High pressure pumps

High pressure fuel pump 

 
The high pressure pump is supplied with fuel at a pressure of about 4.5 bar and generates an outlet pressure of up to 110 bar. (11.000kPa). Unfortunately, this is the weakest part of the injection system due to the use of an unusual solution, i.e. a diaphragm pump. These types of pumps have never before been used for such high pressures. They are usually used for pressures of 1000 PSI (69 bar) and in this case the pressure is 110 bar. Despite the special design, the diaphragms break if the engine is often operated under high load, which results in reaching the maximum working pressure.
If the engine is handled fairly gently, the fuel pressure will not exceed 70-80 bar and the pump can run out for much longer.
 
 
 
 The pump performance can be checked under road conditions. In 3rd gear, at approx. 1500 rpm, press the accelerator pedal as far as it will go. The engine should pull evenly up to 6,500 rpm. If, around 3000 rpm, there is a noticeable drop in power, jerking or switching on the limp mode, it means that the high pressure pump has probably reduced efficiency.
 

Dissasembly and assembly 

 

Very important ! The high pressure pump may only be removed when the engine is cold. You should also have a fire extinguisher nearby, just in case. Attempting to remove it while the engine is hot may result in fire. The fuel is under high pressure and temperature of approx. 100 ° C. Unsealing of such a system leads to the immediate boiling of gasoline and its discharge outside, which may cause ignition and explosion of vapors or burns.

 
Remove the connector of the fuel line and unscrew the steel conduit connecting the pump with the rail with a wrench [17]. Then unscrew the three [torx] screws securing the pump to the head body. The pump should slightly pop out of the head.
Plug all open fuel connections, both in the car and in the pump. Do not leave the fuel connections open.
    
The assembly should be carried out in the reverse order, keeping in mind the utmost cleanliness. If the system is not plugged and the fuel has evaporated, prime the system with fuel and bleed air before starting.
After starting the engine, check the system for leaks. The tightness of the system is essential for proper engine operation and safety. Therefore, all operations are performed at your own risk. 
 

Demage to the pump

 
The subject of GM pumps damage is well known, because in most cases the diaphragms burst. Although the diaphragms have an internal reinforcement, the pressure of 110 bar creates such great forces that they systematically stretch the diaphragms until they burst. Unfortunately, there is nothing we can do about it, we can only drive so that the system does not reach its maximum pressure.
 
Of course, the pumps can be repaired, but the problem is that in the past there were no, and will not be, original diaphragms on the market. Pomps can be repaired on used or fake diaphragms (photo of fake diaphragms market "GM" attached). This is not complicated procedure but pay attention to the fact that the pump must be fully filled with oil, and the amount of oil must ensure a free increase in volume as a result of reaching the engine temperature (about 10% / 100C)
 

Alternative pumps

 
Now we have alternative solution to replace very weak diaphragm GM pump to the piston pumps other brands.