Another fuel relay related topic

[Lucass2T]

Since I couldn't find a topic where this specific symptom was discussed, I created a new thread.

Context:
88' Hawk 650.
Bought the bike few months ago with 16k miles on the odo (probably rolled back). Bike ran fine.
Did some way overdue maintenance on it. Fluids, filters, valve clearance and cleaned (ultrasonic) and rebuilt the carbs. Set float height to 9.2mm. Membranes all in good shape.

Problem:
While riding, now and then the bike gets starved of fuel and cuts out.

Diagnosis:
After it stumbles or dies, the fuel filter is empty or only filled up a little (maybe 20%). In my perspective it should be full.
It doesn't care whether you are pinning it, cruising riding on the highway @ 80mph or slow stop and go city traffic.
It comes and goes at random moments.
I did check the fuel pomp as described in the manual. Inspected, sanded and cleaned the points behind the black cap. Pulled fuel line T joint on carbs, pulled relay and connected blk/blu and black. Pump works perfect with ignition on. Reconnected fuel line to T joint and with float bowl drains open checked again. It's happily clicking away like it should.
It also stops by itself after the bowls are full.

The relay's contacts are obviously not welded since it works most of the time.
But it seems to hesitate now and then and doesn't want to power the pump.
I am suspecting the relay here being faulty, what do you guys think?

Thanks Lucas

[squirrelman]

a common problem, wire a switch to bypass the relay at the plug.

[Lucass2T]

a common problem, wire a switch to bypass the relay at the plug.

Thanks Squirrelman, luckily its not some weird obscure problem! With 'wire a switch' you mean a remote switch to manually engage or disengage the pump? Why not permantly wire the blu/blk and black together at the relay's connector?

[squirrelman]

Thanks Squirrelman, luckily its not some weird obscure problem! With 'wire a switch' you mean a remote switch to manually engage or disengage the pump? Why not permantly wire the blu/blk and black together at the relay's connector?

relay is a safety feature to stop pumping if bike goes horizontal

[Lucass2T]

relay is a safety feature to stop pumping if bike goes horizontal

Hi Squirrelman,
Thanks, but yes I know.
Wiring in a manual switch (I assume thats what you meant) defeats the safety feature.
So what exactly did you mean?

[Captain 80s]

Why not permantly wire the blu/blk and black together at the relay's connector?

I find it nice having a switch for times I may be working on the bike (like the fuel system) and I don't want the pump able to operate every time I (or anybody) might turn on the key.

I typically keep my relays, but wire in a parallel switch so I can prime the system after winter storage or if it has sat for an extended period. Also to get me home when the relay fails.

[ParcNHawk]

I put a momentary push button primer on every Hawk I touch.

I use it to prime empty carbs ESPECIALLY when the switch to reserve wasn't quick enough.

Rip out the relay if it's bad. It's a lousy safety feature because it doesn't stop anything if the motor is still running after the crash.

[Lucass2T]

I put a momentary push button primer on every Hawk I touch.

I use it to prime empty carbs ESPECIALLY when the switch to reserve wasn't quick enough.

Rip out the relay if it's bad. It's a lousy safety feature because it doesn't stop anything if the motor is still running after the crash.

You mean if you run out of fuel and need to switch to reserve?
Haven't really experienced it yet but I can imagine you don't want to be waiting too long for the fuel to reach the carbs when you're in heavy traffic and without a shoulder to patiently wait.
Thats a good one actually!
And yeah, the relay may serve a safety function in only a very few and specific situations.
Im heading out on a 2000km (1200mi) roadtrip through the Swiss Alps tomorrow.
For now I'll bypass the relay.
I'll buy a new one eventually I think, or maybe not...
Thanks guys for the help!

[6]

You mean if you run out of fuel and need to switch to reserve?
Haven't really experienced it yet but I can imagine you don't want to be waiting too long for the fuel to reach the carbs when you're in heavy traffic and without a shoulder to patiently wait.
Thats a good one actually!
And yeah, the relay may serve a safety function in only a very few and specific situations.
Im heading out on a 2000km (1200mi) roadtrip through the Swiss Alps tomorrow.
For now I'll bypass the relay.
I'll buy a new one eventually I think, or maybe not...
Thanks guys for the help!

The best thing about the stock pump over the vacuum pump is that you can jump that relay and just let it supply the needed fuel if the ignition is on..

In reading your post I was reminded of two things. A tank I had that was vapor locking and wouldn't feed after running for a while, and a fuel line I routed on an ex500 that looked fine, but would get soft and crimp at a bend when the under tank area got hot.

It doesn't sound like either of those are your issue though.

[Lucass2T]

The best thing about the stock pump over the vacuum pump is that you can jump that relay and just let it supply the needed fuel if the ignition is on..

In reading your post I was reminded of two things. A tank I had that was vapor locking and wouldn't feed after running for a while, and a fuel line I routed on an ex500 that looked fine, but would get soft and crimp at a bend when the under tank area got hot.

It doesn't sound like either of those are your issue though.

I wouldn't suspect those either...but thanks for bringing it up.
From the two you suggested the vapor locking tank is the only one I can't really dynamically check, only visually.
I did inspected the inside of the gas cap, seal, fitment etc, but nothing out of the ordinary. It was running fine before so I wouldn't suspect it immidiately.
It's definitely not a kinked or crimped fuel line. I've specifically checked those over multiple times. They are routed around without any tension or anything.

[6]

I wouldn't suspect those either...but thanks for bringing it up.
From the two you suggested the vapor locking tank is the only one I can't really dynamically check, only visually.
I did inspected the inside of the gas cap, seal, fitment etc, but nothing out of the ordinary. It was running fine before so I wouldn't suspect it immidiately.
It's definitely not a kinked or crimped fuel line. I've specifically checked those over multiple times. They are routed around without any tension or anything.

To check vappr locking I wait till it starts to die, pop the fuel cap and see if she revs back to life. Or pull over when it's dead and open the tank an listen for the "pssst".

But that's just for conversation. Sounds like your pump really will take care of you.

[Lucass2T]

The saga continues...

Two days into my roadtrip and two days of applying various riding styles it's still giving me problems.
I bypassed the relay so the pump comes on when ignition is on, but......

The pump turns on and fills the fuel filter up fully. After about 10mns of riding the sputting starts and the filter is completely empty.

When I tap the black cover on the pump a few times the pump comes back to life and starts pumping again.

I feel like the pump's internal pressure regulator is off. Somehow it thinks the bowls are full and just stops pumping. I took the pump out, disconnecting the fuel lines, hooked up the connector and it worked perfectly.

I tested the pump's flow earlier with the bowl drains opened and it was pumping fuel through the system so no blockages.

Could it be that the pump is clocked wrong and now it thinks it sees back pressure when there isnt any?

How does the pressure regulator work anyway? With a spring loaded valve or something? Could that be broken?

[squirrelman]

might it be dirty electrical contacts [under the black cover] ? very carefully cleaning with fine sandpaper might be helpful.

[squirrelman]

The saga continues...When I tap the black cover on the pump a few times the pump comes back to life and starts pumping again.

only clue needed that it might be helpful to clean the contacts under the cover. being careful not to bend anything, etc.

[Lucass2T]

might it be dirty electrical contacts [under the black cover] ? very carefully cleaning with fine sandpaper might be helpful.

I already did that back home so was already taken care of.

It's very weird. I am overlooking something or I don't fully understand the workings of these pumps.

What does it make turning off at a certain line pressure? How do these pumps regulate pressure?