Fuel injectors pressure

[mauro12]

Hi guys , I just wanted your advice about this issue . I recently overhauled my injection pump and replaced almost every component ( cam shaft bearing , camshaft , delivery valves etc). The car is running perfectly the fuel mileage and power has improved a lot . The only advice  I have been given is to replace also the fuel injectors because they are still the original (r1)and the opening pressure is a little bit lower than normal . Should be around 15-18 atm and mine is around 14 atm. I don’t feel any evident symptoms even with this low pressure , maybe some harder cranking during cold start but nothing in hot start. What do you suggest me to do? Is it worth to spend 1000€ for new injectors ? 2 years ago I bought a set of r2 injectors and the result was that I have been refunded because they were defective , they didn’t give me a new set but only money back , that’s way I’m scared when we talk about buying this item .
Thank you
Mauro

[Pinder]

If you have to buy injectors you can  USD.

[mauro12]

Do I need ?

[WRe]

Hi,
I wouldn't buy new injectors if everything is fine and new injectors are known to be faulty as well.
...WRe

[Taleb]

Injectors will last very long , you can put it under test machine with high pressure it will clean it , even if you want to buy new one BOUSCH company they reproduce them with reasonable price less than 100$ each , I just got my set from BOUSCH Kuwait .

If you ever needs help contact Marty he might have stock or he will clean them for you 632 589-1600


Good luck

[yves]

Hi Mauro , i had those issues with mine , i have used the injector cleaning kit from mercedes source with succes ( test and cleaning)  now that all are fine i can sell you the kit if you need…. PM me in case! 

[mauro12]

I cleaned 2 times in the ultrasound machine. What is included in the kit ?

[Lorsar]

https://mercedessource.com/store/bosch-mechanical-fuel-injector-mfi-tester-and-cleaning-kit

This kit puts the injectors under pressure as they only open under pressure so ultrasound cleaning usually isn't enough.

[yves]

With the kit you can test the specific pressure when the injector open and close  . I have tested mine and only 1 of them had a open pressure correct, the other had big drops instead of a nebulization . After cleaning  ( 20 -40 press) 5/6 were correct, 1 needed a better cleaning by a professional . The close pressure was the same for the 6 .

[Benz Dr.]

If you are only down one atmosphere from nominal opening pressure I'd say you have a good set of injectors. R1 injectors are preferred when you can find them so I would stick with the ones you have.

[mauro12]

Yes , the lowest is injector n3 13.5 atm and the highest is n6 14.9 atm. What is the symptom of a low pressure fuel injector? Hard cold start ?
The spray pattern is good . They are still the original r1 injectors .

[mauro12]

If dr benz says that I should be ok , I feel safe .

[Shvegel]

I don't worry too much about opening pressure.  I am far more interested in residual pressure.  Do they maintain pressure after the engine is shut down? 

[mauro12]

Residual pressure is within the accetable range in 4 out of 6 injectors .
I guess it means the ability of the injector to keep fuel and not release droplets .  I have no issues in hot start . The car is starting perfectly in hot conditions and after a few cranks in cold starts .

[Shvegel]

Mauro,
Residual pressure keeps the fuel from boiling in the lines and forcing the fuel out through the injectors or pump if it is a leaking delivery valve.  Loss of residual pressure is the root of most hot start issues.  Since you don't have a hot start issue I would leave well enough alone. 

[mauro12]

i had 2 delivery valves leaking in the pump but they have been replaced during the pump overhaul. the bench test of the injectors says that 4 out of 6 are ok in residual pressure . Hot start is perfect , even after 1 second of shutting of the hot engine . the only issue is during the cold start , I need extra cranking , but probably has a connection with the cold start and not directly from injectors or pump. I've read many negative reviews about the new r2 injectors .
 

[Shvegel]

Even with 2 injectors leaking it should at least start on the other 4 and run a little choppy for a few seconds.  If you do look into the cold start system be very careful about jumpering any components until you have a through understanding of how the system and in particular the Thermo Time switch works.  The Thermo Time switch is quite sensitive to power being applied in the wrong spot and is quite expensive.  One terminal is a heater and one is a dead short to ground.  Choose wisely.