Usually yes but not all. On a multipoint reducer it is often a screw in the centre of where the diaphragm would be.
The problem with this install would seem to be that the pressure is too high and needs to be reduced but the timings are about right (1.2-15x petrol injection times). If the pressure is reduced then the timings will need to increase to get the quantity of gas injected correct so it is likely that the injector nozzles are too small.
Reducer pressure is usually adjusted using an allen key, allen socket is accessible from outside the reducer (no need to remove anything to access it), inside the reducer the allen socket turns threads which screw a plate in/out to adjust compression of the spring which acts on the diaphragm. I'd aim for 1.5bar diff pressure as a start.Got to adjust reducer pressure with the engine running on gas.
Edit - Just noticed this crossed with Gilbert's post.
Gilbert raised another point (bit about 1.2 to 1.5 multiplier), to add to that, the LPG ECU compensates for pressure so where you have 2.3 bar where we might expect 1.5 bar we might expect your 5.5ms gas pulse for 4ms petrol pulse to rise to 8.4ms gas for 4ms petrol when pressure is only 1.5 bar [(2.3/1.5)x5.5 = 8.4], which would imply your injector nozzles are too small for 1.5bar (8.4/4 would mean multiplier of 2.1 which is outside the 1.2 to 1.5 multiplier range Gilbert mentioned), except AEB ECU's have a limited range of pressure compensation and it could be that your system's pressure compensation is maxed out (actually minned out since we're talking about compensating for over pressure). If pressure compensation is minned out it will mean the engine runs richer (or at least fuel trims will be more negative) when running on gas at 2.3 bar compared to running at a pressure that the ECU can compensate for. That's the basic theory but in practice nozzle size makes more difference at idle than pressure does because higher pressures also have the effect of slowing the speed of the injector opening.
What pressure is set in software? This is the pressure at which the ECU applies zero compensation for pressure, the range of pressures the ECU can compensate for is centred around this pressure. None of this affects the fact 2.3 bar is too much pressure for the injectors to cope with.
LPG injectors wear out don't they?
With them being 12 years old and seeing as I've got no intentions of changing this car, is there any merit to just changing them and being done with it?
I don't want to throw money at it but I'd rather not have it being unreliable in the future either.
If it is worth changing them, are there any particular ones to go for?
David.
You could change injectors but you'd still have the issue of pressure being too high, would sort the pressure issue as the first step and then you might find injectors work OK.
Can you post pics of bits of your system (or find same bits on the net and link to them)? Would want a pic of the reducer, injectors and pressure sensor.
As a side issue here, but possibly related, how do you test an AEB025 MAP sensor to ensure it's actually feeding correct data to the ECU?
This is the pressure sensor that's fitted:
This is the reducer that's fitted:
This is the injectors fitted:
The picture of the injectors isn't brilliant but the label on the box says what the label on my injectors says.
Tartarini
Rail Type 03
Seat D
4.0mm
June 2005
Thanks for the help guys :) It's very much appreciated.
David.
Orangebean wrote:
As a side issue here, but possibly related, how do you test an AEB025 MAP sensor to ensure it's actually feeding correct data to the ECU?
I mentioned one way above... When the engine isn't running the manifold reading should be very close to 1 bar (atmospheric pressure), when the engine is running and warmed up I'd expect to see around 0.4bar at idle on a P38 that runs well. Software shows gas pressure relative to manifold pressure so If there's only atmospheric pressure in the LPG pipe when the manifold pressure is reading 0.4 bar the gas pressure reading should be close to 0.6 bar and as manifold pressure increases gas pressure should drop correspondingly with manifold and gas pressure always adding to very close to 1 bar (and it's easy enough to take an LPG vapour pipe off to ensure pressure in the gas system is at atmospheric pressure), this check to be done with the engine running on petrol of course. It's only a basic check but is usually a good pointer. But some of us can just swap pressure sensors lol..
@Dhallworth
I believe the pressure sensor is a standard AEB025. If not I'd dare bet it'd be the same spec as OMVL Piro's AEB pressure sensor. If you look at the sensor from the other side where the pipes are connected, does the vacuum pipe or gas pipe attach closest to the wiring connector?
Reducer pressure adjustment is the screw in the middle of the sticky-out bit of the reducer
Valtek type 30 injectors would make for an easy and relatively inexpensive swap (but be sure to order them with 4mm outlet nozzles). Would concentrate on pressure for now, not buy injectors yet.
Thanks Simon, I'll do some more digging into reducing the pressure at the weekend, weather permitting.
David.
How's the weather been Dave? My most recent customer was from Lanark in Scotland, said the weather was OK on his way home until he got close to home, foot of snow there... Foot of snow before he brought his car for conversion last week too, reckons Lanark has a micro-climate lol.
Lanark is indeed a funny place, it's in the middle of the Clyde Valley which tends to get his pretty harsh with the weather. I went to work yesterday and there was no snow at all, by the time I came home there were 5 or 6 inches, I couldn't get the van up the road, I had to get my brother who was visiting my folks to bring my P38 down and drag me home.
There's still a load of snow on the ground today but it's been dry at least so I've had another look at my reducer.
The pressure with the adjuster screw fully unscrewed is 2.40 bar, with the adjuster screw fully screwed in it's showing 2.46 bar.
It's almost as if the reducer isn't actually reducing the pressure and the gas is running straight through it. When running on LPG, the pipe running from the reducer to the injector rail is almost rock hard to squeeze so there must be some amount of pressure in there.
I get the feeling the rebuild kit was an utter waste of time and that I'm going to have to bite the bullet and fit a new reducer.
David.
Daft question Dave but the engine was running on gas when you adjusted the reducer pressure?
