Electronic Fuel Injection 1993 W463
I am a new owner of a 1993 300GE and am very pleased with it.
I have been trying to find a Mercedes specialist in Norfolk whom I could use to care for it. My attempts to find one so far has led to me hearing that the Bosch fuel injection system ECU is no longer supported and I cannot find anyone who has the necessary diagnosis equipment. It seems that the system is obselete in comparison with modern fuel injection systems and MB are unable to help.
A search online yielded this kit to replace the Bosch system and I wonderdd if anyone has installed it:-
https://kjetkillers.pl/en_US/p/Injection-set-piggyback-EFI-Mercedes-m103-3.0/53
There are other options available including fitting a cylinder head and ancilliaries from a 104 engine.
The objective I am following is to improve the efficiency of the engine ( and reliability) and perhaps encourage the MPG to get closer or above 20 (currently it is circa 13 despite being light footed on the pedal). I am not concerned about making it faster although some modest acceleration capability would be welcome.
Any feedback would be much appreciated.
David
I'd carry on trying to find someone to treat what you already have rather than doing something drastic.
Have you tried looking here - https://www.boschcarservice.com/gb/en/workshop-search You need to zoom to roughly where you are but they show 2 or 3 places in Norwich if they might be suitable.
Not sure you're ever going to get above 20mpg - mine is a SWB version of your G and 16.5mpg is what I recently got driving 250 miles on mostly motorways (so a mixture of 70+ mph and 40mph and stuck in M25 traffic). I definitely wouldn't describe me as being light-footed on the pedal.
Yours is going to be a bit heavier, assuming yours is a LWB, but I would have thought you should get a bit better than 13 mpg. As for reliability - apart from when the head gasket blew it's been great in the 6 plus years I've had it.
Well, of course I'm biased but you have the best version there apart from a SWB G500.....but where are they all hiding?
You definitley should be able to get AT LEAST 16.5 mpg - that last run of mine was mostly at 70+ mph on the motorway.
Wait until you hit 90mph and hear the air being sucked in through that vent just forward of the passenger door.
David, I think physics will dicatate that getting 20mpg+ out of a 300GE is asking too much!
I have a 230GE and with 2 less cylinders would struggle to get 18mpg. I decided to put the cost of changing and tinkering towards just enjoying and paying the difference. It tootles along at 70mph (its a 5speed manual) and slower up hills and faster down!
The Bosch KJetronic can't be tuned much at all afaics. Just make sure all your vacuum circuits are good.
Oh, and remember to use E5 premium petrol when you can find it. These engines are on the list to avoid E10. A little higher octane will help, but comes at a cost. I don't think E10 (10% ethanol) will do much harm, but would like to hear from others about that.
I heard that too - only E5 in my G.
Thanks again Mark.
A G500 SWB would be great. However, I have only seen one come up for sale in the past couple of years, and at the time, it was very expensive and I did not have the funds available. So I have my 300GE and need to get the most from it.
From what I have seen on the web, the Jetronic system on the 300GE is an early iteration and more modern systems produce more efficiency. I think my present consumption may be related to set up so hopefully the local Bosch guys can help me.
I have only been using E5 fuel in the 300GE, so hopefully that base is covered.
The car also has 275/70 16 tyres on it whereas the originals were 255 wide. That will also have a mild effect on mpg. However, on start up, which sometimes takes a couple of attempts, there is a heavy fuel smell from the exhaust. The oil level has not gone down since she arrived. The diagnostics at Bosch are scheduled for Saturday morning, so I hope that I may have some news then.
Normal for Norfolk.
So I took the car round to the Bosch garage from the link you kindly posted. They are an independent MOT and repair company. Sadly they did not know of my confirmed appointment from Bosch and indeed had never received or expected any appointments either. So Boosch are are advertising them without their knowledge. It was all very amicable but no progress with the car.
They have limited capacity to test the K Jetronic system but suggested that the injectors could probably benefit from a service.
I shall try and find a classic Merc specialist......
Oh No!
I feel guilty now. 
