Amount of total fuel return (1.6 HDI)?
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Aretius
- Posts: 9
- Joined: 22 Mar 2022, 09:32
- x 2
Amount of total fuel return (1.6 HDI)?
Does anyone know how much fuel in total that is returned to the tank when idling? - in this case regarding a 1.6 HDI (2007). 'In total' covers the injectors and the HP pump. The thing is mine is about 1 liter/minute, which I find quite a lot (and seems to be causing a lot of dissolved micro air bubbles in the fuel - the fuel turns opaque after some hours of driving). The rate of return fuel from the injectors are low (and normal), so nearly all of the return fuel comes from the HP pump. I am asking because it has become increasingly difficult to start the engine. It's has been tricky ever since I bought it 1 year ago: I've had to give it a little gas when cranking in order for it to start. But now it won't start at all unless I prime it (using the primer bulb). The bulb gets rather slacken soon after the engine stops (the internal check valve in the bulb works fine), and then needs to get primed (and hence hardened) in order to start the engine again. It feels like the fuel in the both the inlet and return line is getting pushed back to the tank. And so regarding the inlet line the fuel needs to get sucked back by the primer bulb to the HP pump (there's is no lift pump in the tank) in order to start the engine. But it can't be an air leak causing this, since no diesel is spilled on the floor. And all sensors seem to work, even the fuel pressure regulator should work too. One of the injectors might have a small back leak (but really not that much), so I'm rather baffled. Any idea?
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mickthemaverick
- Moderating Team
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Re: Amount of total fuel return (1.6 HDI)?
Hi and 
Just a thought about your situation, it is possible to have air leaking into the system without a corresponding drip on the floor. The air entering simply forces fuel back into the tank so you don't see a leak of fuel. As the primer is going soft I would think there is a leak somewhere allowing the line pressure to dissipate and the chances are it's the same leak that is aerating your fuel!
I'm sure much more expertise will be forthcoming but they are just my instant thoughts.!
Just a thought about your situation, it is possible to have air leaking into the system without a corresponding drip on the floor. The air entering simply forces fuel back into the tank so you don't see a leak of fuel. As the primer is going soft I would think there is a leak somewhere allowing the line pressure to dissipate and the chances are it's the same leak that is aerating your fuel!
I'm sure much more expertise will be forthcoming but they are just my instant thoughts.!
I used to be indecisive, now I'm not so sure!
I used to ride on two wheels, but now I need all four!
I used to ride on two wheels, but now I need all four!
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thorter
- Posts: 224
- Joined: 22 Feb 2005, 02:07
- x 41
Re: Amount of total fuel return (1.6 HDI)?
If the system installed is one with the fuel lift pump as part of the injection pump, then the whole of the run from the tank operates below atmospheric pressure. So indeed any leak somewhere near the highest point will draw in air when running and let the fuel run back to tank when parked without any sign of an external leak.
Look for the leak there, often in the filter housing or priming device.
Look for the leak there, often in the filter housing or priming device.
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wheeler
- Posts: 7893
- Joined: 21 Sep 2002, 19:07
- x 1044
Re: Amount of total fuel return (1.6 HDI)?
The total fuel return rate is not something i have ever measured or seen a figure for but 1 litre per minute doesn’t seem unreasonable to me at all. The fuel pump always pumps way more than it actually needs, this will also help with fuel cooling.
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Aretius
- Posts: 9
- Joined: 22 Mar 2022, 09:32
- x 2
Re: Amount of total fuel return (1.6 HDI)?
Thanks for the replies
Okay, I'll accept 1 liter/minute isn't unreasonable. Still think it's quite a lot, though.
After tightening a couple of straps, the primer bulb stays reasonable hard, and it seems no air gets into the fuel lines. That's good. Unfortunately the engine is still hard to start even though there's no need to prime it anymore. Actually, ever since two days ago it won't even start anymore. Spraying a bit of diesel start (ether) into the intake starts it (the glow plugs don't work anymore, so there's no risk). So, I went to the wreck yard and found an injector. Easy enough to pull out, by the way. You see, one of my injectors is back leaking, as I wrote in my first post. The engine runs very well, though, but nevertheless my thought was that the back leaking was the culprit of the fast drop of pressure, when I turn off the engine. And the culprit of why it has been tricky to start for a long time (impossible now, sadly). I got a pressure regulator too at the wreck yard, in case replacing the injector doesn't help.
Long story short, the old injector is completely stuck - and now damaged. And so I killed my car.
On Monday I will ask the local mechanic, if he has an hydraulic puller, though. That's what it will take to pull it out...
Okay, I'll accept 1 liter/minute isn't unreasonable. Still think it's quite a lot, though.
After tightening a couple of straps, the primer bulb stays reasonable hard, and it seems no air gets into the fuel lines. That's good. Unfortunately the engine is still hard to start even though there's no need to prime it anymore. Actually, ever since two days ago it won't even start anymore. Spraying a bit of diesel start (ether) into the intake starts it (the glow plugs don't work anymore, so there's no risk). So, I went to the wreck yard and found an injector. Easy enough to pull out, by the way. You see, one of my injectors is back leaking, as I wrote in my first post. The engine runs very well, though, but nevertheless my thought was that the back leaking was the culprit of the fast drop of pressure, when I turn off the engine. And the culprit of why it has been tricky to start for a long time (impossible now, sadly). I got a pressure regulator too at the wreck yard, in case replacing the injector doesn't help.
Long story short, the old injector is completely stuck - and now damaged. And so I killed my car.
On Monday I will ask the local mechanic, if he has an hydraulic puller, though. That's what it will take to pull it out...
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citroenguy
- (Donor 2021)
- Posts: 251
- Joined: 21 Sep 2017, 18:05
- x 71
Re: Amount of total fuel return (1.6 HDI)?
The glowplugs are important for starting and DPF regen.
Id get them changed..
Getting an injector out on a CR car is always very risky business.
Id get them changed..
Getting an injector out on a CR car is always very risky business.
I have various repair handbooks and wiring diagrams for C5 mk1, Xantia, XM, Berlingo and C3 mk1.
I have Lexia/Diagbox (Sweden) and Servicebox/sedre
I have Lexia/Diagbox (Sweden) and Servicebox/sedre
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Aretius
- Posts: 9
- Joined: 22 Mar 2022, 09:32
- x 2
Re: Amount of total fuel return (1.6 HDI)?
Hmm, the glow plugs haven't been working for years, I believe. The DPF regeneration seems to work alright, though.
By the way, the local mechanic managed to remove the old injector. And after the new (secondhand) injector has been installed, the engine fires up like it should, that is immediately. Also, the fuel economy has improved quite a bit. With the old injector an mixed average about 5.6L/100km was normal. With the new injector it seems 4.5L/100km is the new mixed average. I'm rather surprised.
By the way, the local mechanic managed to remove the old injector. And after the new (secondhand) injector has been installed, the engine fires up like it should, that is immediately. Also, the fuel economy has improved quite a bit. With the old injector an mixed average about 5.6L/100km was normal. With the new injector it seems 4.5L/100km is the new mixed average. I'm rather surprised.