Author Topic: Injection Pump Inspection. (Read 12521 times)

Tyler S · « **on:** February 27, 2016, 20:53:53 »

Having removed the head on my M129, I decided to pull the Injection pump to inspect it. With only 4 bolts remaining to remove it I thought this would be a good time to inspect it. This is a supplement to the head removal thread.
http://www.sl113.org/forums/index.php?topic=23889.0

After removing the rear cover, a serious wear groove was noticeable in the IP space cam. There is a coinciding flat spot in the stylus head on the rack lever. After looking at the wear pattern I am fairly confident it is due to a lack of proper lubrication. When I took possession of the car the pump was under filled and the oil was very diluted in gasoline. Another potential contributor is the "Fuel Cut" system. When the fuel cut solenoid is energized it moves the stylus and its lever off of the space cam. This bottoms out the rack completely closed. When the solenoid is de-engergized it allows the lever and stylus to return to its natural position. This happens very fast and very HARD because of the spring tension. The stylus effectively slams back down onto the cam. I am fairly confident that this contributes to extra wear on these components. This explains the strange rich/lean condition I would experience from time to time. I could get the pump A/F set and it would go rich at times without any rhyme or reason. This was being caused by the flat spot in the stylus lining up directly with the wear groove on the cam. This was intermittent because the stylus is a roller on a pin. The same spot will not always line up. This pump will have to be rebuilt.

Not all IP's have a fuel cut setup, but for those of you who do I suggest disconnecting the solenoid to prevent unnecessary wear. The only adverse effect may be some burbling from the exhaust when decelerating in 3rd and 4th gears only. This is just my personal opinion.

Tyler

Tyler S · « **Reply #1 on:** February 27, 2016, 21:29:22 »

Another problem found. This pump has the wrong dipstick installed in it!
I always wondered why the dipstick threads would get stiff the last couple of mm's. It is bottoming out inside the case. It also looks like since it would bend itself over that the flyweights have been contacting it. It was Re-built 25 years ago by I don't know who but I remember that when my Father had it done it had to be sent back by the mechanic twice for issues.
If someone that has a dual solenoid pump can remove and measure their IP dipstick that would be greatly appreciated. I need the measurement from the seal ring surface to the tip and also to the full mark. Thanks
Tyler

66andBlue · « **Reply #2 on:** February 28, 2016, 17:42:42 »

Tyler,
do you have the correct IP for your car? It should be a PES 6 KL 70 B 120 R18y
They are somewhat rare and I don't know whether other models have the same dipstick.
Call Gus at Pacific Fuel (best in the afternoon) and ask him, he knows these pumps like no one else.

Tyler S · « **Reply #3 on:** February 28, 2016, 20:52:19 »

Alfred, Yes I have the correct pump. The number is actually PES 6 KL 70 A 120 R18y
The PES 6 KL 70 B 120 R18y number on our site technical manual is incorrect. I have verified this with Bosch. The M129 is the only engine that got this "A" designation. Any pump with the 2 solenoid setup will do for the measurment. All of the back covers in these are the same if they have a dipstick.
Tyler

Jonny B · « **Reply #4 on:** February 29, 2016, 16:01:18 »

My 250 SL has pump PES 6 KL 70 A 120 R18z. But it does have only one solenoid on the back, so am posting this for reference.
The screw in type oil dipstick - overall from the top of the screw to the tip of measure rod is 7.3 cm, the length of the dipstick, from the bottom of the threads to the tip of the measuring rod is 5 cm.

Tyler S · « **Reply #5 on:** February 29, 2016, 16:36:41 »

Thanks Jon,

The top of this dipstick doesn't look like any others I have seen on these pumps. Its a 14mm hex top with a flat head groove. Im sure it ended up in there 25 years ago during the rebuild. I wonder if its out of a Diesel pump.

