Excessive Fuel Usage

[basadia]

I've owned my 05 ST1300 for about three years and have noticed consistent fuel usage over the time I've owned it, 430 ks highway and around 390 around town to the reserve.

About three months ago whilst riding I noticed the average fuel usage gauge which normally sits on 16.1 ks/l dropped over a couple of minutes to 15.8 which I thought at the time to be strange. Since then I now only get around 330 ks around town and just over 400 on the highway to the reserve. This would indicate to me that something in the fuel system has either failed or is not performing correctly, the bike itself runs normally, no black smoke or other side effects it's just using more fuel. I've opened the air box and had a look and there are no vacuum leaks, I've just added a bottle of fuel injector cleaner and going to install new plugs when they arrive.

This issue has me confused and I'm not really sure what to look at if none of the regular maintenance items don't correct the problem. Does anyone have any other suggestions? I'm thinking a failed sensor also might be causing the issue as it came on so suddenly.

[Skip]

   That sounds more like a hole in the tank. That is horrendous consumption.

[cravenhaven]

That's a terrible fuel use rate. I normally get approx 20 km/l on my 03 ST1300 and was getting better than that until I damaged something on the Perth rally trip.
Normally the computer would alert you to a failed sensor by blinking the FI PGM LED (Red one on the dash). Have a look in the manual on Page 5-7 to read out the error data stored in the computer.

[basadia]

That's a terrible fuel use rate. I normally get approx 20 km/l on my 03 ST1300 and was getting better than that until I damaged something on the Perth rally trip.
Normally the computer would alert you to a failed sensor by blinking the FI PGM LED (Red one on the dash). Have a look in the manual on Page 5-7 to read out the error data stored in the computer.

20 km/l that's amazing, not sure why mine is chewing the petrol then. It does have a K&N air filter but I've given it a good clean with compressed air, don't have a cleaning kit but am thinking of purchasing one. Wish I could get close to those mileage figures that would have to be around 600 ks to the tank :-).

[cravenhaven]

I can normally rely on about 550, but usually fill up under 500 because I hate it when the distance left display goes blank :).

[alans1100]

The on board fuel usage is only a guide and even the owners manual suggests you'll often get better than indicated.

I use tank to tank and distance per fill at as a better indicator and even that is subject to odometer error. The 1100 figures in my signature below cover all the fills over the last four years ranging from worst (head wind with a trailer) to the best (tail wind riding solo)

I haven't had the 1300 long enough (mid July) and since then she's averaged 19.7 k/l with an estimated range of 535 km based on this bikes odometer error.

Recently I've started to compare the on board reading to the tank fill numbers; e.g. 18.5 on board and 19.2 odometer based and most showed better than indicated and one going the other way as the manual suggested.

[Brock]

Check your K&N filter, if it has the green (??) foam outer, take it off.  Its well known in the USA to cause high fuel usage to blocking too much airflow.

You may have a leaking fuel pipe, better check that as soon as, dont want to burn the bike..

[Gadget]

It could be a lot of things.

- Valve clearances
- Partially blocked injector
- Ignition lead/s breaking down
- Friction in the wheel bearings front or rear.
- Brake pads not clearing properly after application due to not enough 'throw' in the disk or sticking pistons.
- head gasket leaking
- broken hose in the 5 way map sensor area under the Air box.
- broken wire around the engine managment on air box.
- etc.

All the best tracking it down.

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[basadia]

Check your K&N filter, if it has the green (??) foam outer, take it off.  Its well known in the USA to cause high fuel usage to blocking too much airflow.

You may have a leaking fuel pipe, better check that as soon as, dont want to burn the bike..

No foam cover on my K&N so it's not that, just had the cover of the air box looking for any vacuum or fuel leaks so all good there. I've seen leaking vacuum hoses can cause excessive fuel consumption but it's not that either, I've got a cruise control unit that runs off vacuum and it there is any drop in vacuum it stops working. So far no issues with the cruise control so it's not that either. I've got a set of iridium plugs on order which should be here next week so I'll rule out fouled plugs when I change them.
I'll check out excessive friction in the wheel bearings or binding breaks but I roll the bike out every morning by hand and I would have noticed excessive drag when I roll the bike out so I don't think that is an issue.
I'm more leaning towards a faulty sensor, I did notice it has a map sensor in the air box so I may replace that but I'm not sure what other sensors are used in the fuel system.

