OM616 on a test stand - Page 2 - PeachParts Mercedes-Benz Forum

resago2000 · #16 08-27-2021, 12:28 PM

7) 3 is enough, sometime there is a damper on the bottom of the rear of the engine that hooks in to the trans mount, but not many have that I think
8) yes, the 616 was used in the 115 and 116, the intake varied a little. so the numbers are fine

first link in my sig has lots of pics of the same engine you have

resago2000 · #17 08-27-2021, 12:37 PM

BTW, you can control throttle from the circled areas when you install it in a vehicle.

resago2000 · #18 08-27-2021, 12:55 PM

actually, since you have a manual, the butterfly is the only thing you are concerned with as far as throttle, just about connection point should work.
you could get rid of all the rods and turnbuckles and just control throttle with a cable on the butterfly valve.

gmog220d · #19 08-27-2021, 07:37 PM

Quote:

Originally Posted by resago2000

10. you dont need it. you can remove it and the rod running along the top of the valve cover if you want

I'll second this.

With the rod that runs over the top of the engine removed you lose the fast idle option for when starting the engine cold. In the car there's a little knob on the dash that, when rotated, pulls a cable that runs to the bracket that's mounted to the valve cover. That cable then holds the throttle linkage open a bit, upping the idle speed. You can always use your foot instead!

gmog220d · #20 08-27-2021, 07:53 PM

Quote:

Originally Posted by d!0+]@9$f3>yEI$Il3ZQ

Ok so is this labelling correct then?
Attachment 163105

Yes. And as resago2000 pointed out there is nothing else going on inside the injection pump while the run/stop lever is pulled into the start position.

I got curious about that, as I coulda swore I read years ago that when in the start position the rack inside the injection pump is pushed forward to increase fuel delivery during starting. But nope it ain't so. I couldn't find it in the manuals. I took a used pump off the shelf and removed the side plate so I could see the rack and elements while operating the run/stop lever. Pulling the lever back does nothing to the rack.

Quote:

Originally Posted by d!0+]@9$f3>yEI$Il3ZQ

I'm having a hard time imagining the operation of the cable, you say that the cable holds it forward to the stop position by default? So you must pull the cable in the car to start the car? So the car starts with a cable and not with a key?

The gorrilla knob has four positions:
- Stop (all the way in)
- Run
- Glow
- Start (all the way out)

When released after starting, the knob/cable will default to run. To stop the engine push the cable forward into the dash.

The key turns on the electrics, and unlocks the steering.

gmog220d · #21 08-27-2021, 08:29 PM

Quote:

Originally Posted by d!0+]@9$f3>yEI$Il3ZQ

8. Is it common to have part numbers starting with 615 on parts on the 616 engine? I assume these are just leftover from the previous OM615 in the W115, and when Mercedes changed over to the 616 they didn't need to change any of those parts. Or do you think this 616 engine was swapped into this car at some point?

The OM616.916 2.4 uses the same manifolds and most of the accessories as the OM615 2.2 that was in the 220D. I swapped an OM616.916 2.4 long block into the '73 220D without any hassle. Everything fit and worked. One difference I know of is that the alternator setup changed between '73 220D and '74 240D. The valve covers are different, too.

One thing you should check is if the governor system holds a vacuum. If it doesn't the injection pump will deliver too much fuel.

d!0+]@9$f3>yEI$Il3ZQ · #22 08-27-2021, 11:10 PM

Quote:

Originally Posted by resago2000

7) 3 is enough, sometime there is a damper on the bottom of the rear of the engine that hooks in to the trans mount, but not many have that I think
8) yes, the 616 was used in the 115 and 116, the intake varied a little. so the numbers are fine

first link in my sig has lots of pics of the same engine you have

Great, thanks I will check out those pics.

Quote:

Originally Posted by resago2000

actually, since you have a manual, the butterfly is the only thing you are concerned with as far as throttle, just about connection point should work.
you could get rid of all the rods and turnbuckles and just control throttle with a cable on the butterfly valve.

Quote:

Originally Posted by gmog220d

I'll second this.

With the rod that runs over the top of the engine removed you lose the fast idle option for when starting the engine cold. In the car there's a little knob on the dash that, when rotated, pulls a cable that runs to the bracket that's mounted to the valve cover. That cable then holds the throttle linkage open a bit, upping the idle speed. You can always use your foot instead!

Quote:

Originally Posted by gmog220d

The OM616.916 2.4 uses the same manifolds and most of the accessories as the OM615 2.2 that was in the 220D. I swapped an OM616.916 2.4 long block into the '73 220D without any hassle. Everything fit and worked. One difference I know of is that the alternator setup changed between '73 220D and '74 240D. The valve covers are different, too.

