Changing my fuel filters on a '64 PD4106 with an 8V-71....

[bwze]

As the title states, I plan to change my filters and was wondering if pre-filling them with Marvel Mystery Oil was acceptable?

[Barn Owl]

pre-filling them with Marvel Mystery Oil

What benefit is there for doing that? What type of filters do you have? Mine are the old cartridge type and it is a simple process. I do prefill them with CLEAN diesel fuel so I don't have to prime.

[bwze]

Really just curious. I've got new spin on fuel filters and no diesel available. A buddy of mine is a CAT diesel tech and says that you can pre-fill the filters with ATF or MMO and it helps to clean the injectors. I've got three gallons of MMO and was wondering if this could be an old wive's tale or if there is any validity to it.

[luvrbus]

Old wives tell about cleaning the injectors you can use, it, lot of smoke for 10 minutes or so best to use clean diesel DD engines have a different type injection than a Cat engine.
FWIW I have used pure vegetable oil before when I had no diesel to fill the filters



good luck

[bwze]

I bow to the experienced DD owners. Since I am, but a grasshopper, I will go with the apparently tried and true approach of using clean diesel. Thanks Barn Owl and luvrbus.......

[Gary '79 5C]

The only thing I use to clean injectors in my MB diesels is a product called Diesel Purge. Never thought I needed it in the 6V92.

Any opinions on this product?? It is best used by removing supply & return lines and redirect the lines in a container of DP, making it a 100% solution.

[Oonrahnjay]

The only thing I use to clean injectors in my MB diesels is a product called Diesel Purge. Never thought I needed it in the 6V92.

Any opinions on this product?? It is best used by removing supply & return lines and redirect the lines in a container of DP, making it a 100% solution. 

Very, very good on car engines; really cleans up and improves the running of a VW TDI with some miles on it.  Dunno if it's needed on "heavy duty" engines; they may have larger thermal masses and more relaxed clearances.  But if someone was having a problem caused by deposits or contaminants in the fuel pump and/or injectors, this might be a good way to go.

[bevans6]

If you had a priming pump in the fuel line before the first fuel filter, and it could draw from the tank, why couldn't you prime the filters with that?  Probably because the pump wouldn't fill past the engine fuel pump, but you could crack off a fuel line and use it to fill the second filter after the engine pump, couldn't you?

Brian

[Oonrahnjay]

If you had a priming pump in the fuel line before the first fuel filter, and it could draw from the tank, why couldn't you prime the filters with that?  Probably because the pump wouldn't fill past the engine fuel pump, but you could crack off a fuel line and use it to fill the second filter after the engine pump, couldn't you?   Brian 

My engine (different in many details from North American engines) has the lift pump driven by a cam on the fuel injector pump drive shaft.  All you have to do is to position the engine so that the pump plunger is on the lower side of the cam and then press a small hand lever on the back side of the pump unit.  It usually takes 20 - 25 strokes to fill fuel filters.  Usually, just changing fuel filters won't result in a loss of prime on the "high pressure" side of my fuel injection system (I'm talking the actual fuel injector pump, injector fuel lines, and injectors) but if this prime is lost, there are a couple of bleed fittings.  To reprime that high-pressure side, all that it takes is opening the bleed fittings and pressing that hand lever a few times.  You see bubbles, then fuel with a bubbles in it, then mostly fuel, and finally liquid fuel.  At that point, the system is reprimed.  It's a good system -- that little hand lever will prime either or both the low pressure/filter side or the high pressure/injector side.

[TomC]

Don't get fancy and try something new-stay with the proven and just use straight Diesel Fuel.  Make sure everything is clean since your pouring raw Diesel Fuel into the clean side of the filter also.  Best to have the engine warmed up first, then restarting isn't such a problem.

When changing the oil and filter, first warm the engine up to get the oil flowing, then just change the oil and filter and get the engine running again with good oil pressure.  When it has run about 4-5 minutes and you're satisfied that there are no leaks, turn off the engine and then do the fuel filters (most change both at the same time).

It is interesting to note that on the new Detroit DD engines, the filters are built into the engine at the top of the engine and have no way to prime them-since once you open up the filter, it releases a one way valve to drain either the oil or fuel out.  When you change the fuel filters, you put them back in and either you hand prime it up with the built in primer pump (a few hundred strokes) or there is a fitting to use a power primer-a quick release fitting with a pressure tank like an insect sprayer.  Detroit does this because the new injectors are running at 10,000psi rail pressure and 32,000psi tip pressure with extremely close tolerances.  When priming up the fuel filters, all the fuel has to go through the filters first-no raw fuel gets on the clean side of the filters.  So the recommended way is to first change the oil and filter and get the engine running, then change the fuel filters.  Good Luck, TomC

[artvonne]

  Those Rabbit Diesels had been out a while. I remember one time I was at a shop and the mechanic had the injectors out and apart cleaning them. Said that was the only real way to get them spraying right.

  Later I took some injectors (same type as VW, but from a 300D MB) to a place to have the break pressure and spray pattern checked. For those who have never watched it done its quite interesting. Its like a clutch master cylinder with a lever. They fasten the injector to the line, and pump fuel through it while watching a pressure gauge. But, they are able to force much more fuel through than your pump, and can actually clean the injector in many cases, better than through disassembly sometimes, by litteraly blowing them out. I always meant to make one of those.

  Another diesel I had, it always diesel knocked pretty bad. I cleaned the injectors, had them checked, never made any difference. One day at the MB dealer, the parts guy suggested some Red Line diesel fuel additive, some kind of synthetic mixture. I dont know what kind of conconction it was, but one little 8 ounce bottle in a full tank and it was like a new engine. How or why it did it I do not know. But I always felt it was a bandaid that was masking a mechanical fault. I swapped in some different injectors and it made no difference, so it was probably just timed wrong.

  As to MMO, its good stuff, but nobody really knows what it is. I am not even sure if the manufacture knows (JK). Its great for loosening bolts, rings, sticky valves, engine assembly, but too far beyond that and your treading on unknown ground. I am not sure I would want it going through a cold diesel at full strength, nor would I believe it would clean an injector any better than fuel.

  If your thinking the injectors are fouled, the first place to start is to remove them and physically clean them and check them for break pressure, leakage, and pattern. But I should say here right now, I dont really know squat about a DD injector. I just assume its gotta squirt fuel up around 2000 psi like any other diesel mechanical injector.