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Help! SJ80 loss of power and stalling? (Carburetor Icing)
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Author:  Sage [ Mon Jun 05, 2017 9:58 am ]
Post subject:  Help! SJ80 loss of power and stalling? (Carburetor Icing)
Hi guys,

I took my coily down to the snowy mountains skiing over the weekend and back and I had some issues which i believe are fueling related.

The symptoms occurred under the following conditions and were as follows:

1. Driving along at highway speed in mountainous conditions (90-110 kms)
2. Sometime but not always, after a long stretch of uphill climbing at high rpm, the engine would loose power and slow down as gravity took hold.
3. If the hill wasn't too long and the gradient flattened out, letting off the gas momentarily and then getting back on it would see the power return albeit still not to it usual responsiveness until it has been driven on a flat stretch of road for a while.
3. If the above scenario didn't occur or, further pressing the accelerator pedal would not increase rpm/speed and i'd have to pull over where the car would then splutter and then stall.
4. if 3 happened. I'd let the car sit for a minute with the engine off, pump the gas pedal once and then it would kick over and run normally until point 2 would happen again.

The return trip from Sydney to Kosciusko was about 10 hrs and over the course of the journey i only had to pull over 3 times when the car completely stalled.

Have read through the trouble shooting in the FSM my suspicion is that i probably have a clogged fuel filter which is not allowing enough fuel to flow through to the pump and onto the fuel bowl which is running dry and causing the car to stall occasionally. My plan is to order a new fuel filter and fuel pump today as it seems to be a fueling issue.

Does anyone have any thoughts or insight on the issue? any feed back would be greatly appreciated. I really need to get it sorted as konking out mid bend in the national park which has no shoulder in many places is really sketch when the roads are icy and there is very low visibility.

Oh as a side note, apart from it only happening when i've been traveling uphill for a considerable distance it also seems to happen most often when the air temp is very low (-5 to 10 degrees and very humid- low cloud, fog etc). Ive got a snorkel on the car and thought that the cold wet air might be causing a mixture issue?

Many thanks,

Sage.
Author:  MrRocky [ Mon Jun 05, 2017 11:14 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Change fuel filter and keep tank over 1/4
Author:  sideways [ Mon Jun 05, 2017 2:44 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Yeah mine did similar when the fuel pump died. I'd try the filter first of course.

It's worth putting another filter between the pump and carby, my carby ended up with a whole bunch of rubber junk in it.
Author:  Sage [ Mon Jun 05, 2017 3:33 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
No worries,

I've ordered a new fuel filter, fuel pump, carby kit, leads, coil pack and an air filter.

Will start with the filter, then pump, then carbs kit etc if that doesn't work.

Is there a particular filter model that is favored for use between the fuel pump and carby? From what I've read a small motorbike one is preferable.

Cheers
Author:  jdk81 [ Mon Jun 05, 2017 3:37 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Do you still have the warm air intake setup?

It sounds like it's been removed and the carby is icing up.
Mine did the exact same thing everytime I drove it in the conditions you describe.
Author:  Sage [ Mon Jun 05, 2017 3:58 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
No, when i bought the car it had headers on it and so the warm pipe had been removed. Its running TJM snorkel now straight into the airbox which made me think it could possibly be an icing issue. When it it stalled the first time i popped the bonnet and felt the air intake case thing which sits on top of the carburetor and it was very cold. Normally when Ive run the engine in 20+ degree weather it will be hot to touch, not burning hot but pretty warm nonetheless.

If it is an icing issue are there any solutions other than factory headers with the stove pipe setup?

I'll take a picture of the snorkel/intake setup tonight
Author:  Gwagensteve [ Mon Jun 05, 2017 5:17 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
You do need to eliminate carb icing as a possible cause, however, the warm air intake shouldn't be doing all that much once the engine is up to temperature. Icing is relatively rare and is sometimes indicative of other tuning problems. Obviously, just disconnecting the snorkel and taking the car for a drive should eliminate icing. - still, it shouldn't be happening at 10˚C ambient.

