engine knock at idle - stopped w/biodiesel

[BillA]

After putting ~$1k into my '84 SD (did adjust valves, 8 with 0 clearance; did not change the nozzles, did Diesel Purge - to no effect), it (still) had a very nasty knock when cold; and when hot and stopped in gear with the AC on - the same knock. Shutting the AC or putting it in neutral would eliminate the knock when hot.

So I put B100 in it diluted to ~B75, and I have no more knock when hot, and greatly reduced when cold (I let the engine warm up before taking off).
So I put B50 in the '82SD and it too had an amazing reduction in engine noise, though the blowby is still horrible.

Why is this happening ?
Different combustion characteristics ?

[TMAllison]

You've expirienced the lubricating effects of BioDiesel on your IP and injectors.

Both my diesels quiet down with Bio although I dont run anything greater than B20 in the older one as Bio can detriorate the rubber fuel lines causing them to fail (as well as scrub your tank clean and clog your filters) at higher blends.

I typically use a splash of Redline 85 in each tank to accomplish the same when not using bio.

[BillA]

I diluted the B100 to try to preclude plugging the in-tank screen, part of the $1k (for each SD) was changing all the rubber pieces in the fuel sustem.

The biodiesel is 25mi from me so it is not economical despite being ~20¢ cheaper.
How much does a "splash" of Redline 85 amount to ?

[TMAllison]

It is ~$5.00 a bottle and is good for 10-12 tanks.

I've also used as little as 1 quart of b100 per tank and gotten similar results.

Originally Posted by TMAllison

You've expirienced the lubricating effects of BioDiesel on your IP and injectors.

I don't know about "lubricating effects" but I believe that BD does have different combustion characteristics than petro diesel. BD has a somewhat lower heating value, and burns more slowly, which will tend to reduce injector nailing at low rpms. If you are getting significant nailing with petro diesel, consider having your injectors serviced.

[blueranger]

my car runs better on wvo also...

and no longer smokes...

[Jadavis]

Originally Posted by TMAllison

Both my diesels quiet down with Bio although I dont run anything greater than B20 in the older one as Bio can detriorate the rubber fuel lines causing them to fail

I have the viton lines and clips on http://www.fryerpower.com/store/page11.html for the IP return lines. They are typically the first to go.

Originally Posted by TMAllison

(as well as scrub your tank clean and clog your filters) at higher blends.

I am in the middle of that right now! 220,000 worth of junk in the fuel tank is coming out at an amazing pace. On my last trip up to Ohio and back (500 miles each way) I went through a filter each way. Before I do the run again I am going to hook up a small AC powered gear pump that I have to the tank return line (suction side) and the tank supply line (discharge side) to back flush the screen and help clean out the tank. I have a filter housing with a 1 micron nominal sock/bag filter on the discharge of the pump. That should catch any junk the pump pulls out of the tank. Then I want to run the discharge down the filler neck to help clean up the bulk of the tank. Those sock filters are about $4 including shipping and can be partially cleaned. The Spin on filters are $10-$17 at any of the places I have found them. I should have done it a long time ago.

-Jim

[Old300D]

Originally Posted by Craig

I don't know about "lubricating effects" but I believe that BD does have different combustion characteristics than petro diesel. BD has a somewhat lower heating value, and burns more slowly, which will tend to reduce injector nailing at low rpms. If you are getting significant nailing with petro diesel, consider having your injectors serviced.

I agree with that. Bio (and veg oil) will cover for worn injectors to a certain extent. But to get best performance, get some injector work done.

[BillA]

I was hoping to avoid this, guess I'd better schedule it; I presume 180k is a reasonable interval.

Any suggestions as to the advisibility of simply taking the injectors to a shop for a cleaning/rebuild (several in Houston), or should I buy Bosios (sp?) and then have the same shop pop test them ?