Air in fuel when under power but ok when idling

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Barney86

Member
Posts
15
Hello,

I finally got my Defender back after the garage struggled to find my intermittent problem. It went in because I kept breaking down; the fuel pump starts making a noise, then it goes lumpy for a few seconds, then all power is lost. The lights come on, and it's over. It's a pain to restart, which involves going through the priming cycle for ages until the pump gets quiet.

They guy at the garage said he's done everything he can think of. Unfortunately I broke down again on the way home :(

The noise is definitely air in the system. I've heard it before when the injector seals went a few years ago.

I don't think it's any of the following (they've all been changed with genuine in the last few weeks)
- Fuel regulator
- Fuel pump
- Injector seals
- Air mesh thing on the fuel filter housing port.
- Fuel filter

Within the last couple of years I've also changed the injector harness and fuel filter housing. I can't find any fuel leaks.

When it's sitting idling, it runs fine. When I was driving 'harder' - ie demanding a decent amount of power (up a slight hill, accelerating, 50mph) I could hear a hissing noise from somewhere - and I broke down soon afterwards. When I thrashed it to get home after getting it going again, it broke down after 500 yards. Then I tried minimal revs, 3rd gear, and it got me the 2 miles home in one go. The hissing could be from something else I guess, but it does get louder with the amount of power. I left it sat idling on the driveway for an hour and it was fine.

Anyhow, what's left for me to try?! A faulty injector maybe?

Nanocom doesn't show any related errors. The cylinder balancing screen shows variations between 2 and about -4. Not sure if that's good or not?

Help! Please :)
 
Hello,

I finally got my Defender back after the garage struggled to find my intermittent problem. It went in because I kept breaking down; the fuel pump starts making a noise, then it goes lumpy for a few seconds, then all power is lost. The lights come on, and it's over. It's a pain to restart, which involves going through the priming cycle for ages until the pump gets quiet.

They guy at the garage said he's done everything he can think of. Unfortunately I broke down again on the way home :(

The noise is definitely air in the system. I've heard it before when the injector seals went a few years ago.

I don't think it's any of the following (they've all been changed with genuine in the last few weeks)
- Fuel regulator
- Fuel pump
- Injector seals
- Air mesh thing on the fuel filter housing port.
- Fuel filter

Within the last couple of years I've also changed the injector harness and fuel filter housing. I can't find any fuel leaks.

When it's sitting idling, it runs fine. When I was driving 'harder' - ie demanding a decent amount of power (up a slight hill, accelerating, 50mph) I could hear a hissing noise from somewhere - and I broke down soon afterwards. When I thrashed it to get home after getting it going again, it broke down after 500 yards. Then I tried minimal revs, 3rd gear, and it got me the 2 miles home in one go. The hissing could be from something else I guess, but it does get louder with the amount of power. I left it sat idling on the driveway for an hour and it was fine.

Anyhow, what's left for me to try?! A faulty injector maybe?

Nanocom doesn't show any related errors. The cylinder balancing screen shows variations between 2 and about -4. Not sure if that's good or not?

Help! Please :)

just check to make sure your fuel pump fuel connectors are in the correct ports all 4 of them ..should be colour coded not to sure about the defender but my disco is white green black blue form left to right you may also need to check the fuel lines inside side the fuel tank

you will also need to monitor fuel pressure


 
People have suffered similar symptoms when the fuel filter housing has a crack in it, allowing it to draw air into fuel system.
Also try driving with the filler cap off to see if that makes a difference.
 
I know you’ve changed the copper injector seals but this is exactly the fault I’ve just had and I found an obvious gas leak under one of them - probably caused by grit underneath the seal.
It’s probably not enough just to replace the seals but to ensure that the mating surface of the head is scrupulously clean too.

My theory about breaking down under power is that it’s because there must be a higher pressure in the cylinder under load. Mine also ticked over fine and got me 25 miles whilst being driven at 40 mph
 
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