Next time it stalls out have a 10mm spanner handy and rip the carb hat off and have a look - you'll see the ice.

However I think the idea it's connected to long uphill runs does point towards the fuel pump. I'd be surprised if it's the filter but it's easy enough to change.

21 years seems to be the golden age when pumps start failing from my experience.
Author:  Sage [ Mon Jun 05, 2017 8:21 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Yeah that was my thoughts too Gwagensteve. Im fairly certain its the fuel pump/filter but did seem to happen when the ambient temp was below 10 degrees. When we went through Canberra it was -4 degrees and visibility with the fog was about 20 meters. It was humid enough that i had the windscreen wipers on low.

Will pull the carb hat off next time. Also in searching online i noticed that FUCHS sell a fuel additive (FUCHS PRO FST) that is supposed to stop carb icing. It seems to be very popular with vintage motcylclists in Europe. You just mix it in with your fuel.

Might be worth a go if the problem persists after doing the fuel pump and filter. http://www.silkolene.com/motorcycle/fuel-additives/pro-fst/#

Anwho this is how the snorkel is fitted up to the air box. Was installed by a TJM distributor in sydney. The stovepipe and associated gear was binned.


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Author:  Sage [ Tue Jun 06, 2017 9:15 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Just wanted to add that I was looking through the Factory service manual for the coily and noticed that on page 6D-17 (The Carburetor section) it shows that the Australian Spec carb runs a "water hose" from two points on the carb. I double checked my car ensure it's running the original aus spec carby which it is and confirmed that when the motor is running that the "water pipe" is heating up.

The FSM isn't too clear about the way the water/coolant passes through the carby channel wise, but i assume its there to keep the throttle body/carb from freezing. Can someone who has stripped one of these aus spec carburetors down confirm?

Cheers
Author:  Sage [ Tue Jun 06, 2017 9:32 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Image

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Author:  Sage [ Tue Jun 06, 2017 12:54 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Aus spec carburetor exploded diagram:

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Author:  alien [ Tue Jun 06, 2017 1:58 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
I have my snorkel head pointed rearwards.

I did a test years ago after having it installed (all be it in dust) - results were interesting!

- Without a snorkel, after a run on a dusty road, the air filter had some dust on it, but really not that much. A little in the box.
- With snorkel, head forwards, same road the next weekend, air filter and airbox FULL of dust.
- With snorkel, head backwards, same road the next weekend again (conditions unchanged) - no dust at all in the box and filter mostly clean.

For me, that was enough to deal with people saying "your snorkel is facing the wrong way" and "you'll get more power with it the other way". lol

If it is icing, turning the head backwards might help stop moisture being forced in, like it stopped dust for me?
Author:  MrRocky [ Tue Jun 06, 2017 2:17 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Cant put a price on your dignity
Author:  shep [ Tue Jun 06, 2017 6:39 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
Don't drive in dust. I have never understood why people like to drive in the dust of the car in front.
Author:  Sage [ Thu Jun 15, 2017 11:59 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling?
So in addressing the issues, I've replaced the fuel filter, fuel pump, coil pack, ignition leads and have had the carby striped down cleaned and rebuilt with a kit replacing the gaskets, accelerator pump and float needle.

Whilst it was apart it was noted that the float was set too low and there was a bit off buildup of gunk. Has all been cleaned out now and reassembled.

Driving down to Thredbo next weekend so will report back if the issue still persist though hopefully it running nicely now. :peaceout:
Author:  Sage [ Mon Jul 10, 2017 11:38 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Hi guys,

Thought I’d better post a follow up on the coily and its power loss stalling issue. Have just done another weekend skiing down at Thredbo in the high country and had the issue occur about 4 times on the trip down and back and can now confirm the issue is definitely carb icing .

