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[TheBoy]

Fuel light started flashing, so chucked in 10g. Drove around until it started flashing again.

MID claimed:
41mpg
7g used

Reality
29mpg
10g used.

I can smell a whiff of diesel, after a run, when sitting in traffic.

I used to get approx what MID said.

Omegatoy and I located and fixed a leak on back of injector pump.  I'm unable to find any other leaks.

Any ideas?

[dieseldean]

i'd say that return fuel is leaking before returning to tank.
but then you notice a puddle on floor when car is parked.

[TheBoy]

Can't see any puddles of diesel - and diesel doesn't evapourate, so would have thought it would be obvious  :-/

[dieseldean]

could be main return pipe leaking at back of engine and near fuel filter and the sump guard soaking it up.
happened on my old 1994gls when dad owned it years ago and only noticed leak by rainbow puddles after heavy rain

[Entwood]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

[dieseldean]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

[TheBoy]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

That area, although corrosion there, looks OK, but no harm in checking again

[Omegatoy]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

That area, although corrosion there, looks OK, but no harm in checking again

it was a bit damp around the tank pump area!!!!
however bneen thinking since your txts today and if it aint leaking then it must be going through the system?
wonder if yu have a boost leak through the egr where its blowing out oil, ergo its chucking the fuel in for full boost but you not using it as the boost is down? the mid wouldnt know about it so would read normal/?? still thinking abouyt it but thats the theory so far possinle?

[TheBoy]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

That area, although corrosion there, looks OK, but no harm in checking again

it was a bit damp around the tank pump area!!!!
however bneen thinking since your txts today and if it aint leaking then it must be going through the system?
wonder if yu have a boost leak through the egr where its blowing out oil, ergo its chucking the fuel in for full boost but you not using it as the boost is down? the mid wouldnt know about it so would read normal/?? still thinking abouyt it but thats the theory so far possinle?

The ECU knows what its chucking in (via pump and feedback from injector 4), so MID should be in right ballpark.

Still think the smell is related  :-/

If there was a pinhole leak, would it atomise?

[dieseldean]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

That area, although corrosion there, looks OK, but no harm in checking again

it was a bit damp around the tank pump area!!!!
however bneen thinking since your txts today and if it aint leaking then it must be going through the system?
wonder if yu have a boost leak through the egr where its blowing out oil, ergo its chucking the fuel in for full boost but you not using it as the boost is down? the mid wouldnt know about it so would read normal/?? still thinking abouyt it but thats the theory so far possinle?

would that show on eml with code 41 or 42 or 43 or 44? :-/

[TheBoy]

no fault codes - get an occasional general glow plug one if it doesn't start first time (normally due to my laziness)

[Omegatoy]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

That area, although corrosion there, looks OK, but no harm in checking again

it was a bit damp around the tank pump area!!!!
however bneen thinking since your txts today and if it aint leaking then it must be going through the system?
wonder if yu have a boost leak through the egr where its blowing out oil, ergo its chucking the fuel in for full boost but you not using it as the boost is down? the mid wouldnt know about it so would read normal/?? still thinking abouyt it but thats the theory so far possinle?

The ECU knows what its chucking in (via pump and feedback from injector 4), so MID should be in right ballpark.

Still think the smell is related  :-/

If there was a pinhole leak, would it atomise?

would have to be on the high pressure side ie after the pump to atomise so dont think so we checked it out pretty thoroughly the other day, yep agree the ecu knows what it is chucking in but would it know if it had a high pressure boost leak??

[TheBoy]

Might be a total red herring .. but an old Honda I had developed the ability to lose fuel at an alarming rate with no sign of any leaks, eventually discovered the fuel return pipe into the tank (sealed system) was leaking (corrosion), so the leak only occurred when running, and it was going straight down onto the road so wet patches never collected on the car.

As the diesel also has a return feed from the injectors back to the tank, IMSMC, could this be an area worth checking

this also happened to me but spotted it straight away on my sloping drive. the rubber return pipe bending to top of sender unit on top of tank had split. would be quick and simple to check for as only four screws on boot floor to access.

That area, although corrosion there, looks OK, but no harm in checking again

it was a bit damp around the tank pump area!!!!
however bneen thinking since your txts today and if it aint leaking then it must be going through the system?
wonder if yu have a boost leak through the egr where its blowing out oil, ergo its chucking the fuel in for full boost but you not using it as the boost is down? the mid wouldnt know about it so would read normal/?? still thinking abouyt it but thats the theory so far possinle?

The ECU knows what its chucking in (via pump and feedback from injector 4), so MID should be in right ballpark.

Still think the smell is related  :-/

If there was a pinhole leak, would it atomise?

would have to be on the high pressure side ie after the pump to atomise so dont think so we checked it out pretty thoroughly the other day, yep agree the ecu knows what it is chucking in but would it know if it had a high pressure boost leak??

Reckon it would - the boost pressure sensor would know. The MAF would also indicate.

Maybe I should revisit the bodged 'plug' in end bleed off pipe (ie, on the other side of No 6)?

Trouble is, no real sign of leakage anywhere. No oily deposits on back of car. Not excessively oily in exhaust, so not convinced its overfuelling.  Performance still appears to be similar to when mpg was around that of MID

[dieseldean]

i think its a leak on fuel return. mid reads fuel returning but doesn't read it going back into tank.
if it is leak like i had on top of tank then it only leaks when engine is running and what is left in it when engine stops. what leaks when engine stops will not be enough to show by puddle if parked on level ground as it will settle around top of sender unit/pump.
try leaving car tickover for 10 mins then look on ground.

[Kevin Wood]

I would have thought 3 gallons out of 10 leaking would be noticeable.

I assume on a diesel, unlike a petrol engine, the return flow is dependant on fuel demand, i.e. the more is injected the more flows through the return lines. Could it be that the problem is only noticeable under load and the leak doesn't manifest itself under light load and idling, so hasn't leaked on your driveway?

I would have thought overfuelling to this extent would make it smoke and affect running so I'm leaning towards a leak too.

I wonder if it's worth "pressure testing" the fuel feed and return lines? Block them at the engine end, apply some air pressure at the tank end and see if the pressure drops or if any leakage is evident. This could eliminate them at the very least.

Kevin