Hello,

When I had my 1987 300D inspected (prepurchase) by its long-term mechanics (Mitch Carr's in Kensington, MD), they mentioned that it had an engine knock (which it does) that had developed five years ago after the previous owner (or someone who'd borrowed the car, more likely) had filled it up with Regular Unleaded. The car was not driven far--it was towed to the shop, purged of RUG, and refilled with diesel.

After the incident, the car had issues with smoking, which is no longer a problem, and developed an engine knock, which is still around. The shop mentioned it did not seem to be a problem, just a bit loud. I went ahead and purchased the car with only 131K miles a few months ago, but I'd like to work on reducing the knock. (It gets really quiet on Diesel Purge, incidentally, but gets loud again once it's running on pure diesel again.)

What I'm wondering is, what are the effects of gasoline on a Diesel engine? Can this type of incident cause a knock? Does it damage injectors? Has anyone ever encountered a similar problem? What were the damage characteristics, and how did you go about returning the engine to top performance?

Thanks for your help!

--Matt

is it possibly an injector causing the knock? i have seen that before

the 603s are very sensitive to injector issues. a knock that sounds really bad can be a very minor problem with an injector such as it being loose or the seal on the bottom not being exactly right.

much much more sensitive in this way than a 616 617.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

May have just been coincidental as well. If anything major had transpired to cause it I would think the engine would have let go by now. Have you run it down to any particular cylinder yet by letting off the injector nuts one at a time? If you get it down to the cylinder level swap a couple of injectors around to see if it is injector related. I might see the excess running heat on the gas perhaps damaging an injector. Perhaps even a pre chamber but not sure of that. Also I would listen very carefully for equal cylinder drop with each nuts loosening. Thats how I would implement the search and as Tom states they are a more sensitive engine to injectors than the old 616-617 series to start with.

It is very helpful to try to distinguish between a "knock" which can be from a mechanical problem with bearings, etc., and "nailing" which is the sound you get from pre-detonation of the fuel (similar to pinging in a gas engine). From what you describe, you have a nailing issue, because it disappears when you run Diesel Purge through it. Try Barry's suggestions.

Wes

Have you ever tried adding a 2 quart bottle of new VO to the fuel. It might really quiet it down a lot. I love the sound of mine with even such a little VO added. Right off the shelf from the supermarket, either soy or canola or corn or peanut oil. And it is about the same price as diesel. Pour it into the tank and then fuel her up.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

There sure are a lot of threads and posts on here lately talking about upset or ill 603's.... 617's are like a best friend.

*Flame Suit is On*

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Be careful about which kind of oil you use. In the summer it does not matter. In the fall I would stick with canola oil. In the winter I would do without or use a little biodiesel. That all depends on where you live. I'm on the bottom edge of Tennessee near Alabama.

There is another active thread about a 603 pinging when fueled from the tank and not pinging when fueled from a gatoraid/gatorade/gatoraide bottle. I'll see if I can find it and link to it.

-Jim

Found it: http://www.peachparts.com/shopforum/showthread.php?t=131895&highlight=603+nailing

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.

Have you ever tried adding a 2 quart bottle of new VO to the fuel. It might really quiet it down a lot. I love the sound of mine with even such a little VO added. Right off the shelf from the supermarket, either soy or canola or corn or peanut oil. And it is about the same price as diesel. Pour it into the tank and then fuel her up.
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I have two bottles of ransid veg oil that I am temped to use when I fill the tank!
can anyone think of a reason why RANSID oil would pose a problem?

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[B]AlanT
BELEN NM


93 dodge cummins truck~old reliable
01 Volvo AWD XC70 Turbo Wagon
74 450 SE on the way out!
Recent: 1972 Toronado 56k on the clock!

IF it plugs in, lights up, makes noise,
I'M ON IT!

Yes, it usually takes water to have the oil go rancid. Your rancid oil has water in it. Water is bad for the IP and encourages growth in the fuel tank.

__________________
1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.