Author Topic: Backfiring and smell of fuel from exhaust  (Read 11961 times)

Online Shiney

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Backfiring and smell of fuel from exhaust
« on: May 20, 2018, 05:06:35 PM »
So I've been having a few problems with my St 1300 in particular I've been experiencing a lot of backfiring whenever changing gears and just in general use.
When I pull the clutch in to change gears it will backfire and also just when riding it will backfire from time to time, but mainly on deceleration when the clutch is pulled in.
 There is also a very rich smell of fuel from the exhaust and my fuel usage has skyrocketed.
 
I have checked the five way vacuum hose connection and it is clear and I've replaced the spark plugs and done an ECU reset.

 During my latest attempt to diagnose the issue when I block the air hose that runs from the rear of the air box down I get a smoother idle and no backfiring.

This is as far as I have gotten and I'm hoping that someone can make a suggestion as to what I can do to fix this.

 Cheers
 Shiney
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Online Williamson

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Re: Backfiring and smell of fuel from exhaust
« Reply #1 on: May 20, 2018, 05:11:07 PM »
..... I'm hoping that someone can make a suggestion as to what I can do to fix this.

Checked your fuel filter / fuel pump?
Cheers,  Williamson (AKA Michael)

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Re: Backfiring and smell of fuel from exhaust
« Reply #2 on: May 20, 2018, 05:38:26 PM »
It doesn't seem to have any issue with fuel coming through as it smells very rich.
 
However if I blocked the hole at the back of the air box the issue seems to go away.
 
 I've attached a photo pointing out the hole I'm referring to.

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Online Wild Rose

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Re: Backfiring and smell of fuel from exhaust
« Reply #3 on: May 20, 2018, 05:38:53 PM »
 :popcorn
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Re: Backfiring and smell of fuel from exhaust
« Reply #4 on: May 20, 2018, 05:40:23 PM »
And here is a picture  of the hose  that leads to the hole at the back of the air box

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Re: Backfiring and smell of fuel from exhaust
« Reply #5 on: May 20, 2018, 06:04:27 PM »
It doesn't seem to have any issue with fuel coming through as it smells very rich....

My understanding is that fuel blockages at the filter or fuel pump, is that fuel is intermittently blocked, when enough pressure is applied, fuel surges, excess is unburnt and goes out the exhaust, results in excessive fuel consumption and odour of fuel - and if someone is riding behind you they will smell, it very strongly, and may be even see it - black cloudy fumes.
Cheers,  Williamson (AKA Michael)

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Offline winston66

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Re: Backfiring and smell of fuel from exhaust
« Reply #6 on: May 20, 2018, 06:36:19 PM »
if that is the crankcase vent do not block it. From your description of the problem ,it suggests to me that the PCV , (positive crankcase valve) is faulty,
Otherwise backfiring and a strong smell of unburnt fuel, is a symptom of a lazy ,sticky, fuel injector letting too much fuel into the combustion cycle, and possibly causing a miss firing of the associated cylinder ,then hence the backfiring when decelerating etc.
Cheers, Winston66, Northampton, WA.
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Re: Backfiring and smell of fuel from exhaust
« Reply #7 on: May 20, 2018, 06:40:39 PM »
It doesn't seem to have any issue with fuel coming through as it smells very rich....

My understanding is that fuel blockages at the filter or fuel pump, is that fuel is intermittently blocked, when enough pressure is applied, fuel surges, excess is unburnt and goes out the exhaust, results in excessive fuel consumption and odour of fuel - and if someone is riding behind you they will smell, it very strongly, and may be even see it - black cloudy fumes.

Thanks mate :-++
How do I check if the fuel filter and fuel pump is working?


Allso a little more info... nothing can be seen coming from the exhaust (no black cloudy fumes) however there is a strong smell of fuel.
Also when the hole/hose in the pictures is blocked with my finger the smell and backfiring goes away :think1 :think1 :think1



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Re: Backfiring and smell of fuel from exhaust
« Reply #8 on: May 20, 2018, 06:45:14 PM »
if that is the crankcase vent do not block it. From your description of the problem ,it suggests to me that the PCV , (positive crankcase valve) is faulty,
Otherwise backfiring and a strong smell of unburnt fuel, is a symptom of a lazy ,sticky, fuel injector letting too much fuel into the combustion cycle, and possibly causing a miss firing of the associated cylinder ,then hence the backfiring when decelerating etc.
Cheers, Winston66, Northampton, WA.

Thanks mate :-++
Is there any way to check the positive crankcase valve or the fuel injector to see if it is lazy or sticky?
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Re: Backfiring and smell of fuel from exhaust
« Reply #9 on: May 20, 2018, 08:02:49 PM »
A mates sports bike started backfiring and cutting out intermittently chased it for weeks . One morning battery was flat put new battery in problem was solved
just a thought
 
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Re: Backfiring and smell of fuel from exhaust
« Reply #10 on: May 20, 2018, 08:18:20 PM »
A mates sports bike started backfiring and cutting out intermittently chased it for weeks . One morning battery was flat put new battery in problem was solved
just a thought

Thanks mate :-++
I disconnected the battery and left it unplugged overnight when I did the ECU reset :think1 but I'll try connecting it up to another battery and see if it makes a diffrence :thumbsup

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Offline ppopeye

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Re: Backfiring and smell of fuel from exhaust
« Reply #11 on: May 20, 2018, 08:23:25 PM »


Quote from: PC on May 20, 2018, 08:02:49 PM<blockquote>A mates sports bike started backfiring and cutting out intermittently chased it for weeks . One morning battery was flat put new battery in problem was solved
just a thought


With those symptoms a battery should not be the problem but as we all know strange things happen especially where electrikery is involved

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Re: Backfiring and smell of fuel from exhaust
« Reply #12 on: May 20, 2018, 09:24:47 PM »
Thanks mate :-++
How do I check if the fuel filter and fuel pump is working?

