1.6HDI diesel system air-locking at between 1/2 and 1/3 tank

Kencollins

Hi all,

I have a Peugeot 5008 1.6HDI (2010)

When I first bought the car I had two breakdowns on the motorway after going around a tight right turn at 70kph or more when the fuel was below 1/3 tank.

I put this down to the diesel sloshing away from the strainer, and air-locking the system.

Over the last 2 weeks this has happened twice more, but on the straight this time. It is the same sequence...EML light comes on, and 5 seconds later the engine dies.

Fault codes logged say Low fuel pressure, and High Pressure Fuel system below specification.

To get the car going I add 5 L of diesel, prime the hand primer, and hope it starts before the battery dies.

Can anyone suggest where I should start in trying to fix this issue? I have already:
-Changed the fuel filter. No metal filings in the old one.
-Checked the pressures when the engine is running normally (300 bar)
-Checked the OHM readings when the tank was full, and this matches the data proved by Peugeot.

The tank is a pig to get at in these cars but it looks like I might have to drop it to have a look in.

The car drives perfectly when it is driving.

Any ideas?

Thanks,

Ken

mullingar

Cheapest option: Keep fuel over the 1/3rd mark.

mullingar

Next option, change the sender unit in the tank. Hopefully there is a cut-out under the rear seat to let you have access.

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Kencollins

Thanks for the suggestions!

I thought the issue was when it went below 1/3 tank, but it left me on the motorway somewhere between half and 1/3 yesterday!

The tank is an under the car only job unfortunately. It's not too hard to get to really, a few brackets and the exhaust removed should do it.

A nice job for the christmas!

Irish Steve

Does this have a pump in the tank, or (more likely with a primer) the fuel is drawn up from the tank by a pump on the engine.

It would be worth checking all the connections on the fuel filter, and replacing all the hose clips to ensure that no air is being drawn into the lines as a result of a loose pipe. I had something similar on an Isuzu a few years ago, the pipes had hardened over time, and it was made worse that the easiest way to change the fuel filter was to remove the entire filter unit to replace the filter, so I had a combination of a very slightly loose pipe, and a clip that wasn't gripping as tight as it used to, the clips were a quick release rather than a screw clamp.

If the engine moves slightly due to something like a lean in a corner, the pipe moves fractionally, and allows air into the line, which then results in an engine that stops.

rex-x

There may be more to this OP than you think, it sounds like possible HP pump or injector failure. See can you make the car cut out by giving it long extended full throttle runs in 3rd and 4th gear, if so then this is likely your issue. The rail pressure is dropping below the required threshold. I have never seen another cause for this to happen in the manner you describe. It becomes more prevalent when fuel is low because hotter diesel is harder to pump and the less in the tank the hotter it gets from the return feed.

PukkaStukka

There is a known - albeit infrequent - issue with the in-tank pickup inside the fuel tank in some Pug diesels. The pickup pipe splits part way along its length and once the tank level drops below the level where the split is at, the car suffers fuel starvation.

Kencollins

Thanks for all the suggestions!

There is no pump in the tank, just a sender unit.

The section of pipe between the firewall and the primer bulb looks pretty new, maybe someone had a stab at it before!

I hope the issues aren't as rex suggested, I could do without the hassle of replacing the HP pump or pressure regulator. The diagnostic scanner is showing pretty consistent pressure at 300 bar plus or minus 2, so hopefully thats a good sign!

PukkaStukka, I hope what you said is correct! It sounds plausable. When the car breaks down I can prime for an hour but it feels like the primer bulb is drawing up air with the fuel. I can hear gurgling when I release the primer after squeezing it. Adding 5L of diesel to the tank and the primer will go rock solid after 10 squeezes.

I think dropping the tank is a 2 m an job, I will have to see if I can get someone to help over the next few days.

9935452

out of curiosity if you take off the filler cap is there suction.
A vent might not be working right and as the tank empties it created a vacuum and makes it harder to pull diesel from it

jca

Another thing to consider, maybe some clown jacked the car up under the fuel tank leaving a hump in the centre which only appears when the fuel is below a certain level. Although I think the cracked pickup pipe is the culprit.

rex-x

Kencollins wrote: »

The diagnostic scanner is showing pretty consistent pressure at 300 bar plus or minus 2, so hopefully thats a good sign!

This is the idle pressure. It wont struggle to hit that, but under load it will be going to 1800 bar+ and this is where it may struggle, there should be a requested vs actual rail pressure, monitor this under heavy load because if the gap gets too big then it will cut out because it thinks there is a leak.