Fuel starvation

Yoniboi · Post by **Yoniboi** » Fri Jul 01, 2011 1:03 am

I ran out of petrol about three weeks ago, with the tank full. On a hunch, I toggled the on/off switch a few times and the fuel pump didn't make its usual tic-tic-tic noise so I swapped it out and everything was back to normal and fine until yesterday when it did it again.

I was 20km from home, and wondering what to do, so I switched the ignition off, then back on again, just to check, and the pump was working fine tci-tic-tic--tic----tic--------tic----------------tic. Tried the starter and she fired up. 2km later she was out of gas again, turned the bike off, turned it back on again, fuel went did its usual (like it does after you've had the tank off for whatever) started up, ran fine, 2km later the same. I got home, stopping 15 times, 38ºC... sweatfest, but I got home.

What could it be?
It isn't the breather cos I tried with the petrol tank open a couple of times and it made no diff.
It could be a blocked petrol-tap but the inside of the tank is pristine os I doubt it.
What controls the petrol pump? I mean, if it tic-tics for more than 15seconds or so it stops automatically. Might it be doing that while the bike's running???

Thanks in advance for all you help.
John

ThomVis · Post by **ThomVis** » Fri Jul 01, 2011 1:23 am

My fuel pump doesn't tic-tic-tic but hums/buzzes and then stops. Mate of mine had fuel starvation three times one 1 trip, going 120kph when I saw him disappear from my mirrors. His problem was a corroded pump connector.
The ICU controlles the Fuel pump relay which feeds the fuel pump.

spook · Post by **spook** » Fri Jul 01, 2011 2:10 am

I would pull the tap and check the internal filter, as well external one if you have one fitted.

If you disconnect the fuel line put your finger over the end and turn the ignition on. If it sprays fuel under good pressure everywhere. if it is easily held the pump may be playing up

The ticking is the pump pumping fuel into the carbs, the float bowls filling, the needles closing on the seats and the pump coming up to pressure against the closed seats. At that point the ticking stops.

djalbin · Post by **djalbin** » Sat Jul 02, 2011 3:23 am

Tried the starter and she fired up. 2km later she was out of gas again

Sounds a lot like a fuel tank vacuum problem. After the fuel pump has primed the carbs (clicking stops), the fuel flow is basically vacuum/gravity feed into the carbs. If the fuel tank is not venting properly the fuel flow into the carbs stops. Check that the fuel tank air vent is not blocked or plugged-up.

When the bike stops running 2km later - open the gas cap. If you hear a sucking sound, and air rushing in, when you open the cap - the air vent is blocked and causing you problems.

Yoniboi · Post by **Yoniboi** » Sun Jul 03, 2011 8:05 am

Cheers guys,

My first thought was the breather.. so I tried with the gas tap open for a few kilometres and it made no difference.

I'll try my finger over the end of the fuel line, but if it ticks until it winds down/stops (which is does) that means it's fully pressurising the carbs.

Does the pump work while the bike is running, or does it only 'prime' the carbs before the bike starts???

Thanks
John

Post by **FZRDude** » Sun Jul 03, 2011 8:40 am

Should work full time.

McFizzer · Post by **McFizzer** » Thu Jul 21, 2011 1:14 am

Check the positive and the ground leads that go to the resistor above the fuel pump, ran into this problem a week ago andit would only run with the switch on "reserve"

Mike_SS · Post by **Mike_SS** » Thu Jul 21, 2011 2:22 pm

I had a similar problem on a YZF750. Turned out to be a brokem earth lead in fuel pump wiring.

Yoniboi · Post by **Yoniboi** » Mon Jul 25, 2011 4:17 pm

Thanks guys, I'll check both those ideas out in the next couple of days.
Will let you know on the outcome...

Big Jon · Post by **Big Jon** » Thu Aug 04, 2011 10:53 am

ThomVis · Post by **ThomVis** » Fri Aug 05, 2011 12:43 am

More like

Yoniboi · Post by **Yoniboi** » Mon Aug 15, 2011 6:17 am

Deserved smileys there. I know! Sorry!!!

More than a month without approaching a motorbike, or EXUPBroHood as I've been in the Alpes with the DH mountain bike (Morzine) with my mates riding the bikeparks there in filthy weather (it rained every single day) followed by two weeks in a stone house in the French countryside with my girlfriend and the kids.
I had a week to play with the motibikes before I left, as mentioned a month ago, but my car died (coolant rail cracked) and I had to sort it out, no choice.

So I'm in the workshop today, listening to ANR and 'tinkering'. Hope to get the Spondon's fuel probs sorted by the end of business. Then tomorrow I'm off with the bicycles again, this time to Asturias (Spain) to ride decomissioned narrow-guage railway tracks with my girlfriend and a tent for four days.

