300D Fuel system debugging... help? - PeachParts Mercedes-Benz Forum

KenC · #1 05-29-2008, 09:35 PM

Hello all

I have a '84 300D which is not starting. I debugged
it enough to know that the reason seems to be that
it's not getting fuel to the cylinders.

My conclusion is based on the fact that starting fluid
will make it run for a couple of seconds. (I know
that's bad for the engine though...)

History of the car...

It was a daily driver for years... then water pump
quit. I let it sit for a year. Put a brand new battery in
and had no trouble starting it!

Took it to the mechanic and refueled it (?different
fuel formula maybe?) and drove it across town.
A few days later it would not start.

So, I don't know where to begin with the debugging
process...

What would you suggest?

I know possible culprits are: fuel quality (algae) or contaminants, fuel pump(s), filters, and injectors,
(fuses?), and maybe more.

If your car had this situation, where would you start, and what steps would you take?

Thank you for any assistance. I love this car, and actually have two others just like it!

If this requires a diagnostic manual / cd I would be
open for suggestions as well.

Ken
Plano Texas

compress ignite · #2 05-29-2008, 10:09 PM

#1. Take the (ALL) containers of "Starting Fluid" (Ether) ...And recycle.
If you think you need Ether to start a Mercedes...donate the car to some
worthy cause[You are not synapse equipped to safely operate the vehicle]

Hint:Ether will burn out Glow plugs...thereby compounding both your problem
and it's diagnosis.

Based on your alleged automotive symptomatology diagnosis,I offer this
solution to your perceived non-operational conundrum.
('keep in mind...your Mercedes may be afflicted with other un-addressed
[possibly fuel system]maladies in addition to your perceived difficulties.)

StarTron disperses bacteria, allowing the fuel filtration system to function efficiently. Reduces all emissions, including carcinogenic particulate smoke. Prevents fuel oxidation and stabilizes diesel chemistry for at least two years. Lowers fuel system maintenance. Eliminates carbon build-up on injectors and exhaust components. Increases fuel economy, especially in older engines. Eliminates moisture in fuel by dispersing it into sub-micron size that can be safely burned off during combustion.

Because it treats water in fuel, Star Tron aids in fuel gelling issues; with the moisture removed, it cannot be converted to ice cystals at low temperatures that in turn can lead to gelling. For severe low-temperature applications, we suggest using a pour-point depressant.

Look for Startron at West Marine or Boater's World.

TMAllison · #3 05-29-2008, 10:38 PM

Change both fuel filters. Check glow plugs following dieselgiant.com turorial for the W123, check for vacuum leaks at shut off, crack metal line at one injector and pump primer pump 50 times minimum or until fuel leaks out, do each in turn, pump and tighten in turn and then try to start.

If doesnt start, set up temporary fuel tank in engine compartment (see DG's stit again under "diesel purge") using fresh fuel, pump primer pump 50 times minimum and try to start again.

If doesnt start look for small fuel leak allowing air to enter fuel system and repair. Most common culprit is the primer pump itself. If you got the old style primer (white top that you unscrew) replace it with the updated pump.

If still wont start do compression test and check valve adjustment.

Charge battery between steps.

KenC · #4 06-01-2008, 08:43 PM

Thank you very much Compress Ignite, and TMAllison for your assistance!

I have some work to do now, and will report what happens!

Ken

t walgamuth · #5 06-01-2008, 11:32 PM

YOu can use wd40 to run a diesel with fuel delivery problems to isolate it to that problem....perfectly safe. Remove the air filter and spray directly into the intake while cranking. If the glow system is good and the compression is good it will run on it as long as you keep spraying.

Its also good if you have run it dry and lost prime really well and good.

Tom W