W124 OM602 non starter

[mj2k]

I just got delivery of a non-starting W124 with 300k on the clock today. It's a 1990 normally aspirated OM602, but is a non-runner. It's literally a 'barn find' - it's been kept in a barn for the past 4 years and was fine when laid up, so I was hoping to find clogged fuel filters and treacle-like diesel to match it's flat battery - a nice, easy fix.

But when I cracked open the fuel union at the filter, I was surprised to find plenty of clean-looking diesel. And when I cracked open the output to the pump, there was diesel there too.

Annoyingly I've squashed my charger so I can't put the battery on charge to turn it over, but first thoughts are either the battery went flat only a couple of minutes before it fired, or the injection pump seals have failed.

Once I've got a decent battery I'll crack open the unions on top of the injectors and see if fuel's getting through to there, but does anyone have any other thoughts on what else might be causing non-starting on an OM602, or any other diagnosis tips?

 

[trapperjohn]

Not really. apart from may be the pre fuel filter could do with a change. These sometimes get over looked in the maintenance department.

 

[mj2k]

Ah yes, I remember that one well from my 300TD, it had been run on veggie oil and the strainer looked like a fried fish finger when I removed it!

Def need to get one of those on order, but since the fuel appears to be flowing freely to the filter I know it's not totally blocked.

 

[a111r]

Those pumps are extremely robust.
When you cracked the unions open, you let air in.
Needs bleeding out by turning it over with a very good battery.

The in-tank mesh filters can be cleaned easily, btw.

 

[mj2k]

Those pumps are extremely robust.
When you cracked the unions open, you let air in.
Needs bleeding out by turning it over with a very good battery.

The in-tank mesh filters can be cleaned easily, btw.

True, but cleaning the filter is likely to be a little, erm, messy so to save myself from a diesel hairwash I might as well fit a new one Besides, my 300TD's one was beyond saving, so to save myself from any more delays I might as well pre-emptively order one in case this one's in the same condition.

True cracking the unions would have let air in, but I'm hoping there's air in there anyway and nothing more sinister. On the 300TD I had to crack the inlet union, then the outlet union, then each injector union to get the air bubbles out after changing the filters, and I've noticed this new one's got new inline / fuel filters so I'm hoping there's just lots of air in the system.

Wonder why Mercedes didn't fit a manual lift pump to the W124? It'd make bleeding the system after filter changes (or running out of fuel) a whole lot less fraught...

True the pump's very robust, but not if someone's tried to 'fix' it in the past. Look at this very sad case for example:

Mercedes W124 E300 Diesel Automatic Estate 1994 (Non-runner) | eBay

What a shame

 

[mj2k]

W124 Starter!!!

Well, that was encouraging

After 24 hours on charge the battery was still only giving out about 7.5v despite being new, so I pinched my Pug 306 battery (which is much smaller) to try and crank through the fuel...

10 seconds after I'd retightened the injector unions it made a splutter, after another 3 cranks it started and could be revved. It stayed running and I managed to make the car move under it's own power for the 1st time in 4 years :bannana:

So it was just airlocked, and I'm guessing the previous owner must have burned the battery out by cranking for too long without bleeding the airlock.

I've now ordered a new rad and battery, and with a fair wind, a bit of luck and a couple of hours work I should be able to drive it round the block.

 

[Druk]

I was going to suggest the glowplugs but if it's now running maybe they're fine?

 

[mj2k]

I was going to suggest the glowplugs but if it's now running maybe they're fine?

I think they're OK. Normally I'd replace them as a matter of course but it's going to be getting an OM606 once I've got it through an MOT and welded any holes the MOT check missed

 

[mj2k]

Got the new battery today and fitted it this evening, started on the button first time!