Strange fuel pump (?) issues

metropolis2k

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After parking it up one night, I went back the next morning and the bike wouldn't started. Turned over fine and is trying to fire but just woudn't. The pump wasn't priming when turning the key, so it wasn't getting fuel and I obviously suspected the fuel pump controller. As I didn't have the parts to bypass it properly I just picked up a new one but it didn't fix it.

Today I ran the pump directly from the battery and it does allow the bike to start but it died soon after (even if I keep the pump on). Then strangely when I ran a controller bypass it did prime but only started briefly. Now it's stopped priming again.

Any thoughts as to the most likely cause? I don't have access to a GS911 to read for faults. Could it be the fuel pump is dying and it only works getting a direct 12v feed (but not for long)? :nenau
 
What year is the bike ? and what millage has it done ?
A twin cam should have a fuel pressure of 60 psi pre twin cam it should be 45 psi .
I have had a Twin cam run at 25 psi fuel pressure but only just and it was struggling to make progress.
I have had BMW pumps fail at 45K miles and the aftermarket ebay pumps I consider a service item and replace every 30 k miles.
A GS911 will not report a fuel pressure problem as it is a mechanical system without any pressure sensors.
Only way is to read the pressure is with a gauge , preferably under load at speed in top gear.
If the brushes in the pump are on their last legs you can get an intermittent fault.
 
It's a 2008 with 35k miles on it but I've only had it a year.

What I've figured out from some research is whatever is happening has tripped the electronic fuse which is why I was reading no voltage going to the pump. I was able to get it working again once I'd manage to start the bike by running the pump directly from the battery, but then it has tripped again since. I should be picking up a new fuel pump in the morning so hopefully will know if that was the issue over the weekend.
 
see if theirs a few pump waiting due to a recall

the plastic factures and allegedly squirts fuel about - which some suggest is a nuisance, so BM gave a way free one's around this timeline ( I got one)

if you have ESA you might want to get a float fitted if the pump is coming out
 
I fitted a new aftermarket fuel pump kit to my Hexhead at about 46k due to lumpy midrange running and crap acceleration caused by low fuel pressure. It transformed the bike. I think the OE pump gets weak once past 35k. Mistacat has plenty of experience with this issue.

If you search the Hexhead section there are a couple of threads about trying to solve crap acceleration and rough running, finally solved by changing the fuel pump.
 
Just a couple of notes.
When you switch the ignition on the pump only runs for a couple of seconds ( not enough to achieve full fuel pressure but enough to start the bike).
If you switch the ignition off then on again numerous times the pump does not run.
The pump only then runs when you press the starter button.
If the engine has been started then switched off the pump will then run for a couple of seconds when the ignition is switched on again.
 
I forgot to add, I also did the 'Hidden Filter Bypass' on mine to drill out and flush out the clogged plastic unaccessible screen moulded internally between the fuel pump outlet and the pump outlet pipe fitting. I then fitted a remote high pressure fuel filter to the outlet pipe same as an 1150GS has for relatively low cost.

Details in this thread:

https://www.ukgser.com/forums/showthread.php/530719-R1200GS-A-Hidden-Filter-bypass

There are a few comments from me in that thread regarding changing to the Quantum aftermarket fuel pump kit and adding the external filter.
 
Thanks for all the advice chaps.

I went to pick up a new fuel pump from BMW but was greeted by a £400 entire assembly and was told they do sell just the fuel pump (albeit in its white plastic casing and with mesh bag) but it's £385 :eek:

Then I had a theory - the fuel level looked low in the left side of the tank, even though I have half a tank on the indicator so I put some more in. No priming when turned on again so I tried the trick of running the pump off the battery (and it started and ran fine), then reconnected everything and it primed and started. I suspect fuel level was low on the left side of the tank and because the bike didn't think it was low, it wasn't pumping anything from the right side of the tank over. And it wouldn't prime because it somehow sensed it wasn't getting any fuel. What's really strange is that it was running absolutely fine one day then the next wouldn't even start but I guess with the engine running it was pumping the fuel it needed from one side to the other and it's only when I stopped the bike it then stopped doing that :nenau

I still might replace the fuel pump just while I'm at it given it's 35k old and as a few of you have mentioned can impact how well it runs, but it looks like what it needs is a new fuel sensor strip. It has always had an issue at the very bottom of the range (it starts to drop very quickly then recovers when nearly empty) but it appears to be completely screwed now.
 
The return 'sucking jet pump' is a venturi unit driven by fuel pressure. When the fuel pump gets worn and pressure is low, it no longer returns the fuel from the right wing back to the left wing of the tank. Had this issue myself although mine was the fuel pump controller running the fuel pump too slowly rather than a worn pump. Leaning the bike over to the left to slosh fuel back to the pump got me going again after coughing to a stop. My pump got bad around the 45,000 mile mark, some do better some do worse.


My advice:

Buy yourself a Quantum HFP-382-B fuel pump kit (mine was £45 on Amazon), easy to fit, lasts as long as the OE item from BMW, way cheaper. Why not do the filter bypass mod and external fuel filter whilst you have it apart.
 
The return 'sucking jet pump' is a venturi unit driven by fuel pressure. When the fuel pump gets worn and pressure is low, it no longer returns the fuel from the right wing back to the left wing of the tank. Had this issue myself although mine was the fuel pump controller running the fuel pump too slowly rather than a worn pump. Leaning the bike over to the left to slosh fuel back to the pump got me going again after coughing to a stop. My pump got bad around the 45,000 mile mark, some do better some do worse.


My advice:

Buy yourself a Quantum HFP-382-B fuel pump kit (mine was £45 on Amazon), easy to fit, lasts as long as the OE item from BMW, way cheaper. Why not do the filter bypass mod and external fuel filter whilst you have it apart.

+1 :thumb2
 
Thanks Pukmeister. I think I'll switch out the fuel pump while I'm messing around in there. I've also put one of the new fuel sensor strips on order too which I'll do at the same time.

Very tempted to also look at the filter bypass mod as you say. I don't believe in a 'lifetime' fuel filter having seen a few old ones coming off my previous bikes.
 
Very tempted to also look at the filter bypass mod as you say. I don't believe in a 'lifetime' fuel filter having seen a few old ones coming off my previous bikes.

Its not a filter exactly, more a fine plastic screen moulded within the fuel outlet head flange that is inaccessible/uncleanable. Once I had carefully drilled mine out and fitted the external high pressure Mahle fuel filter the bike ran a LOT better, especially at bigger throttle openings. I can only conclude that my bike was being starved of fuel flow at high rpm until modded (perhaps running dangerously lean to boot).
 


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