Found this on a Tinley Tech blog relating to connection problems between AEB LPG ECU and computer. No further information though:
Some of the older LPG ECUs require a pulsed signal on the brown (rev-sense) wire in order to connect.
It implies that "older" ECUs (whatever that means) need the engine running in order to connect.
Anyone ever heard of/ encountered this before?
Nope, new one on me but it's worth a try. It does beg the question of how are you supposed to know why a system isn't working if you can't connect to it without the engine running. Unless it just needs a pulse, in which case you could spin it over on the starter while trying to connect (or have it running on petrol I suppose). To answer your previous question though, I would say downstream of the filter as the temperature is likely to be more stable. Which is probably why the installation manual I emailed you says:
1.1.4 Gas Temperature Filter and Sensor
For a correct installation of these components:
I must using a different installation manual from the one you emailed!
I'm using the one that came with the 4.6.1 software which is the one closest to working at the moment-
Alisei-Zeta General Installation Manual 2nd issue 06/10/2009
Thanks for the info on the sensor. My guess would have been downstream too.
Appreciated
M
Gilbertd wrote:
Which is probably why the installation manual I emailed you says: (etc)
My gas-temp sensor is inside the splitter to the two injectorbanks, but fails at the moment. I was advised to temporarily connect it together with the watertemp sensor, which works. Only it switches from petrol to lpg a bit later. Need a new sensor though.
Piped in series on my own old Chrysler Grand Voyager because it has a matrix in the front and another in the back (matrix's flow in parallel of course)..The reducer is in series with the joint return pipe from both... Thinking was along Gilbert's lines, I didn't want half the flow through the reducer and one quarter flow through each matrix...
There are a lot of iffs and buts regards temp correction. For starters, it seems AEB don't presume gas temp correction works entirely correctly anyway, because otherwise they wouldn't have thought necessary to have compensation for reducer temperature too. AEB default temp compensation figures are a bit exaggerated and reducer temp shouldn't even enter the equation. On some installs (and where it won't effect neatness etc) I try to fit the gas temp sensor in position where it's least likely to pick up heat from the engine (or radiator) or blown cold by external air while driving. On other installs position doesn't make a great deal of difference... most V8 powered stuff gets hot everywhere under the bonnet anyway. The old advice was to fit the temp sensor as close to injectors as possible, thinking was it is at the injectors where the temperature and pressure of gas matters and gas temp could be effected by pipe temps etc between the reducer and injectors ... But I've come to think that in reality when driving gas is shifting so quickly through the pipes it will have little time to be effected much by pipe temperature / At idle gas is shifting slower but still quickly enough for pipe temp not to have much effect on actual gas temp / Though pipe, injectors and temp sensor are more likely to be effected by under bonnet conditions at idle and with slower moving gas the sensor might be effected more by the temperature of whatever it's mounted in than by the gas. One of the iffs and buts concerns compensation particularly at low pulse duration, because unless the ECU firmware correctly accounts for injector latency and temperature related response, no single set of (default) compensation figures will work properly over all possible configurations of pressure, nozzle size and gas injector pulse duration. I.e. you cannot accurately apply Boyle's law without accurately accounting for how injector response is affected by temperature and accurately accounting for injector latency, but almost all firmware seems to get these factors wrong, so temp compensation is best adjusted on individual installs. But again, not much of an issue on a sequential Rover V8 where pulse duration at idle should be higher than it is on most other vehicles and where the petrol system is very forgiving in terms of fuel trims etc - default compensation seems to work fine on them.
Simon
Simon thank you for this lesson.
When I get mine back I want I would like to "service" the system...........any good places or can I do it myself ? dose it need re-setting or anything ? I am in Portsmouth
A "Service" can be as simple as changing the filters (easily done yourself) to going through the complete system doing a full safety check and checking/ resetting calibration.
A good place to start looking (unless someone localish to Portsmouth can recommend anyone), is for a UKLPG certified installer. Have a look for one handy for you.
Decent stuff mate, just want to keep her running sweet thank you.