It does seem the reducer rebuild didn't work out. You don't need to buy the same (now expensive Tartarini) reducer - Tartarini reducer temp sensors can be an unusual spec but there are ways around any problems arising from less compatible reducer temp sensors such as might be found on a different make reducer. .
It was indeed running on LPG whilst the reducer was being adjusted.
I've managed to find a Tartarini reducer that's exactly the same for £159 inc delivery. I'm tempted to buy the same one as the pipes, mountings etc. are already in the right place. Might as well keep things simple, eh!
David.
Yes it'll be simpler to replace the reducer with the same model. It's an expensive model and no better than some reducers that are half the price but you probably wouldn't quite save half fitting a different model if you had to buy bits of piping etc.
Another check to do before you replace the reducer though... One of the problems is that the system switches back to petrol when you drive on gas (it''ll idle roughly on gas but switch back to petrol as soon as you put any load on the engine)? Assuming that's true, start the engine and let it warm up, switch to LPG while idling, drive the car accelerating slowly on LPG while watching the pressure reading. What happens with the pressure reading (does pressure drop away just before it switches to petrol)?
Right, have taken it for a run today with the laptop connected.
With the screw totally unscrewed on the reducer the car is driving better then it did previously on LPG.
To get it to switch back to petrol I had to use quite a bit of throttle, when it did switch it felt like it was bogging down and being starved of fuel and the LPG reading on the laptop was showing 0.5 bar of Diff. Pressure. When it had switched back to Petrol the Diff. Pressure reading was sitting at 3.24 bar.
Switching it back to LPG at idle brought the Diff. Pressure back down to 2.4 bar.
One thing I did notice was that in the LPG software the Lambda 1 reading was showing a constant 0.5v, checking in the software shows it as being set to having 1 lambda and 0 - 1v which is correct.
David.
If the injector solenoids were shagged and not actually allowing enough gas through, would that cause the differential pressure to be too high?
dhallworth wrote:
One thing I did notice was that in the LPG software the Lambda 1 reading was showing a constant 0.5v, checking in the software shows it as being set to having 1 lambda and 0 - 1v which is correct.
Maybe the LPG stuff isn't actually connected to the lambda sensors? Assuming they're actually switching OK when looked at with other diagnostics, then just ignore the lambda value reported by the LPG software. It's only there as a convenience and doesn't interact with the LPG system in any way.
There's probably a setting to say "not fitted" somewhere.
If the pressure drops and it switches back to petrol when you boot it, it isn't getting enough gas. Could be a clogged filter, clogged solenoid or the pipe has been squashed flat under the car somewhere.
I've had a good look over it and couldn't find any other filters then the one after the reducer before the injectors, which has been replaced.. If the gas supply was low, would that not cause low pressure rather then the pressure reading being high all the time?
My "normal" pressure going by the diagnostics is showing 2.4 bar at idle, this drops when driving to about 1.8 bar, however just after it's switched back to petrol the pressure is showing 3.2 bar.
The pipe seems to run along the inside of the chassis, again, I can't see any marks on the pipe to suggest it's been squashed. The previous owner told me that the running issues on LPG occurred gradually rather then just over night.
David.
Adding to Gilbert's point there is likely a liquid phase filter built into the solenoid in the gas feed near the reducer (it's unlikely an installer fitting Tartarini back in the day would be cowboy enough not to fit a reducer filter solenoid). I'd reckon a clogged filter unlikely to be causing the cutting back but it could, it's also possible this solenoid (or the one on the tank) isn't opening fully, though again unlikely.
Unusual to have a high pressure reading after a system has switched back to petrol due to low pressure and 3.2 bar is a very high pressure..Best case scenario - the reducer is set to 2.4 bar above manifold pressure, so when manifold pressure is at atmosphere (1 bar) when you're booting it absolute gas pressure rises to 1+2.4 bar = 3.4bar, since the engine is now switched to petrol and engine is idling manifold pressure is only 0.4 bar so diff pressure (gas pressure less manifold pressure) reads as 3 bar (3.4-0.4, not far from 3.2 bar you're seeing). Middle case - If the reducer gets too cold it can spit liquid gas into the vapour side which then evaporates in the vapour pipes and increases pressure sky high. Worst case - internal reducer fault. But it would seem your 3.4 bar reading is about right after a full throttle switch back to petrol, especially if your reducer solenoid isn't mounted directly on the reducer as the reducer will still be fed with liquid gas from the line between solenoid and reducer when the engine has switched back to petrol (so you get the 1+2.4-0.4 scenario).
I ordered a Tartarini reducer the other day as the company had one left in stock and they were doing it for a good price. That's arrived today but I'm not fitting it yet just incase it's not needed. It's nice and shiny though.
I've had a good look at the front and rear today. I can see the solenoid on the tank, there's no filter there, here's a picture of the solenoid that's fitted just before the reducer:
Looking at that, I can't tell if there's a filter in it or not, there's a brass body that sits near the bracket, if there is a filter in there it must be a tiny one, the filtered solenoid on our other LPG RR has a noticeable bowl that the filter sits in underneath it.
Since undoing all of the tension on the pressure adjusting bolt the car seems to run better, it idles fine on LPG, I can accelerate to 30 on the flat but if I try and go past half throttle or hit a slight incline you can feel it starting to choke, keeping your foot in the same place and switching back to petrol makes a notable difference in acceleration.
With the screw undone totally at idle the pressure is still sitting at 2.4 bar, when driving normally it drops to 1.6 - 2.0 bar and when you floor it, it switches back to petrol.
I put the suspension on high earlier and slid under it for another look at the pipe, I can't see any marks on it that would suggest it's been crushed.
David.