[Gadget]

There's a 5 way connector under the Air box which can get blocked and cause weird stiff to happen.

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[basadia]

There's a 5 way connector under the Air box which can get blocked and cause weird stiff to happen.

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Yep seen that when I pulled the tank cover, I checked that there were no holes and loose connection, might have to pull it off and blow it out with the compressor. Not real easy to get to though. Might do it when I do the spark plugs.

[Gadget]

I used metho and a pipe cleaner because there was a thick grease/gel build up.

There's a thread here somewhere on how to clean it.

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[basadia]

I used metho and a pipe cleaner because there was a thick grease/gel build up.

There's a thread here somewhere on how to clean it.

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Popped the tank open again this afternoon and learned a valuable lesson, if the tank is full drain some of the fuel. I lost about half a liter on my shed floor before I realized fuel was coming from the filler overflow. Cleaned out the five way vacuum hose and the other one on the right side bank of throttle bodies also popped the fuel rail and lifted the injectors to do a visual and they all appeared clean. Crap job getting the injectors, clips and fuel rail back on though. I think I snapped a couple of the locator clips when I was tightening the fuel rail bolts down but the engine is running fine.
I'll run a couple of tanks through it to see if any of the stuff I've done has made any difference to the economy, I'll still install new plugs when I get them. If the economy is still crap in a couple of tanks I'll order a new map sensor. After this I'm not sure what else to do.
I've also attached piccy of the map sensor.

[cravenhaven]

Well beside the MAP sensor there's:
Knock sensors (2 off)
Coolant Temperature sensor
Engine and wheel speed sensors
Oxygen sensors (2 off)
Throttle position sensor
Air temperature sensors

All of which will affect engine performance.
Then their are a couple of sensors which are probably less important in this discussion such as Fuel level, Bank angle etc.

The first thing is to read out what the computer has stored and then try resetting the computer. There are multiple articles on both those tasks on this and other forums.

Allan

[Biggles]

Popped the tank open again this afternoon and learned a valuable lesson, if the tank is full drain some of the fuel.

Tough lesson!  This wasn't an urgent item, so could have waited until your fuel was low. 
For anyone- never try to raise the tank when it's near full.  Firstly it's very heavy and will be hard to pull back in the slots (important if you have bar risers).
And, as you now know, it will spill some.
If you're putting your bike in to a mechanic for a service, it's polite to have less than half a tank of fuel, and leave your panniers and topbox at home. Those little considerations will not only make his life easier, but will save the possibility of your paint getting damaged or the panniers not mounted correctly.  It's relatively easy to mount them wrongly if you're not familiar with the ST1300, and even though the latch locks down, they will come off. DAMHIK

[basadia]

Just a quick update, I've just had to replace a couple of O rings as I pinched one on the fuel rail and it was dripping fuel. Not good when I had a 10 minute ride home from work. I applied some engine oil when I refitted this time and it looks like I've fixed the issue. I've replaced the spark plugs with Iridium's and added some injector cleaner to the fuel tank so I'll run a couple of tanks and hopefully have fixed the issue.

I did do an ECU diagnosis and the only code I got was for the intake temperature sensor (9), I'm not sure if it is faulty or it has the fault in the ECU's memory as I did start the engine a couple of times with the sensor cable plug disconnected checking for fuel leaks. I did try and do a reset but I don't think I got the process correct or the fault is persisting. I'll pop the tank when I run the fuel down and do a voltage check on the sensor and replace it if it is not within spec.

I'm not even sure what a faulty sensor will do as the manual was a bit lite on what it actually does.

[Brock]

There was a yank on the US site that complained about horrific fuel ecconomy, it transpired that he rode every where in 4th gear, as he didnt have enough pick up in 5th/6th   

[STeveo]

Just a quick update, I've just had to replace a couple of O rings as I pinched one on the fuel rail and it was dripping fuel. Not good when I had a 10 minute ride home from work. I applied some engine oil when I refitted this time and it looks like I've fixed the issue. I've replaced the spark plugs with Iridium's and added some injector cleaner to the fuel tank so I'll run a couple of tanks and hopefully have fixed the issue.

