Valve Wear When Running Lpg

[LAURIE MILLS]

:tsktsk: You may have seen my earlier posts regarding an unsolvable cold starting problem in my 97, LPG converted GS300.

The problem is now solved, albeit at the cost of reconditioning the head as two exhaust valves were burnt, at a cost of £2,100. :tsktsk:

The car had done almost 100k miles since its conversion, and did not have the "valvesaver" system fitted, but the main caveat when running on lpg is to make sure you do 15% to 20% of your mileage on petrol, which should give the necessary protection to the valves and seats, and save you my 2k bill.

Now that the head has been done the car runs perfectly, and does close to 25mpg on LPG, at a cost of 35 to 40 p per litre, a cost of 7 to 9 p per mile, or the equivalent of 50 to 60 mpg, so if you can avoid the head wear, it is a big money saver, especially if, like me, you do high mileages.

[danielbroad]

Have you had a flashlube system fitted now?

Daniel.

[ColinBarber]

There have been a number of these cases on Toyota engines. I believe all of them have been without a flashlube.

[eXOBeX]

Had my Mk.2 GS converted a few months ago (must post pics sometime). Got flashlube.

[LAURIE MILLS]

:tsktsk: You may have seen my earlier posts regarding an unsolvable cold starting problem in my 97, LPG converted GS300.

The problem is now solved, albeit at the cost of reconditioning the head as two exhaust valves were burnt, at a cost of £2,100. :tsktsk:

The car had done almost 100k miles since its conversion, and did not have the "valvesaver" system fitted, but the main caveat when running on lpg is to make sure you do 15% to 20% of your mileage on petrol, which should give the necessary protection to the valves and seats, and save you my 2k bill.

Now that the head has been done the car runs perfectly, and does close to 25mpg on LPG, at a cost of 35 to 40 p per litre, a cost of 7 to 9 p per mile, or the equivalent of 50 to 60 mpg, so if you can avoid the head wear, it is a big money saver, especially if, like me, you do high mileages.

←

Nope, only got the car a few months ago, didn,t pay much, and relaxed about this big bill, other than that its a fine car. Will look up Flashlube and have it fitted though.

[Kazi]

You say running the car on normal petrol every so often, how is this possible. Excuse my ignorance. Do you have like a switch in which you flick so the car starts drawing petrol from the stock tank?

Would you need to reset the Ecu to?

Just curious thats all :D

[Rob]

yep most just have a switch so u can switch between normal petrol or LPG

[genius149]

Ouch! :duh:

I've also just bought a 95 GS300 LPG converted and on the way home today it made a strange "Bang" sound, thought I had run over a big stone at first, but when it did it a few more times usually at 40-50mph, I got a bit worried. It idled terribly as well making me think it was only firing on 4 or 5 cylinder. There also seemed to be a weird 'crackling' sound and a burning smell emanating from the cat when I got home. After reading this post a day or two ago I ran it on optimax for a hundred miles or so the other day.

I'm fearing the worst - any pointers??

[andyman1966]

Ouch! :duh:

I've also just bought a 95 GS300 LPG converted and on the way home today it made a strange "Bang" sound, thought I had run over a big stone at first, but when it did it a few more times usually at 40-50mph, I got a bit worried. It idled terribly as well making me think it was only firing on 4 or 5 cylinder. There also seemed to be a weird 'crackling' sound and a burning smell emanating from the cat when I got home. After reading this post a day or two ago I ran it on optimax for a hundred miles or so the other day.

I'm fearing the worst - any pointers??

hi,

it might have been a back fire in ther air box,mines does this now and then .Check tht the blow off flaps arent bent if they r just bend them back .Also on mine if it back fires it normally blows the air box and air filter adrift check this for air leaks

hope this helps Andy

[Raven]

Hi,

Can you explain the nature of your starting problem? I have an LPG converted ls400 that has a starting problem, I wonder if its the same thing. After leaving it overnight, I turn the key and it fires well, climbs quickly to maybe 1000 rpm, then drops to zero. It tends to do this 2 or 3 times, and then on the 3rd or 4th attempt in quick succession, it climbs to 1000, drops to nearly zero, but just catches itself and climbs to idle at about 600rpm.

