Indicator says it's on LPG, but still only using Petrol

[Super Dragpack]

Hi all, and I am sorry that my first post is a call for help. I'll try and be more useful in the future.

The issue is, I have a 1998 Jeep Cherokee 4.0 fitted with a Tartarini Tech 97 Single Port LPG kit. It's been fitted for 10 years, so proven reliable although I haven't had the car long.

It's been running fine on gas but a few weeks back, when it was refilled with gas, a problem started. Everything appears to be fine, the LPG level suggests its full (which it is), the indicator lights do the correct things, but nothing actually happens. Despite what the indicator lights do or what I press, the engine remains running on Petrol and no LPG at all - proven by the drop in petrol (very notable in a small petrol tank) but no change in the LPG levels at all.

I have checked all the fuses I can find and they are fine - in fact if I remove the LPG fuse whilst the engine is running, and assumed to be on LPG, the engine continues running perfectly despite all the indicator lights on the switch going out.

I have little idea where to start.

If it helps, I have removed a screw on brass filter cover which is part of a solonoid valve under the bonnet of the car, and there is no gas there, with the engine on or off, so I assume the fault is closer to the tanks. Could there be a stuck valve near the tanks? Where would I look? If I remove any suspect solonoid, am I at risk of the gas rushing out of the tanks or is there an isolation point I can use to shut them off prior to any valves or components?

If it helps, I am a Plumber and Electrician - so know my way around pipes, gas and electrical principles etc - but I am also a keen part-time mechanic and restore classic Yanks as a hobby and generally am always under the bonnet of one car or another.

Any help gratefully appreciated please.

Mick

[Gilbertd]

There will be an output from the Tartarini unit that goes to both solenoid valves and whatever is being used to switch off your petrol injectors (either a simple relay or an emulator). This is usually a blue wire and has 12V applied to it by the controller when it switches to gas so opens the solenoids and switches off the petrol injectors. It sounds like this wire has become disconnected somewhere so the controller is switching but 12V is not appearing on the blue wire so the gas valves aren't opening and the petrol injectors aren't switching off. Find where this wire comes out of the controller and check for 12V when it is showing that it is running on gas. If it's there, you have a break somewhere further up the chain. If it isn't it may be that the internal relay in the controller is either not operating or it is but it's contacts have burnt out. There have been cases where a short to earth on the blue wire has burnt the track on the printed circuit board in the controller so everything appears to be working but no volts are going out.

[Super Dragpack]

Thank you for your assistance. I would assume, from what you are saying, that my original idea of a stuck solonoid would be unlikely as it would still cut the petrol whilst trying to introduce the gas - therefore leaving it non-running when it's meant to be on gas.

This feed wire, if only one wire makes everything happen, is the likely culprit. I will have a look and see what I can find.

The problem now is, where is my controller. I have two smaller boxes and a slightly larger one that I've found so far. One smaller one is on the passenger side bulkhead next to a gas solonoid, the other is fixed to one side of the vehicles main fuse box on the drivers side of the engine bay, whilst the third, and bigger unit, is fixed to the other side of the same fuse box.

Would the "main" control box be the one that has the fused power feed directly from the battery? If it is, then its the larger of the 3 units found so far.

I fitted a LPG kit on a MPV about 12 years ago - but for some reason I remember very little of the system and install. This would of helped me problem solve this Jeep but I have a great memory for forgetting things.

If I find this suspect Blue wire, and I then find that it has no output, could I directly feed it with 12v (isolate the ECU's obviously to avoid damage to them) to check that everything else is switching over correctly? I could then explore why the Blue wire isn't providing a live feed (relay, connection, short etc) with knowledge that this is the fault.

Thanks again for your wonderful help.

Mick

[Super Dragpack]

Sorry for the quick second reply.

