Mikuni MX40

[Iron-Dutchess]

Hi Everyone,

 

I bought and fitted a Mikuni MX40 heater 18 months ago, since then in constant use it has performed OK. Last week it packed up, blowing the 15 amp main fuse. On inspection the glow plug coil had become distorted and full of carbon deposits shorting it out. I purchased and fitted a new glow plug and the unit worked fine for two days, and then blew the fuse again. On inspection the glow plug had fouled up with carbon and shorted, removing the carbon fixed the problem for another two days when the unit failed with the same problem. Could this be a fuel contamination problem or is there another possible cause? The unit is running on gas oil from a separate tank, and the system is fed with water from the boats domestic water pump through a pressure reducing valve at 0.5 bar with an automatic air bleed at the boiler water intake.

 

TIA

[NB Willawaw]

I have an Eberspacher and have had many problems which I attribute to the "roughness" of red diesel.

In the autumn, when we start to use the Eber in earnest, I fill the tank with road diesel and my perception is that

it runs cleaner and doesn't coke up.

It was always my impression that Ebers were more prone to this than Mikuni ???

[Iron-Dutchess]

I have an Eberspacher and have had many problems which I attribute to the "roughness" of red diesel.

In the autumn, when we start to use the Eber in earnest, I fill the tank with road diesel and my perception is that

it runs cleaner and doesn't coke up.

It was always my impression that Ebers were more prone to this than Mikuni ???

 

Gas oil is the same as road diesel, it just has dye added to show that it has been purchased at the lower tax rate.

If gas oil was somehow of a lower grade than road diesel why do marine diesel engines run equally as well on it? They are mostly the same engine as they put in a road vehicle but with a low speed alternator and a heat exchanger for cooling, my Perkins Sabre M92 4.2Ltr being an example. Plus my Mikuni ran faultlessly for 18 months on gas oil.

[NB Willawaw]

I don't think red gasoil is the same as white road diesel.

 

TTBOMK, there are two types of red diesel available, one is Gas Oil with red dye, and the other is Low Sulphur Gas Oil (City Gas Oil) with a red dye. The latter meets BS EN 590 and has the same specification as road diesel.

 

The main differences between "Gas Oil (non BS EN 590)" and Low Sulphur Gas Oil (to BS EN 590), is the former has a lower 'Cetane rating' 46 against 52, higher sulphur %Wt 0.2 against 0.005, higher Flash point 82 against 67 and Carbon residue, on 10% distillation residue, %Wt .12 against <0.001.

 

The fuel commonly found on the canal system is unfortunately "Gas Oil". The other "Red diesel" available is called "City Gas Oil" (ultra low sulphur gas oil) (Linton Fuel Oil Ltd Stock code 103). This meets BS EN 590 and apparently would cost the marina only 1.5 pence more per litre.

 

The performance of some heaters can be adversely affected by the use of Gas Oil (non BS EN 590), bacterial or water contamination.

 

Unlike heaters, Diesel engines are very forgiving on fuel quality, especially canal boat engines which are often simple engines designed for agricultural vehicles like tractors and lawnmowers, so it wouldn't necessarily show or matter there.

 

There could be a fault with your Mikuni or it could be a cumulative coking effect

caused by running on red gasoil for 18 months.

Edited November 24, 2007 by NB Willawaw

[Supermalc]

Gas oil is the same as road diesel, it just has dye added to show that it has been purchased at the lower tax rate.

 

No it's not the same.......

[Iron-Dutchess]

No it's not the same.......

 

Err, according to my company's fuel supplier it is. But I will check with others and see what they say.

[GUMPY]

Hi there

Firstly did you clean the air swirl holes in the glow plug boss when you changed the plug?

This needs to be done when you change a plug otherwise plugs last a few days.

 

Secondly have you just had a new fuel delivery from a different supplier?

One reader on here had problems and by coincidence changed his supplier and the problem went away.

Mikuni unlike others will run on Gas oil, derv, kerosene, bio diesel about the only thing that they dont run on is SVO.