Sorry if you have checked all this but tyres Psi at least 30PSI? Clean ( new) air filter?New plugs, ? No brakes dragging? Can you push it on the flat in neutral? Try a shot of Forte ( trade only, tho most garages sell it ) fuel / injection cleaner
I have a 300ge but manual 5 speed, no trouble getting over 20 on a run and average out at 19 in mixed driving, even an auto should give you 17/18 mpg in an SWB, theres something wrong I'm afraid, those are the figures you might get with a 280 ge auto
Its 2nd generation KE-Jetronic, the older ge280 had basic k-jetronic, I would suspect the most likely causes are air leaks in the system or you may need a new cylinder head gasket. These go as you approach 150k miles, the other regular issue is that distributors only last 30k or so
these engines have a simple adjustment for octame strength, and should not be affected by the differences between e5 and e10, does it have starting issues, if it does its an air leak
these engines have a simple adjustment for octame strength, and should not be affected by the differences between e5 and e10, does it have starting issues, if it does its an air leak
Concur with that. And you are doing well to get 20mpg methinks.
I'm not aware there is any tuning possible for the KE Jetronic ECU. Just overhauling, cleaning, renewing bits of the overall setup. There is some manual modification online (youtube and lookup the Bosch K-Jetronic manual on tasteslikepetrol.net) for adding an adjustment to the Warm Up Regulator (WUR). See the other post on here for actual links I added. Its a really good guide.
[/quote] And you are doing well to get 20mpg methinks.[/quote]
He's in West Glamorgan! It's all downhill from there.
Oh dear - tried to do the quote thing but it didn't seem to work.
I've deleted the catalyst and added a K&N but being manual is the most important bit
Here is a previous thread where the tasteslikepetrol.net guide can be found, and a few youtube links (see Feb 2022 post) on the KE-Jetronic system:
Newbie | G-Wagen Owners' Association (gwoa.co.uk)
Many thanks to everyone for their input.
I continue to struggle to find anyone who is ready to work on the car, giving its age as a reason/excuse. With this in mind, I have not seen many old mercedes in the Norwich area! Sadly I do not have enough tools, or probably the skills to do the work myself.
I am keeping the tyres (275x70 R16) pumped up hard and being light on the accelerator which has helped. The car already has a K&N washable air filter and a Magnaflow exhaust and cat. A new fuel filter is ready for fitting at some stage.
When looking at the engine, I noticed that the throttle cable has a small jubilee clip holding the plastic end piece together. I believe I need a new throttle cable to fix this, but cannot find such a thing anywhere (or the part number). Could this be linked with the hesitation to start when cold? The car usually takes a couple of attempts and needs some welly to get going. Once warmed up, it is fine.
Thanks again
Problems starting when warm/hot is normally the issue, and can be Fuel Accumulator issue, or generally vacuum leaks.
Problems starting when cold... for me it was timing issue. Old school tipex on the TDC mark and strobe light timing. Twist the distributor to adjust the timing.
Obviously check the distributor cap is healthy and the distributor arm.
Spark plug leads can break down - replacing those is an option.
Check the plugs (carefully) as your symptoms can also be oil dripping past the valve seals and onto the plugs (petrol). If they are oily, cold starts will be harder and warming up is burning it off. Easy check yourself.
Throttle Cable is no longer available from MB (A463 300 22 30 for a 463 with M103 RHD)... RHD specific is the issue and different length and low volumes... and they usualy survive OK so low demand for first 30 years of their life
I am sure there is a little plastic bush that stops the cable pulling thru a bracket on the engine end that always used to split and fall out due to heat and wear and perhaps this is what the jub clip is doing? It does not show the part on the factory pictures any longer but it is availbale A202 301 00 93 / 64 at £1.50 so maybe worth a try!
Many thanks for the helpful replies.
I have bought new Bosch spark plugs, leads, distributor cap and rotor arm as the first fix. I have a fairly complete service history over the passed 10 years and these have not been replaced in that period. If this does not help, it is probably something that needs to be done anyway.
I will disassemble the throttle cable (and hope it does not disintegrate!) and try to see what I can do to get it functioning properly (although I am slightly unclear of the negative impacts of the jubilee clip) Thanks for the part number info.
David
Check the plugs (carefully) before starting as your symptoms can also be oil dripping past the valve seals and onto the plugs (petrol). If they are oily, cold starts will be harder and warming up is burning it off. Easy check yourself.
Reminder
Yes thanks for that. I will.
However, I have noted that there is zero oil consumption or smoke on starting. Would these not be expected also?