Touching the accelerator as I turn the key solves this, but obviously this shouldn't be necessary.

I was wondering if 600rpm was a little slow for a cold idle. Do you think my engine is attempting a 'warm' start, even when its cold? Or do you think it has worn valves like yours? It doesn't have flashlube; I better get that fitted.

Many thanks,

Rob

[genius149]

Hi,

Can you explain the nature of your starting problem? I have an LPG converted ls400 that has a starting problem, I wonder if its the same thing. After leaving it overnight, I turn the key and it fires well, climbs quickly to maybe 1000 rpm, then drops to zero. It tends to do this 2 or 3 times, and then on the 3rd or 4th attempt in quick succession, it climbs to 1000, drops to nearly zero, but just catches itself and climbs to idle at about 600rpm.

Touching the accelerator as I turn the key solves this, but obviously this shouldn't be necessary.

I was wondering if 600rpm was a little slow for a cold idle. Do you think my engine is attempting a 'warm' start, even when its cold? Or do you think it has worn valves like yours? It doesn't have flashlube; I better get that fitted.

Many thanks,

Rob

Hi Rob

It turns out that my car needed a new set of plugs. It didn't help that the air filter was the wrong one for the car and that when the throttle body was bolted back on, their was two bolts missing so that my car still had an air leak (It's getting sorted next week). For your LS, if the spark plugs are easier to access than on mine, have a look at those first.

Good luck!

[Raven]

Thanks genius,

I've followed some advice form somewhere on here, suggesting turning the key to '0n' for 10 seconds before turing to 'start', and this does seem to work, I can hear the pump run. I wonder if, because the car always shuts down when running on gas, the solenoid to turn off the petrol is off. When you turn it on again, you have to give the LPG conversion's 'brain' a chance to open the petrol tap again, and also give the petrol a chance to get back to the engine before firing it up. Just a guess

Rob

[genius149]

Thanks genius,

I've followed some advice form somewhere on here, suggesting turning the key to '0n' for 10 seconds before turing to 'start', and this does seem to work, I can hear the pump run. I wonder if, because the car always shuts down when running on gas, the solenoid to turn off the petrol is off. When you turn it on again, you have to give the LPG conversion's 'brain' a chance to open the petrol tap again, and also give the petrol a chance to get back to the engine before firing it up. Just a guess

Rob

aaah that would seem logical. I tend to do that anyway as part of putting on seatbelt/sorting out radio/phone etc. routine. I'll try starting straight away this morning and see if I get a problem. (apart from being late for work )

Cheers

Neil

[genius149]

Update from this morning...

Started fine, but then I realised that the engine is idling far too high (it is being sorted for the air leak next week) so it was a pointless exercise, but then I'm not a morning person

Sadly though, i had a brief encounter this evening with a young lady in a Citroen AX who was driving a little too fast down a very narrow country lane. Her car was wrecked - I have a dented (well flared) wing, bumper and a smashed headlight. The irony is I had just ordered a new bulb for the o/s headlight as well :duh:

[Clive_W]

I've been running on LPG for a couple of years now and have just experienced overheating and loss of water attributed to a head gasket failure. Has anyone any experience of this? Is it normally just that or is there likely to be damage to the head, for example distorted or cracked.

[Phil Edmonds]

Hi I have has the same problem with my 2002 model IS 200 SE. Ran pretty well for the first year, though there were problems with stalling when engine cold. Finally diagnosed 2 years and 50,000 after LPG conversion. £2500 repair job. New valves hardened seats & still not sorted. phil E.

[eXOBeX]

Problems stalling when cold sounds like underfuelling, mine did that until I upped the fuelling a bit (got the cable to program the Romano ECU). As for valve wear, did you have a Flashlube kit fitted? This is recommended for all Toyota engines.

[Phil Edmonds]

Hi I have has the same problem with my 2002 model IS 200 SE. Ran pretty well for the first year, though there were problems with stalling when engine cold. Finally diagnosed 2 years and 50,000 after LPG conversion. £2500 repair job. New valves hardened seats & still not sorted. phil E.

