Mercedes-Benz Forum banner

1 - 13 of 13 Posts

·
Registered
1992 300 TD Turbo Automatic
Joined
·
10 Posts
Discussion Starter #1
Perhaps someone can shed some light on this problem.

I bought this car about a year ago and had to change the brake master cylinder which lead onto new brake pipes and brake calipers. It took me a long time as it was a kind of hobby project.

The brakes are fine now, but when I got it back on the road, I found that a vacuum leak has developed because the engine won't shut down when the ignition key is turned and removed. I decided to sort this out this weekend but having have run the car for a few days, to my horror, I have used a full tank of diesel to do 175 miles including some city driving. I pull a trailer around some days but I find it hard to believe that this would explain such a high consumption.

My questions are: can the vacuum leak cause high fuel consumption? If so, how? Or do I have to accept this level of consumption as normal for a 300TDT?
 

·
Registered
Joined
·
114 Posts
Is that per 60L?

I get 200km's in the City on 30L (Gasoline/Petrol) and mine is bad to normal.

I would say you have a problem.
 

·
Registered
1992 300 TD Turbo Automatic
Joined
·
10 Posts
Discussion Starter #3
Thanks for the info cacciatore08 - yes that's on 60L. If my maths is right you get about 400km city driving on 60L and I get 280km mixed driving :(
 

·
Registered
'95 E300 DIESEL, '91 600SEL, '92 600SEL
Joined
·
16,920 Posts
WOW!!! You've probably got the biggest dieselguzzler on this site. I get about 750miles (that's 1200km) consistently on my '95 E300 OM606 diesel.

You've got to find out what's causing this as you might have a serious fuel leak somewhere, mine did briefly at one point giving me even worse mileage than yours.

In my case, the high pressure fuel feed line between the fuel pump and injection pump had popped off causing a huge spray which I only noticed by the very quick fuel consumption 90L in 50KM. Strangely enough, this was not enough to stop the engine from running any different as it was still getting enough fuel.
 

·
Registered
1992 300 TD Turbo Automatic
Joined
·
10 Posts
Discussion Starter #5
I've never been a record breaker before! I think the problem is more to do with the amount of fuel passing through the engine. I left it idling for 10 minutes yesterday and there was a wet patch of diesel on the ground at the exhaust.
 

·
Registered
'95 E300 DIESEL, '91 600SEL, '92 600SEL
Joined
·
16,920 Posts
I left it idling for 10 minutes yesterday and there was a wet patch of diesel on the ground at the exhaust.
Check every fuel line, especially the main feed from the tank to the fuel pump, fuel pump to fuel filters, and fuel filters to injection pump.
 

·
Registered
1992 300 TD Turbo Automatic
Joined
·
10 Posts
Discussion Starter #7
Thanks sbaert, I'll have a look this weekend. Do you know whether there could be any link between the vacuum leak and the fuel system?
 

·
Registered
'95 E300 DIESEL, '91 600SEL, '92 600SEL
Joined
·
16,920 Posts
A vacuum leak will usually have an effect on other items such as a change in shifting patterns.

The fuel system is strictly mechanical, except for one item. That is the shut-off diaphragm on the injection pump. Without a functional diaphragm, you will not be able to shut off the car using the key, which is the reason there is a manual shut-off lever or knob (depending on engine model) on or around the injection pump.

If you have a severe vacuum leak you might even feel a difference in the feel of the brake pedal.
 

·
Registered
Joined
·
384 Posts
amount of fuel passing through the engine.
I can't imagine how that would happen. Especially at idle, it's pretty much a set amount of fuel there, if the engine somehow doesn't burn it, it runs rough or doesn't run.

It is far more likely that you have a fuel leak.
 

·
Registered
1992 300 TD Turbo Automatic
Joined
·
10 Posts
Discussion Starter #10
To wrap this one up - sort of ..... I have run the car this week and I did a long run today on the motorway .... so I have been able to calculate consumption three times now.

First 60 litres after car had stood in the garage for months 280km. (This is when I got the patch of diesel from the exhaust).
Next 40 litres 280km.
Today I have done 280km again (coincidently) and the fuel guage is showing slightly more than half a tank remaining which means, allowing for the inaccuracy of the guage, I have used about 30 litres to do 280km.

The three rates of consumption are

1) 21,4 litres/100km
2) 14,3 litres/100km
3) 10,7 litres/100km

Things seem to be improving without me doing anything! I wonder if it might have been something to do with the car standing for so long in quite a dusty room (air filter perhaps?) I have had a look around the engine and there is no sign of diesel leaks. I haven't seen any diesel under the car after a night standing and there is no smell of diesel. I'm going to do nothing for the time being and keep my eye on the guage for a while longer. Thanks for your replies.
 

·
Registered
money pits of various forms
Joined
·
5,885 Posts
To wrap this one up - sort of ..... I have run the car this week and I did a long run today on the motorway .... so I have been able to calculate consumption three times now.

First 60 litres after car had stood in the garage for months 280km. (This is when I got the patch of diesel from the exhaust).
Next 40 litres 280km.
Today I have done 280km again (coincidently) and the fuel guage is showing slightly more than half a tank remaining which means, allowing for the inaccuracy of the guage, I have used about 30 litres to do 280km.

The three rates of consumption are

1) 21,4 litres/100km
2) 14,3 litres/100km
3) 10,7 litres/100km

Things seem to be improving without me doing anything! I wonder if it might have been something to do with the car standing for so long in quite a dusty room (air filter perhaps?) I have had a look around the engine and there is no sign of diesel leaks. I haven't seen any diesel under the car after a night standing and there is no smell of diesel. I'm going to do nothing for the time being and keep my eye on the guage for a while longer. Thanks for your replies.
Algae will make for bad mileage. Have you confirmed your odo with GPS?
 

·
Registered
2008 E350 4M, 1988 300TE
Joined
·
5,432 Posts
maybe just a bad batch of gas wherever you last filled up?

I'd run some Diesel Kleen through it to make sure.
 

·
Registered
1992 300 TD Turbo Automatic
Joined
·
10 Posts
Discussion Starter #13
Algae will make for bad mileage. Have you confirmed your odo with GPS?
Had problems with algae in my previous car 1992 300D saloon. This manifested itself as black slime in my prefilter and choked the supply causing the car to stall and not start until the algae had been cleaned out. I eventually had to take out the tank and filter at the exit of the tank and flush with algicide - no problem after that.

No sign of algae in the prefilter this time - so I'm guessing it's probably not this which I think is probably backed up by the fact that you wouldn't have expected the problem to improve - algae will only increase.

Confirming odo - no I haven't done this, I'll have a look at this next time I'm using the GPS. Thanks.

ps2cho - I agree, I thought I might do this next week, thanks.
 
1 - 13 of 13 Posts
Top