One thing you should check is if the governor system holds a vacuum. If it doesn't the injection pump will deliver too much fuel.

Ok, I was getting a bit confused with this stuff so I just made a quick video...

http://www.youtube.com/watch?v=gA8G9mFesOU

gmog220d · #23 08-28-2021, 11:36 AM

Some comments on the video:

- The lever on the back of the injection pump has nothing to do with fuel output control. All it does, when the throttle is at idle, is push a spring-loaded vibration damper against the fuel rack to smooth idle out. You can remove the control rod that runs to the lever, and let the lever stay down under spring tension, without causing any problems.

- Yes, the governor uses vacuum to limit fuel delivery. Think about towards the end of the video where you are looking into the throttle body at the little venturi that's dedicated to the governor. When the throttle plate is closed more air will be sucked through that little venturi thus creating more vacuum. As you open the throttle less of the intake air will go through the little venturi, thus reducing the amount of vacuum created.

The vacuum signal created in the throttle body acts on a spring-loaded diaphragm inside the injection pump. That diaphragm is connected to the fuel rack. The coiled spring pushes the diaphragm and rack forward to increase fuel output, while the vacuum acts on the diaphragm to pull it and the rack back to limit fuel output.

At idle, while max vacuum is created, the rack is held back to limit fuel output so the engine runs at idle speed. Opening the throttle all the way reduces the vacuum to a minimum, which allows the coil spring to push the diaphragm and fuel rack forward thus delivering max fuel output.

If you remove the throttle plate from the throttle body there will be little-to-no vacuum to hold fuel delivery back and the engine could runaway uncontrolled.

- It does appear that you have the later style glow plugs. You are correct that all you need is 12V to that last plug to power them up. The original system was all manual control, and provided a visual aid for determining how long to glow, in the form of a resistor strip in the dash that glows with the plugs. There was no relay to control the cycle.

- RE testing for vacuum leaks - Yes, pull a vacuum on that line and see if it holds. There are two main causes of leaks in the system; bad diaphragm, and worn and leaky "adjusting shaft" and its bushings (this is the shaft that's controlled by that rod that comes down to the lever from above). A leak could be caused by one or the other, or a combination of the two. A less likely cause of vacuum leak would be a cracked housing.

This thread should shed some light on what's happening inside the back of the pump:
Parts for Pneumatic Governor, OM615 and OM616

- Yes on straightening out the bent lever at the throttle body. You are correct that the one is supposed to move the other.

- So yeah, you can remove both rods that run from the throttle body to the injection pump with no ill effects. When you remove the one that runs down to the lever on the injection pump you're making it so the rack damper stays forward all the time. When you remove the top rod you then lose your idle speed controller. All basic throttle related functions are still intact at this point.

resago2000 · #24 08-29-2021, 10:57 AM

that plastic vacuum line running from the throttle to the injection pump. check it for cracks and leaks also.
Mine had a crack and was thus overfueling, replaced it with a standard rubber vacuum line. runs butter smooth now

d!0+]@9$f3>yEI$Il3ZQ · #25 08-30-2021, 10:05 AM

Quote:

Originally Posted by gmog220d

- The lever on the back of the injection pump has nothing to do with fuel output control. All it does, when the throttle is at idle, is push a spring-loaded vibration damper against the fuel rack to smooth idle out. You can remove the control rod that runs to the lever, and let the lever stay down under spring tension, without causing any problems.

Sounds good, I guess I'll leave it until I have a driving car to see how much difference it makes.

Quote:

Originally Posted by gmog220d

- Yes, the governor uses vacuum to limit fuel delivery. Think about towards the end of the video where you are looking into the throttle body at the little venturi that's dedicated to the governor. When the throttle plate is closed more air will be sucked through that little venturi thus creating more vacuum. As you open the throttle less of the intake air will go through the little venturi, thus reducing the amount of vacuum created.

The vacuum signal created in the throttle body acts on a spring-loaded diaphragm inside the injection pump. That diaphragm is connected to the fuel rack. The coiled spring pushes the diaphragm and rack forward to increase fuel output, while the vacuum acts on the diaphragm to pull it and the rack back to limit fuel output.

At idle, while max vacuum is created, the rack is held back to limit fuel output so the engine runs at idle speed. Opening the throttle all the way reduces the vacuum to a minimum, which allows the coil spring to push the diaphragm and fuel rack forward thus delivering max fuel output.

