Para Bailar La Lambda

[Des]

Lambda gauges are old hat nowadays, When I added LPG to my car about 10 years ago I welded a big nut into a downpipe and popped in an O2 sensor that told a little box to flash green, yellow and red lights to give an indication of fuel mixture. It was very shitty and hit and miss, like trying to measure a horses cock with a protractor. It's pretty important to get the mixture right with LPG, it does like to nom the valves and seats, revving the knackers off in the yard whilst observing a CO meter doesn't really replicate real world blatting down lane 3 on the odd occasion it's not bunged with bumbling vauidibummercs. The usual approach is to play safe and tune on the rich side, fine for petrol, not so much with gas, could even be worse, the stuff burns slower after all. The answer is Widebands, Lambda sensory has evolved into fancy digital ones with lots of wires, but gauges to interpret them were crazy money, but not any more, under a ton nowadays, well at least this tacky offering is.

 

 

Gives the fuel ratio wherever it's at, rather than no, mmm, maybe. I've adjusted the ratio that would be right for petrol, assuming the gauge is calculating the reading from lambda, and that lambda is the same whatever the fuel, but I'd best confirm this with a gas meter, getting out of my depth a bit.

[DodgeRover]

Stoiciometric is a bit higher on gas - 15.?

Does yours stay pretty much bang on? Mines set correct at cruise but is rich elsewhere - I've got a lambda feedback system (an old Leo) to put on at some point.

I'm currently open loop with a blos lpg carb.

[wuvvum]

 

hit and miss, like trying to measure a horses cock with a protractor

I'm going to have to find a way to use that phrase in conversation.

[Des]

Stoic is something like 15.5 for the gassy stuff, reading seems to stay pretty close to right at all revs but it leans worryingly if I give it the beans so I probably need to play with the vapouriser diaphragm tension screw, which then upsets all the other settings leading to a whole world of faffing. Getting the right mix at cruise keeps me happy, that's the only thing the old LED gauge was any good for, if I can now achieve a bit rich when accelerating then it's perfection but I'll accept near enough and not boot it as fiercely. I do like the Blos, they're like an SU carbs simple cousin, there is a version with the stepper, quite tempting, but I do fear such technology.

[DodgeRover]

I'm fitting a stepper motor to mine in an attemp to stop it being so rich in mid range, doesn't lean at all on WOT which is good now I've removed an egg cup full of iron filings from the filter on the shut off solenoid

 

Edit haven't seen one with a built in stepper but the instructions for mine said you could just add one near the carb same as for a normal vapouriser.

 

Getting mine right at cruise involved a motorway trip stopping and tweaking at every services or junction.

[Dave_Q]

I think you're right on the reading front, your lambda sensor there is reading excess oxygen (or not) with lambda =1 being complete combustion, this is then converted back into AFR at a rate of 14.7/lambda.

 

There may be some setting on the display for what AFR is stoich, if not just stick with 14.7 as ultimately it matters not what units you measure in.

[wuvvum]

I need to do something about the LPG setup on my Transit - it's running like a bag o'shite on gas - but I think I might end up taking it to a specialist as the above discussion might as well be in Welsh for the sense I can make of it.

 

I do need to do something about it though, it's costing me a bloody fortune to run on pez.

[DSdriver]

Get it sorted next time you're passing through Poland - LPG use is much more widespread over there and they seem to know how it works.

[DodgeRover]

I need to do something about the LPG setup on my Transit - it's running like a bag o'shite on gas - but I think I might end up taking it to a specialist as the above discussion might as well be in Welsh for the sense I can make of it.

 

I do need to do something about it though, it's costing me a bloody fortune to run on pez.

Is it's factory fit system?

[wuvvum]

Yep, dual fuel from the factory.

[DodgeRover]

Argh, there are only a couple of people who know enough about those systems to diagnose them properly. Have you tried new spark plugs? If possible gap them 0.1mm less than the petrol setting.

[wuvvum]

That would tie in with what the previous owner told me, that he'd had the system serviced by a local chap but it didn't seem to make a lot of difference.

 

It supposedly had plugs not long ago, but wouldn't hurt to try a new set - they're only about 4 quid each.

[DodgeRover]

Have you run through the checklist on the transit forum that the mobile lpg guy wrote. There's also a guy called Simon who can diagnose them correctly. Most places will just condemn the system and want to fit a new system to it.

 

Edit here's the fault finding guide:

 

took this very informative post from one of Edwards replies Edward (MobileLPG) a while back. If you are in his vicinity it would be worth your while getting him to take a look at it for you.

 

Hopefully this will help you. >

 

You say you have changed the RPM filter by the ECU, this normally causes the engine to refuse to run on gas at below 3,000rpm, and run like a bag of nails above 3,000rpm (the LPG computer cannot work out the revs basically and this rpm filter just feeds the rpm signal into the LPG system...It also diverts the lambda signal from the petrol ecu to the gas ecu)

The Mk6 Transit from 2000 to around 2006 all have the EGI system with distributor.

