OM602 no fuel flow... stranded - PeachParts Mercedes-Benz Forum

Devon · #1 08-08-2011, 04:00 AM

I will preface my post by saying I seem to know just enough to make a fool of myself at a repair shop, so I will keep it simple.

My 1993 300D 2.5 with just over 80k is not turning over, acting as if it is starved for fuel. It was working perfectly up until this, driven daily, oil changed every 4-5k, air & fuel filters changed once already. I had run it on B50-B70 for about half of the 20k I have personally put on it, switched back to regular diesel during the last month or so out of convenience.

I go to turn it on a few days ago, begin by turning the key into pre glow position but go a little to far accidentally, cranking the engine over for maybe 1-2 seconds. I quickly turn it back off, because I hadn't let it glow for long enough, set it in pre glow position again until light goes out, then crank engine, but no start up.

Since then the car will crank and crank but no life from it, sputtered for a few seconds on its own power the last time I tried, but that's it.

I have changed both of the fuel filters as it's about all I know how to do (for now). After changing both filters and cranking for a good while (20-30 seconds), I see fuel in the smaller filter as it would normally look (3/4ths full), and when taking off the larger filter again, see that it is mostly filled with fuel. (Probably should be filled to the brim though, right?)

What doesn't seem normal to me is that there is fuel only intermittently flowing through the three translucent lines going between the larger filter and the injection pump. i.e. there is more air than fuel in these lines.

So, please god, in a simple manner let me know what I can look at next!

Thank you in advance!

jt20 · #2 08-08-2011, 04:12 AM

Howdy.

On the driver's side engine mount, directly under the fuel injection pump (IP), there is a little alien monstrosity with numerous fuel lines coming and going from it.

Bypass it. Take the incoming fuel line to that 'alien' (fuel thermostat) and connect it directly to the side of the IP where you see a rubber hose attached. This is the lift pump and can be seen in the very bottom of your photo.

jt20 · #3 08-08-2011, 04:18 AM

once you have bypassed the alien t-stat...

make sure all fuel hose connections are tight but loosen the metal fuel lines at the nut on the injectors by one full turn or two.

Now, crank the engine at WOT (wide open throttle) until you see no air bubbles on the nuts at the injectors. (do not crank for more than 30 seconds at a time)

If you get that far and are happy with the fuel coming out of the hard injector lines, then tighten them back up and try to start.

You should inspect your glowplugs also.

ah-kay · #4 08-08-2011, 11:56 AM

Did you fill up the spin on secondary filter before you installed it? There is no primer pump on the 602. According to the user manual you have to floor the pedal and crank the engine for a long time to start the car.

If the glow plugs are good then try to crank it again. It takes a while if the filter was not filled. Do not crank for more than 15-20s then stop for a while and crank again.

Good luck.

Oldwolf · #5 08-08-2011, 01:02 PM

Devon - Air in the clear lines shown in your picture indicate you have air in your fuel lines. I will assume that since you have run the car on the fuel filter since you changed that the seal is tight.

So where else can air get into the lines?

If you change your fuel tank screen and mixed up the vent and fuel line under the car, air will get into the line once the vent is exposed in the tank.

How much fuel is in the tank?

Check all the fuel hose connections for tightness and also for any splits in the fuel line.

The primary fuel pump should be checked also.

Devon · #6 08-08-2011, 02:27 PM

Thank you all for the quick replies! I feel silly though...

This morning, before actually seeing these responses I gave it another look, and success! I removed & rechecked the primary fuel filter, mostly filled with fuel still, so I reconnect everything & crank with pedal to the floor and laboriously she starts!

Seems I was just too timid in my previous attempts, not putting it to WOT. Should have remembered the amount of cranking necessary from last fuel filter change. Looks like it was a clogged filter after all.

Drove for 20-30 miles after warming up, seems good as new. But now I notice another issue.

Seems there is fuel leaking from below the rear of injection pump, at least from my vantage point.

I took a short video, you can see the glimmer of the drop every few seconds.

http://www.youtube.com/watch?v=0XOxaHJpPp8

Fuel runs down what looks like the mounting bracket facing driver's side and eventually reaches the bottom plastic engine encasement. It's enough flow to leave more than a few drips through the drain hole on my driveway as I backed out and pulled back in after my drive.

Any thoughts?

On another topic. OldWolf, I see you are in Raleigh. Would you happen to know any reputable shops in the Triad area? I am from Raleigh originally but my 300D and I are in Greensboro currently. Would even consider a drive to Raleigh if you could recommend someone near you.

Again, thanks to you all!

Oldwolf · #7 08-08-2011, 03:05 PM

hmm...I can't think of any fuel source back behind the injection pump. So maybe it is leaking form on top of the pump, from one of the 5 injector tube connections. You will have to poke around in there to see what is what.

So far I have been able to do all my own repairs. But there is a very good shop in Chapel Hill, "A Better Wrench" it is called.

sixto · #8 08-08-2011, 09:14 PM

Is it leaking from the pump or from the fuel thermostat?

Sixto
87 300D

compress ignite · #9 08-08-2011, 09:33 PM

Below is a Still from your Video (Blown Up).
Have I captured the drip,just under the outflange That Hex Bolt is screwed into?

sixto · #10 08-08-2011, 09:42 PM

That's the port for the IP lock and timing light. The should be only engine oil on the other side of that plug.

Sixto
87 300D

compress ignite · #11 08-08-2011, 09:48 PM

closes the Inspection Port that allows Injection Timing of the Pump (A/B Light)
Also allows "Locking" the Pump during R+R.

I think the Bolt is in the Lube (Oil)[Lower] Section of the I.P.

BUT, above it is the Manual Emergency Shutoff Lever. (SAYS "STOP" in RED)
It has a small rubber O-Ring (Inboard of the Lever and the "Holding Device" on
the Lever Shaft.)
The O-Ring can:
1. Get "Old" and "Brittle" and Leak
2.If Subjected to enough Bio-"D" get "Gooey" and Leak.

I Believe that's your culprit.

A member here ,who sells Fuel Line,Gaskets and O-Rings in a "Kit" of VITON
NOT RUBBER included a shutoff lever o-ring in the kit I bought.

(At that time we were enjoying Pump Diesel that was 5% Bio-"D".)

sixto · #12 08-08-2011, 10:09 PM

Nope, engine oil behind the shutoff lever o-ring, too.

Fuel might be leaking from the relief fitting on the block side of the IP and dribbling down the IP case below the governor. I think it's an optical illusion and fuel is dripping from the fuel thermostat sitting on the engine mount arm.

Sixto
87 300D

sixto · #13 08-08-2011, 10:12 PM

I take that back. I can see the drip originating away from the fuel thermostat. Must be from the block side of the IP then.

Sixto
87 300D

compress ignite · #14 08-08-2011, 10:30 PM

The Most Logical source on the Block side of the I.P. is the Fuel Pressure Relief
Valve "Banjo Bolt" sealing washer.(And It's Torque)

UNLESS one of the Side Gaskets Between the Side Cover(s) and the Pump Body
is Loose,Damaged or Seeping.

ANY way the Vacuum Operated Fuel Shut Off (On TOP Of The I.P.) O-Ring is
Leaking and running down the Pump Face?

compress ignite · #15 08-08-2011, 10:33 PM

BUT, did you put wrench(s) on the Hard (Metal) fuel line attachment Nuts AT
THE Injection Pump (OUTPUT) ?

(I could almost make a case for an I.P. Delivery Valve O-Ring leak,running down the I.P.)

Those would be the Top Nuts in the below picture.