Filter question

[lazza]

HI

I've been running my Xantia on straight vegetable oil in summer for several years. Normally i dont have any problems, but it's been struggling recently on start-up. I changed the in-line filter and the main filter. Changing the in-line filter helped as this was in fact for petrol, as they once again incorrectly sold to me in the car parts shop . The in-line filter i know have is metal gauze.

However the main filter in the filter-housing is still a paper type and i was wondering if there are any special filters of a larger micron size especially for people who run their vehicles on SVO. Or could I consider simply not putting one in??

Any suggestions most welcome

Cheers
Larry

[MikeT]

I've been using standard filters with 100% SVO (and the odd bit of diesel) for years and never had a problem. I would look for air leaks and/or failing glow plugs for starting troubles.

p.s. What's the second filter all about?

[lazza]

I have a VOW in-line preheater system.. dont think the guy does these anymore.

That is installed after the main filter, so the idea is to catch any carbonized debris that might arise after the VOW preheater- just in case

[MikeT]

Ah, I got you.

So what's the pre-heater all about? (More chances of introducing an air leak by the way) I've found it's not required with these Bosch pumps, even over winter. If it gets particularly cold (minu temps) I might dilute the veg with 20/25% diesel. The pump heats the fuel by design, or more correctly the fuel cools the pump.

ETA: If you have a transparent fuel line coming to/from the pump (can't recall exactly), look for bubbles when the engines revving a bit (if none seen at idle). Also, before next cold start, try pumping the fuel primer bulb first until it feel solid and observe any difference in starting.

[lazza]

Yes I did put in a transparent fuel line. Cant see any air bubbles now that I've changed the inline filter etc. However it's still a bit rough on startup. I wonder if I should change the glow plugs? They all gave good resistance readings.. but maybe they're a bit coked ??

[Hell Razor5543]

It is possible for the glow plugs to fail in such a way that they don't heat up at the tip, but further down the 'element'. If you were to pop yours out and check them, any that do this are faulty.

[MikeT]

I wonder if I should change the glow plugs? They all gave good resistance readings.. but maybe they're a bit coked ??

Glow plugs would be my next suggestion too.

[lazza]

Looks like i'll be doing that old chestnut again then.

The reasoning behind the VWO preheaters is the following:

1. The main glow plugs stay on for 2-3 minutes after start-up (if I'm correct)... so the fuel in the pump will get properly heated before combustion.
2. The VWO in-line heater starts to heat up the incoming fuel so that once the main glow plugs switch off, the fuel is up to a reaonsable temperature.

The idea is that no fuel gets to the injectors without some form of preheating, hence allowing for better combustion and to avoid associated problems.

What are the forum's thoughts on this?

Cheers
Larry

[Northern_Mike]

1. The main glow plugs stay on for 2-3 minutes after start-up (if I'm correct)... so the fuel in the pump will get properly heated before combustion.
2. The VWO in-line heater starts to heat up the incoming fuel so that once the main glow plugs switch off, the fuel is up to a reaonsable temperature.

The idea is that no fuel gets to the injectors without some form of preheating, hence allowing for better combustion and to avoid associated problems.

What are the forum's thoughts on this?

I have no idea what difference it would make, as I ran my Xantia, ZX and XM on straight veg from Tesco through three coldish winters (snow in two of them) with no preheating of the fluid and no ill effects. They were a little lumpy for a mile or so until they'd warmed up a bit, that was all.

Before I ran veg I read lots about it, and it all seemed to point me to buying this kit or that kit, and installing this twin tank system or preheaters, and this special filter or whatever, but surely if the veg is cold, when the engine is cold, the preheater is cold... so it's still going to be running off cold veg anyway. So , I simply didn't bother fitting any of it, simply poured in the veg and away we went. Changed the standard fuel filter every 6000 miles (every six weeks at the time of the Xantia!), changed the oil, and that was all I ever did to it.

I can't speak for others, but that is my experience of running on veg.

[MikeT]

Looks like i'll be doing that old chestnut again then.

The reasoning behind the VWO preheaters is the following:

1. The main glow plugs stay on for 2-3 minutes after start-up (if I'm correct)... so the fuel in the pump will get properly heated before combustion.
2. The VWO in-line heater starts to heat up the incoming fuel so that once the main glow plugs switch off, the fuel is up to a reaonsable temperature.

The idea is that no fuel gets to the injectors without some form of preheating, hence allowing for better combustion and to avoid associated problems.

What are the forum's thoughts on this?

Cheers
Larry

When were the glowplugs last replaced?

1. The glow plugs heat the pre-chamber air to aid cold-starting. The fuel would already have increased in temperature from the friction and compression of the fuel pump/injectors. Excess pumped/compressed/heated fuel also returns to the tank slightly warming the fuel in the tank.

Additionally, there's a little "maze" heated from the coolant that runs under the fuel filter (thermostat regulated).

From many years experience of both MK1 and MkII Xantia on neat SVO, the only time I'm concerned about SVO temperature is when it's an icey morning. I'll often leave a small jar of it overnight under the car and inspect it for clouding. If any doubt, I add some diesel to my tank to "thin" the veg oil but that's only happened once in about five years.

I'm not saying my method is right, but it's worked for me so far.

[lazza]

HI

Well i've changed all four glow plugs and the car is still stuttering on start-up with 100% SVO. Bearing in mind it's summer here and the temperature doesnt drop below 20ºC at night. It sounds like it's firing unevenly until the engine heats up.

So i was trying to think what else it could be- injectors??

[oscar]

Could be pump seals getting hard as if doing pump for veg they use non rubber ones as veg oil hardens them.
when fuel(veg)is cold it's harder to compress so puts more pressure on internals of pump.
Where you really need a pre heater is under pump as the starting and first few mins of running are going to be whats in pipes and pump then coming from filter if that makes sense?

[lazza]

I thought it may be a pump question, but I overhauled the pump about 5 years ago, changing all the seals that were leaking.

[MikeT]

HI

Well i've changed all four glow plugs and the car is still stuttering on start-up with 100% SVO. Bearing in mind it's summer here and the temperature doesnt drop below 20ºC at night. It sounds like it's firing unevenly until the engine heats up.

So i was trying to think what else it could be- injectors??

if it starts well now and just hunts for a bit (from cold) before smoothing out, mine does that. I can't be bothered to fix the fast idle.

[Northern_Mike]

HI

Well i've changed all four glow plugs and the car is still stuttering on start-up with 100% SVO. Bearing in mind it's summer here and the temperature doesnt drop below 20ºC at night. It sounds like it's firing unevenly until the engine heats up.

So i was trying to think what else it could be- injectors??

How long is it stuttering for? All my veg cars used to do that, only for maybe 20 seconds until some heat got through the injectors. The Xantia would start in -10c on 100% veg, but it 2 goes and stuttered for about a minute each time.