W463 300GEL - Breakdown
Evening all,
I'm looking for some advice on poor idling once warm please.
To set the scene - 1993 W463 300GEL Auto
Cold starts are almost instantaneous and the engine idles perfectly for circa 10 mins until warm.
Once warm, the idle drops too low and the engine seems to attempt to prevent stalling by increasing the RPM which works, but the engine then settles back at the warm idle RPM for a few seconds before dropping too low once more. And repeat!
After a while (5-10 mins usually), the 'anti-stall' loses the battle and the engine will stall from a low idle.
If the RPM is kept above an idle once warm then the engine seems to run perfectly, it's a case of the warm idle RPM not being constant and the engine stalling when the RPM drops too low.
I did some research and concluded a lack of fuel pressure may be at fault so have replaced the fuel pump / filter / accumulator located behind the left hand rear wheel arch. The fuel pump here was running very noisily and did not sound particularly healthy. This seems to have improved the issue but unfortunately not solved it.
Listening to the car running this evening, I'm now wondering whether there is a second fuel pump located in or on the fuel tank itself and whether this is now causing the warm idle problem due to low fuel pressure.
Equally, I could be on entirely the wrong track so any advice from those more experienced would be greatly appreciated!
I'd check for air leaks in the CIS system, unfortunately its a complex system and it could have many causes
There is a second fuel-pump under the metal protection plate, under the fuel tank. I don't think this is your problem, or you would loose power when driving.
For poor idling, I would check that you do not have any air leaks in the myriad of vacuum lines and hoses, and that your idle-control valve is working properly. It would be good maintenance to remove the idle-control-valve, clean it out with a little amount of petrol and re-lubricate the rotor with a drop of clean engine oil. The valves get dirty and gummed-up so that they fail to respond quickly enough, with the resulting symptoms you mentioned.
(There is a closed-loop control for the idle speed with feedback from an engine speed sensor. There are actually, two sensors, one for ignition timing and the other for engine speed (rev-counter and idle-speed), which is on the front of the engine, just above the crank-shaft pulley. One other possibility is sensor failure, but you would also loose the rev-counter)
Incidentally, there is a fuel-pressure regulator on the system, and worth checking as a last resort.
The system is a KE Jetronic. You can read how it works here:
http://www.berlinasportivo.com/Technical/lancia/Thema832/Bosch-KE-Jetronic-OCR.pdf
or here:
https://www.volvoclub.org.uk/tech/fuel_injection/BoschMechanicalFuelInjection.pdf
or here:
https://www.volvoclub.org.uk/tech/fuel_injection/BoschMechanicalFuelInjection.pdf
Thanks for the advice guys.
I'll explore leaks in the vacuum lines and let you know how I get on.
Max
....and clean out the idle control valve, as it's likely to be that
early 90's 463 300ge had single pump
later on the same had twin, usually 94 onwards
but it will be from a chassis serial number cut off upwards
....and clean out the idle control valve, as it's likely to be that
.....and that too.....
early 90's 463 300ge had single pump
later on the same had twin, usually 94 onwards
but it will be from a chassis serial number cut off upwards
Noted, thanks
This must be a later 93 model as the second pump has been discovered. Probably a chassis number change as suggested
Can I ask where you got the accumulator and how much it was?
Thanks,
Chris
https://www.amazon.co.uk/Bosch-0438170055-Fuel-Accumulator/dp/B0049PI21G
Mercedes part number: A 000 476 09 21
Bosch part number: 0 438 170 055
http://www.bosch-automotive-catalog.com/en/internet/ECAT-RS/vehicle-info/-/vehicle/equip/MB/2280/
I found it on eBay but as above, Amazon looks good too.
Update on my issue - the car has been away for a few weeks for MOT which involved a lot of new brake pipes and rear spring. I'm due to collect it later today and will get onto looking at the running issue at the weekend (weather permitting).
Thanks to the advice here, my issue appears to have been resolved by replacing the ICV and the second fuel pump. The second fuel pump was becoming increasingly noisy when priming in particular. I couldn't find any leaks in the myriad of air lines and the ICV looked past its best so it's now shiny and new.
It's great to have the old girl back on the road and many thanks to those who provided advice here to assist in the process
Sadly my G now has a new problem to diagnose.
Since replacing both fuel pumps, fuel filter, fuel accumulator and the ICV, the car had been driving nicely for a month or so. Took it out a couple of weeks ago (early one morning, cold start) and about a mile from my house it stalled whilst pulling out from a junction (it's auto transmission before you point to driver error ;) ).
I turned the ignition off and back on again and the car started almost instantly so I thought maybe the stall was just a freak incident. Went to pull out of the junction again and the car stalled once more.
