Frosty filter

[Freebird]

Hi All

My car is an MG ZTT with a multipoint Tartatirini LPG system. My problem is that the fuel filter frosts up after a few miles and the car starts to misfire due to gas starvation (I assume) The EML comes on with codes P0171/174 = bank 1&2 lean.

After a while it all seems to warm up and settles down. I have moved the vapouriser down as low as it will go to ensure the water flow is below he header tank (it wasn't originally) but it's made no difference. The filter is about a year old - circa 15000 miles

Any ideas?

Cheers

Glen.

[Charlie Renard]

Blocked filter

[Brian_H]

if its frosting on the filter it suggests to me that the vapouriser isn't heating up enough - others on here that know far more than me have suggested in the past that it can be worthwhile to put the vapouriser in series with the heater rather than parallel as it forces the flow through the vap that way instead of giving it two paths. Is the vapouriser hot to touch? If you have the diagnostic lead for your system what does the water temp show and where is the temp sensor for it?

[Freebird]

if its frosting on the filter it suggests to me that the vapouriser isn't heating up enough - others on here that know far more than me have suggested in the past that it can be worthwhile to put the vapouriser in series with the heater rather than parallel as it forces the flow through the vap that way instead of giving it two paths. Is the vapouriser hot to touch? If you have the diagnostic lead for your system what does the water temp show and where is the temp sensor for it?

Thank Brian.

I thought it was in series with the heater, but may not be. It certainly makes sence that is should be. There is not much access to see down between the bulkhead and the back of the inlet manifold - nor up from underneath, so I will have to whip the inlet manifold off to check for sure.

I do have a lead and the software and will rig it up for my trip home from work tonight. The sensor is screwed into the side of the vapouriser.

Glen.

[rossko]

Which filter? There may be two on your gas system; causes for either frosting are quite different

[Freebird]

Which filter? There may be two on your gas system; causes for either frosting are quite different

The one immediately after the vapouriser. Ali canister type.

I rigged up the laptop on my journey home from work and it's clearly a cold vapouriser causing the problem I think.

At startup both "Temp reducer" and "Temp gas" were at 17 deg C - ambient, after a mile or so the reducer was up to 40 Deg C where it switches to gas. As soon as it had though, the reducer temp started to drop rapidly. Another couple of miles and it was down to -1 with gas temp at 22 and started to misfire. I kept going and after a while is warmed a little and the misfire eased, but the reducer temp never got over 20 degrees.

So at the weekend, I will delve in there and see what's what.

Thanks for all the help so far - keep it coming though.

Glen.

[Brian_H]

Haven't used radweld or similar on the car by any chance? It looks like you know where the problem is now anyway so should be able to sort it.

[Freebird]

if its frosting on the filter it suggests to me that the vapouriser isn't heating up enough - others on here that know far more than me have suggested in the past that it can be worthwhile to put the vapouriser in series with the heater rather than parallel as it forces the flow through the vap that way instead of giving it two paths.

Well, I managed to find time to have a look last weekend and indeed the vapouriser was in parrallel with the heater so I re-routed it in series. The system now warms up faster, changeover is almost imperceptable and there is no sign of frosting, EML lights or missfires.

Pukka - love these forums.

Odd thing is though, it would have been so much easier for the original installer (Autogas 2000 back in 06) to have put it in series in the 1st place. They fitted a tee piece in a very inaccessable place down behind the rear Vee which would have been unecessary.

Thanks for all the help

Glen.

[Gilbertd]

Odd thing is though, it would have been so much easier for the original installer (Autogas 2000 back in 06) to have put it in series in the 1st place.

I think it's habit. Older cars had the heater temperature controlled by a tap in the flow from the engine to the heater, so if the heater was on cold you had no flow through the heater matrix. In that case if you put the vaporiser in series, you would have to have the heater on hot all the time or the vaporiser wouldn't get any heat. Consequently it was normal to plumb it in parallel with Tee's. More modern cars (I suspect just about all of them these days) have full flow through the heater matrix at all times and control the cabin temperature by using flaps to route the air to the cabin through the matrix if you want heat and around it if you don't. If that is the case you can plumb the vaporiser in series.

Both my Range Rovers have full flow heating systems and both had the vaporiser in parallel when I first got them. The LSE would suffer from icing within the first quarter mile of driving it if I didn't warm the engine up at idle first and the P38 heater temperature would drop if I sat in traffic idling for any length of time (as the flow was going through the vaporiser and not the heater matrix). Changing them to series cured both problems on both cars.

[Freebird]

[quote="Gilbertd[/quote]I think it's habit.[/quote]

That makes sense - old habits die hard I guess. I expect they don't do it anymore.

[rossko]

For the other side of the coin, I have never series-plumbed a vap and never needed to. (I always pipe up in response to Richard on this
Much depends on both the car and the vap flow characteristics of course. Many cars have variable pumped heater circulation which kinda buggers the series plan anyway. An L322 Range Rover for example...

[Tubbs]

Again, I very, very rarely serial plumb the reducer either. I've had a few bad experiences with doing that. L322 to name but one. It's better if you are doing a lot of different cars to go into the flow and return from the heater matrix.
I've done a few serial plumb reducers on a certain few audi's and Vw's where the heater pipes are nigh on impossible to get to. I generally use the water heater pipes to the oil filter. They never shut off under any circumstances. So you know it's safe to just use one.

[Gilbertd]

I will concede to those that are doing it every day. If you've got a full flow heater system with only two pipes going to it (flow and return) as on the Classic or P38 Range Rovers, then you can plumb in series. But, if you've got one of these highly complicated new fangled systems with multiple pipes, separate pumps and thermostats, then it probably won't work unless in parallel. I suppose it means that on a really old system it has to be parallel, on something in between, it can be series but on something very new it has to be parallel again. For that reason, plumbing in parallel has got to be the way to do it to be on the safe side.

Showing my age again, I've never even seen a car with heater pipes going to the oil filter! Presumably a modern idea to heat the oil up faster to reduce friction on a cold start and keep the emissions down.