Benz Dr. · « **Reply #6 on:** February 29, 2016, 16:39:55 »

I think a diesel pump is lubed by engine oil and is flow through so no dip stick. I've seen dip sticks that look like the one you described so I can't say it's wrong.

66andBlue · « **Reply #7 on:** February 29, 2016, 17:26:17 »

I thought only the R11/230SL pumps have a dipstick because they are not supplied with engine oil and need to be filled separately.
Why would later pumps with engine oil supply need a dipstick?

Tyler S · « **Reply #8 on:** February 29, 2016, 17:27:27 »

Dan, look at picture 3583 above. Its definately too long but could have come from a different MFI pump.
Tyler

Tyler S · « **Reply #9 on:** February 29, 2016, 17:34:15 »

Alfred, all pumps have an oil feed. The 230 and 250 pumps are fed only to the fuel "rack" side of the pumps and have a seperate oil reservoir for the rest of the pump. The later 280 pumps are fed to the pump case and is recirculated to the engine so hence no dipstick.
See second picture in this link.
http://www.sl113.org/wiki/Fuel/Injection

Tyler

66andBlue · « **Reply #10 on:** February 29, 2016, 17:48:37 »

I know that photo, unfortunately "earlier" and "later" doesn't tell which pump model it is.
Same holds true when you write "230 and 250 pumps"; do you mean R11 (with separate oil reservoir) or R18 pumps with forced oil circulation?

Tyler S · « **Reply #11 on:** February 29, 2016, 18:37:22 »

Alfred, I'm sure the designators have an effect on this. The key would be to find a table that shows this or we could create our own by having others look at their oil feed and post their pump number. The change was sometime in or after the r20 designator. Which would be 280.
Meanwhile, here is a good reference of all cars (not just mercedes) that these pumps were used on.
http://apps.bosch.com.au/AAExtranet_TechSearch/docs/GeneralInformation/Bosch%26Kugelfisher.pdf

Benz Dr. · « **Reply #12 on:** February 29, 2016, 19:07:20 »

I looked at your pic and that dip stick is too long. I should have one on a dead pump I have if you need it.

Tyler S · « **Reply #13 on:** February 29, 2016, 19:59:29 »

Thanks Dan,
So if this stick is too long that could mean this pump has been UNDER Filled for the last 25 years!!! That would explain the significant wear.

Jon, could you get a measurment from the top of the threads (sealing surface) to the full mark? I want to try to see if that is also different. Thanks

Tyler

Benz Dr. · « **Reply #14 on:** February 29, 2016, 20:18:39 »

Under filled and fuel dilution are real enemies when it comes to your IP.

66andBlue · « **Reply #15 on:** February 29, 2016, 22:00:31 »

Quote from: Tyler S. on February 28, 2016, 20:52:19

Alfred, ... Any pump with the 2 solenoid setup will do for the measurment. All of the back covers in these are the same if they have a dipstick.

Tyler, this is the culprit that threw me off track.
My 1968 280SL had a pump (PES6KL 70 B 120 R20Y) with two solenoids but when I sent it to Gus I asked him to remove the fuel shut off solenoid (see photos). Joe A. also removed the switch on the firewall and other wiring parts during the engine overhaul.
Although having 2 solenoids this model does NOT have a dipstick and I had erroneously assumed that your R18 pump is like the R20. I talked to Robert Fairchild today and your R18 is like the earlier R11, that is, it has its own oil reservoir and a dipstick. He mentioned that the R11 and R18 dipsticks are the same in length, slightly less than 2" from thread end to tip, that is the same dimensions that Jonny B typed.
I do have a spare R11 pump, thus we could use its dipstick as a template if you want to cut yours and scribe the filling mark.

Tyler S · « **Reply #16 on:** March 01, 2016, 03:05:09 »

Thanks Alfred, Exactly what I needed. Next time bring it along. We can modify this one to match.
Im curious to see how far off the full mark is from the correct dipstick.

