I have posted this before but the deal has now gone through and I am getting my Mercedes G350DT tomorrow. This is the 3.5 liter 6cyl diesel It is a 1994 so it is pre-electronic(I am aware of the problems with this engine, they have all been addressed) My question is to the Mercedes blenders. I live in Texas, it is pretty cool here now night time temperatures can get down to the high 20's at times but on average it is in the mid 30's at night and 50's-60's during the day. It will be close to this for winter. On my 6.2 diesel I was blending with a heated fuel filter and liked the idea of the heat, this eliminated the usage of rug for the blend due to vapor lock. So I am wondering how I should go about blending in the Mercedes? I know these engines are great with the WVO but what about the fuel pumps? I am not talking about the injector pump but the fuel pump. On my 6.2 I installed a Raptor pump with and internal pressure regulator, it was a great pump. Is the Mercedes pump up to the viscosity of the wvo? And the heat if I decide to run a heated system? What fuel pressure should I be running at the IP? I plan to add a pressure gauge between the filter and the IP so I can keep up with what is going on. Speaking of the filter, how is the Mercedes filter with the WVO? How hard are they to change and how expensive are they? Would it be worth changing to a more common WVO filter?
Rusty

quote:

Originally posted by rtarh2o:
My question is to the Mercedes blenders. I live in Texas, it is pretty cool here now ... So I am wondering how I should go about blending in the Mercedes? I know these engines are great with the WVO but what about the fuel pumps? ... Speaking of the filter, how is the Mercedes filter with the WVO? How hard are they to change and how expensive are they? Would it be worth changing to a more common WVO filter?

Rusty,

The stock fuel filter on your car is 5 micron, and I think that is an absolute, not a nominal rating. Whether you want to replace it or not depends on how meticulous you are with your WVO. If you do replace it, do try and keep the cigar shaped return line. I have NO idea why M-B engineered this way, and it runs fine w/o, but every merc mech I know yells at me to not use straight line. ?. Something about the pulsing of the flow?

On my older 123 chassis I have removed the stock main fuel filter and replaced it with a (coolant lines and mild electric heat exchange) heated DavcoTec 234a. This also includes a water trap which I don't think your car has. You might consider adding one, lotsa older Merc owners do. I like the Davco becasue the filter elements come in 2 and 3 micron ratings. They are not a kit making company. They make products for diesel fleets. Very reliable and excellent customer service.

You might also consider adding another in-line pre-filter or two - the see thru ones. I like to have one right before the IP, one right after the send line and one right before the return line.

I am a big fan of see-thru options! This lets me evaluate all points of the flow. I once solved an extremely troublesome backpressure problem on a heated twin tank system with a looped return ONLY because I had see thru lines to troubleshoot with (and some foreceps to crimp lines). No matter what the owner did, VO would pour back into the diesel AND the other way around I used red-dyed off-road diesel and was able to trace the flow and solve the problem. Turned out to be a hack install of an overly engineered kit. Not the first I'd seen, likely not the last but I was really gleaming when we got it running right

In those kinds of temps, see how long it takes to cold start on ULSD and note the exhaust. Use that as a baseline to evaluate your blends. I was just travelling in similar temps and decided to add 10% RUG to my 75%SVO tank/25% and see if it made a difference on starts, performance or efficiency and I didn't notice much of any difference except that the gas mileage went down over a couple hundred miles of highway travelling.

I have worked on your vintage model for folks WVO fueling and have never seen a problem with fuel pumps. The IP, as you know, is a very robust Bosch (Did you know they are the world's largest NPO!) product. I have installed a lift pump with my Davco Tec, nothing special and I have never bothered checking the actual effective pressure on my ride. Especially if you are blending and not using heat, gravity should do all the work for you. Just make sure the tank and fuel system is properly ventillated and the filters regularly changed. I use compressed air to blow out the hard lines, send return and vent.

You might also try posting your Merc specific questions to the biodiesel.infopop forum over here:
Diesel Vehicles and other equipment: Mercedes

There is also this great Merc resource:
http://www.mercedes.cx/archives/

And I also like this mailing list:

mercedes@mercedesmailinglist.com

But I find that the Mercedes Benz Club of America and their forum

http://mbca.cartama.net

is second only to talking to the mechanics at the dealership or independant, certified shops. For your '94, I wouldn't bother taking it to anyone born after 1974. The 35+ mechanic crowd will likely get you someone who may have actually worked on these cars when they were first introduced. Possibly even fell in love with them

Good Luck!

quote:

Originally posted by rtarh2o:
On my 6.2 diesel I was blending with a heated fuel filter and liked the idea of the heat, this eliminated the usage of rug for the blend due to vapor lock.

