Urgent: cutting out

Cobblesmacker · June 17, 2018, 01:38:07 PM

So my 94 non abs FJ 12 has been sat a month or so awaiting a rear brake rebuild whilst I rode my newer and shitter bike around.
While the FJ was sat I removed all fairing and clocks, replaced the light units and indicators, replaced the battery, took out most of the aftermarket wiring (a shopping bag full), and took the remus slip on off leaving the remus headers and link pipe.

So the issue is I started a new job and on that very morning my first bike fried electrically. So I catch the bus and plan to get the FJ going for work.

So the FJ started and was great for five minutes so I made haste on my test trip when it cut out at a fuel station I thought nothing of it and filled up. Got another mile further from home and it cut out again taking ten minutes before working again and cutting out after another few minutes.

Feels almost like it runs out of fuel but when I turn the bike on I do hear the fuel pump... Though it may be my imagination that it seems to pump a little longer than normal.

Thanks for reading.

racerrad8 · June 17, 2018, 04:14:45 PM

The fuel pump having a longer cycle indicates it is trying to build pressure. But if there is not enough flow to the pump it will never fully build pressure.

Start at the tank.

Rust/debris plugging fuel screen in tank.
Petcock not fully opening.
Fuel cap not venting causing vacuum
Kinked fuel line

Randy - RPM

Pat Conlon · June 17, 2018, 06:58:21 PM

Assuming your fuel path is clear (check first) try bypassing the fuel pump, see if the symptom goes away.

I made the mistake of buying a FleaBay China fuel pump with a "lifetime guarantee" ...never again.

ZOA NOM · June 17, 2018, 11:52:05 PM

Do NOT half-ass your fuel system...

Cobblesmacker · June 18, 2018, 12:41:06 AM

Cheers guys will let you know later after work and after spending a tenner to get there

The tank has been off so chances are as it sat funny some rust has swilled in. Guessing it is a partial block because it seems like it fills the bowls to run for a couple of minutes but then the bowls run dry and it doesn't fill in time. There is an in line fuel disconnect. Will probably start with cleaning that as it's a bottle neck and the only thing in the system I've touched.

Cobblesmacker · June 19, 2018, 03:15:46 PM

So I checked the flow pre pump and it was fine flowing with just gravity both before and after the filter. The pump comes on but seems to build no pressure and stays on for a while and it doesn't sound like it really slows before turning off. Does the pump only turn off when it builds pressure? While the bike was running it didn't feel like the pump came as the bike bogged and stopped as I kept my hand on the pump while it ran. Is it worth buying a pump? As the cheep ones are poor, does anyone have a recommendation to get one ASAP in the UK?

Cobblesmacker · June 19, 2018, 03:35:41 PM

Just took the out pipe off of the pump and turned the key, the pump kicked straight into life coughing fuel everywhere. So it works at least not under pressure. So I'm not sure what all of this means.

Cobblesmacker · June 19, 2018, 03:46:24 PM

Have just read that the fuel pump will cut out after 3-5 seconds with no tach signal... I have no tach so could that be something? If so, anyone know how to bypass? It's not obvious to me on the wiring diagram.

Pat Conlon · June 19, 2018, 04:12:23 PM

Bingo.

Yeppers...No tach signal, no fuel pump after 5 seconds.
It's a safety feature. If you have an accident you don't want the fuel pump to continue to run after the engine stops.

Wire the fuel pump to any 12v keyed power source. Plan on running this way only temporarily.

Cobblesmacker · June 19, 2018, 11:25:59 PM

Brilliant. Now to see whether I trust the hypothesis enough to see if it gets me to work this morn. Not sure if that is 100% the issue as it was taking 30 mins before it would start again.

Pat Conlon · June 20, 2018, 02:06:19 AM

Quote from: Pat Conlon on June 17, 2018, 06:58:21 PM
Assuming your fuel path is clear (check first) try bypassing the fuel pump, see if the symptom goes away.

Did you try this?
If you ever have a fuel pump problem, you need to know how to do this.
Every '88 to '95 FJ owner needs to know how to do this.
It will mean the difference between walking and riding.
Knowing how to do this will get you home.

Cobblesmacker · June 20, 2018, 03:40:14 PM

Wiring the pump to the rear brake light switch power worked just great. Such an easy fix yet so much head scratching.

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Urgent: cutting out