Some of you may remember CharlesY on here, he parked his Discovery in a corner of the yard about 4 years ago and hasn't had it on the road since, the odd trip around a field (usually pulled by a tractor or my 90 to start it) and up and down the private road has been it's lot; 20 miles in 4 years if it's lucky! The reason for this was that it was becoming increasingly more difficult to start and generally it was just being a pig so he switched to the proven reliability of a Volvo and has not really needed the Disco. Recently he decided that the Disco had to be made to go again and a new found enthusiasm has seen the fuel system stripped to it's component parts from the tank to the engine with the injectors taken out etc.

As those of you who remember Charles will know he is an excellent motor engineer (anything engineer to be honest) and his abilities to make machines work is astounding so this TD5 "issue" has become something of a challenge that will be overcome!

Anyway, the injector loom was checked the injectors were removed again (done by him about 4/5 years ago) and the system was pulled apart. He was pleased to find they all appeared in good condition and there were no signs of blow by or leaks at all - the O rings all looked good - these were not a major suspect as there were not some of the usual signs to warrant this but it was worth a check. The FPR was replaced with a new one 4/5 years ago so it was ruled out for now, also the fact that once the thing ran, it ran brilliantly - didn't miss a beat, as long as it was not turned off!

Onto the filter head, on close inspection it was found to be knackered, the metal had gone soft and a mounting hole corner had broken off and the metal looked like it had more than likely gone porous. I ordered him a new replacement and we looked into the hardware for this new head.

We all know about the bleed valve and check valve and the stories and issues surrounding these. The check valve was on a service bulletin to be retrofitted as it was not always fitted from the factory.

So we looked into these bits and Charles then removed and stripped the old filter head. What was found was astonishing. Now look at this image (sorry for the poor quality):

Look to the top left of the filter on this image, that shows the black piece going into the back left union and if a check valve is installed in this location it will stop diesel running back into the tank via the pump low pressure side (i.e. the fuel pickup). This black piece which is part no. VUB503950 is listed as FUEL RETURN CHECK.



It is no such thing - this is not a Fuel Return Check - it is a small black adaptor which slides into the brass union, seals with an O-ring on the OD and leaves you with a hose barb sticking out of the union. Fit this on it's own and you have just wasted about £14.00.

What is required and as far as Charles and I can see is not available for sale anywhere as a LR part is the duck bill valve that actually attaches to this part and makes it into a Fuel Return Check. This valve MUST be fitted in conjunction with the black adaptor. It looks like this:


Now, there is also, as can be seen in the top picture, an air bleed valve, this sits in the bottom left union and allows a lot of air to pass but very little or no diesel, this simply returns to a pipe stub in the sender unit, now if this was to drop full distance into the tank things might be different as there would be no air ingress point! We think that some senders did have a full length pipe and some just the stub and vents into the tank. The air bleed valve is prone to blockage as it works with a very fine membrane. This piece seems to come with the union and is part no. WJN500110.

So we are all clear where the bits belong? This is what was found:



So when the check valve was either fitted from the factory or retro-fitted by the main dealer it was put in the back right, this is the return via the fuel cooler from the fuel gallery. In this location (really at the very end of the fuel system) it cannot really do anything. It needs to sit where indicated as this stops the LP fuel feed from running back which it can as there is an air leak into the filter head, it's called the air bleed valve, it can allow air in from the tank which can let air enter the filter and let the fuel drop back down the LP side.

The old filter head really was in a mess:




I know parts of the above information have come before on our and other forums but I just thought it was worth while posting this as one big post and also highlighting the fact that some monkey may have fitted your duck bill valve in the wrong location!

Selling VUB503950 as a FUEL RETURN CHECK really is a total con and is quite misleading, it is not until you have gone through quite a few posts and a lot of searching that do you even begin to realise this is only half of the check system.

More on this once the fuel system and injectors are back together!

is he coming back then?

Well all I can say on this, nice post although this has been discussed before. Is that the non return "orange " part appears to only be available new as part of the fuel filter housing. The filter housing breaking apart is exactly what happened to mine when I removed it last month.

However , in the position shown, looking at it on the car in car position. On mine the orange rubber duck was fitted closet to the chassis on the front . the air bleed valve was fitted away from the chassis on the back. I would suspect they are all like this.

Cheers

To simplify a bit that "fuel return check" IMO is a waste of money anyway cos it was fitted only for 15(and beyond)P engines, the 10Ps dont have it at all and they are 100% happy without it as long as no other problems with the filter head or pipework is present...actually that return check could hurt more rather than help cos the 10P's which are missing it can be startable and driveable even with dead HP stage of the pump while those which have it will die and not start on LP...i've seen this few times.

the air bleed valve in exchange is a very important bit

The Mad Hat Man said:

is he coming back then?

Click to expand...

I don't know, I will ask. He mentioned you and some of the old clan when we were doing this TD5 stuff.

neilly said:

Well all I can say on this, nice post although this has been discussed before. Is that the non return "orange " part appears to only be available new as part of the fuel filter housing. The filter housing breaking apart is exactly what happened to mine when I removed it last month.

However , in the position shown, looking at it on the car in car position. On mine the orange rubber duck was fitted closet to the chassis on the front . the air bleed valve was fitted away from the chassis on the back. I would suspect they are all like this.

Cheers

Click to expand...

I do despair sometimes. I know it has been discussed before, I was under no illusion that I was inventing the wheel here, I even made the comment, "I know parts of the above information have come before on our and other forums..." but the post was, like many on this forum, is just an educational report on what had been discovered. Also, interestingly not all the posts pertaining to this issue are easily found now as they are buried deep and since the photo hosting lot stopped the third party linking a lot of good images and help has gone. People tend to concentrate on small parts of the system usually not taking the entire thing to pieces.

