Ridiculous gas milage -again..

[Freestyler]

I know this has been discussed over and over. I just want to see if anyone has come up with new ideas..

My w124 300E is using obscene amounts of fuel! I get no more than 9-10 mile/gal. (steady long-range driving)

I have replaced temp. sensors and O2 sensor. The stealership have been adjusting the engine over and over and found nothing wrong -except for the fact that it is using way too much gas.

What to try now?

Injectors? Distributor? What..?

Freestyler

[PaulG]

May have suggested this before............

Check the fuel pressure, if it's too high (caused by shaged regulator) you will get these symptoms.

Vacuum leak?!?

[Freestyler]

Originally posted by PaulG
Check the fuel pressure, if it's too high (caused by shaged regulator) you will get these symptoms.

How do i check the fuel pressure?

And what if it IS too high.. New regulator?

Freestyler

[Imatation]

I have this exact same problem in my 300E, but with mine it seems like the gas mileage changes alot. Some days i get pretty good gas mileage, and others (most) its horrible.

[pentoman]

Originally posted by PaulG

Check the fuel pressure, if it's too high (caused by shaged regulator) you will get these symptoms.

Shagged... hahaha. Gotta be this first time that word has been used on this forum.. :p

[Freestyler]

Originally posted by Imatation
I have this exact same problem in my 300E, but with mine it seems like the gas mileage changes alot. Some days i get pretty good gas mileage, and others (most) its horrible.

Sounds like my story..

When i bought the car i got about 18-20 mile/gallon. Then suddenly i would sometimes only get 10, driving the same route every day?
It went up and down for a month or two, and now it has settled on "ridiculous low gas milage".

-I could buy a decent used car every month for the money i'm spending on gas!

Freestyler

[PaulG]

Fuel Pressure gauges can be bought in tuning shops for about 30 to 40 quid.

Just plumb them into the fuel rail and compare the readings with those in the manual.

If they are too high, the regulator is at fault, but I wouldn't advocate changing it "just in case" because it's failure needs to be proved first.

You can bankrupt yourself by throwing parts at the problem.

[Mike Richards]

Freestyler:

Your signature mentions an 86 300E converted to a 95 E300?
Is this the same car with the poor gas mileage? If so, tell us about the "conversion". That could very well be the problem.

[Jim Anderson]

A bad thermostat will keep the engine cold and running rich trying to warm it up.

[h_shek]

Hi Jim:

I know it has been discussed million times, but just to clarify, how do you define a bad thermostat?

My car (140) stay at 70+ degrees even after 15 minutes driving at temperature of approxmately 18-20 degrees. Is this normal? The 15 minutes driving is mostly down-hill with average rev. of 1500 - 2000 rpm.

I am not sure if there are anything wrong with my thermostat as I have replaced it 2 years ago or 15000 km ago. My car does gets to 90-95 degrees but this is after longer driving and more up-hill.

My question is, should I worry being 70 degrees most of the time and taking so long to warm up? or is it an almost replacement time?

[Freestyler]

Mike Richards wrote:
tell us about the "conversion". That could very well be the problem.

Nope.. The conversion only included bodyparts. The drivetrain is still original.

Jim Anderson wrote:
bad thermostat

The thermostat is almost brand new. -Engine temp. is around 95 C.

h_shek wrote:
how do you define a bad thermostat?

You just did! (Low engine temp. Long heat-up time)
Sounds like your thermostat is stuck in open posistion. -Easy and cheap to replace.

Freestyler