Problems running on LPG

[Mark Lane]

I have a Disco II 4.0 with a Romano LPG system, K&N filter.
I had no problems with LPG for first 20,000 then had new cylinder head
gasket and it has never run well again on LPG.

The car runs perfect on petrol. When I run on LPG I get misfires which on
investigation are mainly 4 and occasionally 1. It does run better on a long
run with only occasional misfires and doesn't appear to misfire on hard
acceleration. On symptom is when I accelerate at a constant rate the rev
meter shows a slight drop in relation to loss of power it will the suddenly
pick up again.

I have had changed LPG, ECU, emulators checked all wiring, changed plugs,
ignition coil and HT leads which are magnacor. I have not changed any
filters or vaporisers on LPG system.

Has anybody come across a similar problem or can give me a guess to what may
be the problem.

Many thanks

Mark

[avonautogas]

is it the old or new Romano sgi system




Dominic

Post by Mark Lane
I have a Disco II 4.0 with a Romano LPG system, K&N filter.
I had no problems with LPG for first 20,000 then had new cylinder head
gasket and it has never run well again on LPG.
The car runs perfect on petrol. When I run on LPG I get misfires which on
investigation are mainly 4 and occasionally 1. It does run better on a long
run with only occasional misfires and doesn't appear to misfire on hard
acceleration. On symptom is when I accelerate at a constant rate the rev
meter shows a slight drop in relation to loss of power it will the suddenly
pick up again.
I have had changed LPG, ECU, emulators checked all wiring, changed plugs,
ignition coil and HT leads which are magnacor. I have not changed any
filters or vaporisers on LPG system.
Has anybody come across a similar problem or can give me a guess to what may
be the problem.
Many thanks
Mark

[Mark Lane]

It was converted in May 2003. How can I tell which sgi system is installed?

Mark

Post by avonautogas
is it the old or new Romano sgi system
Dominic

Post by Mark Lane
I have a Disco II 4.0 with a Romano LPG system, K&N filter.
I had no problems with LPG for first 20,000 then had new cylinder head
gasket and it has never run well again on LPG.
The car runs perfect on petrol. When I run on LPG I get misfires which on
investigation are mainly 4 and occasionally 1. It does run better on a

long

Post by Mark Lane
run with only occasional misfires and doesn't appear to misfire on hard
acceleration. On symptom is when I accelerate at a constant rate the rev
meter shows a slight drop in relation to loss of power it will the

suddenly

Post by Mark Lane
pick up again.
I have had changed LPG, ECU, emulators checked all wiring, changed plugs,
ignition coil and HT leads which are magnacor. I have not changed any
filters or vaporisers on LPG system.
Has anybody come across a similar problem or can give me a guess to what

may

Post by Mark Lane
be the problem.
Many thanks
Mark

[Java Jive]

Valve clearances / timing - workshop that did new head may have set the
timing back to ordinary fuel values.

Post by Mark Lane
Has anybody come across a similar problem or can give me a guess to what may
be the problem.

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[Badger]

Post by Java Jive
Valve clearances / timing - workshop that did new head may have set the
timing back to ordinary fuel values.

Valve clearances are hydraulic on this engine, and if it's the version I
think it is, there's no timing adjustment either.
Badger.

[Austin Shackles]

On or around Sun, 18 Jul 2004 10:20:27 +0100, "Badger"

Post by Badger

Post by Java Jive
Valve clearances / timing - workshop that did new head may have set the
timing back to ordinary fuel values.

Valve clearances are hydraulic on this engine, and if it's the version I
think it is, there's no timing adjustment either.
Badger.

if it's a "Thor" it hasn't got a distributor?

Mind, there's probably a way of setting the timing, or maybe you use one of
those ignition boxes that RPi and other sell.

'ere, Badger...

