blueplasticsoulman wrote:

Lpgc wrote:

may be an option in software to add some petrol to fuelling at high engine loads (and/or switch temporarily fully back to petrol when you put your foot down but resume running >on gas when you lift off the throttle a bit),

I think there is that option Simon. If you remember when we were setting mine up, we had a moment or two where that was happening until you tinkered with the software. I think it's under the "Erichments during acceleration" tab. Which makes sense.

I think you'll be right. Most Tartarini systems have the option but the ECU's change over the years and very early ones won't have the hardware ability to support petrol addition. Unavailable settings are supposedly (and usually) greyed out in versions of software that came out later than hardware but some combinations of software, hardware and firmware can leave unavailable settings looking available... would expect if this were the case then setting petrol addition would just provoke a full return to petrol (with return to gas when rpm falls).

Thanks Miles, I'll try to shift apps to an SD card if you reckon it's possible with the LG?

Off topic a bit, my inexpensive LG phone reports it's running out of storage space, emails no longer work on it. I haven't installed anything, I regularly download and and delete camera pictures etc from it but it came with lots of pre-installed apps that I don't use, many of which have automatically downloaded multiple updates. it's the app updates I believe have sapped storage space but it won't let me delete apps or revert to pre-update versions. A memory card wouldn't do any good as email and apps use internal storage space... Any ideas?

Does the lack of power seem just throttle related or more 50% throttle above a certain rpm? Does it seem to happen at the same time as pressure falls away?

Good luck with the heater matrix problem.

How much stick do you have to give it before it cuts back to petrol? How does it drive on LPG now?

If it drives OK on gas before it cuts back and you have to give it a lot of stick before it'll cut back, some people would be prepared to leave it like that as long as fuel trims / lambda readings are OK. There may be an option in software to add some petrol to fuelling at high engine loads (and/or switch temporarily fully back to petrol when you put your foot down but resume running on gas when you lift off the throttle a bit), where these options are available they can prevent cutting back to petrol because the reducer isn't worked as hard (or even worked at all) when you put your foot down. Not the best setup situation for an LPG system but can mean no further expense on parts and little change in running costs if you seldom boot it to the point the above options are active. You wouldn't want such options set to the point they are applied often or you'd end up saving less money by running on petrol too much.

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).

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)?

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. .

Funny how it's possible to watch a spark jump onto your finger/hand and anticipate the electric shock feeling before the feeling has travelled up your nerves lol.

The arcing might not make much difference when running on petrol but could make more of a difference when running on LPG.

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.

There's a set of miniature relays, one per cylinder, in the older Stag ECU's. If you're getting petrol and LPG to a cylinder at the same time and injectors are OK it could mean a relay is failing to open (closed and off connects the petrol injector to petrol ECU).

To confirm this or other ECU problems you could just swap wiring (affected cylinder's petrol break wiring and another cylinder, also swapping the LPG injector plugs to match) to see if the fault moves with the ECU channel. Seen this happen on loads of Stag installs and years ago had this problem even with a few brand new Stag ECU's.

Even if the ECU cuts the petrol injector it might still have a failed gas injector output, effectively pulsing the affected cylinder's injector for a different duration to the other injectors (too long or open all the time, too short or closed all the time). You've ruled out LPG injectors, which leaves pipe runs (crimped?), wiring, ECU and mechanical (compression?) as potentials. Far more likely there's an LPG problem than compression/engine valve problem. Another thing we could add to the list of potential faults - If the reducer vacuum pipe was connected to the affected cylinder's intake runner and the reducer was leaking gas through it's vac pipe, unlikely it's been plumbed that way on a P38 though.

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.

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.

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.

Diff pressure is the difference in pressure between gas pressure and manifold pressure. The fact that after engine has been off for a while your diff pressure and manifold pressure roughly add up to 1 bar suggests those readings are correct (and also suggests you may have a leak on the gas side, but a leak won't be relevant in this).

But your diff pressure goes up to 2.69 bar when the solenoids first open and to 2.49 bar when the engine is idling on gas, this is far too much pressure and because your pressure readings seem correct this suggests a problem with the reducer.