From then on the engine will not start at all. The starter motor turns the engine over but nothing more than that. I've looked around the fuel pumps for any signs of leaks given the recent replacements but cannot see any issues. The pumps do prime when the ignition is turned on so the power feed to them appears to be OK.
Does anybody have any recommendations for where else to look before I have to resort to having it recovered to a garage?
Many thanks in advance
I had a problem (with a 463 G300) that started out exactly like this
I didn't worry too much about it - until it developed further and wouldn't re-start until it had been left alone for a while (say 30 minutes or longer).
I spent quite a bit on new rotor, new HT leads, new distributor cover etc. but it didn't make any difference.
Then I bought a new fuel pump relay on ebay - chinese copy so bit worried about how that would work out. Popped the old relay out, popped the new relay in and had no problem since. Only cost £27 (MB price from memory was almost £100). It came with a 2 year warranty (not sure whether that's worth anything).
For only £27 it's worth a try. If it solves the problem then great. If it doesn't then it's only cost £27 and you have a spare relay for when it does give up the ghost.
Thanks for the advice - you're right, for £27 why not give it a go.
I don't know how the 300GE's are generally but this car has been nothing but unreliable since day dot!
It has been in my family since brand new in 1993 and with no expense spared on routine maintenance it has gone through two auto transmission rebuilds, 3 or 4 alternators, entire cooling system replacement and even a heart transplant for a newly refurbished engine when the head gasket went, plus countless rear springs which it seems to break just for fun?!
That's in addition to all the smaller repairs / replacements that are picked up along the way with general servicing.
If it had been given a hard life I could understand it, but this G has never been used off road and has been driven by a (very steady) female driver for most of its 140k miles, valeted weekly and serviced more often than required. It has been wrapped in cotton wool!
Right, rant over, I'm off to eBay 
dizzys need replacing at regular intervals on this engine, worth carrying one with you and the tools to fit it
dizzys need replacing at regular intervals on this engine, worth carrying one with you and the tools to fit it
I'll go there next, thanks
Do you generally need to change the rotor arm too or just the cap?
Thanks for the advice - you're right, for £27 why not give it a go.
I don't know how the 300GE's are generally but this car has been nothing but unreliable since day dot!
It has been in my family since brand new in 1993 and with no expense spared on routine maintenance it has gone through two auto transmission rebuilds, 3 or 4 alternators, entire cooling system replacement and even a heart transplant for a newly refurbished engine when the head gasket went, plus countless rear springs which it seems to break just for fun?!
That's in addition to all the smaller repairs / replacements that are picked up along the way with general servicing.
If it had been given a hard life I could understand it, but this G has never been used off road and has been driven by a (very steady) female driver for most of its 140k miles, valeted weekly and serviced more often than required. It has been wrapped in cotton wool!
Right, rant over, I'm off to eBay
Hi Max
I also had a 1993 300GEL which had been in the family since new.
I sold it a few years ago with over 190,000 miles on the clock the last 100,000 of which were done by me and they were a mixture of road and regular off road some of which could be described as extreme !
It had a full MB service history up to the last 40,000 miles when it was serviced by a specialist.
I had no major mechanical problems and it was only really let down towards the end of my ownership by some rusty bodywork (lack of effort on my part) , leaky door seals and ageing electrics. The electrical problems were often intermittent and difficult to diagnose most of them caused by a fuse box with dodgy connections due to corrosion and some failing relays.
In your case I think you will find that the primary fuel pump relay has failed and what you can hear is the secondary pump priming the accumulator which works off a separate relay. You can hear it run for a few seconds when you turn on the ignition but it is not the main fuel pump.
Like you I did experience the breakage of several springs but then I was given the advice to make sure they are installed with the bottom 'tail' facing towards the diff and this seemed to work. Apparently it affects the angle the spring is stressed at under compression, or I just got lucky and they stopped breaking 
.
yes both of them, the service schedule is from memory is 36k or every major service
yes both of them, the service schedule is from memory is 36k or every major service
Thanks for the advice.
I've ordered both, along with a set of HT leads for good measure.
Euro car parts currently offering 25% off if anybody else needs similar
Hi Max
I also had a 1993 300GEL which had been in the family since new.
I sold it a few years ago with over 190,000 miles on the clock the last 100,000 of which were done by me and they were a mixture of road and regular off road some of which could be described as extreme !
It had a full MB service history up to the last 40,000 miles when it was serviced by a specialist.
I had no major mechanical problems and it was only really let down towards the end of my ownership by some rusty bodywork (lack of effort on my part) , leaky door seals and ageing electrics. The electrical problems were often intermittent and difficult to diagnose most of them caused by a fuse box with dodgy connections due to corrosion and some failing relays.
In your case I think you will find that the primary fuel pump relay has failed and what you can hear is the secondary pump priming the accumulator which works off a separate relay. You can hear it run for a few seconds when you turn on the ignition but it is not the main fuel pump.
