Hi All.
I am working my way though a list of fixables on my my '84 300TD wagon, and trying to only have one or two questions per post. I am a reasonably competent mechanic. However, other from having always wanted one, I don't really know very much about these very fine old diesels.

I am trying to diagnose how to get my fuel consumption up from about 21-22 mpg up to around 35 mpg.

I drive my wagon A LOT -- about 120-150 miles every day, six days a week. I am a roofing contractor who is stuck working pretty far from home for a season. I have a happy 20' ladder strapped down on a nice Yakima roof rack pretty much all the time:


I assume the ladder eats up one or two MPG. I tend to drive some what heavy footed, and that also affects my numbers. But even when on long road trips at a steady 70 mph, (without the ladder) I am still only getting about 24 miles to the gallon.

I have noticed an occasional little puff of smoke on cold starts, and sometimes when slowly driving home at night through Austin traffic, I can see a humble hint of haze in the glow of the tailgating headlights behind me. At a stop light I can sometimes smell the presence of diesel smoke.

In addition to this, I have occasionally experienced the sensation that the engine is being starved for fuel -- it will bog down for a moment, and I will loose acceleration. This will last for two to five seconds, and then will pass. It feels like a fuel restriction that gets cleared....

I have recently replaced and verified the correct routing of my vacuum and fuel lines, also replacing the fuel filters. (I have some slightly confusing extra plumbing from a WVO set up).

And, yes the car is set up with a pre-heated dual-tank WVO conversion. I currently have it disconnected as I sort through some other issues.

Using my GPS I have verified that the speedo and odometer are more less accurate, even though I have seen the odometer trip meter get stuck a few times.... Nevertheless I most often get an indicated (+/-) 310 miles per 14 gallon fill up. About 22 miles per gallon.

The engine in general sounds reasonably smooth, and there is little visible blow-by when I remove the oil cap.

So here are my ideas to try to get the car to a baseline from which I hope to take steps to improve the fuel economy:

1. Drop and flush the fuel tank, replacing the pre-filter screen. I suspect there is up to a gallon of crap in there. I'll service the failing fuel level sensor while at it.
2. Flush the fuel lines and replace the filters again.
3. Remove and rebuild the injectors. I don't know if these are serviceable, but I believe I have access to an ultrasonic cleaner, and I am pretty good at rebuilding motorcycle carbs..... so how hard can it be?
4. Verify timing and valve adjustment.

That's pretty much my plan, even though it probably will be another week or two before I get started. Because I work such long hours right now, I need to be careful to only take on an afternoons' worth of work at a time.

I currently am going about 840 miles a week. At 22mpg (costing about $3.00 per gallon) I am spending about $115 a week on diesel. If I could get the fuel economy up to 30 mpg, it would save me about $140 a month in fuel cost alone. That is quite an incentive to me.


So I am interested in whether or not 35mpg is a reasonable expectation, and I am open to any tips and suggestions to help me get there.

Thanks for the input.
-Steve