Re Will not start

chiz · July 07, 2013, 03:47:26 PM

This is still an ongoing problem. A few days ago I noticed the engine would splutter with no choke and no throttle after this initial splutter NOTHING just cranking..
After a long hot day in the shed I hit the button with about 1/4 throttle and the fj burst into life and ran well on the centre stand. a few days have gone by and twice a day i start it like this and it runs well.
Today off with the lawnmower tank and on with the real tank not positioned properly but gas hose hooked up...started no problem.. ran it for a couple of minutes it got good and hot ... noticed an oil leak from bung front lower left removed bung and fitted new o ring on it.
Positioned tank properly hit the button spluttered... back to square one nada nothing zilch what the heck any tips.
Lez

fj11.5 · July 07, 2013, 04:37:12 PM

What year fj, ,kinked fuel line

,,blocking fuel filter,

chiz · July 07, 2013, 05:06:42 PM

Hi Yes 84 FJ new fuel filter just started again cant rely on this beast to go to the corner store, someone said the internal standpipe carb vents may be an issue?
lez

Pat Conlon · July 07, 2013, 05:30:32 PM

Hello Lez, don't give up.

The '84's have a vacuum operated petcock. If the bike starts and runs fine on a aux. tank, and not when you install your fuel tank, a couple of things come to mind.

1) your vacuum operated petcock is not opening, caused by
a) a disconnected or leaky vacuum line. The line needs to be tight on both ends and free from cracks. The line should be connected to the vacuum port on the #1 intake manifold and at the petcock.
b) the petcock itself is not opening or failing to stay open, caused by bad diaphragm seal internal to the petcock. A fact of life is that the seals on these vacuum petcocks wear out. Here's how to check. On the petcock there is a lever with 3 settings: Off....On....Prime (P)
Set the petcock lever to the Prime (P) position. If the bike now starts and runs, then you have a problem with the petcock.
In normal running condition the petcock lever should be set to the On position. That position is where the engine vacuum opens and closes the petcock. With the tank off, put a line on the petcock vacuum port and with the lever in the ON position suck on the open end of the line. You should hear a slight click and the petcock should open up and gas should flow. Now while you are sucking on the line, put your tongue on the open end on the vacuum line. The petcock should remain open. If not then the seals in the petcock are not holding a vacuum. Buy a new oem Yamaha petcock from Randy at RPM and call it a day.

2) something else (besides the petcock) is blocking fuel delivery to the carbs. Drain the tank and remove the petcock and look at the filter screen...is it clean? Or full of crud? Do you have rust in your tank? You should not have any type of inline filter on your fuel line running from the tank to the carbs. The '84-'87 gravity flow FJ's are very sensitive to restrictions in the fuel line (like filters) The only filter you have on your '84 should be the screen on the petcock inlet.

3) pinched fuel line. Fuel line routing is important on the gravity fed FJ's
As the single line leaves the petcock outlet...it should run UNDER the 2 branch lines which feed the carbs.
If it runs over the branch lines, it is wrong and WILL pinch off fuel flow as the fuel line heats up and gets soft.

Again, don't give up.... Hope this helps. Pat

fj11.5 · July 07, 2013, 05:57:22 PM

Well said pat, all that should go straight in the files section, you summed it up nicely

Pat Conlon · July 07, 2013, 06:01:51 PM

Thanks Rod. I wonder if it's me...or are we seeing a lot of vacuum petcock problems lately?

CatTomb · July 07, 2013, 06:05:19 PM

Chiz,

I, too, had a similar problem...

I tried new petcock, new vacuum lines, flapectomy, ensured proper fuel line routing, clean tank and still had a problem intermittently. Sometimes it would start and sometimes it wouldn't. Didn't seem to matter if it was cold, hot or how long it had been sitting (had problems from as little as 10 minutes to overnight and every possible temperature from below freezing to 95F.)

Made a call to Randy at RPM after sitting at a gas station for 90 minutes tinkering with it trying to get it to start. He suggested loosening the screw at the bottom of one of the float bowls. "If it starts to leak gas... it's not a fuel issue it is an electrical issue".

I checked, fuel in the bowls, so Randy suggested disconnecting and reconnecting as many electrical connections as I could find. I already had the seat and side panels off, so I carefully disconnected, blew into and reconnected as many connections as I could get too... It started right up!

Thanks Randy!

When I got home I bought some electrical connection cleaner and did a bit better job. Disconnected, sprayed and tried to clean as best as I could with Q-Tips and nylon brushes.

I haven't had a problem since.

(knock on wood)

Hope this helps,

Jeff

Pat Conlon · July 07, 2013, 06:20:03 PM

ooooh, very good Jeff. That Randy fellow is a pretty smart dude huh?

I thought of that, but ruled it out because Lez said that his bike ran fine on the aux. fuel tank

fj11.5 · July 07, 2013, 06:40:46 PM

Your right pat, seem to be at least one a week lately,

Rod

chiz · July 07, 2013, 07:15:47 PM

All bloody good stuff thanks to all I will remove the in-line filter Pat. Your points were good ones. The gas tap appears to be brand new I guess po had some issues as well, man had bike for 2 weeks and cant ride it sounds sooooo good. Did some dielectric grease to 3 or four connectors today will do the rest hope I didn't f anything up
Lez
Thanks to all

ribbert · July 08, 2013, 02:40:59 AM

Quote from: Pat Conlon on July 07, 2013, 06:01:51 PM
I wonder if it's me...or are we seeing a lot of vacuum petcock problems lately?

Fuel delivery problems with gravity feed have never been far away on the forum.
Ever wonder why Yamaha went to fuel pumps?

With the tank sitting so close to the carbs there is very little head pressure and it doesn't take much to interrupt the flow.

A fuel pump offers reliable supply and the benefit of decent filtering.

For those that might say, it's just something else to go wrong or what if the pump dies? Over the life of the bike you are likely to replace it maybe once. In the event of a failure, it can be bypassed and still ridden home.

I see a time in the future, when, decreed by the right people, it will become part of the "standard package" of FJ mods.

Noel

fj11.5 · July 08, 2013, 03:51:34 AM

And some wondered why I wanted to fit a fuel pump to mine

movenon · July 08, 2013, 04:46:59 AM

Noel and fj11.5, right on ...

If owned a gravity feed FJ, modding to a fuel pump would be one of the first things I would do.
George

Pat Conlon · July 08, 2013, 10:56:18 AM

Yep, that is something to consider, adding a fuel pump.

Other than the benefit of *positive* fuel delivery, none of the vacuum shenanigans, the big plus with the fuel pumpers is the fact that you can run a REAL honest to God fuel filter, keeping shit out of your carbs.

Something to consider with the new fangled ethanol laced gasoline absorbing water and causing rust in our old tanks.

I never had ANY problems with my '92 fuel pumper, that I had with my '84 gravity flow.

RichBaker · July 09, 2013, 09:14:29 PM

Quote from: CatTomb on July 07, 2013, 06:05:19 PM
Chiz,

I, too, had a similar problem...

When I got home I bought some electrical connection cleaner and did a bit better job. Disconnected, sprayed and tried to clean as best as I could with Q-Tips and nylon brushes.

I haven't had a problem since. (knock on wood)

Hope this helps,

Jeff

It's also a very good practice to squirt some dielectric grease into the connectors before reconnecting them... It will prevent corrosion from forming again.

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Re Will not start