Can also see that your manifold pressure goes from 0.41 bar when idling on petrol to 0.55 bar when idling on gas.. There are 3 possible reasons for that:

1. Sometimes when the ECU is supplying power to the solenoids and injectors it's reference voltages are affected due to the extra electrical load.
2. If the reducer leaks gas into it's vacuum reference port (vacuum at the engine side of the vac line, usually a line that's closed at both the reducer and pressure sensor, but if the reducer is blowing the other way and the sensor is in the middle it'll read some average between engine vacuum and reducer pressure.
3. If mixture is incorrect when idling on gas the engine has to draw more air to maintain idle speed (running less efficiently on incorrect mixture). Lambda readings reflect average mixture over a cylinder bank (in simple terms anyway), if average mixture is OK but the engine is less efficient it must be because some cylinders are getting richer mixture while other cylinders get lean mixture (if any cylinder gets lean or rich mixture the engine will be less efficient than if all cylinders get almost exactly correct mixture). Some cylinders getting rich while some get lean could point to injector problem(s) or could just be due to injectors struggling to dose accurately due to the high pressure.

Would expect readings from Testbook to be slightly different to readings from the LPG ECU anyway, not that there are many of the same type of readings to compare between the two. You won't be able to see gas pressure in Testbook.

Where's this.. I'd guess maybe near Tanhill or Holmfirth? I sometimes go for a drive around Tanhill and to the highest pub in England in summer.

Years ago I bought a BMW750 from Paignton, Devon and set off from Yorkshire to collect it in a Volvo with a rather large car trailer on the back. Stupidly I followed Satnav, which took me down some really tight country lanes with very sharp bends and a river ford. It was the early hours of a very cold morning when I got to the ford, had to take my shoes and socks off to check depth before crossing. Made the crossing then at the other side of the ford was a steep wet hill, front wheels kept spinning all the way up. Last time I'd use Satnav for a trip when towing and last time I'd want to pull something so heavy such a distance using the wrong type of vehicle lol.

Morat wrote:

that and you're not allowed to jump the queue ;)

I haven't forgotten you mate ;-)

@Dhallworth - The differential pressure shouldn't be as high as 2.47 bar, you will have problems if that reading is true. If the pressure is really as high as that it'll point to a problem with the reducer. If the pressure isn't really that high (yet it reads that high) it 'll point to a problem with the pressure sensor, loom or ECU.

What happens to manifold pressure when running on petrol? Were aircon, lights, etc on? In park or drive? I ask because most AEB systems on P38 V8's read just over 0.4bar manifold pressure at idle with warmed engine, if your manifold pressure drops lower when running on petrol it's because the engine is struggling more to run at idle on LPG (ICV opens more to keep rpm at idle). If that's the case it could be that even with half decent calibration and injectors that are in good working order the injectors are still giving inconsistent fuelling due to high pressure (as mentioned above). The pressure sensor is really two pressure sensors in one (manifold / gas), a problem on one sensor may or may not affect the other sensor, as sensors get old they sometimes show slightly incorrect readings but that doesn't always affect good results. As ECU's age the AD converters and/or reference voltage to sensors can see the ECU show slightly incorrect readings, again this doesn't always mean an immediate ECU replacement is necessary.

Yes I install and repair vehicle LPG systems for a living, could sort it if you like. But you could be closer to having fixed it yourself already than it seems, hopefully the new cable will work and point to an easy fix such as low reducer pressure, in which case we'd hope turning the pressure adjuster on the reducer will bring pressure back up. That said I wouldn't have bothered rebuilding a Tartarini reducer if the initial problem was low pressure, the kits will repair a leaking reducer but are less likely to repair a reducer that failed on pressure, they don't include all internal bits or the housing... and it seems whatever problem you had before the rebuild was the same problem you're having now?

Two vehicles here for repair at the moment: Supercharged Rangerover with a BRC system just came in which takes a lot of cranking when it's been running on gas, so I'll be looking for a leaking reducer diaphragm / petrol return which continues to dump petrol pressure when the engine is switched off / poor calibration on that one. Merc E500 with LPGTech, Antarctic reducer, V30 injectors with the same long cranking problem, already found the reducer on this one is leaking gas into the manifold and started fitting a new reducer.

V6 software will usually work on anything that V5 does, there was quite a change in terms of compatibility between V4.X and later versions with one of the biggest changes around V4.7 for most AEB stuff. 2005 Is quite old, I'd expect V6 to work but if it doesn't you might need pre V4.7 to work, maybe even V3.X. That said, Tartarini version numbers didn't always follow general AEB trends, the software works in a slightly different way too.

The interface setup you tried may have only 3 wires on the serial side?