Bosch HP Diesel Fuel Pump Detail of Internal Workings Filter - Page 2

Lovel · 27th October 2009, 12:25

Quote:

Originally Posted by Lovel

I checked the inlet fuel feed for the CP1 HP pump today and noticed that there is a check valve inside. The check valve seemed to be stuck solid, but after a little push it started to function again. It should not have been stuck as there was no pressure behind it??. This may explain why I get no fuel going through the CP1 HP pump. Once I get my ECU back from the Doctor we'll see if it starts. In the bill of materials (Item 14) for the CP1 HP pump it described the check valve as a shut down valve assembly. I'm not sure if this is just to stop the fuel draining out once the engine is stopped or if it stop high pressure going back the way from the HP pump which could be interesting.

Pic 1 showing inlet of CP1 HP pump
Pic 2 exploded diagram of HP pump showing components.

Well the check valve inside the HP pump was indeed the culprit. Started first time and is running quite sweetly now. I can only assume that the check valve seized closed and just needed a little persuasion to get it going again.
If I come across a non running Diesel again and I know the LP pumps are fine, then this is one the basic checks that I will carrying out for sure.:lol:

Roverto · 18th January 2017, 12:19

Just to add my two pennies on this one: not an owner of Rover or MG, but still dealing with Cp1 Bosch pump, I found info on another forum stating that this check valve preservs the pump in case of low pressure fuel inlet flow: when closed, the valve allows the fuel flow to go only through the lubrication circuit inside the pump, thus preventing the pump to seize in case of fuel starvation, preventing the non-sufficient fuel flow to get to the compression cylinder stage. When fuel input pressure goes over 0.8 bar approx., the valve opens, allowing the fuel to get into the cylinders and the pump starts doing its job of delivering high fuel pressure into the ramp. If stuck = no compression = no high pressure on rail = no start, even though the pump itself might be perfectly OK! Located at the bottom of the inlet pipe, just pushing it (gently!) with some sort of "stick" (screwdriver?) will free it again (it´s spring-actuated). AFAIK, it´s got nothing to do with preventing a high pressure return to the inlet (knowing the inner workings of the pump that´s not possible). Hope this clarifies a little bit why this valve is in place and how it works, and maybe help someone dealing with fuel related problems! Cheers!

Roverto · 18th January 2017, 12:43

More on Cp1 pumps: it might (depending on model) have a very fine filter (2 to 5 microns) inside, at the tip of the pressure regulation valve, the one at the back of the pump fitted with two Torx screws, having an electrical two wire plug in it. This ultra-fine non-replaceable filter may get clogged with time (and dirt in Diesel fuel!), and one of the first signs of this condition is that the engine keeps running for a couple of seconds after shutting it off, instead of cutting off instantly. Solution: get a carb-cleaner spray, undo the two Torx screws, and thoroughly spray the tip of the valve (looks solid, but it is porous). Done it a couple of times already, never fails, engine seems to run even better after the cleaning! Hope this helps someone

j hitchcock · 21st December 2023, 14:54

Bosch CP1 HP Pump Inlet Check Valve, AKA Shut Down or Safety Valve
I checked the inlet fuel feed for the CP1 HP pump today and noticed that there is a check valve inside. The check valve seemed to be stuck solid, but after a little push it started to function again. It should not have been stuck as there was no pressure behind it??. This may explain why I get no fuel going through the CP1 HP pump. Once I get my ECU back from the Doctor we'll see if it starts. In the bill of materials (Item 14) for the CP1 HP pump it described the check valve as a shut down valve assembly. I'm not sure if this is just to stop the fuel draining out once the engine is stopped or if it stop high pressure going back the way from the HP pump which could be interesting.

Pic 1 showing inlet of CP1 HP pump
Pic 2 exploded diagram of HP pump showing components.
Attached Thumbnails

18th January 2017, 12:19	#12
Roverto Newbie None Join Date: Jan 2017 Location: Buenos Aries Posts: 2 Thanks: 0 Thanked 1 Time in 1 Post	Safety check valve on CP1 Just to add my two pennies on this one: not an owner of Rover or MG, but still dealing with Cp1 Bosch pump, I found info on another forum stating that this check valve preservs the pump in case of low pressure fuel inlet flow: when closed, the valve allows the fuel flow to go only through the lubrication circuit inside the pump, thus preventing the pump to seize in case of fuel starvation, preventing the non-sufficient fuel flow to get to the compression cylinder stage. When fuel input pressure goes over 0.8 bar approx., the valve opens, allowing the fuel to get into the cylinders and the pump starts doing its job of delivering high fuel pressure into the ramp. If stuck = no compression = no high pressure on rail = no start, even though the pump itself might be perfectly OK! Located at the bottom of the inlet pipe, just pushing it (gently!) with some sort of "stick" (screwdriver?) will free it again (it´s spring-actuated). AFAIK, it´s got nothing to do with preventing a high pressure return to the inlet (knowing the inner workings of the pump that´s not possible). Hope this clarifies a little bit why this valve is in place and how it works, and maybe help someone dealing with fuel related problems! Cheers!

18th January 2017, 12:43	#13
Roverto Newbie None Join Date: Jan 2017 Location: Buenos Aries Posts: 2 Thanks: 0 Thanked 1 Time in 1 Post	Filter More on Cp1 pumps: it might (depending on model) have a very fine filter (2 to 5 microns) inside, at the tip of the pressure regulation valve, the one at the back of the pump fitted with two Torx screws, having an electrical two wire plug in it. This ultra-fine non-replaceable filter may get clogged with time (and dirt in Diesel fuel!), and one of the first signs of this condition is that the engine keeps running for a couple of seconds after shutting it off, instead of cutting off instantly. Solution: get a carb-cleaner spray, undo the two Torx screws, and thoroughly spray the tip of the valve (looks solid, but it is porous). Done it a couple of times already, never fails, engine seems to run even better after the cleaning! Hope this helps someone

21st December 2023, 14:54	#14
j hitchcock Newbie rover 75 tourer Join Date: Oct 2018 Location: Worcester Posts: 13 Thanks: 0 Thanked 0 Times in 0 Posts	Bosch CP1 HP Pump Inlet Check Valve, AKA Shut Down or Safety Valve I checked the inlet fuel feed for the CP1 HP pump today and noticed that there is a check valve inside. The check valve seemed to be stuck solid, but after a little push it started to function again. It should not have been stuck as there was no pressure behind it??. This may explain why I get no fuel going through the CP1 HP pump. Once I get my ECU back from the Doctor we'll see if it starts. In the bill of materials (Item 14) for the CP1 HP pump it described the check valve as a shut down valve assembly. I'm not sure if this is just to stop the fuel draining out once the engine is stopped or if it stop high pressure going back the way from the HP pump which could be interesting. Pic 1 showing inlet of CP1 HP pump Pic 2 exploded diagram of HP pump showing components. Attached Thumbnails