E300TD air in fuel lines - no start - PeachParts Mercedes-Benz Forum

Duckman999 · #1 12-01-2010, 12:01 PM

This AM I come out to start the car.....tries to fire several times but never "catches". I pop the hood, and notice a lot of air in the lines. I'm trying to figure out where it's leaking. The car has 1/4 of gas left, and was left parked on an incline (nose up) overnight. I always park it there, and havn't had a problem with it in the last 4 months I've owned the car.

PO told me the injector Orings have all been replaced, and there were some fuel leaks that had been fixed. I've not noticed any fuel leaking/dripping.

I'm NEW to diesels and MB in general, so please bear with me.

Looking down at the filter, from the drivers side of the car. The line in the middle has a LOT of air in it. The line towards the engine (prefilter line?) has bubbles in it as well. The line closest to the fender doesn't seem to have much if any air in it.

Not sure where to start, but being down a car really sucks. I'm assuming I ought to replace the prefilter Oring and maybe go ahead and do the fuel filter while I'm there.

I did notice something weird while I was looking around there. There is a clear plastic fuel line with a white clip on each end. Neither one of these clips was "in", and I was able to lock them in without any problem.

A list of all the fuel components to replace would be great. I've also heard of some trick to get the car to crank for more than the 4-5 seconds it does, to facilitate priming of the system....unfortunately I can't find the procedure.

ANY help is appreciated!!!

pimpernell · #2 12-01-2010, 12:06 PM

Quote:

Originally Posted by Duckman999

This AM I come out to start the car.....tries to fire several times but never "catches". I pop the hood, and notice a lot of air in the lines. I'm trying to figure out where it's leaking. The car has 1/4 of gas left, and was left parked on an incline (nose up) overnight. I always park it there, and havn't had a problem with it in the last 4 months I've owned the car.

PO told me the injector Orings have all been replaced, and there were some fuel leaks that had been fixed. I've not noticed any fuel leaking/dripping.

I'm NEW to diesels and MB in general, so please bear with me.

Looking down at the filter, from the drivers side of the car. The line in the middle has a LOT of air in it. The line towards the engine (prefilter line?) has bubbles in it as well. The line closest to the fender doesn't seem to have much if any air in it.

Not sure where to start, but being down a car really sucks. I'm assuming I ought to replace the prefilter Oring and maybe go ahead and do the fuel filter while I'm there.

I did notice something weird while I was looking around there. There is a clear plastic fuel line with a white clip on each end. Neither one of these clips was "in", and I was able to lock them in without any problem.

A list of all the fuel components to replace would be great. I've also heard of some trick to get the car to crank for more than the 4-5 seconds it does, to facilitate priming of the system....unfortunately I can't find the procedure.

ANY help is appreciated!!!

Dont know your location, with winter coming, if your vehicle was exposed to cold temperatures, your diesel fuel may have gelled up. Just a guess...good luck!!

EdzBenz · #3 12-01-2010, 12:12 PM

Duckman,
Do a search on here for air in the fuel lines. There's a lot of good information. I've had a similar problem with mine before and the air in the lines was caused by the plastic fuel lines going bad. Those clear lines that you see the air bubbles in need to be replaced after time because they let in air. Common problems with the fuel system that I've encountered are:
-Bad Shut off valve
-Bad plastic fuel lines (they run from the filters to the pump, etc.)
-Fuel filter o-rings going bad
-Copper washers in the injection pump need to be replaced after time (I DIY'd this and its pretty involved; sounds like the PO already did this to yours)

TMAllison · #4 12-01-2010, 01:49 PM

The white horseshoes on the fuel lines are "spreaders" that are pushed closed to release the clips attaching the fuel lines. Pull them all back out where they were (loose and floppy) for starters......reseat any lines that appear loose.

To prime the fuel system you manually hold the key and crank for 30 secs at a time. Rest 10-15 secs and crank again. Do that 3-4 times then let the starter cool and your batt recharge for an hour. If it coughs and splutters keep cranking and continue cranking an extra sec or two after you "think" it has started. It won't hurt the starter.

Starting on level ground or nose down helps; as does +1/2 tank of fuel.

The middle fuel line being the only line with air suggests a fuel line oring connecting to the shut off valve (black valve on side of IP) or the SOV oring behind the valve is leaking.

Duckman999 · #5 12-01-2010, 02:25 PM

Thank you all for the responses. Car is a 1998 E300

I just got off the phone with the shop the po took it too. The say the sov and o ring were replaced about 5k miles ago, along with the plastic fuel lines. Nothing on the invoice about the prefilter or fuel filter

The middle line had the most air in it, but the prefilter line has a good amount as well.