 

Thirdly have you just connected a battery charger when they are switched on spikes from chargers can cause the plug to go.

 

These are the 3 most common causes of GP failure.

 

Julian

[Iron-Dutchess]

Hi there

Firstly did you clean the air swirl holes in the glow plug boss when you changed the plug?

This needs to be done when you change a plug otherwise plugs last a few days.

 

Secondly have you just had a new fuel delivery from a different supplier?

One reader on here had problems and by coincidence changed his supplier and the problem went away.

Mikuni unlike others will run on Gas oil, derv, kerosene, bio diesel about the only thing that they dont run on is SVO.

 

Thirdly have you just connected a battery charger when they are switched on spikes from chargers can cause the plug to go.

 

These are the 3 most common causes of GP failure.

 

Julian

 

Thanks Julian, didn't know about your first point, I'll go and take a look. Everything else is as was.

[Supermalc]

Err, according to my company's fuel supplier it is. But I will check with others and see what they say.

 

Most road diesel is (ultra low sulpher) fuel. To reduce emissions. There are other additives as well.

 

Do a simple test. Fill a small tank with each, fit to an engine and work it hard, and watch the smoke. In most cases, there will be more smoke with red.

[GUMPY]

Thanks Julian, didn't know about your first point, I'll go and take a look. Everything else is as was.

You should really replace the gasket under the boos when you take it off.

You will need to disconnect the fuel feed to it and undo the two screws holding it to the body.

Cant remeber the size of the holes but I think a 3mm drill rotated between the fingers will fit.

Have alook here to see how it comes apart

 

http://www.mikuniheating.com/index.php?p=p...0&parent=22

 

Julian

[Iron-Dutchess]

You should really replace the gasket under the boos when you take it off.

You will need to disconnect the fuel feed to it and undo the two screws holding it to the body.

Cant remeber the size of the holes but I think a 3mm drill rotated between the fingers will fit.

Have alook here to see how it comes apart

 

http://www.mikuniheating.com/index.php?p=p...0&parent=22

 

Julian

 

I have removed the boss cleaned it out (well bunged up ) and refitted it, all seems to be working OK. The gasket looks fine, but I have ordered a gasket kit and will fit a new one when it arrives.

 

Thanks again.

[denboy]

Gas oil is the same as road diesel, it just has dye added to show that it has been purchased at the lower tax rate.

If gas oil was somehow of a lower grade than road diesel why do marine diesel engines run equally as well on it? They are mostly the same engine as they put in a road vehicle but with a low speed alternator and a heat exchanger for cooling, my Perkins Sabre M92 4.2Ltr being an example. Plus my Mikuni ran faultlessly for 18 months on gas oil.

Sorry you are 100 % wrong

[bullet]

Hi Everyone,

 

I bought and fitted a Mikuni MX40 heater 18 months ago, since then in constant use it has performed OK. Last week it packed up, blowing the 15 amp main fuse. On inspection the glow plug coil had become distorted and full of carbon deposits shorting it out. I purchased and fitted a new glow plug and the unit worked fine for two days, and then blew the fuse again. On inspection the glow plug had fouled up with carbon and shorted, removing the carbon fixed the problem for another two days when the unit failed with the same problem. Could this be a fuel contamination problem or is there another possible cause? The unit is running on gas oil from a separate tank, and the system is fed with water from the boats domestic water pump through a pressure reducing valve at 0.5 bar with an automatic air bleed at the boiler water intake.

 

TIA

Thought I'd put my two'penneth in! I have had a Mikuni MX7 in the 90's and an MX60 '95-96. Whilst I never had any problems a lot of my fellow moorers with Mikuni's had endless problems with theirs like you describe. There did not seem to be a common reason for the faults. I wonder if, when one considers that these units (whatever brand) are fitted to road vehicles, the problems do not appear to occur - at least with the same regularity as on narrowboats. Perhaps it is something to do with (1) a lack of ventilation or (2) long continuous periods of use or (3) sometimes dubious fuel quality on the cut. We didn't use ours much and did not have problems. We managed to get by with the magnificent Squirrel stove and cool bathroom and bedroom scenario.