3.5i, 1991 or so. Is it common for them to be low on torque at sub-2000 rpm
speeds? it revs nicely, runs smoothly enough at low speeds, and pulls quite
nicely if you get the revs over 3000.

so happens I've a low-mileage 3.9 cam and a set of followers in the shed,
but I doubt it's really worth the effort involved in changing it.

[Mark Lane]

It is a Thor and has no adjustment so you don't need an ignition box from
RPI the ECU with the system is meant to learn and run appropriately.
I have had the ECU changed and the fuel map reprogrammed in case it had gone
back to default mode although I can not think what else it could be.
It is also idealing more slowly on LPG.

It is so strange as it runs fantastic on petrol.

Post by Austin Shackles
On or around Sun, 18 Jul 2004 10:20:27 +0100, "Badger"

Post by Badger

Post by Java Jive
Valve clearances / timing - workshop that did new head may have set the
timing back to ordinary fuel values.

Valve clearances are hydraulic on this engine, and if it's the version I
think it is, there's no timing adjustment either.
Badger.

if it's a "Thor" it hasn't got a distributor?
Mind, there's probably a way of setting the timing, or maybe you use one of
those ignition boxes that RPi and other sell.
'ere, Badger...
3.5i, 1991 or so. Is it common for them to be low on torque at sub-2000 rpm
speeds? it revs nicely, runs smoothly enough at low speeds, and pulls quite
nicely if you get the revs over 3000.
so happens I've a low-mileage 3.9 cam and a set of followers in the shed,
but I doubt it's really worth the effort involved in changing it.
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Would to God that we might spend a single day really well!"
Thomas À Kempis (1380 - 1471) Imitation of Christ, I.xxiii.

[ROBIN DUMPLETON]

could've been the low output model from LR or disco
Small block Rover not RPI now RIP :-((

Robin

Post by Austin Shackles
On or around Sun, 18 Jul 2004 10:20:27 +0100, "Badger"
3.5i, 1991 or so. Is it common for them to be low on torque at sub-2000 rpm
speeds? it revs nicely, runs smoothly enough at low speeds, and pulls quite
nicely if you get the revs over 3000.
so happens I've a low-mileage 3.9 cam and a set of followers in the shed,
but I doubt it's really worth the effort involved in changing it.
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Would to God that we might spend a single day really well!"
Thomas À Kempis (1380 - 1471) Imitation of Christ, I.xxiii.

[Badger]

Post by Austin Shackles
'ere, Badger...
3.5i, 1991 or so. Is it common for them to be low on torque at sub-2000 rpm
speeds? it revs nicely, runs smoothly enough at low speeds, and pulls quite
nicely if you get the revs over 3000.

Try giving it more ignition advance at the lower rpm's, especially if it's a
low compression engine. I'd have thought it'd be a 9.35:1 though. Limit the
max advance to std, if playing with it though. The 8.13:1 cr engines exhibit
this "low torque" at low rpm's and reprofiling the advance curve really
helps them.

Post by Austin Shackles
so happens I've a low-mileage 3.9 cam and a set of followers in the shed,
but I doubt it's really worth the effort involved in changing it.

Unless either your cam is known / suspected to be worn or you know it's the
"soft" cam (introduced by rover as a measure to increase mid-range torque,
but in my opinion only slows you down!) as fitted to late carb rangies,
early 110's and late 101's. Unlikely in an EFI engine. The std 3.5 EFI cam
profile actually produces buckets of low/mid torque, more so than the 3.9
cam which gives a lot more in the upper mid, relying on the capacity
increase to do the business lower down. If your cam is worn and you want a
proper EFI one, I have 2 new ones in stock.
Might also be worth doing a plug-chop (remember them, Austin?) at say
2500rpm light load and see what it's doing. A rising-rate fuel pressure
regulator may help on petrol, take it it's showing up on gas as well?
(Assuming you've converted it by now)
Badger.
B.H.Engineering, Rover V8 engine specialists.