Prior to this trip I had the carburetor striped down completely cleaned, rebuilt and tuned by a carby specialist here in Sydney, replaced the fuel filter, leads, coil pack and fuel pump with a genuine Suzuki one. Driving around Sydney the coily is running faultlessly now and I couldn’t be happier with it. The problem only occurs once I head out of Sydney where the temperature rarely drops below 10 degrees Celsius, and drive for extended periods of time at highway speed through areas where the air temperature drops down to below about 4 degrees with high humidity.

On the drive between Sydney and Thredbo the trouble spots are always Sutton Forrest, Marulan and Goulburn which are all areas of historically high rainfall and low overnight temperatures. When the carby starts to freeze up the engine will begin to slowly lose power, most notable under load going uphill, hesitate on throttle, start running rich before eventually konking out. I then just have to pull over and let the car sit for about 5 minutes whilst the heat soak thaws things out. The engine will then turnover straightway, idle perfectly and run normally for about 45 minutes if the cold humid conditions persist before it ices up again, however if the ambient temperature increases and the humidity drops off, it will continue on perfectly. Interestingly it hasn’t suffered the icing problem in Kosciusko national park but I’ve put that down to the fact that its cold enough there and at a high enough altitude that the air is actually drier.

I tried turning the snorkel head backwards this trip but I can report that it made little to no difference. Looks like I’ll either have to replace the factory stove pipe/airbox setup and disconnect the snorkel over winter, or install some sort of carb/intake warming gear. The coily currently has wildcat extractors so will need to get a small section of pipe welded on to fit a warm air pipe which shouldn’t be too difficult, not a big issue but more of an inconvenience.

Given the average Australian climate I doubt the issue affects too many people but thought I’d document it in case anyone else had experienced the same symptoms and was perplexed by it.

Happy wheeling :peaceout:


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Author:  alien [ Mon Jul 10, 2017 10:23 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Considering it snows in Japan, you'd think it wouldn't have this issue.

Glad to know that snorkel forward/backward makes no difference to air intake =)

You could divert the snorkel intake to inside the cab... lol... it'd be noisy, but it'd work!!
Author:  MrRocky [ Mon Jul 10, 2017 10:51 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Perhaps warmer thermostat for winter, also check the coolant lines to the carb (if it has them) are not completely clogged
Author:  fordem [ Mon Jul 10, 2017 11:46 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
alien wrote:
Considering it snows in Japan, you'd think it wouldn't have this issue.


Considering the warm air intake that the Japanese originally fitted is no longer there, I would think that it might - having said that - I live in a "year round warm climate" and have no personal experience with carburetor icing, so my opinion doesn't really count.
Author:  Gwagensteve [ Tue Jul 11, 2017 6:41 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Did I mention disconnecting the snorkel will fix the problem?
Author:  HarryHoudini [ Tue Jul 11, 2017 9:23 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Also,i've seen on a Tumut, NSW, based Sierra where the standard Suzuki air inlet was disconnected and a hose connected to the air cleaner so it was drawing air straight off the extractors all of the time during Winter,in Summer he connected the standard inlet back up,it seemed to work OK,the guy used to do Control Points during Car Rallies down that way.
Author:  Sage [ Tue Jul 11, 2017 9:24 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Gwagensteve wrote:
Did I mention disconnecting the snorkel will fix the problem?


Yep, I'm heading down skiing again this coming weekend so this trip i'll remove the short pipe between the airbox and the snorkle where it comes through the front quarter panel. Given how far across to the left of the engine bay the airbox sits, and how open air the engine bay is, im not confident it will make any difference. Still, no harm in trying.

Driving short journeys in the cold humid weather doesn't seem to give it long enough to ice up which is good. I've found if I'm stopping and starting such as driving around Jindabyne, it will run fine. Its the long stretches of highway speed and the continual rush of cold humid air that's causing problems.