 

A very well known narrowboat builders in Warwickshire (run by Sam and Dom), have, or had used Webasto units for years and as far as I know they reported the best reliability of the lot........................ I always remember being at a boat show at a well known German branded manufacturers stand, when a very disgruntled boater turned up with a cardboard box containing his diesel unit. He explained to the German representatvie all the problems he had been having. After a short pause the rep said (in complete seriousness) "Vell sir ze problems u are having are not ze fault of our unit zo, it must be your boat". The boater threw the box on the floor and told the rep to put it where the sun doesn't shine (or does in the reps case!!).

 

Having said all that, our Mikuni although lightly used, performed extremely well. If I were to use one of these things in future, I would ensure I took note of the 3 points above - hope this helps.

[GUMPY]

Light use often causes problems

Mine is used for 3 hours every day 365days a year and has only had minor failures ( plug, sealing ring, blocked diesel feed) in the last 5 years.

One other thought is ALWAYS use antifreeze I have aspare unit that was run on water rather than 50% antifreeze and the inside is very rusty, so rusty in fact that its only useful for spares.......

[mickspangle]

I'm pretty sure that the Mikuni adverts in the canal mags make a point of saying that they will definitely run on red diesel?

[Iron-Dutchess]

Sorry you are 100 % wrong

 

Contacted some more fuel suppliers, below is a reply from one of them, the rest are similar.

_________________________________________________

Many thanks for your enquiry to Bayford Direct.

 

Red diesel (gas oil) is the same as road diesel (derv) but it is not a taxable product as it is reserved for use off road. It is therefore slightly cheaper in price

 

Red diesel is used primarily for farming equipment and other off-road machinery so is therefore a non-taxable commodity.

 

Red diesel could be used in a diesel fired boiler aboard a boat.

 

If you have any further enquiries please do not hesitate to contact us.

__________________________________________________

[chris w]

Well they're wrong too which is worrying.

 

For the record, red diesel has a cetane rating (similar to the octane rating for petrol) of 46 as compared to white (road fuel) diesel which has a cetane rating of 52 (ie: one has to burn more red diesel to get the same horsepower output as compared to white diesel). Further, the sulphur content of red diesel is 2000ppm (parts per million) while that for white diesel is 50ppm. Thus red diesel is not simply white diesel to which a red dye has been added.

 

Chris

[Gibbo]

I can quite categorically state that gas oil is not red diesel.

 

I learnt this from hard experience having wrecked about 200 quidsworth of glow plugs in a Mikuni MX40 before realising the difference. Since using proper red diesel the thing has run flawlessly.

 

Gibbo

[Nige123]

Hi there

Firstly did you clean the air swirl holes in the glow plug boss when you changed the plug?

This needs to be done when you change a plug otherwise plugs last a few days.

 

Secondly have you just had a new fuel delivery from a different supplier?

One reader on here had problems and by coincidence changed his supplier and the problem went away.

Mikuni unlike others will run on Gas oil, derv, kerosene, bio diesel about the only thing that they dont run on is SVO.

 

Thirdly have you just connected a battery charger when they are switched on spikes from chargers can cause the plug to go.

 

These are the 3 most common causes of GP failure.

 

Julian

 

 

can Paraffin be used or a mix or Paraffin & diesel ???

 

I make my own Bio Diesel & have done for some years now & run my Combi van & MG ZTT on it the MG works best on 50/50 mix but the non turbo van runs 100% bio all year round.....

 

I have an Eberspacher D1L in my workshop that keeps in warm in the winter & it will not run 100% Bio Diesel as it seems to have more problems starting up but will run a mix of about 25% bio to Paraffin, staight Paraffin seems to run much cooler then DERV but the mix of both types seems much better......

 

the only problem I seem to get is some brown glazing on the glow plug (from the bio) that you can burn off by connecting it to a battery (mind your fingers) for 10 seconds...

 

anyway I have fitted a tank of paraffin & bio to my boat & will let you all know if it goes very wrong in the next few weeks...