Engine shutting down

[michaelc291]

Hello,
I hope someone can resolve a problem I have been living with for a long time.
I have two Cherokee XJs both of which have Tatarini Tec 97 LPG (propane/autogas) conversions, one is 1994 and the other 1996, both have the same problem.
With these conversions the engine always starts on petrol and will change to gas at 2000RPM automatically when selected.
( I can see confusion in your eyes. On this side on the pond our terminology is different. Gasoline is called petrol and gas refers to LPG also called GPL, propane or autogas.)

The cars always start first turn of the key and run very well on petrol. There are no other engine problems.

When the changeover happens at 2000 RPM the engine cuts out dead which can happen in embarrassing places because there is a delay before anything will happen again. The key is totally dead for up to 2 minutes and just to confuse things further sometimes there is no delay.

I have been through the wiring diagrams and I suspect the shut down relay is being triggered by the ECU. I am not sure how to check this.
Connections for conversions are taken from the coil (both terminals), constant live from battery, throttle position,
lambda sensor.

To add another factor into the pile is that once the car has been run and got hot it will be OK for the rest the day.

I would love to hear your suggestions.

 

[Bounty__Hunter]

Sounds like whatever triggers your petrol pump or injectors to turn off at 2000 rpm is also telling the ECU to not run. I think this is a good problem for the manufacturer to diagnose.

 

[michaelc291]

Since posting the first bit I have done some simple tests.
After the engine stops I can hear the gas (propane) valves shut off the flow of gas. This happens about 2-3 seconds AFTER the engine stops. By wiring a lamp into the output from the shut down relay the power remains on for those 3 seconds then I assume the ECU cuts the power because there is no signals coming in and as the solenoid valves are fed from the coil this explains why they close.
The problem is that if the SDR is still powered up when the engine stops what is causing it to stop?
The mystery deepens.

 

[JPNinPA]

Not to insult you but is there propane in the tank? Are there leaks in the line or is it pressurized properly? Intake leaks?

Is there any way the lines are loosing their prime?

I never worked on these but will look up what I could to help you out.

 

[michaelc291]

Hi,
I welcome any suggestions, thank you.
I have got plenty of propane in he tanks and have opened the connections to check it's getting through and the solenoid valves are all operating OK, there are 4 of them. One on each tank, one under the hood and one on the vapouriser. All 4 operate simultaneously. It's a very safe system.
There is propane gas getting to the engine in the 3 seconds before it all shuts down. I can hear it hissing.
Thank you for helping.
I have checked every hose, pipe and connection under the hood.
If you go to tartriniauto.it click on Products then conventional LPG you will find a description of the system (and more).
Happy hunting.

 

[michaelc291]

Hi,
I welcome any suggestions, thank you.
I have got plenty of propane in he tanks and have opened the connections to check it's getting through and the solenoid valves are all operating OK, there are 4 of them. One on each tank, one under the hood and one on the vapouriser. All 4 operate simultaneously. It's a very safe system.
There is propane gas getting to the engine in the 3 seconds before it all shuts down. I can hear it hissing.
Thank you for helping.
I have checked every hose, pipe and connection under the hood.
If you go to tartriniauto.it click on Products then conventional LPG you will find a description of the system (and more).
Happy hunting.

I think I have solved the problem. In the end it was a simple mod.
There is a switched feed to the Tartarini control module that was taken from the coil. I suspected that being close to the coil it could be picking up stray spikes or other electronic interference.
As a trlal I have moved this connection to the ignition fuse in the power control module. It also has the bonus that it does not time out after a few seconds.
That was three weeks ago and it has not cut out once since, even from cold.
The moral of the story is to pick up connections from a 'clean' supply.
Thank you for the suggestions, I did try them.

Special quote: "We havn't really got much data on the subject and without data how can we reach any definite conclusions? (Thomas Edison)

 

[Sundance]

Cool name/avatar, Bounty Hunter. ��