So I’ve got a few things I’d like to do outlined below, but a fundamental issue central to everything: should I really fix what isn’t obviously broken?

1) I snagged four rebuilt injectors from greazzer for my NA OM616, but I don’t have any strange noises, any smoke at all from my tailpipe, or any leaks at the injectors - should I swap out my injectors just for the hell of it given I have no idea if they’ve ever been serviced previously?? Here’s a link to video of a start up and the engine running: https://youtu.be/Xl4P3Fotzpc

2) if I do replace the injectors, I’m not going to bother with giving it a diesel purge this year, and I’d switch out both fuel filters when I put in the new injectors. Is this air bubble in the fuel filter line normal?

3) I’ve been told I should go ahead and replace my original hand primer pump with the updated Bosch pump, but if I’m doing injectors, fuel filters, AND the primer pump, what’s the best order to do those jobs in? I’d think primer pump first, filters second, injectors third, but am open to advice from folks who’ve done the work before!

Many thanks in advance for the help!


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Ive been advised that you should still do a diesel purge BEFORE u put in the new injectors.

So u can clean out all of the lines and all the other fuel components before u put them in. Because if you don't then All of that gunk that may be on there will go into and thru your brand new clean injectors. Dirtying them up and possibly clogging them.

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Ahhhh, seems logical - thanks! So now I’ll add a purge to the front of my list - then hand pump, fuel filters, and lastly the injectors?


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Engine sounds great and I see no shaking at idle. It ain't broke, so don't risk breaking it. Don't worry about dirty injectors. When I opened mine in both diesels, they were pristine inside, and the pre-chambers had no carbon. If you run a few tanks of B20 in the summer, that should help clean the fuel innards, or you can add a qt of vegetable oil every fill-up (best not in winter).

The air bubble in the pre-filter is normal, but the swollen fuel hoses isn't. Replace w/ 5/16" Barricade (for bio-diesel) from NAPA. Several posts on replacing the leaky white primer pump w/ the new smaller black one. It is hard to get at the lower hex, so just smash off the white plastic since you will throw it away anyway. Worst-case, you might have to remove the lift pump to get at it, but avoid since those 3 bolts can be tricky and would need a new gasket. When the woven injector return hoses get wet (weeping), replace w/ 1/8" Viton hose (ebay).

When your power steering hoses show cracks or leaks, search for my post. The H.P. line can be "re-hosed" since it uses field-replaceable fittings (at least on my 300D's).

Your engine looks real clean. The aluminum is oxidizing, but not bad for the Midwest. Perhaps spray it with Rustoleum Rust Preventer (name?). It gives a clear cosmoline-type coating that lasts a few years.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

You've got air incursion...which wiill cause rough starts after prolonged shutdown.

There is a big air bubble in your return line from the IP to the fuel filter head.

The hoses for your primary fuel filter are split allowing air into the system,
The hose clamps should be replaced with the flat style worm gear hose clamps (Norma, etc.)
A clear Hebmuller primary fuel filter (001-477-79-01) will have bronze inserts and be much less likely to deform when the hose clamps are tightened.

The old stlye primer pump with the white handle is prone to leaks, the black pushbutton style by Bosch is a decent upgrade.

These repairs should eliminate most of your air incursion.

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

Thanks Bill and Alec!! I’ve looked for the 5/16 (I don’t use bio diesel or anything else, just regular diesel) line to replace the cracked/swollen lines to and from my primary filter, but every one online at AZ just notes the internal diameter and various pressure ratings - any ideas on the internal diameter/pressure rating I should get to replace those two pieces?! Thank you!!


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Would this work? Assuming 5/16 is the internal diameter of the line, that’s like 7.9mm.

CRP-Contitech high pressure reinforced rubber; 8mm ID; 5 Bar - that sound good?

Link won’t show, but it’s part no. 13311469781 at AZ


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Do the primer pump first and get rid of your air bubble. It only takes a few minutes and if you don't do it, anything you mess with will make the car progressively harder to start.

Dkr.