As id rather not run a stove pipe if possible I've been considering whether i can utilise and electric carb heat element that are popular on rotax powered light aircraft. Would be much more convenient if i could just flick a switch periodically to prevent ice build up in the same manner pilots do during flight procedures.
Author:  Gwagensteve [ Tue Jul 11, 2017 9:44 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
The factory air inlet is beside the battery in the rear corner of the engine bay. It's plenty warm enough. The problem is the snorkel. Forgive me if this sounds rude, but it doesn't look, from the rest of the cars setup, that a snorkel is required for the terrain the car drives. Disconnecting it and reverting to the factory intake will fix the problem and I'm sure still allow adequate fording depth, although it would only take minutes to reconnect the snorkel should you be fording very deep water.

Adding another system to work around the snorkel (when it isn't required) seems to be overthinking the problem.
Author:  MrRocky [ Tue Jul 11, 2017 10:32 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Doesnt factory airbox have an intake lever that allows you to flick between summer/winter settings ?
Author:  Gwagensteve [ Tue Jul 11, 2017 11:07 am ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Not on WT's and sj80's. Only NT's.
On wt's and sj80's it's vacuum controlled.
Author:  Sage [ Tue Jul 11, 2017 12:20 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Gwagensteve wrote:
The factory air inlet is beside the battery in the rear corner of the engine bay. It's plenty warm enough. The problem is the snorkel. Forgive me if this sounds rude, but it doesn't look, from the rest of the cars setup, that a snorkel is required for the terrain the car drives. Disconnecting it and reverting to the factory intake will fix the problem and I'm sure still allow adequate fording depth, although it would only take minutes to reconnect the snorkel should you be fording very deep water.

Adding another system to work around the snorkel (when it isn't required) seems to be overthinking the problem.


No offense taken, I take your point, your are correct in saying that its not really needed.

Unfortunately i don't have the original factor vacuum actuator piece or the plastic piping that runs the intake up near the battery so the best i can do for this trip is to remove the TJM piping from snorkel at the front quarter panel to the front of the air box. This will leave the airbox drawing air from the forward facing collar on the box. If it still ices up this weekend with the above mentioned arrangement (which Im confident it will) I'll go to the wreckers and try to source a second had actuator and plastic pipe to draw air from up near the battery. If that still not enough i'll either by a stove pipe and run the factory setup in winter, or I'll try an electric carb heating element. :D
Author:  Gwagensteve [ Tue Jul 11, 2017 1:07 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
There's nothing special about the hose. If you want an easy to source some silicone bends and a bit of convoluted hose from autobarn/supercheap will do the trick. Just consider it temporary.

This is not a common problem and I expect it's possibly more prevelant with your snorkel design which has a large plenum on the guard which will get very cold at speed, and has fairly low velocity air running through it.

That said, you haven't clairified if you have coolant flow to the carburettor. This is designed to prevent icing.
Author:  Sage [ Tue Jul 11, 2017 1:26 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
Gwagensteve wrote:
There's nothing special about the hose. If you want an easy to source some silicone bends and a bit of convoluted hose from autobarn/supercheap will do the trick. Just consider it temporary.

This is not a common problem and I expect it's possibly more prevalent with your snorkel design which has a large plenum on the guard which will get very cold at speed, and has fairly low velocity air running through it.

That said, you haven't clarified if you have coolant flow to the carburetor. This is designed to prevent icing.


Its certainly not something I'd expect many people here in Australia would encounter that's for sure.

Yes, can confirm that coolant is flowing up to the carby/auto choke assembly. The lines are flowing hot coolant but it's just not enough when the condition are just right.

Good idea re silicon hose.
Author:  Gwagensteve [ Tue Jul 11, 2017 1:42 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
When I say not common, I mean for us in Victoria where we drive in very cold conditions and above the snow line >1400m
Having said that most of us don't run snorkels.
Author:  MrRocky [ Tue Jul 11, 2017 1:57 pm ]
Post subject:  Re: Help! SJ80 loss of power and stalling? (Carburetor Icing
I would pull the coolant lines off and check them for blockages ive seen many completely corroded solid
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