My '95 4.0 Cherokee has an LPG conversion. There is a selector switch giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all runs
well using LPG.

Any suggestions would be appreciated, along with where to look for the parts
that might be faulty/blocked. I've only had the motor a week and a bit so
the geography under the bonnet is alien to me

I need help!

Cheers, Ray

On or around Tue, 7 Oct 2003 02:03:53 +0100, "Raymond Ramsey"
enlightened us thusly:

My '95 4.0 Cherokee has an LPG conversion. There is a selector switch giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all runs
well using LPG.


does it run continuously badly on petrol, or only for a brief period?

does it run OK on petrol when cold?

if so, then I reckon whatever it has for enrichment is sticking on. I
assume it's an injection system, in which case there'll probably be a
temperature sender somewhere to tell it the engine's cold, and allow it to
deliver more petrol. This could be a fruitful place to start looking - if
it thinks it's cold all the time, it'll be running over-rich.

either that or the actual device that delivers increased petrol (these
things are very system-dependant) could be sticking "on" - this assumes that
it doesn't do enrichment simply by doing longer fuel pulses on an EFi
system...



--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
Confidence: Before important work meetings, boost your confidence by
reading a few pages from "The Tibetan Book of the Dead"
from the Little Book of Complete B***ocks by Alistair Beaton.

In message , Raymond Ramsey
writes
My '95 4.0 Cherokee has an LPG conversion. There is a selector switch giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all runs
well using LPG.

Any suggestions would be appreciated, along with where to look for the parts
that might be faulty/blocked. I've only had the motor a week and a bit so
the geography under the bonnet is alien to me

I need help!

Cheers, Ray





Faulty emulator perhaps if you have them fitted. Most systems use these
to switch off the petrol injectors when running on gas. When engine is
misfiring disconnect one plug lead at a time to see if one makes no
difference.
--
hugh
Reply to address is valid

Austin,

Thanks for suggestions. In response to you questions. The car runs fine when
cold starting on petrol switching to LPG (as and when the system tells it
to). I tried to keep the motor running when hot and running rough - It
didn't like it at all. The problem didn't seem to go away, but i didn't try
for long. I was more interested in getting going, this has happened twice
outside a shop i stopped at on my way home. When home i tried starting
again, same problem. Left the car for a while and it started and ran fine.

As a self-employed gardener, I pull a small trailer the problem happened
after being in slow, heavy, stop-start traffic.

The engine is an injection 4.0 litre, straight 6, Automatic Gearbox

Cheers, Ray


Austin Shackles wrote in message
...
On or around Tue, 7 Oct 2003 02:03:53 +0100, "Raymond Ramsey"
enlightened us thusly:

My '95 4.0 Cherokee has an LPG conversion. There is a selector switch
giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is
the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and
runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been
running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all
runs
well using LPG.


does it run continuously badly on petrol, or only for a brief period?

does it run OK on petrol when cold?

if so, then I reckon whatever it has for enrichment is sticking on. I
assume it's an injection system, in which case there'll probably be a
temperature sender somewhere to tell it the engine's cold, and allow it to
deliver more petrol. This could be a fruitful place to start looking - if
it thinks it's cold all the time, it'll be running over-rich.

either that or the actual device that delivers increased petrol (these
things are very system-dependant) could be sticking "on" - this assumes
that
it doesn't do enrichment simply by doing longer fuel pulses on an EFi
system...



--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
Confidence: Before important work meetings, boost your confidence by
reading a few pages from "The Tibetan Book of the Dead"
from the Little Book of Complete B***ocks by Alistair Beaton.

On or around Tue, 7 Oct 2003 19:20:08 +0100, hugh ]
enlightened us thusly:

Any suggestions would be appreciated, along with where to look for the parts
that might be faulty/blocked. I've only had the motor a week and a bit so
the geography under the bonnet is alien to me

I need help!

don't know anything more specific about 'em, I'm afraid.

Faulty emulator perhaps if you have them fitted. Most systems use these
to switch off the petrol injectors when running on gas. When engine is
misfiring disconnect one plug lead at a time to see if one makes no
difference.

This is a possibility, if it's not turning the injectors back on. Mind, it
sounds as though it's starting cold on petrol OK.

Raymond: try switching it to the "petrol" position, start from cold, and see
how it runs, also see if it gradually gets worse as it warms up.

if it runs badly from cold, then Hugh's suggestion may be more likely than
mine, if it starts OK and deteriorates, then I'd still favour it not
stopping the cold-start enrichment.

meanwhile, if it's running OK on gas you shouldn't hurt it by starting from
cold on gas, 'til you get the petrol side sorted. Starting on petrol is
mainly considered good 'cos it makes sure the petrol system is working. It
should start from cold on gas, provided you set it to do so.
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
Appearances: You don't really need make-up. Celebrate your authentic
face by frightening people in the street.
from the Little Book of Complete B***ocks by Alistair Beaton.

"Raymond Ramsey" wrote in message
...
My '95 4.0 Cherokee has an LPG conversion. There is a selector switch
giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and
runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been
running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all
runs
well using LPG.