Like you I did experience the breakage of several springs but then I was given the advice to make sure they are installed with the bottom 'tail' facing towards the diff and this seemed to work. Apparently it affects the angle the spring is stressed at under compression, or I just got lucky and they stopped breaking .
Interesting reading, particularly re the springs. I'll look more closely at how mine are currently fitted. I hope you're right and the relay is a simple plug in fix for the current issue.
Thanks for the info
Update to my tale of woe...
...New FPR arrived today and has not made any difference sadly. I did notice there was a spot of damp right at the back of the fuse/relay box so will investigate where that has come from and make sure it's better sealed.
New dizzy/arm/leads should arrive by the weekend so I guess that's the next one to hope for!
Sorry! 
Sorry!
Not at all!
I appreciate the advice and for £27 it was definitely worth a shot. I've left the new relay installed for good measure anyway, and I'll keep the old one as a spare.
Out of interest, how much fuel is in tank? Had a similar problem with my diesel solved by investigating the tank internals. Does it happen when tank is below a 1/4/ ?
Out of interest, how much fuel is in tank? Had a similar problem with my diesel solved by investigating the tank internals. Does it happen when tank is below a 1/4/ ?
Around a quarter of a tank currently.
Fuel level doesn't appear to have made any difference that I've noticed but I'll keep an eye on it.
Cheers for the suggestion
Out of interest, how much fuel is in tank? Had a similar problem with my diesel solved by investigating the tank internals. Does it happen when tank is below a 1/4/ ?
Around a quarter of a tank currently.
Fuel level doesn't appear to have made any difference that I've noticed but I'll keep an eye on it.
Cheers for the suggestion
Jason has a very valid point here... try putting some fuel so its up to half a tank and try...
Its not mythical... seen lots of early 463 in the last year with this issue both petrol and diesel...
Hard plastic pipe goes brittle and snaps causing the issue inside the tank
It can be fixed if you know how and have some skill and patience... or keep the tank above a quarter...
Or spend £1000 on a new tank
Worth a try...
A happy update on my G's non-start problem - she is alive again!
The successful diagnosis was the dizzy as suggested by prwales - thanks very much, I owe you a drink if we ever cross paths.
I'll post a photo of the old one which is pretty self-evident why there was an issue. For anybody else who needs to change theirs, the whole job of changing the HT leads, the distributor cap and the rotor arm took approx. an hour with some very cold hands. With warmer hands it might only take 45 mins and it's a really straight forward job.
Once the new parts were fitted she fired up almost instantly and ran very smoothly.
Thanks to all who have offered suggestions/advice in the process.
Until the next breakdown.........
Photo of the old dizzy below showing corrosion of contacts..
Out of interest, how much fuel is in tank? Had a similar problem with my diesel solved by investigating the tank internals. Does it happen when tank is below a 1/4/ ?
Around a quarter of a tank currently.
Fuel level doesn't appear to have made any difference that I've noticed but I'll keep an eye on it.
Cheers for the suggestion
Jason has a very valid point here... try putting some fuel so its up to half a tank and try...
You can ( at your own risk) tell if internals broken by loosening fuel Union underneath tank when fuel low, if fuel comes out no problems)
Its not mythical... seen lots of early 463 in the last year with this issue both petrol and diesel...
Hard plastic pipe goes brittle and snaps causing the issue inside the tank
It can be fixed if you know how and have some skill and patience... or keep the tank above a quarter...
Or spend £1000 on a new tank
Worth a try...
they have a fixed life span, I lost the one on my g-wagen and my w124 300e saloon with in a couple of weeks of each other in 2011 so now I carry a spare and the tools to fit in both cars
they have a fixed life span, I lost the one on my g-wagen and my w124 300e saloon with in a couple of weeks of each other in 2011 so now I carry a spare and the tools to fit in both cars
Yes, they do indeed, and using WD40 or similar on the internals only accelerates the wear, as the oil gums up the carbon electrode in the centre. I reckon about 10,000 - 15,000 miles per set.
JOIN THE GWOA
This website and forum are provided for the benefit of enthusiasts and owners of all Mercedes Benz off road vehicles, in particular the G Wagen. The costs of development, upkeep and provision of the site are met entirely by the annual subscriptions of club members. If you are using the site and are not a member of the G Wagen Owners Association please consider joining. You will have access to areas on the site that are not open to non members, to club trips and meetings and to technical assistance. In addition your contribution (only £25 annually) will help us maintain and develop our website for future users.
Who's new
- Jaffa_JIM_23
- Wrabstar
- GG
- KTMSCANIA22
- 280ge
Thanks for the advice guys.
I'll explore leaks in the vacuum lines and let you know how I get on.
Max