Agree with all above PLUS do that purge. The fuel in your clear primary filter looks awfully dark.

Yeah, I put in a lot of the winter formula diesel kleen to stabilize the fuel, but I thought maybe the color change was from that. I plan to park sideways on a boat ramp when I’m low on fuel, take the fuel sender out, and use a flashlight to check the tank strainer and see if it’s clean - a little concerned there could be some water/algae in the tank and if there is, I’d certainly want to hit it with some biocide before putting on new filters/injectors!

Anybody use those tank tampon things before to soak up water? Have any recommendations?


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Hose sizes refer to ID. Metal tube sizes refer to OD. I forgot the "correct" metric size, but 5/16"D hose is "close enough to fit fine". "Rated for bio-diesel" = "superior quality". It has an inner liner (Viton, I recall) that is more resistant to all the extras put in fuels today. I try to use it in my gas cars too. You can use regular rubber fuel hose, but probably won't last as long.

Fill the new primary fuel filter to the brim w/ diesel, then spin it on (actually center bolt pulls it up). Per manual, crack the return banjo fitting (aft) as you operate the hand pump to purge all air up to the IP and tighten as you keep pumping. You may still get some air in, but it should eventually sweep thru. If hard to start, crack the fuel tube nut at the top of each injector (17 mm wrench, I recall), one at a time, as you crank and tighten it slowly as fuel dribbles out. That should get all the air out. That is also a good cylinder check when running. You should note each cylinder fall out (engine gets rougher) as you crack each nut, since the fuel dribbling out isn't going thru that injector (requires 1600 psig to pop open your non-turbo injectors).

BTW, good your engine is diesel. My sister once had me look at a ~1970's Volvo wagon w/ electronic fuel injection. Unlike modern engines, it used short rubber hoses off the injectors and each was dribbling gas - i.e. major fire hazard. Good your wetness is diesel since it won't ignite from a spark. When MPFI injection came out (~60 psig), I predicted future engine fires. While we do occasionally see burnt gas cars, it seems no worse than w/ carburetors, probably thanks to Viton O-rings.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

I think 8mm i.d. hose is the original MB specification, but metric diesel fuel hose hard to source locally in most areas.
The rubber fuel supply hoses only see low fuel pressure, so 5/16 works okay if you snug the hose clamps adequately.
Parker 5/16 Super-Flex FL Series 397 hose is an excellent barrier fuel hose (compatible with biodiesel) that I use on my MB diesels.

Change your primary (plastic) and secondary (metal) fuel filters before doing the diesel purge.
Sicnce you have an '01' fuel filter head (615 092 01 08) you may need a new aluminum crush washer and also an o-ring for the hollow bolt when you change out the secondary fuel filter.

I upgraded my W116s to the '02' fuel filter head when I did the CAT 1-7050 fuel filter upgrade.
Fuel filter upgrade

If anyone needs a kit, they are still available. Just send me a PM.
http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/386988-fs-cat-1r-7050-fuel-filter-upgrade-kits-om61x.html

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

If you can wait on installing the injectors...run a few tankfuls of diesel treated with Biobor and StarTron Diesel Fuel Tank Cleaner beforehand.

Go ahead and do the diesel purge now, as you are going to run off a mini-tank under the hood.

Get a couple of spare primary and secondary fuel filters to have on hand.
Virtually a guarantee, you will go through a couple of primary fuel filters clogging up as you drive the vehicle.
Fresh fuel will dissolve and stir up the old tank sediments, causing fuel starvation issues.

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

Thanks Alec!! Saving my bacon again - biobor being delivered Friday and will go into the tank same day!

And awesome filter upgrade kit, that’s really good work!!



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So arriving tomorrow along with the biobor is a large plastic syringe and four feet of plastic tubing - I figure there’s a decent chance that once I let a shot or two of biobor sit in the tank a few days that there may be a lot of fine sediment (also likely some water) at the bottom of the tank. Rather than removing the drain screen, I’m going to see what sort of success I have vacuuming that settled and undisturbed crap right off the floor of the tank through the filler neck. Will be sure to get a video and report back.


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