fuel filter wich way - PeachParts Mercedes-Benz Forum

markmam · #1 07-25-2006, 07:20 PM

i have a mercedes 300e 1987 model and i change the fuel filter but when i saw a sign in but it was going the wrong way which one shoul go on the fuel pump and which one shoul go to the tank .......... and also that is how i took it out the connections are that way its written on the picture but after i saw the arrow and in i had doubts on how it goes

by the way which one go first (tank, filter, pump) or (tank ,pump ,filter)

here is the pic

[IMG]http://us.a2.yahoofs.com/groups/g_18307533/cea7/__sr_/1399.jpg?grg9txEBYuyzFjFL[IMG]

http://us.a2.yahoofs.com/groups/g_18307533/cea7/__sr_/1399.jpg?grg9txEBYuyzFjFL

markmam · #2 07-25-2006, 08:15 PM

i just wanted to know which way it should go

Gilly · #3 07-25-2006, 10:03 PM

The arrow is the direction of flow, so by following the arrow, it will take you up towards the engine. Does this answer the question?
Gilly

markmam · #4 07-25-2006, 10:10 PM

yess it does answer my question but which one is it and also when i change it thats how it was the connection is that way but after seeing arrow and in i had doubts

tank, pump, filter or tank, filter, pump

Gilly · #5 07-25-2006, 10:12 PM

Well just go in the opposite direction of the arrow and you tell me! I think it's tank, pump, filter, engine, not 100% sure though.
Gilly

Gilly · #6 07-25-2006, 10:14 PM

Yeah I think I'm right because those are high pressure fittings on the filter, so it's going into the filter at high pressure, meaning already through the pump.
Gilly

markmam · #7 07-25-2006, 10:24 PM

im having doubts because if it goes filter first then pump its safer because the gas get clean first before it goes on the pump so it wont damage the pump when some dirty stuff gets in but ill hold your word for it i think you have more experience

Tomguy · #8 07-25-2006, 10:59 PM

It's almost always tank -> pump -> filter -> engine (-> tank)

The pump is (theoretically) protected from large particles by the strainer in the tank. The filter is after the pump because, if it were before and got partially clogged, it can lead to premature pump failure. The pumps on these are all gravity-fed, they don't have much suction power.

dkveuro · #9 07-26-2006, 12:09 AM

On you car Mark...the fuel enters the lower fuel pump first, then the upper pump, then to the main large filter which can only be installed one way due to size of inlet/outlet....The filter should have a metal outlet fitting already installed.....if not, the ARROW or FLOW should face to the rear of the car.

To qualify....the BANJO fitting with the hard steel line is the pump high pressure supply to the filter.

.

markmam · #10 07-26-2006, 01:03 AM

i brought the car to the place. i left the car there at 7 in the morning but when i got there i dont have an appointment so i left it there and then when i got there about 6 this night and the car hasnt been touch so i just decided to take it home. when i got home i check the old filter and found that arrow, and your right dkvuero on the opposite side is a metal connection.

but when i got home the pump seems to be so week or the filter is cloged again but i just change it yesterday with a brandnew one so im having doubts on the fuel pump because when i start the car i put the key on position 3 and i can hear the pump (zzzzzzzzzzzipppp) for about 4 sec. and then i pump the gas for about 9 times and then start the car then it would idle for about 25 seconds and then it shuts off by itself then i tried it again i did the same but before i start it i step on the gas and it would shut off about 4 seconds later so i think the pump is not doing its job.

by the way when i change the pump what is the actual psi for the fuel pressure. and i would bring it and have the pressure check and the fuel line and what do you call that check. and what are all the parts that i should buy and where is the fuel pump check valve located

dkveuro · #11 07-26-2006, 01:58 AM

Mercedes says...Fuel pump must deliver 1 liter of fuel in 40 seconds with a minimum of 11.50 volts and less than 7 to 10 amps draw at the pump.

To power the fuel pump, you remove the fuel pump relay and bridge the #7 socket to #8 socket.

To test fuel system pressure with motor running you need a special three way valved pressure guage set, Mercedes part #103 589 00 21 00. with various adaptors.

So unless you have these, you will not be able to determin what your problem is, if it is fuel related or not.

I would think that Frank's Mercedes has a work back log, so they would need a couple of days to work your vehicle in to thier schedule.

you really need to allow Frank's to set a time to test the system and pin point the problem you have.

Fuel check valve is located on the end of the upper fuel pump.....not sure if Mercedes used a check valve on both pumps...but might have done.

.

markmam · #12 07-26-2006, 04:20 AM

so the engine doesnt desire a right psi as long as there is a flow the engine would idle by itself even the pump is not working at its standard

dkveuro · #13 07-26-2006, 12:31 PM

Yes it does require correct fuel pressure .....the volumn test is a check that supply is okay.

Unless you have a pressure guage to test ALL the systems pressure values, you are shooting in the dark....let someone who has test guages check the system.

If you persist in just throwing things at it, I can no longer help. You'll finish up with more problems than you started with.

.

Gilly · #14 07-26-2006, 05:30 PM

The pump puts out more pressure than required, the pressure is regulated by the fuel pressure regulator (don't ask for specific pressures, not sure). As long as the pump puts out at LEAST what the regulated pressure is it should run. If there is not enough volume (amount of fuel) it won't run well at all. If there is not enough pressure it won't run.
Gilly

Gilly · #15 07-26-2006, 05:33 PM

Mark: What is the actual problem you are having with the car? What is it doing wrong?
Gilly