[roncallo]

I just replaced the fuel injector seals on my M120 V12, It uses the same rail and fuel injector connectors as the M113 and I believe the M119. I had a huge leak on first start up that left a puddle on the floor. Next day I got maybe a drip out of it and now nothing. I'm not sure if it was from the injector seals or possibly a cracked injector rail. I'm wondering if anyone else had this self sealing phenomenon after replacing seals. I am worried about a cracked fuel rail as it appeared to be dripping down from the fuel rail. Unfortunately I cant run the engine for extended periods of time because there is no water in it. I will have to wait until the weather is warm, like probably Wednesday so I can complete my engine flush with straight water before putting in ani freeze.


Gas on the floor. Stunk the whole house up.

 

[Ken S]

How snug were the new seals when reinstalling the fuel rail?
On my M119, it took some effort to re-seat everything (even with a light coat of motor oil on the seals). If it was not a very snug fit perhaps double check the part number. I used common aftermarket seals with no issues. Perhaps one had a little nick and then swelled up enough to stop the leakage for now. It wouldnt take much of a leak under that pressure.

If your M120 has a fuel pressure regulator mounted in the fuel rail with the little vacuum line attachement, perhaps check that line for raw fuel (that vacuum line is there as a safe guard if the FPR starts leaking internally).

Also, does your M120 have the Siemens Deka injectors with the seam in the middle of the body? If so, they are prone to leaking at that seam when the internal seals get old and tired. I had to replace my Seimens injectors because a few of them started leaking after fuel pump replacement brought the pressure back up to spec. My injectors didn't leak any significant volume, but they looked like this and my initial thought was to replace the seals (which I did in vain):

 

[roncallo]

How snug were the new seals when reinstalling the fuel rail?
On my M119, it took some effort to re-seat everything (even with a light coat of motor oil on the seals). If it was not a very snug fit perhaps double check the part number. I used common aftermarket seals with no issues. Perhaps one had a little nick and then swelled up enough to stop the leakage for now. It wouldnt take much of a leak under that pressure.

If your M120 has a fuel pressure regulator mounted in the fuel rail with the little vacuum line attachement, perhaps check that line for raw fuel (that vacuum line is there as a safe guard if the FPR starts leaking internally).

Also, does your M120 have the Siemens Deka injectors with the seam in the middle of the body? If so, they are prone to leaking at that seam when the internal seals get old and tired. I had to replace my Seimens injectors because a few of them started leaking after fuel pump replacement brought the pressure back up to spec. My injectors didn't leak any significant volume, but they looked like this and my initial thought was to replace the seals (which I did in vane):
View attachment 2810996

Thanks for the replay.

The old seals were very hard to pull out. In fact they were so hard to pull out I thought I might have cracked the fuel rail taking them out.The new seals went in with the amount of drag I would expect for that type of connection also using motor oil. Not sure who made the injectors but they were purple in color. I'm starting to think now that maybe there was a residual bit of seal remaining in the fuel rail since the old ones were so baked in in place. Old seals were green. New seals were black and made by BOSCH. Will check for fuel in the vacuum line. Leak was occurring in the vicinity of the pressure regulator.

 

[roncallo]

On the road a couple of days now. No signs of a leak.

 

[Ken S]

I like your theory of some old seal residue in an injector seat in the fuel rail. Keep an eye on it.

 

[roncallo]

I like your theory of some old seal residue in an injector seat in the fuel rail. Keep an eye on it.

Luck was not with me. I have no leaks at all now but it was idling like crap and stalling, I could also here backfiring in the exhaust at idle. Ran great otherwise except at idle. No apparent signs of seal leakage or any trace of residue in the fuel rail so injectors are now back out and I will send them for flow testing. I believe one of them got damaged when I first pulled them out. They are Siemens injectors but no signs of a cracked seam.

 

[Ken S]

Sounds like some of your injectors may have got old and grumpy when they were disturbed from their resting place.

 

[roncallo]

Sounds like some of your injectors may have got old and grumpy when they were disturbed from their resting place.

Absolutely, but not sure if the original leakage is related to the ruff idle. Problem with the leakage was I could only see it coming off the rail. That means if the seals were leaking it would have had to bounce off something and go up and hit the rail. I guess that's possible since it was a big leak when it happened. Now that I have the rail back out I'm going to try to pressure check it.

 

[roncallo]

I decided not to send the injectors out. I purchased this instead.

CT160 Fuel Injector Ultrasonic Petrol Car Nozzle Cleaner&Tester Cleaning Machine | eBay

Find many great new & used options and get the best deals for CT160 Fuel Injector Ultrasonic Petrol Car Nozzle Cleaner&Tester Cleaning Machine at the best online prices at eBay! Free shipping for many products!

