Is it time to get my IP timed and my chain changed?
 

Hi,
Over a 400 miles mostly highway trip I took two weeks ago, I averaged only about 23MPG and change. This was at an average speed of about 70 MPH. This seems kind of off doesn't it? What could be causing it? Power seems ok, it starts great, and there is relatively little smoke on hard acceleration. Is it time to change my filters? Does my IP need timing? Do I need to change my timing chain? Replace my injectors? I have some money to throw around this summer (not a terrible amount) and it'd be nice to get my car running as good as possible.

Alex

Diesel head,

Which filters are you planning on changing? The air filter is the only one that will affect fuel mileage.

To determine if the timing chain needs replacement, you have to check the elongation. There are many posts here how to check it. Use search function. If the cam is late less than 4 degrees, the timing chain is OK and IP timing is OK. If more than 4 degrees you should replace the chain or put an offset woodruff key in the cam drive gear. If you use a woodruf key, the IP might need timing.

To know whether to replace your injectors you have to take them out out of the engine and take them to a Diesel injection shop and get them tested.

P E H

Might pay to do a valve adjustment. Maybe you have already, but if not...

PEH,
I was thinking about the fuel filters, but you're right, those wouldn't really change much. I'll look in to the air filter. I'll also have to have my mechanic look at the timing chain stretch. I don't know what I'm doing nor do I have the time to learn (which I'd like to) :(

Old Deis,
Thanks, I completely forgot about the valve adjustments. I did them a while ago, I forgot when and how many miles ago. This should teach me to start recording the work I do.

Where can I find a good reliable feeler guage? I don't have one.

Alex

For the feeler gauge try www.samstagsales.com. They carry all sorts of usefull tools for Mercedes. If you need one sooner you should be able to find one at good sized auto store. Just be sure to get the metric version.

Dieselhead,

If you can take off a valve cover, line up 2 marks and read numbers, you can check the timing chain elongation yourself.

While valve cover is off, check the valve clearances and adjust only valves that are out of spec.

P E H

Pictures....
 

....here.

Thomas,
Thanks for that amazing bit of work you did on creating a pictorial journal on how to adjust valves. I have done them before, but you're reference guide will be super helpful the next time.

Alex