I maintain a number of companies fleet Transits and the faults are always the same-

 

DPFE sensor- this sensor tells the ecu whether the EGR valve has opened as it should have, with no signal from the DPFE sensor the ecu will open the EGR valve further which causes a lean mixture and rough running on gas.....I have replaced so many of these now that what initially was a nightmare job (fixed to the back of the engine) is now literally a 10 minute job providing the exhaust has cooled down.

This sensor being faulty would give you a fault code P1402, most garages read this as an EGR fault and replace the EGR valve but trust me it will be the DPFE sensor not the valve itself....the best way to test for this is to disconnect the EGR valve solenoid, if the EGR cannot be opened, even though you will get a new fault code, it will eliminate this as your problem.

 

RPM sensor- As mentioned above this causes the van to massively overfuel and will not maintain any revs unless you force it above 3,000rpm and even then it will splutter and cough.

 

Faulty switching relay- when the vehicle switches to gas it just makes 4 relays go open circuit to kill the petrol injectors, a few times I have seen a misfire on petrol but fine on gas, this is what happens when one of these relays sticks open, on the other hand if one isn't cutting off the petrol injector you would have a nasty misfire through overfuelling on one cylinder that isn't as noticable at higher revs (simple test, stethoscope the petrol injectors when running on gas)

 

Faulty stepper motor- Randomly cutting out when slowing to a junction, not sure if this is the stepper motor closing too far but replacement has sorted this a few times but it is rare.

 

Water logged coilpacks - water runs down the screen and creeps past the rubber seal at the bulkhead and makes its way past the coil pack cover seal, the front coilpack of the 2 then goes faulty and causes a misfire, usually only on gas due to the nature of gas needing a strong ignition

 

Faulty vacuum pipe to LPG MAP sensor/regulator- if you look on the front of the regulator there is a vacuum pipe attached, this runs up the bulkhead and then tee's, one side goes to the MAP sensor located in the far corner of the bulkhead, the other side goes to an elbow fixed on the inlet manifold. This elbow over time becomes really mushy and can literally just be lifted off the nipple on the manifold.

The problem with the pipe being damaged or lifted off the manifold is that this pipe (well the vacuum) varies the pressure at the regulator, with no vacuum the LPG pressure going to distributor will be over 1 bar, however without the pipe the pressure will be around 1/2 bar, if the regulator is seeing no vacuum it will effectively act as though the engine is under load and cause a higher gas pressure at the distributor and over fuelling, at higher revs and under load this wouldn't mater so much as there would be little vacuum anyway but damage to this pipe will cause major problems at low revs/load.

 

Clogged LPG distributor- This is the No1 fault with these systems, because the distributor feeds gas via little V grooves (smaller section exposed for lower revs and larger section exposed at higher revs/higher load) if the V grooves are dirty then you get a low speed misfire, at higher revs there is more area exposed for the gas to flow so it is less of a problem but at lower revs the gas flow is restricted and causes the problem you seem to be having...this is such a common problem that I strip and clean the distributor on these EGI systems as a routine part of the service.

 

 

Right the Necam/Koltec system is a good system but not without its faults, however yours do not fit the 'standard' faults that I see every week.

I have never had one with a faulty ECU yet so would be surprised if your ECU is faulty.

If you are getting the orange light above the switch but no click from the solenoids there are a number of things to check-

Firstly, is the green light flashing in the instrument panel? if it is then it means it is waiting to switch over but has yet to have a suitable signal from the temperature sensor on the regulator, if this has failed (or no water is flowing throught he regulator) then it will never switch over, however you would still get the solid 'clunk' from the rear tank solenoid as it primes the system regardless of temperature.

The next thing would be the main fuses, on the passenger side of the dashboard there is a tray with a cup holder, pull this out and you will see one of the main fuseboxes, to the right of this fusebox all on there own are 2 x 7.5amp fuses (small brown fuses in a seperate holder) check these as one powers the electronics and one powers the solenoids.

The next things would be the wiring to the rear solenoid/tank, looking underneath the vehicle there will be next to the tank a wiring loom that goes to a connector (attached to the chassis rail) this is the live, earth and fuel level signal wire, this connector can corrode and cause the fuse in the dash to blow.

The next power area to check would be the relays under the steering wheel part of the dash, up above the accelerator pedal is the LPG ECU but in front of this will be a row of 5 black relays, the one on the left is the main changeover relay, the 4 to the right are all the petrol injector relays, when power is applied to these from the relay on the left they all go open circuit and kill the feed to the petrol injectors.

If the relay on the left either isnt receiving power from the fuse, or is dead then the system will not even attempt to switchover.

 

[wuvvum]

That's interesting.  One of the things it does (when it actually deigns to run on LPG at all) is run on 3 at lower revs - sounds like this could be the petrol injector not cutting out and overfuelling on one cylinder.  There are other issues as well, but that gives me a starting point.

 

Sounds like the not switching to LPG if the engine isn't up to temperature is a design thing - I don't have much experience with LPG motors, the only one I've owned before this is the CX which would start straight up from cold on LPG, even in sub-zero temperatures.  The engine is running on the cool side as well which probably won't be helping.

[DodgeRover]

At least it gives you some ideas to work from, plugs and coil packs might be an idea to start with as well.