Changing the filters and checking for flapping or deteriorated pipes is the easy bit. Checking the calibration is slightly more difficult but can be done by looking at the long and short term trims when running on petrol and comparing them with running on gas. If you detect a problem here, then it really does need to go to someone that has the software and knowledge to set it up properly. If you don't have a means of checking the trims, there is a crude way of doing it using the trip computer, but more of that later.
To understand how the gas system works in a car, you need a basic understanding of how the petrol injection system works so we’ll start there. Petrol is pumped from the tank to the engine where it goes through a pressure regulator. This keeps the fuel at a constant set pressure and returns excess fuel back to the tank (pressure regulator is on the back of the fuel rail on a GEMS but integrated with the in-tank fuel pump on a Thor). The fuel under pressure sits at the back of the fuel injectors which are nothing more complicated than electrically operated valves. Think of them like bathtaps but capable of being turned on and off very quickly.
The injectors are switched on and off, to open and close them, by the cars petrol ECU. It takes signals from various sensors, engine temperature, intake air temperature, throttle position, engine revs and, by using an internally programmed ‘map’ knows how much fuel is needed at any one time. The amount of fuel is altered by altering the amount of time that the injectors stay open for. At idle, it can be as short a time as 2mS (2 milliseconds, or 0.002 of a second), at full throttle under load, it can be as long as 15mS. As the fuel is at a set, known pressure, the length of time that the injectors are open for directly affects the quantity of fuel injected.
As a check, the engine is fitted with lambda sensors in the exhaust system. These measure the amount of oxygen in the exhaust gasses and can tell if the air/fuel ratio (the ‘mixture’) is correct or not. If it isn’t, the ECU will ‘fine tune’ the length of time the injectors are open for to keep the mixture correct and the engine running at maximum efficiency. This is the short term fuel trim but if there is a problem somewhere that causes the amount of fine tuning to be greater than a preset amount, the ECU alters the long term fuel trim so the short term is always flipping between a bit rich and a bit lean (the positive and negative fuel trims) So if the air filter gets a bit clogged, the mixture will be permanently rich (not enough air) so the short term trims will be going constantly negative to reduce the amount of fuel and get the fuel/air ratio correct again. This will cause the long term trims to go a little negative so the short term trims are back working either side of zero.
When running on gas, the pulses that would be used to open and close the petrol injectors are used to fire he LPG injectors instead. Again, you have a preset pressure so it is only the injector open tines that vary. However, due to them being a bit clunky, not as fast responding as petrol injectors and are injecting a vapour not a liquid, they need to be open for slightly longer that the petrol injectors would. Ideally they need to open between 1.2 and 1.5 times the duration of the petrol injectors. So if the petrol injectors need to be open for 3mS at idle and 15mS are full throttle, they'll need to be open for around 3.9mS at idle and 19mS at full throttle. This is done by the calibration in the LPG controller. It has a map stored and adds the additional time to the pulses from the petrol ECU and uses that to hold the LPG injectors open for the correct amount of time. But, if the calibration is wrong and instead of adding the required 4mS at full throttle, it is only adding 2mS, the mixture will be lean. This will be detected by the lambda sensors and fed back to the petrol ECU which will adjust the fuel trims, initially the short and then the long term so instead of a 15mS pulse, it sends a 17mS one to get the mixture correct again by giving a 19mS pulse duration.
So you can see that by looking at the long and short term trims when running on petrol and again when running on gas, you can see if the calibration is correct. If you've no way of looking at the trims, you can use the trip computer. The trip computer doesn't measure the amount of fuel you use but calculates it from the fuel trims so can give a good indication of something being correct or not. With the car running on petrol, reset the trip computer and go for a drive. Preferably 20 or 30 miles of mixed driving and at the end check the mpg figure it is displaying. Then reset the trip computer and do the exact same journey only running on gas this time. The displayed mpg figure should be the same. If it says you are doing more miles per gallon, then the petrol ECU is having to lean the mixture off (make the fuel trims go negative) so the gas ECU is adding too large a correction, if it says you are doing less miles per gallon, the petrol ECU is having to increase the petrol injector pulse lengths to get the mixture correct (make the fuel trims go positive) because the LPG controller isn't adding enough.
Simple really......
