Intermittent non-starter (Fuel flow back?)

[Mloclam]

Greetings all.

My 2002 C220 suffers from an intermittent problem, sometimes it is more intermittent than others. On occasion it just won't start. The problem is overcome by squirting "Easy Start" up the air intake after which time it sometimes starts immediately, sometimes it takes three or four attempts as it coughs and splutters into life. It seems that the fuel is draining back into the tank over time. On four occasions in the last 2 years the car has been more stubborn and the battery has flattened before the engine sprung back into life. Currently the car is failing to start maybe once every two cold-starts, it previously went several weeks without issue but before that was worse, it is unpredictable. The problem may "go away" again at any time but now seems like a good opportunity to find the less-intermittent problem.

I have had three separate garages look at the car and have had glow plugs replaced (the light was staying on), a corroded injector bolt tapped out and replaced and on one occasion a local garage simply started the car successfully twice a day for over a week and couldn't replicate the fault. I'd gladly take a recommendation for a garage or individual (in or around Bedford or Glasgow) that will be able to diagnose and fix the fault for me with some discernible enthusiasm.

Here is what I know about the issue:

1) Once the car starts it has never cut out or failed to restart after a short shut-down (eg for a refuel or meal stop)
2) I don't believe it is a problem with the breather pipe - I suspected this and for a time left my engine running for a couple minutes with the fuel cap removed and also removed the cap before attempting a restart the next morning - the problem persists.
3) The problem persists regardless of the fullness of the fuel tank - it fails when the tank is full, nearly empty or any condition in between.
4) It transpires that about half the time my car is in "Limp-Home" mode (??) I didn't notice as I drive sedately and limp home to Glasgow every week at a steady 80 mph on the cruise control! There are no displayed error codes and I don't know that the cause of the limp-home mode is related to the non-starting issue.

I used to have an old citroen that had an inline, hand pumped bladder valve. Could I add something like that and simply top the fuel filter up before attempting to start the car?

When I lift the bonnet I see a collection of dirty lumpy metal and plastic objects. That's about the extent of my mechanical knowledge. I can see a shiny cylinder with what could be two fuel pipes entering the top. I am guessing this is the fuel filter.

What I think I should like to do is locate the fault by blanking off the breather to the tank, adapting the fuel cap with the addition of a schraeder valve so I can raise the pressure in the tank by a few psi and look for a leak. But I really don't know the arrangement of the plumbing.

Any practical suggestions for how I might be able to identify and fix the fault greatfully received.

TIA

 

[a111r]

Air ingress. Sounds like it needs new O rings on the fuel pipes, or new fuel pipes.
If those garages had ever worked on MB diesels, surely they'd know that?
Take it to a good Indy.

 

[Benzowner]

Agree with above, worth even having a go yourself, parts are relatively cheap for a Merc and easy to fit. Have a look under the bonnet at the fuel lines, there will probably be air bubbles in them.

 

[Mloclam]

Thanks both. Does anybody have a link to an under-the-bonnet photo that shows the run of the fuel lines?

 

[a111r]

Remove the engine cover, usually 4 bolts, and you'll see them at the front and right of the engine.

 

[Tuercas viejas]

If you like to read this I can add.
You are most likely having a very small leak at the filter. Since on it's underside is a water in the fuel sensor and a small drain thumb screw sealed by a very small O ring.
This leakage causes a void in the fuel line and the mechanical fuel pump found on the front of the engine can't pull the fuel up fast enough during normal cold start cranking.
A whiff of ether causes the engine to speed up faster to pull the fuel and you get a start.
To detect if you have a leak simply locate the fuel filter and run a dry finger under the filter around the sensor or drain plug. If your finger is wet upon removal it is leaking and needs rectifying to resolve the problem. In short it's failed the wet test which should always be conducted before the car is handed over after service.

As a precaution there is often a small black looking box affair on top of the filter which has two hoses connected to it.
These are return lines and inside the box jointer is a small ball and spring seat which is there to maintain residual line pressure.
It often gets misplaced or the spring collapses. Under initial cranking it causes losses of pump lifting action.
Remove the two self tap screws holding it in place and twist it off to inspect. Replaced it if defective or suspect, cost is minimal.
Finally as an overview look at the fuel lines especially at the mechanical lift pump (these are sealed by O rings and held by plastic claws). Any broken or cocked sideways?
The other can be at the HP pump itself (the black looking affair below the lift pump). These pipes are sealed by flat sealing rubber like sealing washers. These over time can get flattened out causing leakages. All often overlooked
All the best
Tuercas viejas

 

[Mloclam]

Thank you a111r & Tuercas Viejas . . . I think this is the filter in the picture below? I will go see what I can find at lunch time. a111r - could you please point out the cover you suggest I should remove?

 

[a111r]

No. Because it's already been removed.

Yes that's the filter.

 

[Mloclam]

Thanks - that explains why I couldn't figure out what to remove But still a little confused, where might I see air bubbles that Geoff referenced? I only see black hoses?

 

[a111r]

Pull back the black corrugated tubes. Underneath them lie the clear fuel pipes, the home of bubbles.

 

[91dm]

If you look at the center of the picture, the primary pump that has two pipes on the right. That's a good place to start with replacing the o-rings, I find it's usually the two that go the first. 5min job to change.

 

[Mloclam]

Thanks a111r, Geoff . . . there are indeed bubbles. The car started fine anyway but it was parked only for 4 hours. Tuercas Viejas I removed the filter (it is clamped in a cage with a single screw) but couldn't find any drain plug, its just a smooth canister (photo). I'm nervous about disconnecting anything as I don't have any replacement seals and I need the car.

What does the presence of the bubbles tell me for sure please?

Thank you all for your help and patience with me.

 

[Mloclam]

One of the pipes is held in place where it joins the fuel filter with a plastic clip and two tie-wraps, does this look normal?

 

[a111r]

No, it's broken.

 

[Mloclam]

Right - I'm going to buy a replacement fuel filter and fit it over the weekend. Hopefully that will fix my non-starting problem, thank you all for sharing your experience with me.

 

[Mloclam]

Hmmm . . . there are two different filters for my car. I think it is the connector that is broken on mine, not the filter itself. I can't find a source for a replacement connector - could I just use the smaller, alternative filter and use a jubilee clip instead?

 

[91dm]

You can't buy the ends separate, you need the full pipe with both connectors, usually between £10-20. It will be worth fitting a new filter while you are at it. Remember to fill the fuel filter before fitting. It would be worth buying the o-ring seal kit from ebay and replacing them on the other pipes if you see bubbles.

 

[Mloclam]

The car filed to start this morning so I'm stuck. But I have found the root cause of the problem I think. I removed the pipe from the filter to the pump (I think) and blew down it quite gently. Diesel came out of the joint at the other end, where it is connected to the fuel pump (?). So it looks like that is the source of the air ingress.

Can anybody in the Bedford area help or recommend someone who can? My battery is flat and I need a new diesel pipe to connect from the filter to the pump (both connectors snapped as I removed the pipe). I need the car working ASAP :-(

 

[a111r]

The pipes look pretty old from you photos, probably the originals. They darken / harden with age.

You can change each them or their O rings piecemeal ... but unless you're enjoying the experience, buying a full set of new pipes and a filter is the best / quickest fix.
Pop down to your local MB dealer with your VIN.
The pipes at a guess would be around £50 / £60?

 

[91dm]

Yes that will be the problem, bring the broken pipe to the dealer and get a replacement and fuel filter. Most second hand pipes will break taking them off or need o-rings anyway. You'll need to charge the battery and connect up another car or battery pack as it will take a bit of turning to start. Let us know how you get on.