LPG Conversion - 80s Mercs

[BGarside]

Following my recent thread (W124 vs W201) I thought the best way to get decent performance with sensible fuel bills would be to buy a 6-cylinder car (probably either a 190E 2.6 or W124 300E/CE) & convert to LPG.

However, my local Prins installer tells me they cannot convert cars which use the Bosch KE-Jet fuel injection system, only cars with EFI.

Has anyone here had any experience of LPG conversion on older cars with mechanical / semi-mechanical injection systems? I can't believe it hasn't been done somewhere as there are still loads of K-Jet / KE-Jet-equipped cars running around...

[74merc]

They might not be able to run a multipoint system on KE, but they would be able to run a single point system. I've never seen one, but I understand they're effectively a gas ring from a cooker on the inlet manifold. They're pretty unsophisticated and are hard to tune to allow the engine to run well on both gas and petrol.

[BGarside]

Yeah, the mixer ring system would probably work but they seem to be rubbish in terms of fuelling control, economy and power.

I guess I'll give the LPG idea a miss. Perhaps an EFI conversion would be another way to get better economy and maybe more power as well. God knows what that'd cost though...

[chazola]

How about a E220 or 220E- only a 4 pot but 16v and still 150bhp, 30mpg or better on a run. I've not driven one but hear they still propel the W124 around nicely. Or just suck it up and get an E280- super smooth and about 28mpg.

[BGarside]

Do any of the post-facelifts 124s have EFI?

I know the earlier M102/3 engines run KE-Jetronic but these are apparently unsuited to LPG conversion...

A 'six' would be nice but I'd have to be able to run it on LPG.

[74merc]

M104s can be converted to LPG. I know that the E320 coupe I had a few years ago, got converted by the next owner.

[BGarside]

Cheers. Does the later M104 still use KE-Jet or was it fully electronic injection?

If I could get a multi-point system fitted to a later 124 then an E280 or E320 could be viable.

[74merc]

The later M104 engine uses HFM sequential fuel injection, so you should be able to use a multipoint system.

[BGarside]

74merc said:

The later M104 engine uses HFM sequential fuel injection, so you should be able to use a multipoint system.

Thanks, that's worth knowing. If my current interest in 190Es falls through then I guess i'll start looking at post-facelift W124s...

[Bonefish Blues]

I was asking a similar Q of our local LPG installer and got much the same answer, 1st gen ones a definite no, later ones, fine.

Estates a pig as nowhere to put a decent-sized tank, incidentally.

[Boyjoe]

Chap living near to us had a 1988 merc 3.0 litre on LPG I remember it was an "S" class, so it can be done, he had the car for several years and covered a big milage.

When I bought the 320 ( straight six merc) the LPG experts (?) A, insisted that Ssangyongs only ever had Diesel engines. Others Said not recommended , Yet they were showing pictures of a merc ML. When pointed out a Ssangyong is basically an ML wearing a different dress the wouldn't have it.
So much for experts.

Have a look in LPG websites for info.

[12v3pot]

I sold my last 2.0 190 to a Polish chap and he said that many 190s in Poland are LPG converted.

FWIW, at some point MB must have had bi-fuel thoughts for the W124. Some of them (including my 280) had a stamped and blanked-off hole for an LPG filler right next to the petrol filler (i.e. under the filler flap).

[British Shareholder]

Hi there,

I think I can help in-re LPG for Merc's equipped with mechanical fuel injection.

I owned two Mercs' – a 1983 W123 and a 1989 W-126.
Both were converted to LPG.
There is a big problem with the conversions but it is capable of being overcome.
The system has to be single point. Basically the LPG is added to the air outside the combustion chamber in the air inlet manifold below the air flow meter. The rising and falling actions of the pistons draw the air/fuel mixture into the combustion chamber and the spark plug ignites same in the conventional manner. In other words the mechanical fuel injection system effectively becomes a gas carburettor.

Now to the problems:

The air/fuel mixture can in certain situations ignite outside the cylinder which will cause the car to “fail to proceed” to use a RR euphemism! The flap in the air flow meter will be jammed by the force of the explosion. With luck the meter will be repairable. If not, a new or second hand one has to be sourced. This event can be avoided by adopting the following measures:

Replacing the HT leads to the spark plugs from the coil at the time of conversion with special ones designed to be used on such conversions. A competent LPG installer should have these. If they have not go to an installer who has and has knowledge and experience of converting such vehicles. This is not the case of going to the cheapest supplier!

Furthermore, the leads themselves should be replaced every 12,000 miles or three years – whichever comes first. These leads are more expensive than the M-B own brand leads bye the way.

In addition, one must be very careful about switching onto gas from petrol. Any single point system fitted will switch over when after revving the engine. The system will also have a switch – located in the unit that passes as a fuel gauge (is totally inaccurate bye the way) to switch from petrol to gas. It can be switched to just run on petrol. NB: This switch must be switched to petrol when you turn the ignition on! This is because you have to run the car on petrol until you are sure that the engine is fully warmed up. And by that I mean the engine block itself. This means on a cold winter's day you can find yourself driving 3 miles before the engine gets hot. If that happens, and your journey is that short the answer is this: use petrol for that journey.

The reason why this is so important is because the system has a device called an evaporator. This uses the heat from the cooling water to gasify the LPG which is very cold in the fuel tank. The evaporator is designed to create the correct gasification at the full temperature the water will reach. What happens in practice is that the system will switch over automatically far sooner than it should. This damages the valves and the upper part of the engine. This is a classic case of penny wise (petrol cost saved) and pound foolish (an expensive engine repair).

If you follow this advice your old Merc' will become much cheaper to run.

PS: I did not notice a significant degradation in performance.

Edited by British Shareholder on Friday 7th February 13:19

Edited by British Shareholder on Friday 7th February 13:20

Edited by British Shareholder on Friday 7th February 13:21

Edited by British Shareholder on Friday 7th February 13:23

[BGarside]

Hi. Thanks for the reply but 7 years later!

I didn't buy a Mercedes in the end but have had two BMW E36s instead. The current 328i just runs on petrol but mostly on occasional long trips so at 37mpg I decided I would cope without LPG!