Poor fuel economy - Page 3 - PeachParts Mercedes-Benz Forum

cavaliers16 · #31 11-09-2006, 09:05 PM

The car just consumed another tank of diesel. This time it got a whopping 12.8 mpg. Would poorly adjusted valves or bad timing really do that (15 mpg drop)? The odometer is fine as far as I can tell (it is around the average of the other cars' odometers). I really want to find a leak somewhere but there is no leak.

Again, no burning oil- I changed it the first week I had the car and I haven't touched it since- still full
Grey smoke at startup, some black on heavy acceleration (only attempted a few times)

This is starting to bug me

I'm going to adjust the valves this weekend regardless.

t walgamuth · #32 11-10-2006, 12:22 AM

now how did you check the odo?

tom w

cavaliers16 · #33 11-10-2006, 07:09 AM

I checked the odometer against our other cars. It was way off from the Jetta but right on line with the two Volvo's. Would it be more accurate to do it on the highway?

blackestate · #34 11-10-2006, 10:46 AM

even if the odometer is off, it should be consistant. So you should always get the same mpg. Not dropping like this.
I would look real close for a leak at the IP connections, the manual pump on the IP, sepage at the cigar hose, connections to the injecotrs.
Is there anything wet under the car? thinking that the IP, or connections on it, could leak and drop fuel right to the ground un-noticed when working hard.

Just an idea.

t walgamuth · #35 11-10-2006, 11:09 PM

i would only trust the mile markers on the highway.

and the odos when they fail often do so by slipping sporadically for a while and gradually getting worse til they fail completely.

tom w

Hatterasguy · #36 11-10-2006, 11:22 PM

Does it smoke a lot? How good could it run getting mileage that bad?

There must be a ton of carbon loading up the head. Time to get cracking on Brians list.

Get the IP and cam timing set, move on to other things.

I'd say you have a leak, but you should have noticed that by now? I mean diesel leaks make a mess they are pretty noticeable.

networkboy · #37 11-11-2006, 02:56 AM

So as you can see in my sig I've been working on milage as well.
I know some of this has been covered, but anyway:

return lines bought me about 5 MPG.
Valve adjust (mech said they were tight, but not too bad) bought about another 1Mpg. (if yours are as bad as they sound, likely 3 MPG here)
New filters all around (fuel, air, oil + change) bought 2.5ish MPG. (bad crush washer install on secondary fuel filter cost a ton of fuel though. Found that quick when I came out from work and there was a puddle under my car )
found a source of decent fuel, +~2MPG. tried another tank of the other stuff and milage dropped back down to 17.xxMPG
Next: put a video camera under the hood B/C everyone thinks I still have a leak, but I can't find anything at idle... Primer pump(old style) leaks above ~ 3K rpm (I'm bettin that there's another 2 MPG.)
Finally, unchecked as of yet, but there's a bit of rubber in the back worth looking at (between the tank and the steel lines).

Also, did you use a knife to cut off the old return lines? if so the barb may be scored.

Something major though if you had an immediate 8+ MPG drop.
good luck
-nB