'87 300D will not start, fuel delivery problem?
 

At the moment my 1987 W124 300D is in the driveway and will not start. The engine turns over and the glow plug system appears to be working properly. It looks like the injectors are not getting any fuel. I removed one of the injector fuel lines and turned the engine over .... no fuel came out. The clear inline fuel filter has fuel showing. The tank is more than half full. The engine turns over as normal. This vehicle has always had a small fuel leak from the injection pump. Could the problem be the fuel pump? If so is there any way to test this part to confirm? All ideas?

Did you get a bad tank of fuel? Has it happened just after filling up? I would suspect a bad fuel/dirty fuel filter type of issue before an IP problem.

I'm not familiar with this engine, but if there was a leak in the pump, could the system need to be primed? I have a vague recollection of a post stating that this engine was self-priming. But I would get a clear answer to this question before proceeding further.

This engine has a self-priming fuel pump system.

How long has it been since you changed the main (spin-on) fuel filter? You should be able to carefully loosen the "banjo" bolt at the front of the injection pump and see fuel spurt out when the car is cranked. I'm talking about the short fuel line that runs from the main fuel filter to the injection pump, with banjo bolts serving as the connection at each end.

This test will tell you whether the fuel pump is pushing fuel all the way through the filter system. If it is not, you troubleshoot back toward the fuel tanks and know its not the injection pump itself. If you do get fuel at this place, you know its not the fuel pump or filter system, but something related to the injection pump.

If you know the main fuel filter is due for a change (30,000 miles service interval) then I'd suggest you avoid disturbing the banjo bolts and just try this test with the old fuel filter removed. You should get fuel pouring out the filter attachment bracket. Just put the new filter on (better to fill it with fuel) and try starting the car.

The higher chances are with a clogged fuel filter, bad fuel pump, or broken / cracked fuel line somewhere.

Ken300D

I had to replace the suction side fuel lines on my 300D this summer, they were leaking and also allowing air to get sucked in. Check all the lines from the standpipe to the fuel lift pump on the side of the IP.

I'd bet you have a combination of clogged filters and leaking lines, so you get only air delivered to the injectors, and no start.

I'd also verify that the shutoff lever is all the way up and not stuck down.....

Peter

Thanks for all the prompt replys. OK I checked and replaced both fuel filters. The main (spin-on) filter was almost empty of fuel, so I filled a new filter with diesel purge (did not have any diesel fuel handy) and put it back on. The clear in-line prefilter was also almost empty. I filled the in-line filter also with diesel purge. When I checked the prefilter a couple of days ago it was two-thirds full. Before replacing the spin-on filter I unscrewed the fuel line going to the filter from the primer pump and cranked the car. No fuel came out of the banjo bolt. With all the attempts to crank the engine I have run the battery down. I have it on a charger now. It looks like there is a fuel delivery problem. Any further suggestions?

You don't have fuel coming up from the tank.

Take the tank filler cap off -- do you have LOTS of suction (not pressure)? If so, tank vent is plugged.

Blow some compressed air GENTLY down the suction line with the cap OFF. If this temporarily fixes the problem, you need to get the tank clean, it's got lots of algae. If it only hisses and doesn't bubble, the guage is bad and you are out of fuel! Car wont' start then....

Make SURE the suctin lines are good -- the old style fabric covered ones go bad under the fabric. Hoses wet with deisel have holes in them, letting air it.

It's going to take some cranking to get fuel up after it's completely dry.

Peter

Out of curiosity, is the engine stop lever on the IP fully in the 'run' position or perhaps stuck in the 'stop' position?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

His problem seems to be happening in the fuel line system before the stop lever. The stop lever is an injection pump device, and he's not getting fuel even to the filters.

So its got to be bad fuel pump, or more likely bad fuel line, clogged fuel strainer in the tank, or clogged vent, or out of fuel, as previously mentioned.

You can test the fuel pump by providing a supply of diesel from a jar with a section of fuel line pushed down in it, and then connected to the pre-filter. Or a can of diesel purge would work too. If it comes to that - this might not be the desireable first test.

More important to verify fuel level and lines.

Ken300D

In answer to some of your questions:

• *fuel level is OK, at least half full tank
  *engine stop lever is in the run position
  *fuel lines in engine compartment appear OK, no leaks
  *removed tank cap no significant pressure/suction
  *did blow some compressed air down the suction line and fuel ran back out the line after the air hose was removed

Still does not crank. I will try using a jar of fuel at the prefilter as a test tomorrow. Thanks to all for your help. I will report back later.

OK, here is the latest. If I disconnect the line going to the in-line prefilter, fuel will flow freely out of the line from the tank, so I don't think the problem is the tank or fuel line from the tank. If however I disconnect the line on the spin-on filter coming from the fuel pump on the side of the injection pump and turn the engine over no fuel will come out. It appears to me that the fuel pump is not working otherwise, with the line disconnected, fuel should squirt out. Other opinions?

You seem to have done a good job of narrowing down the problem.

Now its a matter of being a bad fuel pump, a pretty big hole in the fuel line between the pre-filter and the fuel pump, or whatever part drives the fuel pump is broken.

I haven't done a MB fuel pump yet, so I don't know how integrated it is into the injection pump assembly - and if it is a replaceable sub-assembly.

One thing I'd suggest you do before any substantial fuel pump disassembly, and that is to replace the fuel line temporarily between the prefilter and the fuel pump. Or take it off and pressure test it somehow. I'd hate to see you replace a component only to find out its a bad fuel line.

Ken300D

Success! I replaced the fuel pump on the side of the IP and the car will now crank. But now I have the opposite problem -- the engine will not shut off. I suspect a vacuum problem with the shut off on the IP. The engine can be shut off using the manual "Stop" lever.

Found a vacuum line that had been disconnected. Reconnected it and everything is fine now. I think the fuel pump correct the original problem, however each time that the car would not start it would be after setting overnight. We will see if in the morning all goes well. Thanks to all for you help.

Found a vacuum line that had been disconnected. Reconnected it and everything is fine now. I think the fuel pump correct the original problem, however each time that the car would not start it would be after setting overnight. We will see if in the morning all goes well. Thanks to all for you help.