Steady on Richard, that's almost as long as one of Simon's posts ;)
Gilbertd wrote:
Lpgc wrote:
Post contains a couple of minor errors, unlike my posts ;-)
What's that then?
Only messing mate ;-)
Gilbertd wrote:
So if the air filter gets a bit clogged, the mixture will be permanently rich (not enough air) so the short term trims will be going constantly negative to reduce the amount of fuel and get the fuel/air ratio correct again. This will cause...
Would be true of a petrol carb, LPG mixer system or AlphaN based fuel system but isn't true where fuel injection system meters air flow and/or manifold pressure..
OK- the random on and off of the switch lights continues.
My hopes were high yesterday, with grounds repaired, replaced and added where appropriate, new perm +ve feed from batt to ECU plug, new switched +ve feed direct from fuse box to ECU plug.
I switched it on- straight away switch lights jumped appropriately into life, ran engine to bleed cooling system, switch continued to behave. With ignition switch in pos 2 could hear solenoids operating at tank when gas selected.
Didn't try running on gas as focussed on getting cooling system sorted.
Drove car home from workshop. Switch still lit.
This morning, nice and frosty, started car to see which elements of screen/ rear heaters worked. No lights at switch.
One brief flash of petrol light (maybe 2 seconds) on switch after idling for a while then nothing.
Still got panels off inside so will probe switch wires later at workshop to test grounds and volts.
Suggestions for next areas to attack most welcome!
So....
Probing the intermittency at switch, had to dismantle switch as base glued to binnacle trim (why???). While dismantling switch, the tiniest bit of copper track fell out of case:
It's the little speck between the PCB and cover!
Hopefully the smoking gun, but in the meantime back to probing...
Probing socket, without switch plugged in, shows pin 1 (red) power wire "switching" between millivolts and 5v at random intervals. 5 v for a second or two then millivolts for between 10 and 30 seconds and repeat.
Petrol light with switch pcb plugged in shows same behaviour.
Looking at schematic/ pinout it shares 5v supply with pressure sensor (red/ white p50) so probing there next.
Oh and now have a permanent Drivers Airbag open circuit fault that has flashed up while watching light on switch!
Won't clear down
F ing car is generating issues faster than I can fix them
5v supply to pressure switch shows same random behaviour. Cant get 5v at ECU out connector. The fact that the pinouts for ECU dont match my diagram/ colours for the pressure switch doesn't help!
So, if I can't get a good 5v at the ECU connector out, then I guess next step is into the ECU itself as that's where the 12v in is converted into 5v?
Been down this road many times before! Old ECUs sometimes fail in this way. Usually before the system fails to operate completely the 5v line goes wrong, which leads to incorrect readings such as temperatures, pressures and tank levels, all of which barring tank level throwing calibration off.
While you're connected with the laptop things can seem better because the 5v is held correct by the serial connection - Installs effected by the latter symptom can seem OK while setting up with the laptop but as soon as laptop is disconnected calibration goes wrong. If the serial connection can make all the difference, so too can a 7805 wired to the 5v wire at the serial port (or attaching 5v from elsewhere on the vehicle, since many vehicles use 5v sensors).
Gilbert might disagree... He took the 5v advice on LPGforum (working on someone else's car) a while ago and found it didn't work in that case.
I suppose if the 5v falls to miilivolts, could be that the main power feed voltage is pulled down when the system tries to power solenoids / injectors, i.e. solenoid coil or wiring short. Or 5v could be pulled down by failed pressure sensor. The temp and level signals can't really pull the 5v down even if shorted because of the ECU internal resistor on each sensor between the 5v rail (each sensor forms half of a voltage dividing circuit, meter of which is what respective AD converter gets).
The bit of track coming out of the switch seems ominous too.
Simon
Doesn't sound too hopeful Simon! I know it's not pressure sensor pulling things down cos same lack of continuous 5v with sensor disconnected!
Trying to join LPGForum but still waiting for an Admin to approve me- 4 days and counting :)
A 7805 being an IC that takes 12v down to 5v I assume?
Main input volts steady at 12 to 14.8v depending on whether engine running or not.
Optimistically ordered a new switch anyway. Should be here tomorrow. Even if that's not the problem, they're still not supposed to have bits of track falling out!