New petcock and intermittent starting issues...

CatTomb · May 21, 2013, 11:29:28 PM

Ughh!

New petcock a couple of weeks ago. 3/4 tank of gas...

Bike starts up instantly...Rode 30 miles @ 50/75 mph, stopped for 5 minutes, bike starts right up... runs great...

Ride for 30 more miles, stop for 15 minutes, bike won't start. Cranks easily, doesn't seem like it is getting any gas.

Let it sit for 20 minutes bike starts right up.

Any ideas on where I should start looking???

Thanks,

Jeff

p.s. I searched and will check fuel line routing and give the new petcock the suck test.

Pat Conlon · May 22, 2013, 01:46:57 AM

Yep, 1) fuel line routing...then 2) cracks in the vacuum line and/or connections at #1 manifold and petcock.
If you bought a *new* petcock, that should be fine.
You do have your carb heat shield installed, correct?

Tank venting ok? Any negative pressure when you open the gas cap?

FJmonkey · May 22, 2013, 07:18:31 AM

Fuel line routing is critical. If you still have your air box then look closely at the diagram. The fuel line comes up from the carbs to the "Y" splitter (84 to 87 only), loops around the top of carb #3, then routes back under the two lines coming up from the carbs. It is not intuitive, but if the line coming out of the petcock is over the line coming up from carb 1 & 2 then both lines will fight for the same space causing them to pinch each other.

In this picture I noticed the same routing that I had while I was having fuel delivery problems. Notice that the line to the petcock is not routed under both lines.

I hope that helps.

Billsy5150 · May 23, 2013, 06:53:26 AM

My bike is doing the same exact thing. Not having much luck finding a petcock for my bike. Do you happen to know if an FJ600 Petcock or a mechanical /gravity fed one would work on the 85 FJ1100? Mine seems to pass the "suck" test so it may just be a fuel line routing issue as I have an inline filter. Any help is appreciated.

CatTomb · May 23, 2013, 07:47:08 AM

Quote from: Billsy5150 on May 23, 2013, 06:53:26 AM
My bike is doing the same exact thing. Not having much luck finding a petcock for my bike. Do you happen to know if an FJ600 Petcock or a mechanical /gravity fed one would work on the 85 FJ1100? Mine seems to pass the "suck" test so it may just be a fuel line routing issue as I have an inline filter. Any help is appreciated.

I got my petcock from Randy at RPM racing. If you spend any time at all on these forums his name and company will become very familiar to you.

http://www.rpmracingca.com/proddetail.asp?prod=M%2FC%3A84-85Petcock

I'm going to try the suggestions posted above in mine today. I'll let you know.

Jeff

VaughanCustoms · May 23, 2013, 09:37:19 AM

Is there a way to check if the petcock is working properly?

CatTomb · May 23, 2013, 10:40:14 AM

I got this from FJmonkey... (thanks to Mark!

)

On bikes with the vacuum petcocks, remove the seat and then remove the two bolts at the back (seat side) of the gas tank. Pay attention to the grommet placement and orientation. Lift the back of the tank enough to see the petcock from the left side of the bike. I used a folded shop towel to prop up the back of the tank. There is a vacuum line, electrical line(s) and a fuel line attached to the petcock. The vacuum line is the smaller of the two and leads off toward the front of the bike. Follow it and disconnect it from its terminus. Put the vacuum line in your mouth and quickly suck on it. No fuel will come out. If it is working you will feel the vacuum you are creating engage the valve. Don't disconnect the fuel line or fuel will spill. If you remove the tank to test, place a catch can under the fuel line.

If the valve isn't working the valve won't engage or will continue to allow you to suck air. In my case, if I sucked quickly on the hose the valve would engage but if I sucked slowly it wouldn't. Even when it engaged if I continued to suck it leaked air. I got a piece of vacuum hose and replaced the stock hose to make sure the vacuum line wasn't leaking.

I bought a replacement petcock from Randy at RPM racing.

Jeff

CatTomb · May 23, 2013, 01:39:58 PM

Thank you Mark, Thank you Pat...

I rerouted the fuel line. It was over BOTH sub-lines.

Rerouted to this:

I replaced the vacuum hose. It didn't seem to be cracked. I removed it and bent it to and fro. The ends did seem to be flared.

I tested the petcock vacuum (suck test) with the new hose in place. Huge difference from my old hose and old petcock. I feel better about spending the $$$ on the new petcock.

I verified the heat shield was in place.

Now, it is time to give it the ride test!

p.s. to my above post... you also have to remove the side panels to lift the tank.

Billsy5150 · May 23, 2013, 09:16:31 PM

This is very useful! Thanks for sharing. I have an inline filter just before the fuel line splitter, so I need to figure out a way to keep it and get the fuel lines int heir proper placement.

oldktmdude · May 23, 2013, 11:26:37 PM

Quote from: Billsy5150 on May 23, 2013, 09:16:31 PM
This is very useful! Thanks for sharing. I have an inline filter just before the fuel line splitter, so I need to figure out a way to keep it and get the fuel lines int heir proper placement.

Gravity feed and fuel filters don't usually work well together. If you have a free flowing filter with large inlet and outlet tubes it may work for you. If you are riding along and the bike starts starving for fuel, you have created a restriction in the fuel system delivery by installing the filter. Hope it works for you, I couldn't find a filter that would work on my '85. Pete.

Pat Conlon · May 24, 2013, 12:05:13 AM

Billy, Listen to Pete, he is spot on.
You should already have a screen filter on the petcock inlet in the tank.
Unlike the fuel pump models, gravity fed FJ's don't like restrictions in the fuel flow.

Cheers.

CatTomb · May 24, 2013, 09:36:00 AM

Ride report!

Took a ride after making the above "improvements" and then let the bike sit.... and whistle.

It started right up after two minutes, five minutes and twenty minutes.

I'll test it a few more times before my Wednesday departure for the WCR.

If I have further trouble, taking the gas cap apart is next on the list.

Jeff

movenon · May 24, 2013, 11:18:00 AM

Like the easy problems..
George

FJmonkey · May 24, 2013, 06:16:23 PM

Yeah!!! I can leave your name on the WCR rally roster.... Looking forward to meeting and seeing some of you for the first time.

Brian Penney · May 24, 2013, 08:48:53 PM

I'm having the same sort of "lack of fuel" issues, my lines are not pinched but I will try the new vacuum hose. When my tank is low on fuel "Still lots of fuel in the tank" it starts to stumble, I flip the reserve switch and it doesn't make any difference, starves for fuel then I push it to the gas station, fill-er up and away I go. BUT when I open my tank to add fuel it sucks air, bigtime! Where am I getting this negative pressure from? Why does it starve for fuel with a 1/4 tank?

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New petcock and intermittent starting issues...