I have just found (downloaded) a wiring diagram for this system - isn't the internet wonderful - and it does appear that this single blue wire does almost everything. It actuates the solonoids, supplies power to the tanks (for their solonoids) and powers the injection emulators. If this wire fails to feed, then everything stops. Wow. Who would of thought this would all be done on a single wire. I will get the meter out and check for a short before even thinking about directly feeding this wire as it would be a very long wire and connected to everything. A failure in any part of that long wire or attached component could cause a short circuit and failure of the system.

I've uploaded it to my photobucket account and linked to it below.

[Gilbertd]

The two smaller boxes will be the injection emulators (probably marked Pitagora) so the larger of the three (with two multiway sockets on it) will be the Tec 97. The install on my LSE Range Rover has a fuse in the blue wire to stop any shorts burning out the controller. As you say, it's a long bit of wire and there's been cases where the feed to the tank solenoid has come adrift and the insulation has been melted through on an exhaust. An internal short on one of the solenoid coils is also a possibility although unless a short has damaged the actual controller, it would normally take out the main fuse in the supply to the controller. Yes, the one with a fused power feed will be the controller.

[Super Dragpack]

Well progress. This morning, armed with meters and tools I started the Jeep - and it ran on Gas. How strange. Anyway, soon after smoke started coming from the now hot control unit and it shut off. I removed the control unit and took it apart and it has lots of melted components and bad soldering.

The verdict is, I need a new Tech 97 control unit.

Where can I get one from please? If I power the blue wire, all the solonoids work and the gas comes through (it ran fine for 5 minutes until the heat got to it).

So I now desperately require a Tech 97 suitable for this vehicle. Will any Tech 97 do the job? Will it need to be calibrated? How much are they and are they available new?

Many thanks, and I'm thinking we're getting somewhere now.

Mick

[Super Dragpack]

[Gilbertd]

Tec97 came out in 1997 and was replaced a couple of years later by the Tec99 and are interchangeable. Either will need setting up for your car though and they aren't available new these days. You could fit an alternative controller such as the AEB Leonardo or Bigas Pegaso sold by Tinley Tech (http://www.tinleytech.co.uk/acatalog/El ... nents.html) which would connect to your existing hardware (the electrical connections are virtually identical) and is actually a much better unit (which is probably why you can buy them but not a Tec97 or 99 any more). Not sure why TT sell both as the Pegaso is simply a rebadged AEB Leonardo (see http://www.aeb.it/products/feedback-systems/leonardo) which is widely regarded as the best lambda controller ever designed.

Before fitting a new controller you'll need to see what it was that was drawing so much current it burnt out your Tec97, you don't want the same thing happening to a new controller. That appears to have overheated both output relays and a few other bits beside. Dustbin job.......

[Super Dragpack]

I am very interested in the suggestions of upgrading the system if this is cost effective.

I have been offered (thank you Tubbs) a used Tech97 unit, but even Tubbs suggests looking into the upgrade route as this may not cost much more once I add the cost of leads and software to set it up properly - based on a rough price of £70 for all the above.

So assuming I have a standard Tech97 install, what would I need to buy (and where from) and what would it cost to obtain all the parts to convert my Tech97 to a more modern controller and get it setup correctly?

Could someone also talk me through what is involved as I am very new to terms such as "stepper motor" etc.

Thank you all for your help. I'm sadly consuming lots of Petrol until this is fixed.

[Gilbertd]

The stepper motor is the valve that fits in the hose between vaporiser and mixer. This is the bit that is adjusted by the controller to alter the amount of gas going in to keep the mixture correct. The controller looks at the output from the lambda sensor (which is part of the petrol injection system) decides if the mixture is weak or rich and opens or closes the stepper to keep things right.

The stepper used on your Tartarini system is the same as is used on the Leo but the switch is different and I very much doubt the connections on the loom will be the same so you can't just buy the LPG controller. You'll need the controller, loom and switch which TT don't seem to sell. They'll do you just the controller or the complete kit including the stepper which you don't really need. Might be worth calling them but you'll still need the lead and software to set up a Leo too.