Yesterday went for a ride as the weather ended up clearing up, rode 30 mins to pick a friend up and we had plans to eat and then cruise the back roads in the Hill Country and swing by some middle of nowhere bars.

From where we meet up to the food joint was another 30 mins, about 15 mins into the ride my bike started surging slightly and feeling as if the clutch was slipping and then biting with anything more than about 3/8 throttle input.

Symptoms:

Pulled over to check things out and discovered that while the bike was running the fuel pressure regulator was constantly bypassing. You could hear it hissing non-stop, so I shut the bike off and let sit for a minute. Key back on and when the fuel pump primes it just bypasses. Removed fuel line to try and relieve some pressure to see if I could it to stop bypassing. Same thing though through several cycles and starts, kept bypassing non-stop. Pulled main fuse and reset my ECM (Thundermax) but still got some results.

Through my lower gears I have decent pick up through the throttle range with 1/2 to 3/4 throttle surging. Once I am in 6th gear I pretty much surge constantly getting on the throttle and have major loss of power. At stop lights sometimes the bike would die out but always restarted easily.

Done so far:

This morning checked diagnostics on both ECM and through speedo on bike, no codes thrown.

I am sure this will be mentioned, about a month ago or so I did pull my fuel pump, changed filter, replaced hoses with nice rubber internal fuel line and put worm clamps on everything. Also changed the pre filter sock and lubricated the pump with some 2 stroke oil (not sure that actually did anything to help).

General consensus:

Maybe the pressure regulator is going bad or I also read a thread that if your fuel pump is going out it will not generate enough pressure to keep the pressure regulator closed (which doesn't make sense to me). Anyone got any ideas before I take it to the dealership? I am sure fuel pressure test is in order as the first step of diagnosis but I don't usually like taking my bike to the dealership unless I am just completely stumped.

 

From what you say it sounds like it's starving for fuel. Don't know what bike you have or how many miles on it, so it could be the regulator or the pump. Before bringing it in I would try another fuel pump relay, or at least make sure the connectors are clean, as well the fuses.
That ain't much but maybe somebody who knows better will chime in.

 

@nevil Sorry didn't even think to put my bike....Its a 2007 Dyna Street Bob, has close to 14,000 miles. It's funny you mention the relay, I actually pulled the relays both, the black one which is Part # 31511-01B was pretty stinkin hot to the touch in comparison to the gray one.

Harley has replaced one of them once before due to intermittent issues with the bike dieing out and sputtering up a storm, running super rough. I want to say it was the starter relay they replaced but I am unsure. Part # 31522-00C

I do have di-electric grease on every fuse and in every hole on the fuse box, along with as many plugs as I had access to back when I went through the fuse box last year.

Thanks for the advice so far!

 

I think that relay is a common one you can get a an auto parts store, so it's worth a shot to replace it.

 

Dug out my Pop Off tester for carburetors and hooked it up to an old fuel hose that I had replaced some time ago. Before I put the gauge on I tested, free flowing the pump kicks in as it should and gives a nice good long squirt of fuel.

Pressure test - http://vid621.photobucket.com/albums...psh5dtkod0.mp4

With the gauge on and system allowed to build pressure you can see that it for sure is not building correctly. Also I found that the relays are swap-able with no issues, so swapped the relays since I know the starter relay is working fine, Still same results.

So that leads me to believe it has to either be the fuel pump or the pressure regulator.....Any thoughts? Don't want to order a fuel pump or regulator or both and that not be the issue.

Thanks so far!
Robert

 

What's the filter sock on the pump pickup look like?

 

Possible the fuel line from the pump to the tank outlet is leaking? That's known to happen.

https://www.hdforums.com/forum/dyna-...fuel-line.html

Edit: I just re-read your original post, obviously you've already addressed that issue...

 

The regulator is in a plastic housing that has a clip on each side to hold it in place. If one of those clips has broken, fuel will spray out of the housing around the regulator (which will lift on that side). Had it happen to a friend, installed a new housing and all was good.

 

Filter sock is not but a month old if you read the original post. The clip thing for the pressure regulators could possibly be it, I'll be draining the tank tomorrow and pulling the pump out to check everything. Will go from there and post what I discover. I'm having a feeling since the fuel system seems to of given me a problem in the past that it very well could be going.

Thanks for all the responses thus far!

 

" nice rubber internal fuel line"
I hope that fuel line is the high pressure submersible type.