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Nov 16 2016
02 January 2018 - 19:59

If you bought the AEB cable you'd need the adaptor too.

As said, you can use your cable but you'd need to make the mods I talked about. If you look at your interface Molex and your LPG system Molex the pinouts don't match up, you'll have a couple of wires that connect when you plug the Molex ends together but will need to (at least temporarily) hardwire the couple of wires that the Molex connection doesn't make (because Tartarini Molex pinout is different to other AEB system Molex pinout).

Or you could buy another 8 pin Molex connector and wire it to your LPG system, that way you'd wire the new Molex plug the same as your Leonardo system's Molex plug so and it would work with your existing cable.

03 January 2018 - 12:31

Can anyone tell if this will be a BMW or Jag engine'd model?

If Jag engine'd I wonder if under bonnet petrol return piping has come off..

03 January 2018 - 17:38

On The Sun link there's talk of the interior looking burned out

03 January 2018 - 20:18

OK thanks Gilbert.

I wonder who converted it, someone must be sweating! No worries, I always make triple sure with fuel returns lol!

04 January 2018 - 10:03

Early software might need low com port numbers, later software usually works on just about any com port. Early software may need com port selection.

Depending on age of ECU you might need early / late software. Latest software is version 6 and is the most compatible version (works with most year ECUs unlike say V5 which is less likely to work on very early or very late ECUs) so V6 software is a good bet.

Pulling the LPG ECU fuse can sometimes sort connection failures (after putting the fuse back in of course). Molex pins soon get corroded if exposed and can even snap off sometimes leaving the snapped pin in the female end. You'll have noticed in Gilbert's diagram that the Tartarini Molex is pictured the other way up to the other system Molex. Some interfaces (mostly out of those that use USB to serial dongles before the actual interface but also some USB ones such as ESGI's own brand cable) which work OK with Leonardo's won't work with sequential systems, these tend to have 3 wires to the serial connector at some point in the chain as opposed to 4 wires.

05 January 2018 - 09:54

As OB said you'll know when you can see readings but it'll probably need the reducer output pressure turning up.

05 January 2018 - 12:17

Gilbertd wrote:

I can't remember if the pictures of the connections are of the plug on the cable or the plug on the ECU. Easiest way to check if you have a Leo/Millennium is to identify the 12V pin and work the others out from there.

Your diagram shows pinout looking from the rear of the interface cable plug, or to put it another way the diagram shows pinout looking at the LPG ECU's plug from the front socket end. I just compared to one of the AEB interface adaptors I linked to above.

07 January 2018 - 21:33

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?

08 January 2018 - 11:02

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.

09 January 2018 - 19:15

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.

14 January 2018 - 12:27

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.

16 January 2018 - 09:59

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.

17 January 2018 - 12:04

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.
19 January 2018 - 10:06

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.

22 January 2018 - 19:04

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. .

17 January 2018 - 12:21

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.

18 January 2018 - 10:23

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.

18 January 2018 - 19:52

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.

21 January 2018 - 18:47

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.

21 January 2018 - 18:41

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.