Mercedes-Benz Forum banner
Status
Not open for further replies.

Fuel consumption problems on W123 230E AT

31K views 20 replies 7 participants last post by  alibttb  
#1 · (Edited)
Hi,

I need advice, I bought a 230E three months ago. I got the same fuel consumption as stated in the manual, but I had to replace the exhaust.
Afterwards the fuel consumption dropped from about 10km/l to 7.5km/l on the open road and in town from 8 km/l to 4 km/l.

I have tried everything including dyno-tuning the best we can get is 8.8km/l for the open road and 4.5 km/l in town. The Merc is a 1985 W123 230E AT with 360k on the clock. I even had a free-flow and branches installed which increased the performance many fold, but did nothing for the fuel consumption. The mechanic is proposing to replace the fuel injection with a carburator.

Any Ideas on what I can do?
 
Discussion starter · #5 ·
Thank you for all the replies.

I will start to look for a replacement manifold. As I understand I shouldn't have replaced it unless I was planning to have the head ported and gas flowed. I will look into the gear box as it does feel like she is pulling heavy.

LaubscherCalitz I have the fuel line on the "to do" list we did fix it as it ruptured with the last service but I will check it to make sure.

Thanx
 
Discussion starter · #15 · (Edited)
Decel Shut-off valve

Hi LabsherCalitz

I checked it and it is working but I noticed that via a valve or two the main breather tube is connected to the Decel valve. This tube has a strange connector that is in fact a flow restrictor that was blocked and disconnected. I will have to see if this sorts the problem. I will also remove all the tubing and check for any other blockages tomorrow.

Will keep all up to date as I get a chance.

One more thing to check is the Decel Shut-off valve. It is a cylindrical shaped valve below the Inlet Manifold. The pipe from the top of the Air filter connects to it. a small vacuum pipe comes from it and connects to an electrical valve on the left front fender. If you remove this pipe during idle, and you suck on it, the engine should stop. If it does not, the valve is probably shot. It operates on the micro switch next to the throttle that senses when your foot is off the pedal.

The principle of this system is that when you take your foot off the pedal at speed, high vacuum in the lower intake manifold opens the air valve, allowing air from the air cleaner directly into the lower intake manifold, bypassing the upper intake manifold's fuel sensor plate and throttle. The resulting absence of vacuum in the upper intake manifold makes the fuel sensor plate return to its idle position, cutting off most of the fuel. The un-throttled rush of air into the cylinders also decreases pumping losses. The electrical switch is to ensure the valve only opens during deceleration/overrun, not at idle. If you connect the air valve directly to high manifold vacuum at idle, the engine should die. If it doesn't, the air valve may not be working or some adjustment may be off, or there may be a vacuum leak. You can live without this system, but your fuel consumption will be higher by 20% or more.
 
Discussion starter · #18 · (Edited)
Solved!

Hi guys,

Well it worked. The fuel consumption now is 12.32 km/l. Wow just a little blocked and disconnected tube caused all this mayhem. Nutz I will check it out as a lot of tuning was done and it may be that she is running lean now.

Thank you guys for all the input.
:D

Hi LabsherCalitz

I checked it and it is working but I noticed that via a valve or two the main breather tube is connected to the Decel valve. This tube has a strange connector that is in fact a flow restrictor that was blocked and disconnected. I will have to see if this sorts the problem. I will also remove all the tubing and check for any other blockages tomorrow.

Will keep all up to date as I get a chance.
 
Discussion starter · #20 · (Edited)
Thank you plane,

I am not quite happy yet, there is still a few tricks that can be done, but I need to fix a few things before I experiment further, and I have to save a little before I can continue...

And I am looking at a 220/240D w115 or older project to do next.

Mighty impressive consumption for a 230E there:thumbsup:
 
Status
Not open for further replies.
You have insufficient privileges to reply here.