Back in the 80's I had a problem of engine stuttering, surging excessive fuel consumption in a Nissan Bluebird on a road trip from Melbourne to the Gold Coast.  Re-fuelled for the second time in 580km at West Wyalong, normally that distance on one tank - excessive fuel consumption.

Car would start after re-fuelling, called NRMA (4:00am, -4C, two kids asleep for a while in the back seat, Helen not very happy), NRMA man arrives quickly, you have a blocked fuel filter man, new fuel filter fitted (no charge), car starts, back to 500km plus between re-fuelling - blocked fuel filter.

Skip to 2014, trip around Tassie with Phil on his GSX1400, bike spluttering, surging, excessive fuel consumption, me following (at times) could smell fuel, see little puffs of black, gassy fumes (the smell and the fumes were making me sick), in the end bike would not proceed.  We would need to wait on side of road for 10 to 15 minutes every 30 minutes or so.  After cooling the bike would start and run (sort of) okay, until it would conk-out again.

We finally made it to Lake Leake where were to camp for a few nights.  Phil strips removes tank and strips fuel pump, in-built filter full of gunk, cleans it all up, bike runs okay for remainder of trip - blocked fuel pump filter.

How these are checked on an ST1300 - I don't know, I'm like the deer with no eyes.
Cheers,  Williamson (AKA Michael)

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Online PC

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Re: Backfiring and smell of fuel from exhaust
« Reply #13 on: May 20, 2018, 09:28:52 PM »

With those symptoms a battery should not be the problem but as we all know strange things happen especially where electrikery is involved
[/quote]
Yes Garry I hear you I bought a new v6 Mazda Tribute  from day one I complained about fuel economy,power , auto lag on kick down , motor reving slow to return to idle when stopped at traffic lights
and short battery life
Their response.   put car on computer nothing wrong  At 120k needed to replace alternator and BAM
all these problems vanished the car went like the clappers and was a pleasure to drive .
But Hey try to convince so called Mazda engineer
 
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Re: Backfiring and smell of fuel from exhaust
« Reply #14 on: May 20, 2018, 10:35:45 PM »
Thanks guys, I will be trying to check all the things that have been suggested tomorrow :thumbs

I really appreciate all the suggestions and if you have any other ideas please let me know  :-++


Cheers
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Re: Backfiring and smell of fuel from exhaust
« Reply #15 on: May 21, 2018, 09:25:54 AM »
Try the easiest 'fix' first and work your way towards the more complicated one.  :grin Good luck Shiney.  :thumb
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Offline Jdbiker

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Re: Backfiring and smell of fuel from exhaust
« Reply #16 on: May 21, 2018, 09:44:35 AM »
Also check the mass airflow sensor (Map) is clean and has proper connection as faulty MAP sensor could cause similar problems.
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Re: Backfiring and smell of fuel from exhaust
« Reply #17 on: May 21, 2018, 12:30:46 PM »
So far have checked the battery and map sensor but the issue remains.
I have checked the fuel lines and they all appear to be fine.

 The hose that I was blocking with my finger is the pair solenoid valve hose.
 When this is blocked all issues go away but I have no idea why ?

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Re: Backfiring and smell of fuel from exhaust
« Reply #18 on: May 21, 2018, 02:10:57 PM »
Shiney - Would it be a dirty or faulty injector? - The excess unburnt fuel is being passed thru causing the exhaust smell.
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Re: Backfiring and smell of fuel from exhaust
« Reply #19 on: May 21, 2018, 03:07:01 PM »
I don't know how to check the injector :fp
 
However I've narrowed it down to occurring on the left side of the bike only.

If I disconnect the spark plugs on the left the bike runs with a lack of power but no backfiring.
With the spark plugs connected it backfires from the left side exhaust only but has a lot more power.

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Offline winston66

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Re: Backfiring and smell of fuel from exhaust
« Reply #20 on: May 21, 2018, 04:14:51 PM »
When the engine is cold  start up the motor and when running at idle speed then check the individual exhaust pipes for heat, use your finger , but be careful to not get burnt. One pipe that is colder to the others will indicate that its associated cylinder has a problem,It is my guess that the problem will then be either fuel, or spark related ,Over to you how you then solve that problem .
Cheers, Winston66, Northampton WA.
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Re: Backfiring and smell of fuel from exhaust
« Reply #21 on: May 21, 2018, 04:23:25 PM »
I don't know how to check the injector :fp
 
However I've narrowed it down to occurring on the left side of the bike only.

If I disconnect the spark plugs on the left the bike runs with a lack of power but no backfiring.
With the spark plugs connected it backfires from the left side exhaust only but has a lot more power.

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Shiney swap the spark plugs over to the other side cylinders and see if it transfers the problem to the other side, thereby pointing to a spark plug

Cheers
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Re: Backfiring and smell of fuel from exhaust
« Reply #22 on: May 21, 2018, 04:32:10 PM »
Same heat from both pipes

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Re: Backfiring and smell of fuel from exhaust
« Reply #23 on: May 21, 2018, 04:33:27 PM »
Sparkplugs swapped from one side to the other with no changes resulting.

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Offline winston66

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Re: Backfiring and smell of fuel from exhaust
« Reply #24 on: May 21, 2018, 04:40:01 PM »
Please make sure that you check the heat of the pipes as close to the individual cylinders as possible,and only do it when starting the motor when dead cold.
When disconnecting or swapping spark plugs around only do them one at a time,this will help you to isolate a problem to a specific cylinder if it is ignition related,
Cheers, Winston66, Northampton WA.
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