Fuel delivery problems

[Bigfoot]

Sorry if this has already been gone over but I did a search and it wasn't much help. The problem I have is the carbs keep running out of fuel at anything over 55mph for an extended period of time (15 - 20 minutes). It was real bad the last ride I took it on. In fact, I got passed by a group of Harleys as I sputtered down the road until I could find a safe place to pull off and let the fuel catch up. That is just not acceptable.

I have changed the fuel filter. I tried running with the petcock in Prime position, that should rule out vacuum problems or blockage in the petcock. Fuel ran out nicely on prime when I had to drain the tank awhile back. I even ran for awhile with the gas cap open to see if it was a problem with the tank vent (is there a vent in the cap?)

This is on an 84 that otherwise runs great. Any suggestions would be appreciated.

[andyb]

Probable places for restriction:

Fuel filter.
Gas cap vents.
Within the carbs, above the float needle seat, the screens (unlikely, some bikes also don't have them at all).
Pinched fuel line to carbs.
Floats not opening fully (again unlikely for all to be doing the same thing).

My guess is the gas cap venting system is clogged full of junk.  The typical answer is if you have a spare key, go riding down the road and when it starts to splutter, use the spare key to open the gas tank; it should "woosh" in and the bike will pick up shortly after.

Within the gas cap are two orangey rubber diaphram valves.  Take it all apart carefully (there's a spring and a ball bearing, do the math on what happens when they're right over a gas tank?  SPROING!), and remove the rubber valves from the cap.  Reassemble and grease it while you're at it.

The fuel line routing is another questionable area.  FJ's have to have the lines just right or they immediately f'king kink themselves and are useless.  Not that I'm bitter about this.

Running the petcock in prime will remove the vacuum diaphram portion of the petcock from the equation, you're right.  Petcock petcock petcock.  Pet cock?  Pet cock.


From what you describe, check the fuel line routing with extreme care.  Make sure also that there isn't a second filter in the fuel path (from a PO possibly?).


And for the last question, are you certain that it's a fueling issue?  Not possible that the battery is getting boiled on or something?  Not questioning you, just make sure you're not barking up wrong trees.

[Bigfoot]

Thanks for the reply. Yeah, I am pretty sure that it is a fuel problem. I at first suspected the vent, but I actually opened the gas cap completely and it still happened. Sort of ruled that out but I will clean those vents anyway. I will take a look at the fuel line routing. I have intended on replacing the fuel lines anyway so I guess that would be a good time to do it. It has a small inline filter that I replaced with a new one of the same style. Little cone shaped type that they sell in the bike shops. Is it possible that it is too restrictive even when new? I guess I will eliminate it (for now) when I replace the fuel lines.

[Fred]

I don't think the 84's are supposed to have a fuel filter. Since this does I have to ask if its the stock fuel hose and how is it routed? FJ's are very particular about the type of hose and routing.

[RichBaker]

Thanks for the reply. Yeah, I am pretty sure that it is a fuel problem. I at first suspected the vent, but I actually opened the gas cap completely and it still happened. Sort of ruled that out but I will clean those vents anyway. I will take a look at the fuel line routing. I have intended on replacing the fuel lines anyway so I guess that would be a good time to do it. It has a small inline filter that I replaced with a new one of the same style. Little cone shaped type that they sell in the bike shops. Is it possible that it is too restrictive even when new? I guess I will eliminate it (for now) when I replace the fuel lines.

Everyone on the FJ forums who has an 84-85 that they had installed an inline filter on has had the same problem...... 1st gen FJs MUST have the stock-length fuel line and NO added filter, otherwise the fuel line kinks and cuts off fuel flow. Some have replaced the hose with one slightly longer to facilitate removing the tank and they had to cut it down to the correct length.... and route it according to the factory routing diagram under the seat.

[Dan Filetti]

... and route it according to the factory routing diagram under the seat.

I seem to remember somewhere, someone saying the diagram under the seat was incorrect -This ring any bells with anyone?  Or am I imagineering?

Dan

[SlowOldGuy]

I seem to remember somewhere, someone saying the diagram under the seat was incorrect -This ring any bells with anyone?  Or am I imagineering?
Dan

I think the routing diagram was a problem in '86.  It showed the line to the petcock routing on top of the  hose loop.  It needs to go below the loop.  I think they tried routing it on top to make disconnecting the petcock line easier.  Unfortunately, this causes the tank to compress the hose and cut off flow.

DavidR.

[Pat Conlon]

Everyone on the FJ forums who has an 84-85 that they had installed an inline filter on has had the same problem...... 1st gen FJs MUST have the stock-length fuel line and NO added filter, otherwise the fuel line kinks and cuts off fuel flow. Some have replaced the hose with one slightly longer to facilitate removing the tank and they had to cut it down to the correct length.... and route it according to the factory routing diagram under the seat.

+1  The gravity fed early FJ's are very picky about fuel hose routing and length, and absolutely NO in line fuel filter should ever be used.

[Bigfoot]

Thanks everyone. I guess that would explain my problem. My FJ has a very nice Corbin seat on it with no fuel line routing diagram. Does anyone have a picture of the diagram that they could share and maybe the length of fuel line that is needed?

[SlowOldGuy]

Haven't checked the files section here, but here's a link to the Yahoo file on fuel hose routing.

Looks kinda long, you may have to cut and paste.

http://f1.grp.yahoofs.com/v1/QMb5Si2bGCKffmjMK7woRRVYAyalez8sEMjpmSHsNjw0IL7gFo41dZ76IgGrYxnGHGuHzQfZZ1I49A1ZEFho6LIMgzW8yA/Fuel%20Line%20Routing.pdf

DavidR.

[Bigfoot]

I couldn't get the link to work. I went to the yahoo site and found a couple files for the routing of the fuel line for the 86 and 87 model. Would that be the same for the 84.

[SlowOldGuy]

Hmm..., link doesn't work for me either, stupid Yahoo, no wonder no one likes their groups.

Yes, the fuel hose routing for the '84 through '87 is identical.

DavidR.

[Harvy]

Hmm..., link doesn't work for me either, stupid Yahoo, no wonder no one likes their groups.


DavidR.

Except for George.

Harvy

[Dan Filetti]

While you're replacing hose anyway, I wonder if anyone has ever replaced the standard hose with a more crush-resistant version, thereby perhaps making routing a bit less of a critical path item?

Anyone?

Dan

[56 CHEVY]

While you're replacing hose anyway, I wonder if anyone has ever replaced the standard hose with a more crush-resistant version, thereby perhaps making routing a bit less of a critical path item?

Anyone?

Dan

On my 86 I replaced my hoses with automotive fuel line and I've never had a problem.