Diesel fuel pressure thingy?

allypug

allypug

A2OC Donor
Following the new fuel pump replacement the car now usually starts fine, though occasionally when left for a few hours it needs to be cranked for 10+ seconds until it chugs into life. Just wondering if there is a diesel pressure regulator or some sort of valve that keeps pressure in the system even when the engine is off?
When the car is in use and not left for more than a couple hours it fires up on the first spin.
 
Have you tried turning the car on and waiting for the glow light to go out and then repeating ? It may be a sign the glow plugs are failing ? Or that if the car has a fuel non return valve it’s not working. Good luck
 
allypug said:
Following the new fuel pump replacement the car now usually starts fine, though occasionally when left for a few hours it needs to be cranked for 10+ seconds until it chugs into life. Just wondering if there is a diesel pressure regulator or some sort of valve that keeps pressure in the system even when the engine is off?
When the car is in use and not left for more than a couple hours it fires up on the first spin.
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This has all of the hallmarks of a slight air leak in the fuel system, the fact that the pump has been replaced means that this area is a good place to start to look for a small leak.

Sometimes a leak like this results in a car that is easy to start when it has been left parked pointing downhill and it needing a lot of cranking when it has been left pointing uphill. (due to the flow from the tank.

Steve B
 
a2sumo said:
Have you tried turning the car on and waiting for the glow light to go out and then repeating ? It may be a sign the glow plugs are failing ? Or that if the car has a fuel non return valve it’s not working. Good luck
Click to expand...
doubt it's the glowplugs.. this has happened in very high heat before, yep I was thinking some sort of valve or pressure accumulator.. if there is one?
 
Birchall said:
This has all of the hallmarks of a slight air leak in the fuel system, the fact that the pump has been replaced means that this area is a good place to start to look for a small leak.

Sometimes a leak like this results in a car that is easy to start when it has been left parked pointing downhill and it needing a lot of cranking when it has been left pointing uphill. (due to the flow from the tank.

Steve B
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has happened when parked nose up and down.. I'll have a look under the bonnet for leaks next then!
 
How do you look for an air leak in this case? Unless fuel is also leaking out the air will be going in so won’t be visible. Are we thinking the air is only leaking in at rest so under pressure the fuel will be leaking out?

On a carburettor petrol engine you check for air leaks by spraying carb cleaner on the air hoses until you hear the engine tone change as the highly flammable liquid is sucked in to the line and is burned. Would that work okay for a diesel? No idea.




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Pinkythelabrat said:
How do you look for an air leak in this case? Unless fuel is also leaking out the air will be going in so won’t be visible. Are we thinking the air is only leaking in at rest so under pressure the fuel will be leaking out?

On a carburettor petrol engine you check for air leaks by spraying carb cleaner on the air hoses until you hear the engine tone change as the highly flammable liquid is sucked in to the line and is burned. Would that work okay for a diesel? No idea.




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Click to expand...
I'll be looking for fuel leaking out, hence air leaking in.. through fuel pipes etc. That method of finding airleaks in carb engines is for finding leaks in the air inlet side of things.
 
Dropping the car off to the garage in a bit to hopefully sort the problem out.
It's now got to the stage where every morning, and after work starting the car takes well over 10 seconds cranking.
 
Got the car back from the garage, every time they started it, even when left for the whole weekend, it started! Picked it up last night, and in the morning I got the same 10+ seconds cranking before it would start...
I did notice though, that while it was in the garage they had it parked on a decent incline, nose down, whereas my driveway has a very very slight incline.
So looks like Birchall could be on to something here. Taking it back on Saturday so they can check the aircon for leaks (they put dye in it).
Looks like I may be back on the motorbike again next week!
 
The fuel supply system for the 1.4 TDI is really quite basic. The fuel pump on the end of the camshaft just lifts diesel from the tank to supply the injectors. There's no pump in the fuel tank or any in-line trickery. If air is getting into the system, that doesn't necessarily mean that fuel is escaping. The fuel wants to return to the tank under gravity, but the system being sealed stops it from doing so. If there's a leak around the fuel pump, air gets in and the diesel falls back down the tubes into the fuel tank. If the fuel supply hose that's connected to the lift pump is replaced with a bit of transparent tubing, you can usually see if you've got the problem I describe.

Cheers,

Tom
 
Thanks Tom, I know where to look next now!
I don't suppose a smear of high temp silicon sealant around the rubber hose ends could help isolate the location..??
 
Just as a test.. I parked the car last night with the rear up on ramps, and it fired straight up first click this morning! will have a nose around the fuel pipes under the bonnet at lunch time.
 
This really is confirmation of an air leak in the fuel piping. Start at where the recent work was done on the fuel system.

Steve B
 
Had a look just now and it looks like the rubber tube at the fuel pump isn't pushed fully on so as to butt right up against the fuel pump, and at the other end, I assume the hose should be pushed over the 'ridges' on the metal fuel pipe that runs around the front of the engine?
 

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Good news, fingers crossed for you.

Lots of help on here from thevmbers, so never be worried about asking

A couple of words of help from the members can save you a lot of messing.

Steve B
 
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