LPG in Volvo

Your Old-timer Amazon on LPG

In this chapter, we will clarify the working of LPG, the pros and cons and what to look out for, as well as detailed information on how to drive with your Volvo on LPG.

Below a short report

LPG means Liquefied Petroleum Gas. This is a mixture of predominantly two gases: butane and propane. Both gases have certain characteristics relating to evaporation temperature. In winter, more propane will be added to the mixture because propane evaporates a lower temperature than butane. A secondary consideration is the fact that in summer greater part butane will result in more kilometres based on the same driving style (disadvantage of propane is less kilometres).

In short, LPG gets into the gas tank through the refuelling connection somewhere on the outside of the car. Both on tank-side as well on the side of the refuelling connection is a one-way valve that avoids escaping of LPG. In the tank is a pressure relief valve, which, at certain (high) pressure lets go of gas via the outside vent. This valve closes when the pressure is at an acceptable level. With a good pressure relief valve the pressure in the tank will never be too high. Because there is no oxygen in the tank, it will not explode. In addition, the tank has a so-called 80% refuelling/filling mechanism, which will shut off when the 80% level is reached.

The third valve is the electronic remotely controlled service valve from the LPG to the evaporator. This valve will allow LPG to pass when car is set on contact. Because of the fact that during the evaporation process will withdraw heat from the evaporator, coolant will have to pass through to avoid freezing of the evaporator. The evaporator also arranges the idling tuning and the quantity of LPG. From the evaporator gas is transmitted to the carburettor. In the carburettor (just like with petrol) air is mixed with the LPG, so that the fuel can do its work.


  • The tanks always takes space
  • Striking of the carburettor’s control needle is hardly avoidable. You can partly keep it free by vacumising it or secure it with a cable (or remove the control needle during while driving on LPG.
  • LPG is a gas and so invisible. And although leakages happen hardly ever happen, you will be able to smell LPG thanks to the addition to the gas of aromatics.


  • LPG  is a clean fuel: both and engine and oil  remain cleaner
  • Although the burning of the gas mixture is slower in comparison to petrol, the engine  will get warmer, however the wear and tear will be less in comparison to      petrol
  • Although that  due to the hard winter, the prices of LPG  have risen significantly, LPG as a fuel is still of interest to the  owners of tax free Volvos
  • LPG is more  environmentally friendly than petrol


Detailed Information & Points of Interest

  • Make sure that the ignition is functioning properly
  • A shut petrol valve that still passes some petrol will lead to irregularity of the idling revs
  • A too poor or too rich a mixture cannot be seen in exhaust pipe and spark plugs


A too poor a mixture will lead to a higher combustion temperature. It will influence capacity and temperature negatively. A poor mixture in combination with a delayed ignition time might lead to back firing (ignition time can be forwarded with 2 degrees). The (only) disadvantage of a mixture that is too rich, might lead to unnecessary over use of fuel.


  • When trying to start the engine for too long, heat will be withdrawn from the evaporator, which can result in too rich a mixture.
  • When trying to start the engine for too long in winter, the evaporator can freeze (this will lead to even more starting difficulties)

Unfortunately, traces of sulphuric acid can be present in the LPG. This sludge (oily condition) in the evaporator will absorb the sulphur. Too much sludge will shorten the life span of the evaporator.

  • Over time and after many years, the rubbers in the evaporator might harden. When this happens, it will be impossible to (re)adjust the evaporator, though it is possible to revise it.
  • Check the valve clearance regularly to avoid burning (the valve clearance does not need to be greater than with petrol adjustment). Striking of the valve seats (narrowing the valve clearance) occurs due to the absence of led in fuel and being longer exposed to a higher temperature of the exhaust fumes. The combustion temperature of LPG is nearly equal to that of petrol. Possible soft valve seat will have to be replaced by hard valve seats after an x-amount of kilometres. This can well be after 50,000 kilometres.

At higher revs (higher than 4,000) the chance of striking valve seats will increase. Due to a different gearing ratio, a combi will have a higher revving rate than a sedan when at the same speed.

So-called de-aeration of the LPG-tank is a fairytale, as air cannot get into the tank.

In order to get good idling revs, it will suffice to give a short nudge of gas before starting the engine by using the choke button.

Qualitatively almost all LPG-brands are equal. A noticeable difference could be the ratio butane versus propane, which is not the same everywhere.

As petrol ages after 6 weeks, and as a result hoses and membranes might damage. Make sure your petrol tank is not filled to capacity when driving on LPG.

The first 1,000 kilometres, revised engines will have to run in on petrol, because a lower combustion pressure when using LPG, will hinder pistons and piston rings.

In order to avoid too much striking of the floater needle, it is advisable for every tank of LPG to drive a few kilometres on petrol. By doing so, possible problems will not occur during the night when you run out of LPG unexpectedly.

Before you drive to your holiday destination, where is not or hardly LPG available, make sure that you drive a substantial amount of kilometres on petrol. It could be that the floater is leaks and fills up.

If the car has not been used for a while (for instance during the winter period), then this will not have negative results on the rubbers of the evaporator. As there is coolant present in the evaporator drying out of the rubbers will not occur.

There are two options to install an LPG-tank without losing space:

  1. Install a double gas tank on top of the existing petrol tank. This will result in a slightly elevated floor.
  2. Replace the existing petrol tank and to install an LPG-tank and a smaller petrol tank.

In principle, all (conventional) evaporator brands are suitable for old-timer Volvos.








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