 100 ml of gas will also vent out out with the air.

 

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Bleeding out the air
 


Conclusion
 
Having ridden the bike for another 12,000 miles, all seems normal.  The original problem was a gremlin.  Probably my XR was just mad at not being ridden for a few weeks.  But, while the reason for the failure to start may be a mystery, it got me to post this page, so not all bad.  I'll add pictures of the actual filters at a later date to show what they look like after a few miles in the bike....

Although I needed to open the tank for this troubleshooting, I will note that I am not a big fan of opening the fuel tank more often than necessary since the parts, and particularly the internal connecting hose, lose their flexibility over time.  Leaving the fuel tank empty, or disassembling it and pulling everything out in the air, can cause more problems with a fuel system failures than just riding regularly and being sure to park the bike with a full tank of good fuel.

 





 
 

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