[Austin Shackles]

On or around Mon, 19 Jul 2004 08:47:34 +0100, "Badger"

Post by Badger
Unless either your cam is known / suspected to be worn or you know it's the
"soft" cam (introduced by rover as a measure to increase mid-range torque,
but in my opinion only slows you down!) as fitted to late carb rangies,
early 110's and late 101's. Unlikely in an EFI engine. The std 3.5 EFI cam
profile actually produces buckets of low/mid torque, more so than the 3.9
cam which gives a lot more in the upper mid, relying on the capacity
increase to do the business lower down. If your cam is worn and you want a
proper EFI one, I have 2 new ones in stock.
Might also be worth doing a plug-chop (remember them, Austin?) at say
2500rpm light load and see what it's doing. A rising-rate fuel pressure
regulator may help on petrol, take it it's showing up on gas as well?
(Assuming you've converted it by now)

it is a 9.35:1.

I couldn't remember which engines had the funny cam. I just remember
looking at valve timings and so on and wondering why...

seems to go much the same on gas as on petrol. it's not exactly slow - if
provoked, it'll go plenty quick for a 2-ton vehicle.

it might need a few more degrees. Book say TDC for this engine on UL, IIRC,
ISTR I set it at 6°BTDC.

[Java Jive]

Not acquainted with that particular engine, but it remains true as a general
principle that on most the timing has to be different because of the
different burn rates of the fuels (IIRC, it's the LPG that burns slower, and
therefore needs the timing advanced a little from the optimum for for
petrol)

Post by Badger

Post by Java Jive
Valve clearances / timing - workshop that did new head may have set the
timing back to ordinary fuel values.

Valve clearances are hydraulic on this engine, and if it's the version I
think it is, there's no timing adjustment either.
Badger.

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[Stewart Hargrave]

Post by Java Jive
Not acquainted with that particular engine, but it remains true as a general
principle that on most the timing has to be different because of the
different burn rates of the fuels (IIRC, it's the LPG that burns slower, and
therefore needs the timing advanced a little from the optimum for for
petrol)

Yes.

And no.

Take a look at this investigation that someone posted here a while
ago:

http://tinyurl.com/2k95y

The specifics will probably vary from engine to engine, with many
variables involved.

[tzb6js]

Post by Java Jive
Valve clearances / timing - workshop that did new head may have set the
timing back to ordinary fuel values.

Post by Mark Lane
Has anybody come across a similar problem or can give me a guess to what

may

Post by Mark Lane
be the problem.

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Can't see the beginning of the thread. Is the LPG system induction or
injection ? I only ask as I have a Disco 3.9 running on LPG (induction)
for the last 25,000 miles. Runs perfect except that it hunts at idle on
gas. No problem on petrol. After a lot of searching we put the problem
down to a slight induction leak somewhere. On petrol injection the very
small air leak only adds more air. On gas it weakens the mix so it's
compensating all of the time on idle. It obviously over compensates then
leans off and cycles through this. Now the real problem is finding the
leak ! Still can't find it after two and a half years. LR use really
crap rubber pipes that perish on the cruise control and in fact all over
the engine bay. When the engine is cold sometimes I can hear the slight
whistle on the overrun, but every time I stop and pop the bonnet it
stops whistling.. probably warmed up enough to silence it. If you have
induction it could be a similar problem ?

P.S. If anyone has a tip on finding the leak - let me know.

Thanks,

Neil.

[Badger]

Post by tzb6js
Can't see the beginning of the thread. Is the LPG system induction or
injection ? I only ask as I have a Disco 3.9 running on LPG (induction)
for the last 25,000 miles. Runs perfect except that it hunts at idle on
gas. No problem on petrol. After a lot of searching we put the problem
down to a slight induction leak somewhere. On petrol injection the very
small air leak only adds more air. On gas it weakens the mix so it's
compensating all of the time on idle. It obviously over compensates then
leans off and cycles through this. Now the real problem is finding the
leak ! Still can't find it after two and a half years. LR use really
crap rubber pipes that perish on the cruise control and in fact all over
the engine bay. When the engine is cold sometimes I can hear the slight
whistle on the overrun, but every time I stop and pop the bonnet it
stops whistling.. probably warmed up enough to silence it. If you have
induction it could be a similar problem ?

