berardini

I have owned this far for years and has been a dream, 120k miles. Car was my go to car for years and I like to think it still is but, I bought an old ford bronco. I have been driving it a lot and packing the miles on it. I start the Mercedes once a week let it idle, drive around the parking lot. Basically enjoying the Bronco for now, well I haven't driven in it in a month other than stated above. My tank shown near empty, range showed around 35 miles until empty, that was normal. I drove 2 miles to work. Left work and went to fill tank up, it did not register on the gauge. I parked car turned off turned on, let sir for a second then it went up to where it should have been. I drove for about 45 minutes all seemed well, Range showed 280 milesIsh which sounds right. The bad news is my mpg showed 5 mpg after all this. I can literally reset the trip at idle and watch it go from 20mpg to 10mpg in about a minute. Car had tune up less than 15k ago, I feel like sending unit could be acting up? I'm lost and pissed. Thanks for help in advance

Anker

You need to get a code reader on to the car.

It sounds like you have two different problems:

The first has to do with one or both of your fuel level sensors.

The second is bizarre, because the mpg is calculated from fuel flow and distance.

I have a suspicion that both problems are caused by low battery voltage. Check your battery with a voltmeter.

I bet that if you put a code reader on your car you are going to get a bunch of low voltage codes.

Rudeney

+1 on the low voltage.

berardini

Are we talking low voltage as in battery is weak, or I have a short somewhere? Is it possible that this car really is only getting 6mpg? It runs amazing I mean amazing, I have always kept great maintenance on her, anything benz tells me I pull out the checkbook. It's just odd that one month ago when I parked it all was well, I started it occasionally. It has been super cold though for my neck of the woods it sat through our snow and 10 degree nights. Any more input is greatly appreciated, if it's low voltage will driving it charge up the battery? If it's not low voltage am I looking at a fuel sending unit ? I assume it's in the tank but do you have to drop tank like old cars ? Thanks again

Yidney

They mean battery. These cars get weird with a less than healthy battery.

Rudeney

And even with a good alternator, a dead battery cell can make it act like a giant resistor and rob power from other circuitry.

MacVidMB-V8

Mine always starts at 20MPG and then goes down. Usually shows 11-12 MPG by end of (maddening) trip in LA.

I stopped doing the math myself. Was almost always obvious ious I got less than 10 MPG. (i.e., 90 miles, 10 gallons, etc) Sitting still idling the MPG will drop like licorice in the sun.

berardini

I posted an update on here earlier today, basically its saying I am getting 7mpg, but I reset the trip meter and drove it and filled up and it came out to 17.5 MPG which was my average all the time before this mishap. Gas Gauge is working fine and has been other than the delay in registering after fill up. Battery Levels Check out, my indy mechanic thinks its fuel sending unit. I really dont want to spend 700-1k on this job right now, I am wondering if maybe since I let it sit on near empty tank there was some dirt in the bottom and when I filled it up kind of messed up the sending unit, Throw some STP Cleaner in it? And Drive it? Or bite the bullet and spend an arm and a leg right now Thanks for help guys

berardini

Also is it the fuel sending unit that calculates fuel output? Thanks

insame1

I bought one online for much less than 1k and it is fairly easy to do.

berardini

I'm currently doing the front radiator core support on my ford bronco and timing cover and water pump, there's no way it can be that hard. My only question is do I need to reset a computer at all? I don't have to software to reset anything

insame1

I didn't have to when I changed mine.

berardini

Just dropped car off at stealership, 140$ for diagnostic. Left it there for the day. Will keep you posted.

berardini

They didnt charge me the diagnostic fee, they said that since I reset the MPG after start and reset it all, I need to drive for a few hundred miles for it to balance back out. I guess all is good.