Fuel Starvation? Help me confirm my Hypothesis - PeachParts Mercedes-Benz Forum

TylerH860 · #1 01-09-2008, 02:07 AM

Got my 300d up on the highway today, noticed a considerable power loss. My foot was to the floor and I can barely maintain 70mph at around 3,000 rpm. City driving acceleration seems normal until about 30 mph, then gets more labored.

A new noise has developed as well. After I turn the car off I hear somethings similar to when you blow on you straw with an almost empty drink instead of suck, (something kids do) or kind of like a fast dripping, though no fuel reaches the ground.

I'm guessing fuel filters, hopefully I'm right.

I've searched thread after thread looking for an idiots guide to changing fuel filters. (I'm clueless on where they are and how to do it)

A picture of where it is would be nice.

Mismost · #2 01-09-2008, 09:23 AM

Start by changing the fuel filters....sounds like the classic dirty, starting to plug filter. I suggest you clamp off the fuel line before removing the filters....it'll make re-priming a lot easier.

#3 01-09-2008, 09:25 AM

Take off the fuel tank cap and listen for a whoosh of air.

kernelpanic · #4 01-10-2008, 06:53 AM

Restricted exhaust ???

Mice are a real problem out here in the sticks. They love to go up inside the muffler and build a nest. I put a big piece of steel wool in the tail pipe before winter storage.

Happened to my bike one year.... started on 1 cyl and acorns were shooting across the shop out of the other muffler

Should have seen it ! Oh, and the smell........

LUVMBDiesels · #5 01-10-2008, 07:57 AM

Since nobody told you how to change the filters, here goes...

There are two of them, a primary (clear plastic inline filter) in the fuel line coming from the rear of the car. it is located on the left side of the engine near the Injection Pump. It is held on with two hose clamps. Buy a few of them from Phil as they can get clogged pretty quickly.

The second filter is a canister that looks like a typical oil filter. It is located at the top left part of the engine near the cruise control acutator. It is held on with a rather large (19mm - I think) bolt. Yo will need to turn the bolt to the left to loosen the filter. Do not try turning the filter itself. as it does not work. You should get a couple of these from Phil as well.

Once you have the second filter off, fill the replacement with either diesel fuel or Diesel Kleen or Diesel Purge as having the secondary filter full of fuel will save time priming the system.

If you have access to an air compressor, I like blowing about 20psi into the fuel line to make sure it is clear. You will hear the fuel bubbling in the tank. I give it a quick shot of about 3 seconds.

Once you have replaced all the filters and tightened everything push the priming pump located on the engine block near the Injection Pump about 10-15 times to get fuel flowing from the tank back tothe primary filter.

Then start the car. It might take a few tries go get it started due to air in the system.

Things to watch out for...

The rubber fuel lines can get old and brittle. If they look bad, before doing anything order some replacements.

The 'cigar' hose from the top of the secondary filter housing to thefuel return line can also get brittle and go bad. We do not have to mess with this to change the filters, but if it looks bad, order one and replace it.

If you do not clamp the fuel line from the tank to the primary filter you will get a mess of fuel on the ground. SInce I hit the line with air, that keeps the fuel from spilling out, but if you are not going to do that, either clamp it with a vice grip (wrapped in electrical tape) or stick a 1/4 inch drill bit int he hose while you are changing the filters.

This is also a good time to do a diesel purge -- look for Diesel Purge threads on the site for instructions.

If this does not help, try this...
On my car, the vacuum shut off switch was leaking and sending vacuum to the shut off valve on the Injection Pump. There is a small brown vacuum hose leading to a rubber tube on the side of the Injection Pump. pull it off and see if the car has regained it's power. You will have to stop the engine with the 'STOP' lever as the key will not shut it off with the hose removed.
I am saying this because the symptom I was having was the car would have normal power until vacuum built up in the valve then it would loose power and eventually shut off. It took me a while before I realized that the shut off valve works inside the IP and overrides the accelorator pedal.

Good luck!

toomany MBZ · #6 01-10-2008, 11:01 PM

Pic.
Follow LUV...'s advise, I did not clamp off anything, no drips. When replacing the primary, inline, filter, I was able to lift up, remove, re-install. When I installed a new spin on, secondary (24mm, on mine), filter I did spill a bit after I filled it up with Power Service, Diesel Kleen.
I did not blow any air through.