Greetings gents,

I've owned a diesel car for almost a week now, so please excuse my ignorance. But, feel free to skewer my stupid questions with gusto. I love flames!

My inline fuel filter (clear) contains no fuel. I believe that someone has installed it in a vacuum line instead.

What appear to me to be the two fuel lines are configured as follows...

There are two rigid fuel lines coming out of the firewall. Both have rubber hoses spliced to them. One has the Cigar hose and that goes to the spin on filter housing. The clear strainer should be upstream of the cigar hose, correct?

The other hose is connected to the injector pump by the plunger, so I figure that's the return.

The car runs great except it seems to be a slug when climbing a hill climbing. I am trying to diagnose this, and would like to begin with changing the filters. This week I ordered rebuilt injectors with Monark nozzles. I figure at 155000 miles it wouldn't hurt to proactively change them out.

I think that its possible that I have a linkage adjustment issue and may be the culprit. In order the get the car to downshift at speed, you need to stick your foot through the firewall to make that switch close. Anything less than a very hard push on the pedal and it won't.

one of the metal lines should have a hose that goes to a small plastic fuel filter, which then goes into the lift pump (what i guess is the primer pump you're calling a plunger?) thats the feed line. the return line goes through the spin on assembly and cigar hose, and then back to the metal line to the tank.

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1981 NA 300D 310k miles

The filter in the vacuum line is not a fuel filter. It is there as a visual indication of engine oil entering the vacuum system (bad). I think it started from about 1985, although it is possible that a previous owner could have installed one in an earlier car.

Now that I think of it, there might be 2 of those in the vacuum lines.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

BAM! Two great answers in ten minutes.

MANY thanks. I have two spares and will install one tomorrow in the Feed line TO the "lift pump". I'm learning. Sweet.

The filter in the vacuum line is clean as a whistle, so I've got that going for me!

Thanks for the info.

The car starts instantly and typically runs quite will. It nails a bit on startup (I think that's what I hear) and has fairly low (I think) blowby. No smoke at start up, and only a little bit under full throttle acceleration.

It would help a lot if you told us what year and what model car you have. If it is sluggish, you might take a look at the switchover valve. Make sure it has two lines attached and one nipple is open to the air. If it is clogged up, there will be very little power; same if the lines are switched.

You should try the simple fixes before doing something major. I have a 1981 300SD and am still running the original injectors; not sure you should focus on the injectors at this point.

So sorry,

The car is a 1985 300CD with the 617.952.

I'll look for the switchover valve today when I add the inline and replace the canister fuel filters.

The clear "filter" on the fuel feed line, although it acts as a pre-filter to trap large particles, is actually a dampener used to compensate for surges in the fuel supply. It is not unusual to see a bubble of air in this part.

Filtering of the fuel is done by the element in the canister located between the lift pump and the injector pump.

The pre-filter, if not completely plugged with debris, can be cleaned for re-use. Do not install a paper element type filter in its place. This can cause restriction of the fuel volume entering the actual filter.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

Here's a pic after I changed the filters. One question, the white thing downstream from clear pre-filter, right next to the lift (?) pump, is this a type of pre-filter?

I've never seen one like this. So, IOW, if it is, I have to remove it since I now have two. I just bought the car and have no idea how long that one has been in place. Additionally, I can't visually make out its condition.

The second question, when I unscrewed the lift pump and gave it a few strokes, it was leaking fuel. Not hemorrhaging, but definitely leaking. If it's only leaking when in use, I suppose that it;s not a big deal. But if it is, I'll change it out. May I assume that there are bolts at its base to hold it tight? I didn't get under the car to examine and couldn't see any from above. Below makes sense. If I change it out, will there be any issue getting the IP primed again? Thanks

Attached Thumbnails

   

Odd, someone has installed prefilters in series. You only need the one. The clear model is preferred so you can spot debris.

The white, screw down primer pump is notorious for leaking. Order the new updated one here:

http://www.pelicanparts.com/catalog/SuperCat/3281/MBZ_3281_FULINJ_pg2.htm#item3

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Sam

84 300SD 350K+ miles ( Blue Belle )

Well, that someone would be me. I didn't realize that the white one was actually a prefilter until I started working on the car today. I thought it was co-located with the primer and didn't realize how stupid I was until I saw its directional arrow. "I'm not a smart man, Jenny" Again, this is my first diesel and I've owned it less than a week. I've looked at 50 or more video's on YouTube and never once saw anything other than the clear units, so I had significant expectation bias.

Here's some really good news, the car has quite a bit more power now. You can really feel the turbo spin up and if you're watching, you can see the tach jump! Pretty heady stuff until you remember the car's actual 0-60 times! Hey, it's my first turbo! When I want to play speed racer I'll drive the SEC and annoy Johnny Law.

I will remove the old filter (white) soon and re-plumb so that it's easier to change and with less spillage.

The white handle Bosch primer does leak like a sum***** when in use. I see no evidence of a leak when it's stowed, but when in use its no good. I'll change that soon.

I really like the fact that I will now have an obvious indicator of fuel contamination and state every time I raise the hood.

Great forum guys! Many thanks for your responses and bonhomie. I promise to read ahead and search, but I've already got a ton of questions about this stinky beast.

Beer's are on me.

Get these ones with brass end sleeves 2 Mercedes Hebmuller Fuel Filter Inline w Brass Ends Upgrade 0 450 904 077 | eBay

These are hard to find and superior. Unlike the ones w/o the brass sleeves, these won't let air in on the suction side.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I'm a fan of these filters, just received 10 of these for $60.71, tax and shipping included.

http://www.***********************/sku/Hebmuller/Fuel_Filter/W0133-1641402.html

Came in two days.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Today I went out to remove the old non see-through in-line filter. Imagine my dismay to see a fair amount of black crud trapped in the see-through which I installed only yesterday! I took the old one out and cut in half for inspection and expected to find it clogged. Oddly enough, it wasn't, but it was filthy.

I've got another question for you guys,

I was going to run a can of diesel purge through the injector pump but was stymied by something I didn't quite grasp, and a shortage of parts.

1. There is a clear hose delivering fuel from the primer pump to the main fuel filter. It is pushed on barbs at each with no clamps. The hose appears old and is very stiff.

2. There is another clear plastic hose (feed) between the main fuel filter and the injector pump. There is another between the injector pump and the main fuel filter (bypass or return).

I'm surprised to see clear hoses and no clamps. I'm anxious to run the purge because the car was driven very little for the last 5 years, but I want to do this properly. Should those clear lines be replaced and clamped?

The clear lines don't need to be touched to do a diesel purge. They don't need to be replaced unless they crack and leak air and/or fuel.

There is an excellent step-by-step writeup of doing a diesel purge at this webpage. Diesel Purge Mercedes diesel maintenance tips

The NAPA store near me carries the Lubro Moly and they offer a AAA discount. You can fashion a mini-tank from an old sports drink bottle.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Many thanks!