All,

I have a 87 300D Euro Non Turbo since 95, purchased with 50K mi now 135K and starting last winter cold (0 to 10 deg) starting entailed glow plug for 10 sec followed by stumbling with plumes of rich diesel smoke. This was without plug in access (airport parking).

I had never opened the fuel system or replaced filters (in 9 years) so this fall replaced primary and secondary filters and the cold start stumbling continued. SO on to injectors and glow plugs, replaced these two weeks ago and the "nailing" is worse with cold starts being the same stumbling and stuttering. Once warmed up or sounds like other 603 I listened to here.

In effort to isolate the issue of rough cold starting:

- Temp 30 Deg F - Glow Plugs 1x - Rough start, engine searching, stumbling, blue diesel smoke, with smooth operation above 12-1500 RPM - finally smoths out after 1-2 Minutes
- Temp 20 Deg F - Plug in block heater 2 hrs - easy start - minimal smoke, stumbliing, idles a bit rough, smooths out in 15-20 seconds

So what are the first and second issues to look at and why? Once warm the car runs fine and no problems. I use Rotella 15W/40 oil, use some Techron fuel cleaner.

Based on my experience this was not a significant problem for the first 7 years why is this occuring now, and why only in cold weather?

Thanks in advance for your replies

Carl

From what I've read here, OM603 engines are cold-blooded. Mine is no exception.

I've not heard of a NA OM603, but I'll guess it behaves the same as a Turbo OM603 at start up and idle.

1. Glow plugs. You said you have replaced yours. One can be be bad and the glow lamp on the dash still lights and times off. Let's move on...

2. Normal wear of the timing chain will slowly retard the injection pump. Later injection timing will emphasize blue smoke and rough running. Has the IP been retimed? Has chain wear been checked?

3. You said you have replaced the injectors. I'm curious, why?

More to the point, were the replacement injectors tested and balanced? New, or re-man replacement injectors have been getting a bad rap for being less than pure quality. Replacements have been reported as being sub-standard, worse than what they replaced, etc.

My guess, assuming all glow plugs are good (can't hurt to check them again?) would be the injectors themselves are not set up correctly. The timing of your problems sounds like it coincides with their replacement, since you said, the nailing got worse when you replaced them.

I'd be interested to know the history of the new injectors.

Best Regards,
Jim

I hope you have saved your old injectors. More likely than not, your old ones had better spray pattern than the new ones. I think your main problem is that you're not letting your glow plugs do their job. Try glowing them in one cycle for 30 seconds. If that doesn't help, make sure all your plugs are working by checking their resistance through the connector at the relay.

__________________
2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Jim H & Diesel Addict

Regarding the replacement injectors - I procured one set to find they were incorrect for my engine so went to MB with P/N in hand and got the correct injectors though a rebuilt. They had a core return so, no I don't have the old injectors tho I wish I did save them now!

No I did not check the injectors for balance, no bench unit to do this, however when asked MB tech about increase in nailing noise he explained the original injector probably had a different pintle setup.

Another interesting side effect is the engine now runs on average 5C cooler than before replacement of the glow plugs/injectors. Is this indication of it running leaner?

Your comments about the IP and timing, and timing chain is likely the next step, since when slight throttle is applied when cold it runs smooths out, although from what I have heard this is more typical at 200K.

Thanks

Carl

Carl, you might see if the M-B shop who sold you the injectors would test them for you. If they are aware of quality issues, even if they don't admit it, they might do this for free since you bought them there.

I wouldn't think that new injectors should not nail, regardless of the type or style of pintle, and they could offer some help here. Perhaps if you remove them, they will test them? Couldn't hurt.

Do check the chain wear and IP timing. Maybe M-B could make you a 'package' deal of check chain, timing and injector pop pressure and spray pattern?

Running cooler, I have no clue. If it's running 'leaner' you might be able to tell more from miles/gallon than cooling temp. Could be a result of the injectors, could be coincidence, no idea.

If you get the chance, keep us posted.

Best Regards,
Jim

It just occurred to me that increased nailing after installing new injectors could be delivery valve seal(s) leaking. If the new injectors are OK, they might have a higher pop pressure than the old injectors. A leaky seal might mean it takes even longer for the IP to build up enough pressure to 'pop' the injector, resulting in even later injection and increased knock. Check what psfred has to say in #6 in this thread.

new to me 300tdt

Best Regards,
Jim