Tyler

Tyler S · « **Reply #17 on:** March 02, 2016, 23:57:02 »

So thanks to Alfred, A correct dipstik for comparison was made available. The one in the IP was definately too long and the full mark lower down. Has been running underfilled. $:-\$ Correct stick on the right in photo.

Benz Dr. · « **Reply #18 on:** March 03, 2016, 00:05:01 »

Yup, dip stick was too long alright. Looks like something was hitting against the one you had in there. I'd say the oil level was 10 mm too low. Maybe not enough to damage the pump but still not good.

Tyler S · « **Reply #19 on:** March 03, 2016, 00:12:58 »

Dan, The flyweights were hitting! Was only able to see it after removing the cover and manually extending them out.

Tyler S · « **Reply #20 on:** May 14, 2016, 01:57:06 »

So I recently stumbled across a R18z pump for sale cheap on e-bay and got lucky. I had purchased it for a spare to be sent out to be rebuilt while leaving my original on the car. When I got it I was amazed how clean it was. Yellow tamper paint and stamping's suggest it had been rebuilt. I decided to put it on the car to see if it even needed to be sent in. WOW! What a difference. I can now dial in my mixture settings and they STAY PUT. My part load lean condition is now gone and it idles like it never has before.
So the years of a low oil level because of the wrong dip stick in my original pump really did do it in.
The question now becomes do I send my original pump in to be rebuilt and keep for a spare? Put it back on the car after?
Let it ride?

66andBlue · « **Reply #21 on:** May 14, 2016, 03:52:38 »

Quote from: Tyler S. on May 14, 2016, 01:57:06

... The question now becomes do I send my original pump in to be rebuilt and keep for a spare? Put it back on the car after? Let it ride?

If the current one is satisfactory or better why would you want to put the old one back?
Fortunately, IP part numbers are not listed on the data card so your "originality record" cannot be challenged!

Having the old repaired and keeping it as spare is might be a good idea because repair costs will only go up and/or the repair knowledge will be dead before you know!

Tyler S · « **Reply #22 on:** May 14, 2016, 15:25:51 »

Good point Alfred, The only visible difference between the 2 pumps is the "z" pump does not have the fuel cut solenoid. The internal difference is a slightly richer profile on the space cam. My car does have non functional wiring for fuel cut during decel in 3rd and 4th. It is a seperate harness from the main. I'm thinking of removing it anyway since the position switches on the transmission are missing.
One thing I did transfer over to the e-bay pump is the ball type delivery valves that must have been installed when the original pump was rebuilt. I dont think R18 pumps ever came with them.
I think I'll let it ride for now and send the original pump to Fairchild. Its possible its just an adjustment item. My Father always complained the car never ran right after the pump was rebuilt 25 years ago. That lean condition probably contributed to my burnt valves.

66andBlue · « **Reply #23 on:** November 07, 2017, 01:44:00 »

Quote from: Tyler S. on February 27, 2016, 20:53:53

.....
Not all IP's have a fuel cut setup, but for those of you who do I suggest disconnecting the solenoid to prevent unnecessary wear. The only adverse effect may be some burbling from the exhaust when decelerating in 3rd and 4th gears only. This is just my personal opinion.
Tyler

I remembered that way back George Davis (https://www.sl113.org/forums/index.php?topic=3277.msg19073#msg19073) made the same comment which I did not understand then and still do not now.

Why would disconnecting the solenoid create a burbling sound?

Tyler S · « **Reply #24 on:** November 07, 2017, 16:38:42 »

Alfred, The fuel cut solenoid effectively cuts all fuel to the injectors.
When Disconnected, The burble is caused by the high vacuum produced under deceleration. Because the injectors are still delivering fuel (idle quantities), you end up with a lean condition. On occasion, the mixture does not ignite and ends up in the exhaust. It is then ignited by the heat from successive exhaust strokes.

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Author Topic: Injection Pump Inspection. (Read 12521 times)