LPG and valve seat recession

[DuncanOfEngland]

I've had 2 LPG converted Ford Explorers in my workshop recently which have been running badly. In both cases, I identified the cause as valve seat recession, caused, no doubt, by running on LPG. The spark plugs told some of the story, their white glazed apperance indicating a lean mixture and high combustion temperature.

Both of these cars had professional LPG installations and both had the 'check engine' light on. Both owners had been told, by the LPG installers, that it didn't matter and was perfectly normal for this to happen, so both cars had been driven a considerable distance in this condition. The fault code indicated a lean mixture on both cylinder banks.

The only cure was to replace both heads - an expensive job - so, if you are running on LPG, please check that it is set up correctly.

Duncan
Ford Explorer Services and Parts
Aylesbury, ENGLAND

 

[SB98UKexplorer]

good point that, ill have an eye on that next time i change the spark plugs, im running a single point system and has very bad wiring setup, lots of exposed connections which iv wrapped in electrical tape, i will be purchasing the software and wiring kit on ebay as the seller has a wide range on there. one thing a while back in january, i noticed the black plastic box on the right cam cover returning from the egr and melted away, which i understand is from high combustion temperatures? thats now been replaced and seems to running all right, i have exprienced some blow backs on hard accelration, which i end up have to plug in all the intake pipe connections, that reminds i need one now as i have a split near the throttle body end. its not as good as driving on petrol, feels like a 1.1 lol

 

[BIGHVM]

Thats a worry if you have lpg- I would be inclined to pull my plugs and check to see whats happening......
Maybe it for the better I never fitted it- any savings may well be wiped out by the cost of repair-Yikes!

 

[gwar]

Am running a multi point system on mine. Got new plugs and HT leads fitted just after getting the conversion done. Engine management came on once, with a lean mixture going to one bank. I reset this and took the car back to the installers who made a few adjustments. Since then it's been running with no issues. Running on Lpg is great but it's not covered in the annual MOT or usual servicing so needs to be done separately and not just left without regular checking.

 

[BIGBALLS]

Explorer with LPG need FLASHLUBE pumps fitted. Mine was done for £70 when i had it converted BB

 

[DuncanOfEngland]

Flashlube is recommended by many LPG installers, as a salve to their customers who are concerned about valve seat recession. Most Flashlube pumps work off engine vacuum and so introduce most of the Flashlube when the engine is idling (i.e. when it's not needed) and hardly any at all under full load when the engine vacuum is lower. A bit arse about face, assuming that Flashlube does any good at all. What Flashlube does do is to cause the vacuum pipe rubbers to expand, thus causing vacuum leaks. It probably also coats the inside of the Catalytic converters as well.

Duncan

 

[BIGBALLS]

What you state may be true, but i get through quite a bit of Flashlube
don't idle very much (motorway work)and i certainly don't suffer from
greasy pipes BB

 

[italianbigsky]

Searching thru the forum I found this thread, it's old but to me it's still interesting because my 96 limited has LPG.
Actually, after a few miles with LPG on, the "check engine" light comes on and stays till I turn the engine off.
I've been told (and this forum confirmed it) that it's temperature issue, because of LPG properties are different from gas.
Some told me to go with LPG for a couple of full tanks, and then alternate a gas full tank. This should help valves and engines to last longer.
Anybody doing this way?

Also, I haven't driven with gas for a long distance yet, but in a short trip to reach the LPG pump, the check engine light turned on , even with the LPG off.
The one who sold me the car, told that this is normal and I don't have to woryy about that, it's a side effect of LPG conversion.
Is that right?

 

[janolsson]

Searching thru the forum I found this thread, it's old but to me it's still interesting because my 96 limited has LPG.
Actually, after a few miles with LPG on, the "check engine" light comes on and stays till I turn the engine off.
I've been told (and this forum confirmed it) that it's temperature issue, because of LPG properties are different from gas.
Some told me to go with LPG for a couple of full tanks, and then alternate a gas full tank. This should help valves and engines to last longer.
Anybody doing this way?

Also, I haven't driven with gas for a long distance yet, but in a short trip to reach the LPG pump, the check engine light turned on , even with the LPG off.
The one who sold me the car, told that this is normal and I don't have to woryy about that, it's a side effect of LPG conversion.
Is that right?

Hello and welcome to the forum.
Whats your engine ohv or sohc as in the uk we generally only have the sohc.
I would say any time you get the check engine light on i would get the code. It could be something unrelated to the LPG. Also worth a visual inspection of things like the plugs, vac lines and dpfe (?) sensor (the black thing on the side of the head SB mentioned. Is your LPG multipoint or single point as the single point can blow inlet manifold gaskets. To be fair the upper and lower inlet manifold gaskets deteriorate with age anyway thus letting in air and causing lean running.
As i said read your codes, if you have obdII buy a cheap reader or if you have obd have a look in the US section for how to read the codes with flashes for free.
HTH
regards
Jan

 

[Neil Tucker]

Lpg

Hi Duncan

Neil from High wycombe here...you did my camchain for me last year

How many miles had those cars been running on LPG.

I had mine converted by Oxford Autogas last year and have done 20k miles on the LPG without any trouble.

I'm gonna pull the plugs this weekend to check, but would be interested to see what your experiences were with the mileage.

All the best

Neil

 

[jcasey007]

mine has done 140k on LPG, I'm very aware of mixture control and have a air-fuel guage plumbed in always. I also don't run valve lube and use less than a gallon of petrol a month