Next week will see 6 days dedicated to the workshop, girlfriend's working and the kids are with their mum. Want to get the EXUP back on the road after two years languishing unloved in bits. I've got no shame, I know.

Cheers
John

spook · Post by **spook** » Mon Aug 15, 2011 10:22 pm

Shame? Sounds like the good life to me

djalbin · Post by **djalbin** » Tue Aug 16, 2011 12:55 am

John wrote:Want to get the EXUP back on the road after two years languishing unloved in bits.

Good luck getting the bits back together and running again. Mine is in one piece but has been languishing too. As soon as the Monsoon season is over, and the triple-digit heat breaks, I'm going to have some work getting mine back on the road too.

Post by **FZRDude** » Tue Aug 16, 2011 9:57 am

Due to neck/pinched nerve, mine has been sitting for almost 2 years now.

Yoniboi · Post by **Yoniboi** » Tue Aug 23, 2011 12:53 pm

Dude... I thought your problems were leg based! Ouch, good luck with the neck. Is there any progress/impreovement or is this going to be permanent?

Got the Spondon back together today.
New fuel lines
Removed the in-line filter just in case.
Checked all connections. All good.
Re-soldered the connectors to that big oblong white resister (which is more than a bit tatty).
Checked petrol tank... fuel flows out no prob, with as without filler cap.
Re-charged battery.

Fired up first time, on a whiff of choke. Left her running 30 seconds. Killed the engine. Turned it back on again and the petrol pump went mad re-filling the carb bowls..... ergo, problem NOT fixed. WHY DOES THE PUMP NOT PUMP WHEN THE ENGINE'S RUNNING?

Big Jon · Post by **Big Jon** » Tue Aug 23, 2011 4:49 pm

Yoniboi wrote:
WHY DOES THE PUMP NOT PUMP WHEN THE ENGINE'S RUNNING?

Just ran this past a mech friend, apparently (on the Ace and probably the 750) there is a tie-in for the cdi and sidestand switch as part of the safety system. The computer is responsible for stopping the fuel pump when the engine isn't running, hence the whirrrr, tictictic tic tic tic tic. before you start the bike. Once the engine is running the pump should run. If the key is on and you dump the bike, allowing fuel out of the bowls and the needle valves to be open (preventing pressure from stopping the pump like I thought it did) the pump should still stop and not pump all your fuel through the carbs onto the ground. If the pump is running like mad and not supplying fuel you may have another issue with the pump or lines, but if it's not running at all and your running out of gas the pump may be getting a signal to stop running. (you did replace the pump, but how about the relay and, god forbid, the cdi?)
Good luck.

Post by **FZRDude** » Tue Aug 23, 2011 5:10 pm

Yoniboi wrote:Dude... I thought your problems were leg based! Ouch, good luck with the neck. Is there any progress/impreovement or is this going to be permanent?.....

There was a problem with the leg 2 years ago, I broke it snow skiing. The neck thing started about 3 months before the leg. It comes an goes, w/o rhyme or reason and lasts for as long as it pleases. Until it is cronic (more than 12 months straight) I won't have surgery.

Yoniboi · Post by **Yoniboi** » Wed Aug 24, 2011 9:57 am

Dude... Have you been to see a chiropractor (sp)? My ex-wife has scoliosis and would be bed ridden for weeks at a time. A Texan bone cruncher who lives here sorted her out and off anti-inflamatories for the first time in decades. It's lasted too, something like 7 years without any further probs or return visits for further treatment.

Everybody. I HATE ELECTRICS!
Found the problem.. a blown INDICATOR fuse!!! Somewhere along the line someone fitted a 5amp instead of a 10amp and it'd blown. Nothing to do with fuel pumps or side stands or CDIs or anything else AND THE INDICATORS WORKED FINE!!!!

OK.Shoot me down in flames for not checking the fuse first, but who checks an indicator fuse when the indicators work???

Just went for a blast and everything's just like it should be.
THANKS FOR ALL THE HELP. Even if you didn't nail it, who would? And you do serve as enormous encouragement just knowing you're there.

CHEERS
John

Big Jon · Post by **Big Jon** » Wed Aug 24, 2011 10:36 am

Yoniboi wrote: Everybody. I HATE ELECTRICS!

I totally understand, Electrical is black magic. Mechanical issues are so much easier; "Oh look there's an oil leak, let's fix, The oil leak!" I've an electrical issue with my trucks trailer wiring, it's annoying but not something that keeps me off the road like a fuelling issue. Glad it's sorted!