bio fuel and injector pump - PeachParts Mercedes-Benz Forum

John Schroader · #1 02-26-2007, 03:24 PM

I'm wondering if this is coincidence or there's some connection. Been running bio in my 300D for about 3K miles. Vacuum shutoff quit working recently. I've read that bio (w/ alcohol remaining) is hard on rubber parts. I sometimes wash my bio, sometimes don't . Think the alcohol may have contributed to the failure (or does the vacuum shutoff even touch the fuel)? Or ----- are there any parts in the vacuum shutoff that alcohol would damage?

BPaulsen · #2 02-26-2007, 03:44 PM

What matters is the quality of the fuel you're using, whether it's gasoline, dino diesel, or BioDiesel.
If you're using home-brewn Biodiesel, made from WVO in high concentration, perhaps even 100% . . . yep, that could be the cause of the problem.
That said, your '83 should have none of the "rubber" problems owners of pre-'80 Diesels have to expect. Slowly introduced to a good quality BioDiesel, with frequent fuel filter changes, your car should run fine.

rackley · #3 02-26-2007, 03:48 PM

Biodiesel dissolves rubber. It is an extremely good solvent. Any component that is not Viton (including fuel line and any and all seals) WILL dissolve, especially if you're using 100% Biod. That's why the stuff they sell at the pump is B5, not B100. Most of the newest cars have Viton or other BioD compatible compound throughout, but the older ones certainly do not and replacing all the fuel lines and seals with Viton (if you can) is a must if you're going to run B100. The only other alternative is to skip all the hassle involved and just burn straight WVO in a properly designed 2-tank conversion (no Lovecraft or Greasecar stuff.)

Thanks,
Ray Ackley
www.vocontrol.com

John Schroader · #4 02-26-2007, 04:07 PM

This homemade brew is good quality. In the spirit of scientific experimentation, I run unwashed in my IH 7.3 (305K miles) and washed in my 300 D (195K miles). Regular filter changes in both. Both have performed beautifully. I changed the fuel lines out on my old 7.3 prior to running bio. Have done nothing but keep a close eye on the 300D. Just not real certain whether my vacuum switch or whatever plunger it closes are affected by the bio.

BPaulsen · #5 02-26-2007, 04:12 PM

Oh . . . those urban legends. They live on and on and on . . .

I have several friends who run home-brewn Bio, at 100% in their cars, such as W123 as early as 1977, W124, Cummins-powered Dodges, Jetta TDI . . . for many, many years, and literally tens of thousands of miles, without as much as a hickup.

Yes, there are issues with non-restistant rubber parts on pre-1980 cars though, which can be solved for about $50 bucks.

There's a guy on eBay who specializes in parts and manuals for old Mercedes Diesels. While I usually don't endorse such sellers, this one I do. Learn by checking out his Web site:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=008&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=180088212675&rd=1&rd=1

jshadows · #6 02-26-2007, 04:13 PM

Quote:

Originally Posted by John Schroader

I'm wondering if this is coincidence or there's some connection. Been running bio in my 300D for about 3K miles. Vacuum shutoff quit working recently. I've read that bio (w/ alcohol remaining) is hard on rubber parts. I sometimes wash my bio, sometimes don't . Think the alcohol may have contributed to the failure (or does the vacuum shutoff even touch the fuel)? Or ----- are there any parts in the vacuum shutoff that alcohol would damage?

Have you verified that this is not related to another leaking component in your vacuum system? Any leak in the system (e.g. climate control, line to brake booster, etc.) can and will affect your engine shutoff. I know this from first hand experience. I thought for sure my valve was toast until I started plugging lines realizing that I had a significant leak in the feed to the ACC.

Most members here agree that viton lines is overkill for running even b100. While it is a solvent of natural rubber, most more recent fuel systems hold up quite well to b100. Even the old ones do well too and should last much longer than 3000 miles. I replaced my engine compartment rubber with the kit from DieselGiant as well as my return lines because they were well aged anyway. My tank fuel lines are still holding up with no signs of weeping.

Verify if there are other vacuum leaks for starters before condemning the shut-off. Shut-off valves do fail over time too and this may be wholly unrelated to biodiesel use.

John Schroader · #7 02-26-2007, 04:25 PM

Pretty well certain it's the shutoff. Replace the transmission modulator and all others hold vacuum well. Have ordered a new shutoff from Dieselgiant and am awaiting its arrival.

probear · #8 02-26-2007, 04:39 PM

I would definitely wash at least once. To make Bio-D, you run a concentration of 20-22% Methyl alcohol, while the actual reaction takes less. You will always have some excess Methyl alcohol unless you did not have enough initially, and then, you will end up with an incomplete reaction.
The other alternative is to heat the fuel to 140F, which will vaporize any remaining Methyl alcohol. As usual, beware of the fumes, especially from unwashed Bio-D.

bgkast · #9 02-26-2007, 05:12 PM

To answer your question, no..I don't think the shutoff diaphram contacts fuel. Careful when you replace the diaphram. Read up on the procedure and runnaway diesel!!!

John Schroader · #10 02-26-2007, 05:28 PM

OK, many thanks.