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[roncallo]

Oh No

I think I may have Fd up all 12 injectors.

Yesterdays results As received.

Cylinder Number

1​

2​

3​

4​

5​

6​

7​

8​

9​

10​

11​

12​

Idle Speed Test

20​

19​

20​

20​

18​

18​

20​

20​

20​

20​

19​

19​

Medium Speed Test

54​

54​

56​

58​

54​

54​

54​

56​

58​

56​

54​

57​

High Speed Test

87​

88​

94​

98​

86​

85​

90​

92​

92​

92​

88​

92​

Accelerating Test

10​

10​

10​

10​

10​

10​

10​

10​

10​

10​

10​

10​

Variable Speed Test

8​

8​

8​

8​

8​

8​

8​

8​

8​

8​

8​

8​

Leakage Test

0​

0​

0​

0​

0​

0​

0​

0​

0​

0​

0​

0​

Idle Speed Spray Volume Test

14​

14​

14​

14​

14​

14​

14​

14​

14​

14​

14​

14​

Medium Speed Spray Volume Test

12​

12​

12​

12​

12​

12​

14​

14​

14​

14​

14​

12​

High Speed Spray Volume Test

14​

14​

14​

14​

14​

14​

14​

14​

14​

14​

14​

15​

Todays results after cleaning and back flushing

Cylinder Number

1

2

3

4

5

6

7

8

9

10

11

12

Idle Speed Test

98​

38​

24​

25​

40​

38​

66​

112​

30​

21​

100​

40​

Medium Speed Test

98​

70​

70​

74​

58​

54​

62​

102​

58​

50​

72​

62​

High Speed Test

110​

88​

88​

92​

90​

90​

74​

102​

72​

62​

105​

98​

Accelerating Test

19​

10​

10​

10​

14​

10​

16​

48​

16​

10​

17​

12​

Variable Speed Test

13​

10​

8​

9​

12​

9​

16​

28​

14​

8​

12​

9​

Leakage Test

18​

4​

0​

0​

8​

2​

70​

12​

30​

4​

16​

14​

Idle Speed Spray Volume Test

78​

42​

37​

38​

49​

37​

38​

40​

52​

40​

80​

40.5​

Medium Speed Spray Volume Test

44​

38​

38​

38​

39​

36​

37​

38​

42​

38​

44​

40​

High Speed Spray Volume Test

42​

38​

40​

40​

40​

38​

38​

40​

42​

40​

44​

42​

Not sure what caused the problem.

Could the injectors just not like, Ultrasonic cleaning, Maybe they don't like back flushing, Or possibly my test fluid Isopropyl Alcohol messed them up. Manufacture recommends Medical Alcohol > 75%. I was using 99.9%.

My guess is the back flushing, but now I'm afraid to purchase a used set of injectors on Ebay and try to even run them if I don't know what cause the problem.

12 injectors are $1500.00 ouch. On E-bay ~ $450.

I did find out that injectors can leak on the case when initially pressurized and then seal. That does explain the initial problem I had. Now I have several that do that.

 

[Ken S]

Your experience has some aspects in common with mine. As mentioned earlier, I had a fuel leak at a few injectors and I assumed it was the seals at the fuel rail. I removed the rail and the injectors, replaced the seals and then after reassembling everything I had 2 more of the Seimens Deka injectors leaking. All leaking at the seam in the body. It appears that they do not like to be disturbed at this age.

I bought a set of reconditioned injectors (ultrasonically cleaned and tested) of the same part number and most of them leaked. The vendor was very responsive and sent me another set of which many of those leaked also. In talking with some other injector remanufacturers, they told me the issue is common on old Seimens Deka injectors of this type. The internal seals eventually lose their magic and they are not replaceable.

I ended up buying the Bosch injector with the one-piece body (online "upgrade" purchase from an Injector seller with a good reputation). No leaks, runs well, slight improvement in fuel consumption.

 

[Photodude]

12 injectors are $1500.00 ouch. On E-bay ~ $450.

Seriously? Wouldn’t these fit your engine? $31 a piece, I installed them on my friends M104 few years back. No complaints since.

Mercedes-Benz SL600 Fuel Injector Parts | FCP Euro

 

[roncallo]

Your experience has some aspects in common with mine. As mentioned earlier, I had a fuel leak at a few injectors and I assumed it was the seals at the fuel rail. I removed the rail and the injectors, replaced the seals and then after reassembling everything I had 2 more of the Seimens Deka injectors leaking. All leaking at the seam in the body. It appears that they do not like to be disturbed at this age.