If you remove the throttle plate from the throttle body there will be little-to-no vacuum to hold fuel delivery back and the engine could runaway uncontrolled.

Ok so I had to do some research on basic diesel engine operation and how a diesel governor works. I think I've got it now. I was confused because on a gas engine the throttle plate is there to restrict air flow, remove the restriction and the engine revs. Diesels restrict fuel, not air. The throttle plate on these engines does not exist to restrict air at all, it just tells the IP how much fuel to restrict. The venturi created between the tube and the throttle plate is just a mechanical sensor, providing information to the IP. Other diesel engines could use an arm on the side of the pump to do the same thing, but this one doesn't.

I found your previous thread helpful...
Pneumatic Governor Questions

Quote:

Originally Posted by gmog220d

- It does appear that you have the later style glow plugs. You are correct that all you need is 12V to that last plug to power them up. The original system was all manual control, and provided a visual aid for determining how long to glow, in the form of a resistor strip in the dash that glows with the plugs. There was no relay to control the cycle.

Great, thank you.

Quote:

Originally Posted by gmog220d

- RE testing for vacuum leaks - Yes, pull a vacuum on that line and see if it holds. There are two main causes of leaks in the system; bad diaphragm, and worn and leaky "adjusting shaft" and its bushings (this is the shaft that's controlled by that rod that comes down to the lever from above). A leak could be caused by one or the other, or a combination of the two. A less likely cause of vacuum leak would be a cracked housing.

Thanks, how much vacuum should it hold there?

Quote:

Originally Posted by gmog220d

This thread should shed some light on what's happening inside the back of the pump:
Parts for Pneumatic Governor, OM615 and OM616

Cool, good to know the parts may be available if I need them.

Quote:

Originally Posted by gmog220d

- Yes on straightening out the bent lever at the throttle body. You are correct that the one is supposed to move the other.

- So yeah, you can remove both rods that run from the throttle body to the injection pump with no ill effects. When you remove the one that runs down to the lever on the injection pump you're making it so the rack damper stays forward all the time. When you remove the top rod you then lose your idle speed controller. All basic throttle related functions are still intact at this point.

Have you run your car without the idle damper? How does it behave?

resago2000 · #26 08-30-2021, 10:09 AM

I had it disconnected before, didn't notice any difference

d!0+]@9$f3>yEI$Il3ZQ · #27 08-30-2021, 10:26 AM

Quote:

Originally Posted by resago2000

that plastic vacuum line running from the throttle to the injection pump. check it for cracks and leaks also.
Mine had a crack and was thus overfueling, replaced it with a standard rubber vacuum line. runs butter smooth now

Thanks, I'll check it after I get this thing running.

I was looking at your card from your signature link and saw this one. Are you running an electric vacuum pump or something?

resago2000 · #28 08-30-2021, 10:29 AM

yes

electric vacuum pump, lower right corner

gmog220d · #29 08-30-2021, 01:31 PM

Quote:

Originally Posted by d!0+]@9$f3>yEI$Il3ZQ

I found your previous thread helpful...
Pneumatic Governor Questions

Wow! That was an old one, and I see that I never followed up on it.

Quote:

Originally Posted by d!0+]@9$f3>yEI$Il3ZQ

Thanks, how much vacuum should it hold there?

The book doesn't specify this in terms of "how much". It's pretty much left as "it should hold vacuum". For me, I'm happy to see that it'll hold vacuum I create using my mouth on the tube for 10 seconds or more. That's not very scientific, I know!

Quote:

Originally Posted by d!0+]@9$f3>yEI$Il3ZQ

Have you run your car without the idle damper? How does it behave?

No, I've not run it without the damper. Removing the rod and letting the spring hold the lever down keeps the damper in the forward position, where it engages the fuel rack at idle regardless. The control rod pulls the cam back from pressing the damper forward when you are off-idle. Seems silly to have mechanism releasing the damper when the fuel rack is already moving forward and away from the damper. Earlier versions of this system didn't have this feature.

But, I can say that removing the control rod and leaving the lever down made no noticeable difference in how the engine behaves.

Just wanted to say that you can remove the governor housing from the pump without causing problems for yourself. If it's helpful for you to open it up and see what's in there go for it. Just watch out for the big spring and its shims. There is no gasket between the governor housing and the rest of the pump. There is a gasket between the poppet cam housing and the rest of the governor, though, and I have not been able to source that gasket by itself, outside of buying a complete kit for the pump. If you take that off you'd have to reuse the existing gasket, make a new one, or use something else to seal it.