....The objective I am following is to improve the efficiency of the engine ( and reliability) and perhaps encourage the MPG to get closer or above 20 (currently it is circa 13 despite being light footed on the pedal). I am not concerned about making it faster although some modest acceleration capability would be welcome.
Any feedback would be much appreciated.
David
The KE Jetronic is a great system and as far as reliability goes, it's capable of operating in a completely mechanical modes., should the closed-loop electronic control system fail.
If I were you, I'd read up on the KE Jetronic system and find a garage that knows what they are doing. If it isn't broken, don't fix it.
Your MPG should be around 20 -25. Mine is. If you are getting 13 MPG, you might have other issues or a system that already been tampered with by someone that doesn't understand it.
Oh, I should mention that you should avoid doing over 60 MPH or MPG will drop drastically due to barn-door aerodynamics. The vehicle is not really intended for motorways. Although the eninge is quite silent, the gearing is too low for comfortable cruising.
Your MPG should be around 20 -25. Mine is.
Blimey! I was quite worried when I read this Arnie.
Then I read on ..............
Oh, I should mention that you should avoid doing over 60 MPH
So really my 17 mpg is perfectly understandable 
.
Yes, well, drag Force is proportional to speed squared and drag Power is proportional to speed cubed so you'll need 59 % more engine power at 70mph compared to 60 mph. The engine's fuel consumption will vary according to its power output, as determined by engine speed and torque. It's not a linear relationship, but as an approximation, your 17 MPG at 70 mph would be around 27 MPG at 60 MPH.
However, there are other losses to consider, such as transmission and road friction, so 25 MPG would be about right.
(It's why the Bugatti Veyron needs 1000 HP to do 250 mph)
The OP said he was being 'Light footed' so 13 MPG is very much on the low side, even condidering that it's an LWB.
Additionally, the EFI kit mentioned/ linked above does not show an air-mas-flow meter nor any other sensors normally found on more modern ECUs.
The M103 engine in the G-Wagen has separate ignition and fuel-systems. An integrated, "Motronic" type system with an engine map to control both ignition and injection would be preferable if going the upgrade route. However, the proposed system looks like it may actually be a downgrade step as at least the KE Jetronic has an air mass meter and uses a closed loop system with oxygen sensor to maintain Lambda at the ideal value of 1.
Thanks to all for the feedback.
New plugs, leads, distributor cap, rotor arm, distributor cover all helped. The cooling temp sensor was also replaced. Cold start performance is much improved. I need to keep a mild pressure on the throttle on start up for it to get going easily. But it is much better.
The MB "expert" who looked at the car thought the the fuel distributor may need a service. I am looking into this. If I decide to go ahead, then I will also replace the injectors, which at nearly 200k miles, have had a good innings.
Next step will be to check the consumption. At the moment, I have only been doing short distances into the village....
I have a 1991 300GE SWB. It has done about 173 000 miles. On long trips I get about 16.5mpg - on the freeways my speed probably averages closer to 60mph than 70mph. The car accelerates well and sits comfortably at that kind of speed. Hope that this reference point is of assistance.
Thank you.
I am off station for a while now and will not be driving the car until my return. Hopefully I can take her for a run and test the mpg.
Just checked my MPG with a fairly gentle trip to and from Southend (170 miles) at not more than 70mph plus another 100 local miles and returned 18.5 mpg.
Quite happy with that and should definitely be achievable.
Probably won't be able to get that again until after the winter - shortish journeys so quite a lot of automatic choke on start-ups.
Hello again.
After replacing plugs, leads, distributor cover, cold start valve my fuel consumption improved from 13mpg to 16mpg.
I then replaced all the tyres with new Michelin 255/70 R16 (in place of 275/65 R16 budget tyres). The consumption is now 18mpg. This is for local driving into Norwich and pottering on country roads.I hope that on a longer run, the consumption may yet improve further. I have yet to tackle anything to do with the fuel injection system as I have yet to find anyone within 50 miles who is ready to work on the KE Jetronic system.
Thanks for all the support.
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Thanks Mark,
Mine is a SWB too. Only tried up to 60mph so far.
I have booked it into a local Bosch specialist from the link you included in your reply. I am sure there must be achievable improvements to be found. I will keep you posted on how I get on.
Thanks again.
David