Just taken the IS200 in again to the LPG garage, and there is valve wear again, one year on from strengthened valve seats and new valves. They are going to repair the damage and fit a flash lube kit. I would be interested to hear of anyone running an IS200 long term on LPG, and know the secret of their success. Also I have heard that if you run 20% of the time on Petrol that this is helpful but surely if there is a problem, then that is only going to delay the problem by 20%, or am I missing something?

[lukasm]

£2000 for a exhaust valve - that's crazy. You should switch back to petrol, when such problems accour it's much cheaper to leave the lpg thing. .

[tonyricha]

£2000 for a exhaust valve - that's crazy. You should switch back to petrol, when such problems accour it's much cheaper to leave the lpg thing. .

That is why Lexus say no to LPG and they are right I tried my MK2 GS and WHAT a disaster, ruined a decent car. and yes I did use 20% petrol and flashlube and yes I had the head re built and yes it did it again ! I still go cold remembering the ordeal, it does not work on VVTI engines.

[Simon12]

Butting in a long time after this thread opened but I'm not sure this thread is a bit unfair in its generalisation across all lpg conversions being a no no. There are a couple of reasons.

The first is down to the lpg system and installation. It's pretty well known that these cars need to have a valve lube system fitted otherwise premature valve seat regression can happen. Second, the valve lube system needs attention as it can clog up thus reduced flow to the valves can also happen - I suggest checking this flow regularly and sometimes flushing out the delivery system.

Additionally, there are some poor systems out there that really don't work very well but there are some very good ones.

With regard to the lpg system being blamed for multiple problems and the valves, it may not necessarily be the case. I am aware that the Lexus engines, the GS in particularly, require the valve lash to be checked and replaced at regular intervals (64k on the mkII GS). I'm also aware that Lexus dealerships do not as a matter of course always check them as part of this service because it is time consuming and expensive (it's a pain basically). When I ordered new valve shims at Lexus they asked if I had a burnt valve because it's only when there's a serious problem or noise they normally check them (worrying huh? - they didn't know it had lpg either so it obviously happens with non-conversions).

Valves will regress as part of normal usage and this will eventually cause valves to burn out - especially the exhaust valves because they get hotter and the less the lash the less time they have to cool by transfer of heat to the cylinder head. My own GS needed about 8 replacement valve shims at a bit over 128k but that can't be blamed on LPG alone. 2 valves at this service were at zero lash and further driving would have caused a burnt valve on petrol or lpg - eventually.

Coolant leakage that is assumed to be the cylinder head may actually be caused by the lpg cooling system that is taken from the oem system. I had two leaks in my system after a couple of years driving that caused some confusion but only needed a tightening up of some connectors on the lpg system - the lost coolant was dropping onto the exhaust and evaporating hence couldn't be located easily.

I can't speak for all lpg systems but typically one would expect the lpg system ecu is simply a piggy-back ecu taking most data through the oem ecu - for example, the lpg injector pulses based on the petrol injector pulses by the oem ecu. Some lpg systems however will have some of their own sensors such as a map (manifold absolute pressure) sensor and others but where they can they use oem signals as it's easier. I would caution blame on the lpg system causing cold starting difficulties as they often don't cut in until the engine has reached a certain temperature and therefore I would first look at the OBD data from the car's oem sensors as this could be more likely - often it could just be a faulty connection somewhere, especially if there's been some maintenance work. Otherwise, as mentioned earlier in this thread, check spark plugs and other basic maintenance and/or mechanical things as they're probably more likely.

In 4 years of running on LPG I've had one problem where the lpg system used to switch over to petrol when I spent a long time in heavy traffic - the solution was really simple in that it was the lpg map sensor fitted above the exhaust manifold and it was getting too hot - a relocation solved the problem. Otherwise, apart from using a different pump at the pertol station, and paying a lot less money, I'm hardly aware I've got the system.

Personally, I wouldn't hesitate to install another lpg system on a Lexus as it has paid for itself several times over for me and has been absolutely reliable.

All the best,

Simon

[wow300]

£2000 ? Thats a lot !!

I have been running LPG on 2 GS300 mk1 s for the last 250,000 miles, never had a problem, toyota valves are very hard anyway, but it always starts on petrol and occasionally i do run on petrol.

You must have a quality conversion, lots of cowboys out there...

Also the flashlube has its draw backs to !