I have a 1982 240d with 308k miles
The car idles very rough. I'm thinking it may be the engine mounts but I notices some vacuum line going to the injection pump are cracked.

Do you know the the plastic piece on the injection pump is(see picture)?

Do you know what the vacuum is supposed to be on the different connections on the vacuum pump?

Thx

pete

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That is the vacuum control valve that controls how much vacuum the transmission/transmission modulator gets, when you apply the throttle that valve bleeds out vacuum in a controlled way according to how far the accelerator is depressed. Shifting is propably haywire as a result, do you have enough vac line (couple inches?) on the other side of the green plastic "vacuum dampener" to replace the cracked vac line? By the way that white plastic vac valve is hard to find so go easy.

Any vac leaks are harder on your vac pump also so it's best to find the leaks and fixem.

There is a list of things the effect the idle smoothness.

Idle rpm too low.
Valves need adjustment.
Engine/Motor and transmission mounts need replacing.
Injectors need rebuilding.
Uneven compression.

Do or check what is cheapest or easiest to do first.

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84 300D, 82 Volvo 244Gl Diesel

The car is a manual 4 speed. It's not an automatic. I don't believe there are any vacuum lines going to the transmission so I'm not sure what the modulator is doing.

The motor mounts are cheap so I will change them first. I can also do a compression test. Any idea what the allowable variance between cylinders should be?

I recently adjusted the valves but that didn't help much. I also did a diesel purge.
I guess I'll buy new injectors since I'm not sure when the previous owner replaced them.

I'm a little reluctant to raise the idle to fix the problem. The can doesn't have a tachometer. Is there an easy to to calculate the rpm's?

Thanks.

pete

Harbor Freight has a battery powered tachometer that is very easy to use. You place a small piece of reflective tape (included) on the crankshaft pulley and it reads the RPMs. What a huge difference when you can zero it in and have it running at the right speed.

I'd fix the vacuum leaks first though.

$36 now. You can usually find a 20% off coupon to be used on your most expensive item (not the entire purchase). Some things from HF are fine. Others break the 1st time.

Digital Photo Sensor Tachometer

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Doesn't your 240d have a little knob on the dash board that you can turn and manually adjust the idle? I know mine does. It is to the right of the headlight switch, directly below the brake light indicator.

" little knob''
Mine does but I have read that they are often non functioning... and I think there is a ' procedure' to allow it to work properly...
but I do not think the OP needs a tach...
just increase the rpms until you do not have bad shake..

then after doing the recommended fixes....
and the engine and trans mounts are really suspect...
then re adjust the idle to lower if the car will allow it...

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

The idle knob just connects to a cable. The cable just simply pulls on the throttle cam

" just connects '' to a thirty year old cable..
lol
and there is a procedure to get it to pull on that cable... it is in the archives...
have you checked... or does it change the rpms when you use it ? Does it set the rpm's to high enough to stop the vibration ?

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

The knob is turned all the way counter clockwise and it's idling rough. It gets rougher if I turn it clockwise. I guess I might be able to adjust the cable.

I checked the timing chain stretch and there was zero stretch in the chain. Hard to believe since the car has 309k miles on it but the previous owner may of had the chain replaced.

My next step will be to replace the motor mounts. I'll already have a set of motor mounts but I'll have to order some tranny mounts.

It could be 1 or more bad fuel injectors. I need to get a pop tester to test.

Thanks for the help.

pete

It is not a complicated adjustment. It is similar to adjusting the brake calipers on a bicycle. you are not adjusting anything on the injection pump. If the knob alters the idle some, that means it is not frozen or rusted. Simply spray a little oil of Liquid Wrench on the adjusting nut loosen the nut and tighten the cable a little. It shouldn't be harder than a 2 on the difficulty scale.

Let the engine warm up. Take a thermal temperature reader. Spot the laser on each glow plug base. Post the results on your thread if you want.

These devices are very cheap on ebay now. If you do not own one perhaps you can borrow one.

If the engine has a reasonable power balance all readings will be very simular. To be really rough you would need a missing cylinder or at least you want to eliminate the chances of it being there.

The other test is to loosen one injector line at a time at the injector with the engine running. All lines when individually loosened should make a difference. If you find out one does not then there is a problem there.

Starting to do things before the power balance is known to be present might be wasted effort. Unless something else pretty obvious is evident.

You have checked the valve clearances? A check is a good ideal every fifteen thousand miles. The manufacture recommends it. At the same time there are some of these cars out there were the valve clearances have never been checked for the longest time. Too many owners just assumed the engine had hydraulic valve lifters. Maybe its been 100k since they were last checked? Unless you know when they were you just do not know.

hbs, I'll head out shortly to adjust the knob cable. I'm not even sure where the cable is in the engine compartment but I might be able to get a neighbor to turn the knob while I'm under the hood.

The valves were all tight expect the exhaust on #4 cylinder.

I just ordered an IR Temp gun. I will post the temp of the glow plugs when I get back in town next week.

I assume the bad injector have a lower temp reading?

Thanks.

pete

It is a little cruder test than I like. Yet if a cylinder is off line at idle the glow plug base will be lower in temperature. Cylinder totally down about a fifty degrees lower temperature than the others at hot idle.

You essentially are just reading the coolant temperature in that area. Where the cylinders that are firing will have a hotter glow plug base.

Increasing the idle will make the engine seem a little smoother in itself. Also from a dynamic perspective the cylinder may fire up at increased revs.

Depends on what is wrong. On a rough running engine at idle I always check to make sure all the cylinders are firing first. Unless something else is obvious.

I could have spend a lot of time and effort otherwise in many cases over the years. You may not find a dead cylinder but you will then know it is not the problem. If you do find one there can be many causes. You at least know where the problem is located though. For the crowd post the temperatures you read when you get to it.

When you said the adjustments on the valves were tight. Do you mean no clearance at all on some? Or just less clearance that what it should have been?

Over the years ahead you will find many applications for the temperature reader.

You could have an injector with no fuel output. If that were the case in all probability it would not be the injector. Too early to even consider it. You just want to establish quickly that all the cylinders are running decently. Or not.