Any suggestions would be appreciated, along with where to look for the
parts
that might be faulty/blocked. I've only had the motor a week and a bit so
the geography under the bonnet is alien to me

It sounds to me as if its trying to run on petrol and gas at the same time
when starting from hot for some reason. This would definately be the case if
the exhaust is smokey and it smells of excess fuel when you are having the
problems. The Emulator and or wiring is up the spout for whatever reason..

Tim..


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.522 / Virus Database: 320 - Release Date: 29/09/2003

From a point at sea, to the circles of your mind, this is Austin
Shackles:

if it starts OK and deteriorates, then I'd still favour it not
stopping the cold-start enrichment.

I've been thinking this. Although my car is an earlier generation of
fuel injection, I found that I had to patch the wiring of the
cold-start enrichment device into the LPG system. If I didn't do this,
then switching to petrol on a warm engine would still register as a
cold engine to the petrol system, since the enrichment device had not
had a chance to warm up[1]. Result - very rich mixture, rough running,
and hard warm starting on petrol.

But, Raymond, you don't need to keep re-starting on petrol. Once a day
is more than enough to keep the petrol system working properly. All
subsequent starts can be on LPG without any problems. That's how I do
it.

[1] If you're confused by the logic of this, the cold start enricment
device is artificially heated by a small coil; it doesn't simply
detect the heat of the engine. Turn the coil off, and it behaves as if
the engine is still cold.

Am I being clear? More beer, vicar?


--

Stewart Hargrave

A lot faster than public transport


For email, replace 'SpamOnlyToHere' with my name

On or around Tue, 7 Oct 2003 22:18:15 +0000 (UTC), "Tim.."
enlightened us thusly:

It sounds to me as if its trying to run on petrol and gas at the same time
when starting from hot for some reason. This would definately be the case if
the exhaust is smokey and it smells of excess fuel when you are having the
problems. The Emulator and or wiring is up the spout for whatever reason..


IME, this results in it not working at all, but it varies according to make,
no doubt. Had this fault on the Ford when the relay that was supposed to
cut the petrol stopped working (w*nker of an installer put it underneath the
car, so of course the terminals corroded off it) and the result was that it
died within seconds of changeover, but ran OK on petrol (obviously).


--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Nessun maggior dolore che ricordarsi del tempo felice nella miseria"
- Dante Alighieri (1265 - 1321) from Divina Commedia 'Inferno'

I had this exact same problem for 2 years on my 97 4.0 Grand Cherokee, and
at last a few months ago I managed to get the problem solved after the LPG
system was not properly installed.

The problem is that the engine ECU is learning whenever you switch on to LPG
that the parameters such as ignition timing etc, are different to the
factory settings for petrol, so therefore the ECU adapts these settings to
those suited for gas (although it still thinks that it is running on
petrol). So this means that whenever you switch back on to petrol, that the
parameters are clearly not right for petrol, hence the misfiring and rough
running!

The solution to this problem is that the ECU needs to be reset from these
"learnt" settings back to those of the factory settings whenever switched
back on to petrol. The way to do this is to go to a reputable LPG installer
where he should be able to order and install a little electronic box (approx
£100) that fits inline to the ECU and resets it whenever the ignition is
switched off.

In other words the ECU must always be reset back to the factory (petrol)
settings each time the engine is turned off.

Good Luck

"Raymond Ramsey" wrote in message
...
My '95 4.0 Cherokee has an LPG conversion. There is a selector switch
giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and
runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been
running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all
runs
well using LPG.

Any suggestions would be appreciated, along with where to look for the
parts
that might be faulty/blocked. I've only had the motor a week and a bit so
the geography under the bonnet is alien to me

I need help!

Cheers, Ray

On Tue, 7 Oct 2003 02:03:53 +0100, "Raymond Ramsey"
wrote:

My '95 4.0 Cherokee has an LPG conversion. There is a selector switch giving
the following options 1-Petrol..2-LPG..3-Start using Petrol automatically
switch to LPG shortly after starting. I've been advised selecting 3 is the
best option.

Cold starts do not seem to be a problem. However starting when engine is
warm either switch position 1 or 3 is murder! The engine miss-fires and runs
rough. Obviously a problem with the Petrol feed. Switching to 2 and all
seems fine (so far) as does switching to 3 after the engine has been running
for a couple of minutes.

It seems obvious the problem is running using petrol. Have any of you any
ideas on where to start looking? I assume the electrics are fine as all runs
well using LPG.

Any suggestions would be appreciated, along with where to look for the parts
that might be faulty/blocked. I've only had the motor a week and a bit so
the geography under the bonnet is alien to me

I need help!

Cheers, Ray

LPG cars are quite widely used in Australia. I have owned several and have one at the moment.

The first thing we are told to do when there is any rough running is
to change the air cleaner filter. Most taxis run on LPG and they
change air filter elements at 12000km (7,500 miles). The taxi people
are the best ones to do the maintenance as they have the greater
experience.

Our gas is 13.8 pence per litre at the moment.

All the best

Russell