Neil, this is a characteristic of every rover V8 I have ever converted using
a closed-loop gas induction system (AEB Leonardo), the rpm at idle sitting
rising and falling by about 80-100rpm. It can be tuned out (AEB Leonardo
systems) by adjusting the number of steps you allow the stepper motor valve
to close below idle default, after the vapouriser has been adjusted.
Basically tune it to stop it swinging over-lean as it controls. It's more
pronounced on the hot-wire efi engines than the earlier flapper types as
they have an idle speed control stepper motor that is also trying to
compensate at the same time as the gas ecu!
Badger.

[Austin Shackles]

On or around Tue, 20 Jul 2004 11:29:00 +0100, "Badger"

Post by Badger
It's more
pronounced on the hot-wire efi engines than the earlier flapper types as
they have an idle speed control stepper motor that is also trying to
compensate at the same time as the gas ecu!
Badger.

and it actually works, on mine, amazingly well on LPG with an open loop
system. get the tuning right, and it idles happily at the prescribed 750
rpm.


... except when the bloody stepper motor sticks open; then it idles at 1200,
14oo, 1500, 1800. Turn the motor off, restart it, and it goes back to
normal. I guess one day I'll have to pull the thing off and clean it or
something. it does this both on LPG and petrol, although it idles faster
when in fault mode on LPG than on petrol.

[hugh]

Post by Austin Shackles
On or around Tue, 20 Jul 2004 11:29:00 +0100, "Badger"

Post by Badger
It's more
pronounced on the hot-wire efi engines than the earlier flapper types as
they have an idle speed control stepper motor that is also trying to
compensate at the same time as the gas ecu!
Badger.

and it actually works, on mine, amazingly well on LPG with an open loop
system. get the tuning right, and it idles happily at the prescribed 750
rpm.
... except when the bloody stepper motor sticks open; then it idles at 1200,
14oo, 1500, 1800. Turn the motor off, restart it, and it goes back to
normal. I guess one day I'll have to pull the thing off and clean it or
something. it does this both on LPG and petrol, although it idles faster
when in fault mode on LPG than on petrol.

A venturi LPG system can often idle better at just a few revs higher
than the petrol norm.

[SimonJ]

Post by tzb6js
P.S. If anyone has a tip on finding the leak - let me know.

With the engine ticking over, spray WD40, or easy start round the manifold,
pipes etc (not into the inlet).
When the revs increase, it indicates it is sucking some of it in, so the
leak must be where you are spraying the stuff at

[entrepeneur]

Post by Mark Lane
I have a Disco II 4.0 with a Romano LPG system, K&N filter.
I had no problems with LPG for first 20,000 then had new cylinder head
gasket and it has never run well again on LPG.
The car runs perfect on petrol. When I run on LPG I get misfires which on
investigation are mainly 4 and occasionally 1. It does run better on a long
run with only occasional misfires and doesn't appear to misfire on hard
acceleration. On symptom is when I accelerate at a constant rate the rev
meter shows a slight drop in relation to loss of power it will the suddenly
pick up again.
I have had changed LPG, ECU, emulators checked all wiring, changed plugs,
ignition coil and HT leads which are magnacor. I have not changed any
filters or vaporisers on LPG system.
Has anybody come across a similar problem or can give me a guess to what may
be the problem.
Many thanks
Mark

I have an RR 4.6 GEMS that started to lack performance on gas. We
changed the filter (should be done at 20k mile intervals apparently -
mine had done nearly 30k) but this did not cure it. What I did find was
that one of the covers on the evaporator (?) had lost two screws and
was obviously leaking. It restored performance immediately and fuel
consumption too. Not certain if that is of any helpas I had no
misfiring.