Fuel pressure regulator failed?

Mnstguy

Joined
Jun 5, 2017
Messages
2
Location
Minnesota
Hey riders,

I recently got a st1100 that has sat for 12 years with fuel in the system that went bad and everything got really nasty. I've replaced or cleaned everything up through the fuel system now my problem is that I can get fuel to the fuel filter and up to what I think is the fuel pressure regulator. It gets to it but won't go through. I took the spring that's in it out and tried it and it works when that's not in there. Is it a vacuum deal or??. Just curious how they work and if anyone can help me troubleshoot this problem. I'm stumped.

Thanks,
Nick
 

the_gr8t_waldo

Joined
Apr 7, 2007
Messages
624
Location
Tacoma, wa
It's more likely the fuel shut off- vacume actuated. Check to see if vacume is present when engine is running. And check to see if the rubber inside is damaged( rebuild kits are avaulable). Can be bypassed without buying any parts to accomplish. A lot of people just bypass. Once you get fuel past this, you.ll most likely find the carb set need cleaning as well. Good luck, the problems precipitated by bad fuel get involved, but once you get past 'em the bike shines
 
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dwalby

dwalby

Joined
Mar 13, 2012
Messages
5,062
Location
soCal
Bike
'97 ST1100
STOC #
687
Mnstguy said:
Hey riders,

I recently got a st1100 that has sat for 12 years with fuel in the system that went bad and everything got really nasty. I've replaced or cleaned everything up through the fuel system now my problem is that I can get fuel to the fuel filter and up to what I think is the fuel pressure regulator. It gets to it but won't go through. I took the spring that's in it out and tried it and it works when that's not in there. Is it a vacuum deal or??. Just curious how they work and if anyone can help me troubleshoot this problem. I'm stumped.

Thanks,
Nick
Click to expand...
It sounds like what you're calling the pressure regulator is actually the vacuum-shut-off unit. Its on the right side of the bike, just to the rear of the airbox. That can be easily bypassed. link the two fuel lines together, and cap off the vacuum line so it doesn't leak, and you're good. Many, if not most of us have done this mod without any problems.

edit: I think gr8t_waldo has a good suggestion to make sure you have vacuum at the shut-off because that's coming from the #3 cylinder. If no vacuum, then that's another issue you'll have to track down.
 
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OP
OP

Mnstguy

Joined
Jun 5, 2017
Messages
2
Location
Minnesota
Thanks guys that's exactly what it is and I was curious if I could just eliminate it but wasn't sure I'll let you guys know what happens when I get that fixed! Carb is clean and set up right I tested all that and what not. Another question how did you guys plug it? Screw? Silicone? Both? The vacuum that is. Any pictures?
Thanks again
Nick
 

the_gr8t_waldo

Joined
Apr 7, 2007
Messages
624
Location
Tacoma, wa
I picked up a small machine screw laying on the floor. pushed the shank in until the head met the tubing.. you could do that or just double over the tube and hold it with a turn or two of e.tape .
 
dwalby

dwalby

Joined
Mar 13, 2012
Messages
5,062
Location
soCal
Bike
'97 ST1100
STOC #
687
I twisted a machine screw in the end of the vacuum line, not in front of it now but I wanna say it was a 5mm screw. It made a snug fit so I didn't use any other sealant.
 
John OoSTerhuis

John OoSTerhuis

Life Is Good!
Joined
May 10, 2005
Messages
5,222
Location
Bettendorf, Iowa
Bike
1991 SSMST1100
STOC #
1058
Buy the OEM tube and cap like is used on the #1 cylinder intake manifold vacuum port hose. BTDT I can dig up the part numbers if asked. You need to use the vacuum hose you unplugged from the Auto Fuel Valve to sync the #3 cylinder's carb.

John
 
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