I hope I can source the parts locally/quickly so I can get this back in the road....

anghrist · #6 12-01-2010, 02:34 PM

Quote:

Originally Posted by Duckman999

Thank you all for the responses. Car is a 1998 E300

I just got off the phone with the shop the po took it too. The say the sov and o ring were replaced about 5k miles ago, along with the plastic fuel lines. Nothing on the invoice about the prefilter or fuel filter

The middle line had the most air in it, but the prefilter line has a good amount as well.

I hope I can source the parts locally/quickly so I can get this back in the road....

Just because the o-ring was replaced, doesn't mean that it can't go bad, or wasn't seated well. SOV can go bad, but not as likely as the o-rings.

GregMN · #7 12-01-2010, 02:51 PM

Finding an air leak into the fuel lines can be tedious. I had an intermittent air leak in a 1996 E300D. I put a low pressure (around 5psi) electric fuel pump in the fuel line where it first enters the engine compartment. Within 30 seconds of pressurizing the line I found the leak. It was well worth the $30 and the time it took to install it. I fixed the leak and removed the pump.

As mentioned by "TMAllison" the clips on the fuel line fittings are counter-intuitive. The state you found them in was the correct, installed, position. When you pushed the clips "in" you released the fitting.

Diesel911 · #8 12-01-2010, 01:47 PM

Anything with an old O-ring to seal it on the suction side of the Fuel Supply/Lift Pump can be an area that can leak air.
You might also want to give what year your Car is.
If your Engine has a Fuel heater that can be a source of Air leaks.

If the Prefilter is gunky it could be that you have something growing inside of your Fuel Tank that is plugging the Fuel Filters and/or Fuel Tank Screen.

Duckman999 · #9 12-01-2010, 03:17 PM

I will make sure to reinstall those clips correctly when I get back to the car. I've ordered:

Prefiler
Prefilter Oring
Filter
Filter Oring
SOV Oring

Parts probably 2 days, so I should have something to do friday.

I would be grateful for any more info on the fuel pump trick you used. I'm guessing just a cheapie external 12V pump, a cup of fuel, and some clamps/line to get it on there.

GregMN · #10 12-01-2010, 04:42 PM

Ask for an low pressure electric fuel pump. Install a hose nipple on each end and a short piece of fuel line on the "input" side. Remove the fuel hose from the hard fuel line on the driver's side of the engine bay. (Make sure you have the fuel source line, not the fuel return line.) Install the pump connecting the pump "out" to the fuel hose and the pump "in" to the hard fuel line. Ground the pump's ground wire. Run a wire to the positive post near the fuse box that is used for jump starting. Connect the power to the pump until it has pumped up to the cut off switch pressure and stopped pumping. Look for the leak.

My leak was the o-ring seal between the fuel control valve and the IP.

Good luck.

nhdoc · #11 12-01-2010, 04:47 PM

Just replace the o-ring on the prefilter before you do anything else. If the clear plastic lines and o-ring on the SOV were recently replaced I would bet a dime it is the prefilter ring which is leaking. It takes 2 minutes and costs almost nothing...so what have you got to lose?

Duckman999 · #12 12-02-2010, 08:28 AM

I parked it overnight nose slightly down. After holding the key over to crank it (approx 10 seconds). I gave it a little bit of access pedal and it sputtered to life.

No bubbles in the lines at the moment, no issues driving it to work. I went ahead and filled it up with fuel this am, and will park nose down tonight. Fri the parts should be here, and hopefully that will fix her up. I'll report back then

Thanks!!!

nhdoc · #13 12-02-2010, 01:52 PM

You will likely have no problems as long as you keep the tank full and/or park nose down. The trouble is when the level in the tank falls below the high spot in the fuel system under the hood (which also just so happens to be the o-ring for the pre-filter) then the fuel will drain back to the tank because that o-ring is letting air in.

Duckman999 · #14 12-03-2010, 09:17 PM

I replaced the prefilter and Oring today. I can't imagine the Oring being bad on the prefilter that was in there...it was in there pretty good and the ring looked fine. Filter was pretty sooty looking though.

I parked it nose up, but it's full of gas again. I was hoping for some definitive "yup, theres a bad oring" when I pulled it out. But nope. The line going to the prefilter was in there pretty snug as well.

Bill Ladd · #15 12-03-2010, 10:47 PM

Quote:

Originally Posted by Duckman999

...but it's full of gas again...

Think I found your problem.