I bought a set of reconditioned injectors (ultrasonically cleaned and tested) of the same part number and most of them leaked. The vendor was very responsive and sent me another set of which many of those leaked also. In talking with some other injector remanufacturers, they told me the issue is common on old Seimens Deka injectors of this type. The internal seals eventually lose their magic and they are not replaceable.

I ended up buying the Bosch injector with the one-piece body (online "upgrade" purchase from an Injector seller with a good reputation). No leaks, runs well, slight improvement in fuel consumption.
View attachment 2813006

Where did you find Bosch injectors and how do I know which part number crosses with the M120 injectors.

 

[roncallo]

Seriously? Wouldn’t these fit your engine? $31 a piece, I installed them on my friends M104 few years back. No complaints since.

Mercedes-Benz SL600 Fuel Injector Parts | FCP Euro

Looks like they will work but after reading Ken S post, I'm a bit wallet shy. Do you know if the M104 also used Deka.

 

[Ken S]

Where did you find Bosch injectors and how do I know which part number crosses with the M120 injectors.

Rightly or wrongly, I trusted the seller (they had a good reputation) and they said they offer it as a common sub because the Bosch units were more reliable with excellent performance, proper flow rate, response time etc. After my experience with the "reconditioned" Seimens-Deka units, I was getting tired of removing the fuel rail.

I spoke with some different injector sellers and most were aware of old Seimens injectors being prone to leaking externally. I also reached out to GB remanufacturing and that's were I learned that the internal seals cannot be replaced on the Seimens-Deka units. GB says that they pressure test all units. I wonder if GB even uses some sort of seal conditioner during their process to stop the internal seal from failing when it dries out or gets old and shrinks (which is just my laymens observation for what we may be witnessing with these old injectors).

GB has a good reputation, but I paid about $40ea for "reconditioned" Bosch units (edit: but they looked new... probably some sort of Bosch clearance special with the Mercedes part number removed as you can see in the picture... not uncommon in the OEM parts world). I probably would have gone with those GB units if I had not found the attractive deal on the Bosch units.

 

[roncallo]

Rightly or wrongly, I trusted the seller (they had a good reputation) and they said they offer it as a common sub because the Bosch units were more reliable with excellent performance, proper flow rate, response time etc. After my experience with the "reconditioned" Seimens-Deka units, I was getting tired of removing the fuel rail.

I spoke with some different injector sellers and most were aware of old Seimens injectors being prone to leaking internally. I also reached out to GB remanufacturing and that's were I learned that the internal seals cannot be replaced on the Seimens-Deka units. GB says that they pressure test all units. I wonder if GB even uses some sort of seal conditioner during their process to stop the internal seal from failing when it dries out or gets old and shrinks (which is just my laymens observation for what we may be witnessing with these old injectors).

GB has a good reputation, but I paid about $40ea for new Bosch units (apparently they were some sort of Bosch clearance special with the Mercedes part number removed as you can see in the picture... not uncommon in the OEM parts world). I probably would have gone with those GB units if I had not found the attractive deal on the Bosch units.

Looks like the GB rebuilds are Bosch. PN 000 078 50 49. They are called out as replacements for the early LH M120 according to Mercedes. Interesting note about the 95 fitment it actually says "Stamped 000 078 50 49". That was the last year of the LH system. Doesn't say that for anything else, but it says it will fit the later years of the SL's. According to EPC the PN 000 078 50 49 is only used on the LH models and they don't offer the Deka PN 000 078 84 23 from the later Motronic models for the LH models as an alternative. Likewise 96 and up Motronic models offer only the Deka PN 000 078 84 23. I will have to call the company and confirm if these will replace the Motronic injectors and will they except a Deka as a core.

 

[roncallo]

Not looking very promising. FPC Euro still hasn't gotten back to me, maybe next week. Others Ebay sellers sell the same model injector but say it only for the SL600 up to 95. Used Siemens Deka's are sounding out of the question.

 

[Ken S]

See what you might find in the coming week

 

[Photodude]

Do you know if the M104 also used Deka.

I don’t remember for sure, it’s been a while, but I thought they were Bosch rebuilds.

 

[roncallo]

See what you might find in the coming week

Good news is, I found a set of 12 on E-bay for $400 and no mention of cores. That saves about $300. I also found a set of used ones for ~ $150. I also found that if you order an injector from Mercedes online dealer for a 1995 or earlier SL600, you are offered both the newer Siemens Deka PN 000 078 84 23 as well as the Bosch rebuilds. This is contrary to EPC, but its a good sign. Apparently the new Siemens Deka PN 000 078 84 23 are backwards compatible. This should mean the Bosch are forward compatible. Hopefully FPC will get back to me Monday.

Set of 12 Bosch 0280155219 fuel injector 1993 Mercedes-Benz 600SEL A0000785049 | eBay

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