I'm finishing the suspension repairs and am moving onto the filters and other driving concerns.

Should I pre-emptively remove and clean the strainer in the fuel tank, or drive the car for a while and see whether I'd be fixing something that isn't broken? Should I take advantage of the near-empty tank (fuel light on) and remove it and clean it out of algae or other crud? I'm new to diesels, so the concept of algae in the fuel tank is completely new to me.

More info about the car:

'83 300CD w/ 283,000 miles
No history of WVO or biodiesel that I'm aware of.
Maintenance records and history are a bit schizophrenic - I was provided extensive records showing lots of routine maintenance was performed, but in those same records I saw where the PO opted not to do the difficult or expensive repairs - e.g. he had a repair list where he crossed off the LCA bushings although they were obviously gone, but went ahead and did other minor repairs as documented by the garage work order.

The car allegedly sat for about a year, but was then driven on a multi-hundred mile round trip from San Antonio to Del Rio and back right before I bought it, so I'll assume any old fuel was blended with new and burned off or greatly diluted.

The car starts very strong with no hesitation and little-to-no smoke, even after having sat on jack-stands in my garage for about 45 days. I plan on a complete R&R of the filters along with a diesel purge in the near future.

Any recommendations for a specific sequence of fuel system maintenance? Start with cleaning the tank and then working forward to the engine?

There is no current evidence the fuel tank filter is obstructed. Since you may be chasing other faults for awhile you can defer the cleaning of the tank filter in my opinion.

If you want to just check the tank filter no harm is done either. If the fuel feed hose is disconnected at the back end and fuel flows very freely from the tank I would not bother. Save the time and effort for other items that initially show up.

Primary and secondary filter changes are just good housekeeping though. Unless the last owner just reciently changed them to your knowledge.

When I removed the tank screen, after nearly 25 years, it was sparkling clean. If you do a biocide treatment and don't notice any changes in the primary filter (clear) then chances are you don't need to go to the trouble. If the car has been, primarily, in the San Antonio area, fungus/algae may not be as big of a concern as other parts of the country where a more humid climate makes it a little more prevalent.

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Sam

84 300SD 350K+ miles ( Blue Belle )

If the Tank is empty and the Hose that hooks to the Tank Screen is the original you might want to change it now; just because it is a pain to drain the Tank later if you have to do that job.
File or grind off the crimped on Collar that holds 1 end of the hose to the brass fitting and just replace it with a 5/16 section of fuel hose and a hose clamp. Overall cost about $3 or so.

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84 300D, 82 Volvo 244Gl Diesel

I think for the time and cost (0) you should pull it. I think it makes a good barometer on what the fuel system is like. Right now you are guessing and wondering, I did the same when I got my 83 300D with no records. I finally pulled the screen after about 4 months and it was spottless. Good piece of mind and now I can move on to other unknowns. I wish I had replaced the hose but oh well I wasn't thinking. Thanks

X2 especially if you plan to run biodiesel at some point.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

I'll chime in with if the tank is not causing problems, leave it alone.
I'll also suggest doing a purge, then change filters. You'll be low on fuel again in the future if you decide to drop the tank.
If any suspension bushings are toast, you'll be going through tires quickly (at best) until they're replaced.

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83 SD

84 CD

I'm from the "if it ain't broke, don't fix it" camp as well.

Unless you are trying to do some kind of unsupported marathon trip, leave stuff alone if it's already working properly. Those under-tank fittings can be a real PITA anyway.

Just drive it and enjoy it.

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner

I had two questions on this same topic:

1) just bought a sweet '79 300D in great shape....the owner said there was moss in the bottom of the tank. I'm guessing it is an algal bloom. Anyway, the guy was aware of every fine detail about the car so I'm inclined to believe him. What's the best way to rid the tank of the alge? If I use a biocide, does it just push the stuff thru to the filters or should I use a biocide with little fuel and then drain in all at once thru the bottom?

2) my other car is a '85 300TD....when I get to about a third of a tank, I notice it runs, not rough, but in a way that the car shakes more than normal. At this point, if I go up a hill the car will die but start back up with some effort. The lower the fuel level, the worse the problem. Once I fill it up above 1/3 of a tank, the problem goes away. I've ruled out clogged fuel filters by changing both of them. Does this sound familiar to anyone?

Thanks -harv

Yak,

I think it is a great misconception that this is a very likely cause for a clogged strainer.....but it is true..in a way...let me explain.

One of the effects of using Biodiesel or WVO(properly filtered)/SVO is that it cleans the tank, so that any algea will loosen and clog up the strainer. So yes it is the cause...but not the root-cause in my opinion.
I think a car that has been powered by bio has a much cleaner tank from the inside than a car that has not...unless the previous owner has not taken care to clean the strainer.
This is what they can look like:

Cheers,
Ingmar

Attached Thumbnails

 

Plugged tank vent Try cracking the fuel cap and see if there is vacuum present when it next happens. You will hear a whoosh of air if there is a vacuum.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

I'll probably take a wait-and-see approach, but I may change the fuel hose. It's not my daily driver, yet.

I did some research on diesel algae and came up with the following link (...brief, internet research - so it must be true!)

http://www.dieseldoctor.com/messageboard/data/584.html

The info does eventually market a specific product or treatment, but I did learn that diesel "algae" isn't algae, per se, but sludge and by-products. Assuming the info is correct, it's a good "Diesel Fuel 101"

Sample info: "There are three basic areas of concern in fuels and oil. They are: 1. water 2. in-organic debris (sand, dust, rust, etc.) and 3. organic debris (fuel breakdown products and waste products of fuel deterioration and re-polymerization). The organic debris represents more than 90% of all the contaminants found in fuels and oil. It is this organic debris, the sludgy, slimy, acidic material that people refer to as "diesel fuel algae". It could also be called polymer, tar or wax and asphalt!

---------edit, another sample---------

4. Can diesel fuel plug your filters?

Yes, it can. The stuff that clogs your filters is actually fuel in some way, shape or form. In excess of 90% of this organic debris are fuel breakdown products. It is not sand, dust, stones, rust or in-organic matter that blocks your filter.

The inorganic material like sand, dust and other particles will not cause your filters to clog. In fact, a lot of sand in a fuel filter would act as extra filtration. The pores between the sand particles are much larger than the pores in a standard fuel filter element. Sand filters are commonly used to filter water. A hair is approximately 40 micron and fuel filter elements range all the way from 30 micron for a prefilter to 2 micron in a fine filter."

Again, I'm not saying this is accurate (since I'm not a petroleum engineer) but it's interesting stuff and worth a quick look if you're having fuel problems.

Yak

Lots to check out here starting with volume of flow from the tank when fuel level is low. Take a minute to make sure someone did not swap the pickup and return lines. Also I would remove the gas cap and blow compressed air back down the line from the engine compartment. Or do it when the rear hose is disconnected for the fuel flow test.

If those check out and there is a chance they will. You then get into things like rock hard or missing cigar hose, Lift pump rebuild with a ten dollar kit, Open relief valve on the pump.

My opinion is that it is a possible error to leave a situation like yours existing too long. There are many other side effects in not having fuel supplied at the proper pressure. If a 616 four cylinder even more so. I also believe it is wise to have a fuel pressure gauge permanently installed to monitor the base fuel pressure in the injection pump. If for no other reason than to tell you when filters need changed.