98 E300 fuel system questions... - PeachParts Mercedes-Benz Forum

KarTek · #1 07-12-2007, 12:14 PM

Guys, I'm looking at doing the purge thing to my car and I'm trying to figure some things out.

What's the deal with the "clear" plastic lines in and around the fuel fileter/pump? should they be clear as glass, flexable? How are they removed? If they're removed can they be re-used? I can't figure out how to remove them without damaging either the tubing or the plastic fittings. Do they need to be clear or can they be replaced with Viton lines?

Which is the feed line from the tank and which is the return? Does the car have a "lift pump"? If so, where's the fuse?

Thanks!

scott19_68 · #2 07-12-2007, 01:38 PM

Quote:

What's the deal with the "clear" plastic lines in and around the fuel fileter/pump? should they be clear as glass, flexable?

When new, the lines are semi-transparent and white. If your's are 'cola' colored, I'd recommend changing them all since they seem to leak once you've disturbed them. New ones come pre-molded to the correct shape and have fitting and O-rings ready to go. You could try changing the O-rings to Viton on some of them, but I'd advise you buy new ones.

Quote:

How are they removed?

Push the white horse-show clips 'in' so the fitting is closer to the bottom of the U-shape and pull. I had good luck with some gentle prying with 2 flathead screwdrivers at the same time.

Quote:

Which is the feed line from the tank and which is the return? Does the car have a "lift pump"?

The fuel 'suction' side goes like this:
tank -> heater -> pre-filter -> shut-off valve -> lift pump

The lift pump feeds the main spin-on filter directly. From here, the fuel delivery passes through the shut-off valve and into the IP. Overflows from the pump, injectors, and the spin-on filter feed back to the tank. The lift pump is mechanical so no fuse.

Hope this helps,

F18 · #3 07-12-2007, 02:07 PM

Evan,
I replaced all the clear fuel lines on my 98 E300TD when I bought it two years ago because a few of the "O" ring seals were leaking. The original lines were discolored (dark yellow) but not brittle.......in fact when I removed them I deliberately banged them around a bit and they are as tough as nails! I probably could have replaced just the "O" ring seals on them and they would have lasted another 150K. It depends if you want "pretty" new lines for a price or functional old discolored ones........
I kept all the old ones for back up parts!

TMAllison · #4 07-12-2007, 02:47 PM

If you purchase new lines make certain to keep the smallest one that connects the fuel heater (in the head) to the pre-filter as you can use that one as a tool to help set up a temp tank to run a DP in the future.

KarTek · #5 07-12-2007, 03:55 PM

OK, thanks for the help! So, since the lift pump is mech., how do you keep it from spewing fuel when running on purge? Also, looking at the top of the filter assy., which line do I remove to feed the engine for the purge?

So too, the plastic lines are not intended to come off of the plastic ends? Is this correct? You actually remove the whole thing?

Sorry to sound like an idiot but I just have no experience with this fuel system and I'd much rather ask dumb questions than find out by breaking something...

Thanks!

TMAllison · #6 07-12-2007, 04:23 PM

The pre-formed fuel lines have ends that do not come off. You either replace the o-ring only or buy the entire line. The set is ~$50. Is nice to have new clear ones so you can actually see the fuel flow.

To set up the DP. Take your old line I previously mentioned and cut it in half and take it to McParts store and get 6' of clear tubing that will fit over that fuel line. Cut 2 - 3' pieces. Disconnect fuel line from top of pre-filter (leave other end connected to pre heater), inset modified line with 3' tubing attached into pre-filter. At top of main filter housing, disconnect clamp holding black fuel hose and pull it off the nipple it attaches to. Connect 2nd piece of tubing to nipple and stuff both ends of tubing into prefilled temp tank and fire it up. Turn off before running out and will be MUCH easier to restart when you connect main tank back up.

Lift pump will never be disconnected. Only supply and return lines.

KarTek · #7 07-12-2007, 04:49 PM

Ahhhh! Now I get it! Route the lift pump to the return line and the fuel flows in a loop while purging! Light bulb on... Thanks! Terry, where'd you get your Viton O-rings? Thanks again.

TMAllison · #8 07-12-2007, 06:05 PM

The fuel flows in a loop normally; we are just tapping inot it and bypassing the tank. You're not tocuhing the lift pump or shutoff valve.

I bought my orings in 10 paks from McMaster Carr.

JADAVIS on the forum has a website and now has a prepackaged kits for sale for the 606.962. Its cheaper to get them from him.

deltajetfixer · #9 07-12-2007, 08:20 PM

Quote:

Originally Posted by KarTek

Guys, I'm looking at doing the purge thing to my car and I'm trying to figure some things out.

What's the deal with the "clear" plastic lines in and around the fuel fileter/pump? should they be clear as glass, flexable? How are they removed? If they're removed can they be re-used? I can't figure out how to remove them without damaging either the tubing or the plastic fittings. Do they need to be clear or can they be replaced with Viton lines?

Which is the feed line from the tank and which is the return? Does the car have a "lift pump"? If so, where's the fuse?

Thanks!

http://www.peachparts.com/shopforum/showthread.php?t=113596&highlight=diesel+purge

KarTek · #10 07-12-2007, 10:00 PM

Fantastic! Thanks!

KarTek · #11 07-16-2007, 08:39 AM

Well, I did the purge this weekend and so far, I'm pleased with the results. The engine starts quickly and there's much less clacking and drama from the cylinder that's missing a glow plug.

It was really very simple - I just unhooked the supply and return lines and hooked up the "juice bottle". The supply line just sits there during the process with no leaks. To hook the feed from the bottle up, I simply wrapped a piece of 5/16 fuel line with a couple turns of electrical tape and stuck it down into the pre-filter.

The fluid in the bottle quickly turned dark during the process but the engine ran smoothly with no extra smoke and just a little odd odor.

The next time I do this, I'll rig it up as Terry suggested with the nipple from the supply line and longer hoses so I can drive the car while purging.

Thank you all for your input. I appreciate it!