Jeffrey might take this as further proof of my "fillibustering" against RUG blenders (LoL!! ) but I recently read on-line about the dangers of storing diesel/gasoline mixtures. I am not saying this means it is recklessly irresponsible to use RUG/VO blends, but I was surprised to hear that RUG/diesel blend vapors are, apparently, much more flammable than the individual constituents (kind of the same way that alcohol and water have lower boiling points when mixed together?) My readings went on to say that diesel tanks are not designed to handle the extra vapor pressure of gas/diesel blends. I'm not saying this is true, but possibly this explains the tendency towards vapor lock some RUG (or other low boilers) blenders here have experienced in their heated systems? If your tank vent is clogged, this would exacerbate the gravity delivery even more.

I have a small 12V lift pump installed just prior to the Davco in the engine compartment (on the drivers wheel well). I have seen some people install these right where the tank send line is in the back, under the car.

Aloha!

Rusty,

If I recall correctly, you said the car has recently been serviced. I forget, does your 6 have mechanical or hydraulic valve lifters? Either way, if the clearances are within spec and the fluids and filters have been attended to, I would check the tire pressure and start with a coast down test to determine your current maximum POTENTIAL efficiency (miles per gallon)

Check out: http://unwiredtools.com/utcoastdown.asp
and take your ride to a weigh station to get it weighed. The weight and the average of 70-60 coast down times will help you determine the max fuel efficieny of your car.

Now, test the ACTUAL m.p.g. How far off are they?

IF the POTENTIAL m.p.g. is really far off from either:

1) the manufacturers estimates for the E.P.A.

or

2) your ACTUAL m.p.g.

then you will want to start troubleshooting. I would start with the wheel bearrings, brakes,alignment and toe-in.

All this will give you a good baseline and help you to evaluate thecondition of the car before you start adding the variables of unregulated fuels.

Once you've done this, get an idea of your performance and note you 0-62 times on a straightaway and evaluate how that performance test changes with your fuel blends.

Lastly, make a mental note of how long it takes to turn the engine over in the cold on ULSD first. Also note the emissions.

By the time the weather warms up you will be in a great position to make educated decisions about what will work best for you.

I look forward to hearing about your successes

Aloha!


FROM: http://unwiredtools.com/utcoastdown.asp

"Coast Down Power Test

This tool calculates the amount of power needed to move a car at a steady speed as measured in MPG. This tool is useful for measuring the total power load and thus MPG capability of the car.

Power produced by the engine is used for/consumed by:

1. Accelerating
2. Going up hills
3. Aerodynamic drag
4. Overcoming mechanical friction including:
* Drag due to toe-in. (Learn more about toe-in)
* Wheel bearings
* Tire rolling friction
* Brake drag (if any)
* Drivetrain friction

Many cars are capable of getting far better MPG! This tool is intended to help identify problems which cause excessive drag and friction. This tool uses a measurement of how long it takes to coast from 70 mph to 60mph. This duration (in seconds) is used to calculate the total power consumed by aerodynamic drag and mechanical friction.

Here's how to perform the test:

1. Find a level strech of highway.
2. Accelerate to just above 70 mph then put the transmission in neutral.
3. Time how long it takes for the speed to decrease from 70 mph to 60 mph.
4. Repeat the test in the opposite direction and average the results. This will serve to cancel out any effects due to wind or slope.
[the integers entered are hypothetical]

Weight of the car, including the driver and any passengers (lbs) 3595
Starting Velocity : Vstart (mph) 70
Ending Velocity : Vend (mph) 60
Time to get from Vstart to Vend (seconds) 12

Horse Power consumed by your car is 23.652
Miles Per Gallon = 30.739"

Note, the test presumes that you have attended to any mechanical or fuel delivery issues first.

Replace the engine.

The engine was just rebuilt, I know all the history with this engine and I find it hard to believe it could be as bad as everyone says. I spoke with a Mercedes mechanic (actually from Germany) who used to own a 350 in a sedan, he said not to believe everything you hear about them. Most people can get over 100,000 miles with them which gives me alot of time to figure out what to do.
Rusty

The rodbender OM603 in my 350SDL lasted 240K. When it died I dropped in a 3.0L OM603. Same engine with a slightly smaller displacement. Not that hard to find a 3.0L version and you can rebuild it yourself if so inclined. You will loose a small amount of low end grunt with the 3.0 over the 3.5 but it more than makes up for it when the turbo spools up.

Everything from your 3.5 will bolt onto the 3.0 so no need to scrounge odd bits and pieces. Best thing to do is find a short block 3.0 and put your newer head from the 3.5 on it.

Anyway, U have lots of options if it ever pukes a rod.

HTH,