82 240d underpower, need help! - PeachParts Mercedes-Benz Forum

sphinx_57 · #1 10-23-2007, 06:56 AM

So I recently picked up an 82 240D from a friend, I had test drove it for a few weeks and compiled a list of things to fix. Just tonight on my way to vist my girlfriend the car felt seriously underpowered compared to normal. Like it was hard to get it to go 60 on the speedo.

It idles fine, and power seems normal in the first three gears. Other odd ball stuff that is happening is the brake pedal feels very stiff at times, and the car does not always shut of once the key is pulled out.

Things that I have messed with recently, Changed to of the glow plugs because it wasn't starting, starts fine now and I'm going to change the next two tomarow. I had bumped one of the plastic fuel line hoses and it fell apart so I put a new length of hose on it, this was on the first injector that leads to some device that I don't know its function. Tanks is about half full.

Any adivce would be much appreciated, thanks

Ken300D · #2 10-23-2007, 07:04 AM

You probably have more than one thing going on.

The issue with the brake pedal and the shutoff is vacuum related. These cars get their vacuum from a vacuum air pump, unlike gasolene cars which can get vacuum from the air intake. Diesels free flow air into the intake with no throttle plate - it is the throttle plate that generates the vacuum on a gasolene engine. In a diesel, it is fuel supply from the injection pump that regulates power, and the air flow is left unregulated.

So, you likely have a vacuum leak or a malfunctioning vacuum pump. One of the best tools to troubleshoot and isolate vacuum problems is a Mity-Vac with vacuum gauge. With it you can pul and measure a vacuum, and even watch whether or not it bleeds away.

The power issue is most likely something to do with fuel supply. Have you changed both the in-line and the "spin-on" fuel filters? They may be clogged up. A leaking fuel line will pull in air while the car is running, so this is worth an inspection too.

So, I think these are the first areas to try. Look for a vacuum leak, and change your filters if you never have before or if they are due for a change.

Ken300D

sphinx_57 · #3 10-23-2007, 07:26 AM

I was thinking it might be fuel related, My next step was actualy to change the filters. Is there a quick way to check for vaccum leaks?

Stevo · #4 10-23-2007, 10:45 AM

Another thing too check as to your loss of power is your throttle linkage. There is a linkage rod that comes out almost perpendicular from the fire wall and has two prongs at the engine end which go through a couple plastic "gromits". These gromits can fall apart resulting in no power but the car idles fine. you might check those out and have someone mash the go pedal while you see if the linkage is working OK.

chetwesley · #5 10-23-2007, 11:01 AM

Quote:

Originally Posted by sphinx_57

I had bumped one of the plastic fuel line hoses and it fell apart so I put a new length of hose on it, this was on the first injector that leads to some device that I don't know its function.

I think that what you are referring to there is the secondary or "spin on" fuel filter.

300SDog · #6 10-23-2007, 04:28 PM

How much mileage on engine?? If it's over 250k miles then gotta expect normal slight drop in compression. And at/near 200k timing chains stretch. Adjust injector pump timing to compensate. Better yet thread new timing chain or install woodruff key to adjust camshaft timing via the sprocket. Adjusted IP timing at 180k on 240D of mine and immensely improved performance. Yep, I'd deffinitely look into TC stretch effecting camshaft and IP timing as primary culprit. Check valve adjust too.

Quote:

Originally Posted by sphinx_57

Like it was hard to get it to go 60 on the speedo....... It idles fine, and power seems normal in the first three gears.

Am guessing the car's an automatic. 4th gear lugs like slug under 60mph with all of em including 5cyl 617's. If it totally pigs out at 55 then drop into 3rd "S" on the shifter. Driving hammer down with narrow power bands makes these old diesels hilarious fun to drive. Get the 240D up to 75mph in 4th and oughta do this speed all day long.

Stevo · #7 10-23-2007, 06:45 PM

If you dont mind getting your hands dirty these cars will last a long time. I agree with MrDog, you have too get in there and "freshen them up" Then when you drive down the road you can listen to that engine and feel like you know whats going on in there.

sphinx_57 · #8 10-23-2007, 07:34 PM

I'm not sure how to adjust the timing, or check the valve. The odometer says 130k but doesn't work. I know the guy who owned it for a while and he didn't drive it much but who knows for sure.

I finished with the glow plugs, and tightend up the throttle cable just a tad, in town it seems fine but my problem was on the freeway so it will be a couple of days before I know. Also the car stops now when I pull out the key.

Ken300D · #9 10-24-2007, 08:28 AM

There isn't a throttle cable on these cars. All the accelerator pedal linkages are metal rods. What you adjusted is probably the "Bowden cable" that hooks into the linkage and runs to the automatic transmission. The purpose of this cable is to sense the position of the accelerator pedal and changes the shift points to higher or lower rpms.

What you want to do in solving a problem is try the "low hanging fruit" first. That is, the cheapest and easiest things are what you do first. If you have a choice between changing the fuel filter and overhauling the engine to fix your problem, you change the fuel filter first.

That's an extreme example. To be more practical, from the suggestions you have received, maybe the fuel filters and the valve clearances are the first things to try, along with the accelerator linkage check.

The valve clearances can be done with common hand tools, like a pair of 14mm wrenches and a feeler gauge. It is easier to deal with the lock and adjusting nuts with the special bent wrenches, but not impossible to do some good with just regular wrenches. I was not too intimidated to do this adjustment because I grew up around Honda motorcycles that required tappet adjustments often. It is not too tricky, and is something that really needs to be done on these old cars in order for them to breathe well and to avoid damage to the camshaft.

Ken300D

t walgamuth · #10 10-24-2007, 08:43 AM

Filters first....fuel filters.

Tom W

winmutt · #11 10-24-2007, 09:27 AM

Yup filters filters filters. And new fresh diesel. Also your tank strainer might be clogged, try swapping the tank to and fro lines to blow out any old gunk. There are no plastic fuel lines on these other than the ones that run from the ip to the filter. Take pics.