I did do an ECU diagnosis and the only code I got was for the intake temperature sensor (9), I'm not sure if it is faulty or it has the fault in the ECU's memory as I did start the engine a couple of times with the sensor cable plug disconnected checking for fuel leaks. I did try and do a reset but I don't think I got the process correct or the fault is persisting. I'll pop the tank when I run the fuel down and do a voltage check on the sensor and replace it if it is not within spec.

I'm not even sure what a faulty sensor will do as the manual was a bit lite on what it actually does.

If the intake sensor is giving a wrong reading to the ecu then it will think that it is colder than the actual temp and will be putting more fuel through the injectors, bit like leaving the choke half on on a carby model.

[Skip]

There was a yank on the US site that complained about horrific fuel ecconomy, it transpired that he rode every where in 4th gear, as he didnt have enough pick up in 5th/6th   

 

[Biggles]

There was a yank on the US site that complained about horrific fuel ecconomy, it transpired that he rode every where in 4th gear, as he didnt have enough pick up in 5th/6th   

Obviously didn't own an ST then.
But there was an Ozstocer who lives in Sydney commented a few years ago that he was surprised to hear other members get into 5th in the city.
With traffic lights on every corner I can understand his problem. 
On that note, rather than let people use their intelligence and wits at roundabouts here in Brissie, they're replacing them with traffic lights.

[hobs]

Had a similar situation on my 1998 ST1100P. The non-return valve near the fuel in-line filter was leaking, but only noticeable when I took the plastic off and ran the engine. Was enough of a minor leak to dry up when dripping onto the tank flange, but enough to affect the fuel usage. Couldn't see any reason for the fuel usage drop just looking around the bike for hose failure or blockages. Was a tricky find.

Cheers,
Hobs

[basadia]

I though I'd Post an update on my issue, I removed the air intake temp sensor and tested it with a multi meter. It is faulty showing not showing any resistance, the manual says 10-40 ohm at 20 degrees. Mine is showing zero resistance, so I've ordered one from the States. Works out 2/3 the price of one through my local motorcycle dealer or Honda, only down side it'll take a week longer to arrive. So I thought I'd be clever and pick up some resistors from Jaycar and a 30 ohm one stops the F1 light but am unable to reset the ECU fault code, don't really know why though. I'd assume it only looks at the resistance coming from the sensor and adjust the fuel/air mixture accordingly. If when I install the new sensor I cannot clear the ECU error code I'll do a full ECU reset as per: http://ozstoc.com/index.php?topic=11334.0

I've been trawling through other sites looking for reason for the additional fuel usage and found a reference to a 'Safe Mapping Mode' which apparently richens the mixture by 20 % to allow for faulty sensors. If found the reference on this US ST1300 forum here: http://www.st1300.us.com/showthread.php?t=4725
"the fuel consumption average showed that the ECU had switched to a safe maping mode ,showing approximately a 20 percent increase'

[Gadget]

That'll do it. Good fault finding.

It'll be interesting what your consumption is after the repair.

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[basadia]

Grrrrr My new sensor arrived today, swapped it over and did an ECU reset as described until the fan came on then turn off with the kill switch. Did an ECU fault code check afterwards and still showing a fault on the air intake sensor (9), I'm thinking the only thing left is to chase the wires back to the ECU and do a continuity check. maybe one of the wires has rubbed through and it's gone open circuit. Can anyone advise where the wiring for the temp sensor emerges so I can do a continuity check before I pull it all apart?
tks

[basadia]

I found the issue the thermostat had died, as most of my trips to and from work were around 15 ks the bike was only just at operating temp by the time I got to work. it had the telltale third temp blink which I'd read about which is apparently another symptom of a faulty thermostat. On longer runs it was not an issue because the bike would get to temperature for longer periods so it would mask the issue. Genuine thermostat sourced from my local dealer (took nearly 3 weeks) and have run two tanks since the change and back to my normal fuel usage.
Happy day.