Darrnw

New Member
HP pump crank driven! How does it work? You have a fuel feed in a fuel out then the feed to the common rail. You have a connector on the back of the pump with a few wires in it. When does it re direct the flow o fuel? How does it know when to divert fuel etc?
 
I cant be sure on this system, but some others use a pump to pressurise the fuel - a pressure release then lets fuel out to the common rail and surplus fuel is pumped back to tank. this would explain your three connections.

Others will know for sure.
good luck
 
Er yes flippy quiet right lp/in regulator lp/out when max pressure to common rail ,after lp/outinto a 2 port with a bi metalic switch,if hot ,through cooler and back to tank,if cool straight back to tank,best oh luck earthling. . .:)
 
Am I right in thinking the regulator is basically a valve actuator?
The reason I am digging at this is that the LR bloke said that the pressure at the common rail wasn't building up, therefore if the regulator on the HP fuel pump is frigged the fuel would be diverted back to the fuel tank. I took the return hose off the LP and it was ****ing fuel back as SOON as the ignition was switched to position 2! So I reckon the regulator is frigged I am planning on taking it off this aft can someone tell me how to test the reg if I take it off the pump?
 
on some systems there is no pressure relief to the common rail - the pump just pushes fuel out to both rail and back to tank - the rail side just takes what it needs.
on the principle of "check fuse before dismantlin tv set", have you checked that the fuel pipes after the pump are not blocked, so that fuel can get from the pump to the injectors?

does anyone have a schematic of the TD4 fuel system?

if it is a simple rubber diaphragm system - check for holes.
 
Wot a helpful fellow that Minge is (watch out for his missus tho!)

looking at the diagram then if yu is getting flow out of the bottom of the injection pump and not to fuel rail, It can only be one of 5 things...
1) pump shot
2) pipe to rail blocked.
3) pressure regulator knacked
4) Rail blocked
5) pressure sensor knacked

good luck - some are easy to check - others hmmm!
 
Darrnw said:
Am I right in thinking the regulator is basically a valve actuator?
The reason I am digging at this is that the LR bloke said that the pressure at the common rail wasn't building up, therefore if the regulator on the HP fuel pump is frigged the fuel would be diverted back to the fuel tank. I took the return hose off the LP and it was ****ing fuel back as SOON as the ignition was switched to position 2! So I reckon the regulator is frigged I am planning on taking it off this aft can someone tell me how to test the reg if I take it off the pump?
When did he mean the pressure wasnt building - I assume he meant during cranking,if so then there could be a problem in monitoring it as live data displays tend to freeze or crash during cranking.Does the Hp side read correctley when its running ? If it does then that pretty much cuts the high pressure sensor out of the picture.That leaves you with the pressure regulator,which I cant think of a sensible way to test off the car,or the high pressure pump.If as you say it runs ok once started and there is no rising of fuel in the leak off pipes - my money is on the regulator.Despite what the rave cd says it can be changed without removing the starter etc.Subbing it with a new one is probably the safest bet.Bearing in mind that the Hp pump is lubed by the diesel,I think if it was so shot it couldnt provide a decent start quantity/pressure,then performance would be very poor too.
 

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