So on your vehicle, the duck bill valve was fitted back union, front of vehicle? This is wrong, if you suspect they are all like this then you suspicions may be correct, perhaps a LR technical bulletin was written incorrectly and lots of them ended up going in the wrong place? The air bleed valve is in the correct location, it should bleed to the open pipe stub in the tank.

Having the NRV in the location Charles and you found it would not do a hell of a lot, think of the route the diesel must take to run back to the tank. It would need to go back through the cooler, FPR, through the diesel gallery, back to pump, through the HP pump, back out to the filter, and back to the LP pump... What is likely going to happen is as explained about is air will enter the wrong way via the air bleed valve, into the filter, allowing diesel to return down the LP pump feed and into the tank.

discomania said:

I don't know, I will ask. He mentioned you and some of the old clan when we were doing this TD5 stuff.

Click to expand...

Don't believe all he said

Well, mine starts and runs OK, so I think I will leave it where it is.

Thanks.

So on your vehicle, the duck bill valve was fitted back union, front of vehicle? This is wrong,

Is that a statement based on a direction from LR , or on the supposition of how it should work? That picture from the internet, also has raised concerns ( if you do a google search) that the defender was piped differently at the beginning compared to the D2. If this is true or not I have no idea as I am not duly concerned as I said , mine starts and runs OK after changing the filter housing which was knackered, and the rubber duck was open.

Cheers

sierrafery said:

To simplify a bit that "fuel return check" IMO is a waste of money anyway cos it was fitted only for 15(and beyond)P engines, the 10Ps dont have it at all and they are 100% happy without it as long as no other problems with the filter head or pipework is present...actually that return check could hurt more rather than help cos the 10P's which are missing it can be startable and driveable even with dead HP stage of the pump while those which have it will die and not start on LP...i've seen this few times.

the air bleed valve in exchange is a very important bit

Click to expand...

It may be, actually you are correct, it is a waste of money because you get about 5p worth of nylon and a little 2p O ring for about £14 and the duck bill valve seems to be like hens teeth unless a filter head is bought, but it's purpose isn't, it is fact that if diesel has a tendency to run back overnight, then this check valve will stop that making for an easier first start - I suspect if this TD5 starts to behave Charles would have spent £200 on the check valve just to get his LR to start!

Let's see how this one goes because it has been a pig to start at various points since it was 2 years old.

Also, your comment re. the different engines, the 10P was the first iteration of the engine? I also seem to remember the reason it may start on the LP pump is that the FPR arrangement was different with an internal spill and it worked slightly differently, not because there is no check valve on the LP feed, it sits and allows diesel to sail through it anyway. Also by adding this check valve to later engines does suggest that LR thought, "Hey, maybe we need a check valve here to stop diesel run back". Another thought I will propose is that did the 10P engine fuel senders have a full tank depth air bleed pipe? If so then the system was closed and unless there was a leak no air could get into the system. Did they then work out it was 5p cheaper to put a halfpenny silicone duck bill valve into a union rather than have a piece of pipe 300mm long?

I think it is safe to say there are many TD5 owners who would just be pleased to get their TD5's starting well and with us discussing it on a public forum and relaying more anecdotal evidence, thoughts and findings it may help some more.

Did you see / read the tech bulletin ref the air bleed valve and checking if the "o" ring was in good condition , the TB was written exactly for the bad starting issue.

Cheers

neilly said:

So on your vehicle, the duck bill valve was fitted back union, front of vehicle? This is wrong,

Is that a statement based on a direction from LR , or on the supposition of how it should work? That picture from the internet, also has raised concerns ( if you do a google search) that the defender was piped differently at the beginning compared to the D2. If this is true or not I have no idea as I am not duly concerned as I said , mine starts and runs OK after changing the filter housing which was knackered, and the rubber duck was open.

Cheers

Click to expand...

Both to be honest. I don't know about the Defender as we are only looking at a Disco here but I have only ever seen diagrams which all show the same arrangement. How was the Defender routed? Did they have different heads, I guess the back and front unions could all be swapped from side to side and it would still work. As long as you took the two back pipes and put them into the front and the two front and put them into the back, you could also swap them from side to side but you would always want the LP feed and return on the same line of sight and the same said for the HP feed and air bleeder. So could it be that if some were done differently LR mechanics in the dealers got them mixed up, just put them all in one location?

From how it was piped on this Disco and what we can see, I can say that diesel comes from the LP pump into the back left union, that is a clear drilling across the head and there is the return from the cooler, the diesel (tank and returned) all passes down the through the filter, it then comes back up and out the front right union on route to the HP pump, it then goes to the engine. The front left union is the where air is meant to go, although I see no reason why some trapped air would not also head to the HP feed as diesel scoots past - what was wrong with a banjo on the top and an air bleeder like every other filter had?

neilly said:

Did you see / read the tech bulletin ref the air bleed valve and checking if the "o" ring was in good condition , the TB was written exactly for the bad starting issue.

Cheers

Click to expand...

No, thanks, I will look it out. The bleeder was inspected and checked for a good seal, the O ring was good but the mesh on this bleeder was probably a bit clogged, maximum air bleeding was probably not being achieved towards the end but at 2 years old... in those days was something else causing it issues? We will probably never know and at this stage the key is just to renew and replace all these bits and check the system is in as best fettle as we can get it.

neilly said:

Well, mine starts and runs OK, so I think I will leave it where it is.

Thanks.

Click to expand...

I am a great believer in "Don't touch what ain't broke" I wouldn't move it either in your case. Obviously in direction of flow it is totally passive so it will just sit there and, well, do nothing.

FYI,

from Mar 14th 2011 this is what CharlesY wrote, stating he did not have a NRV in his filter head. See posts #19 and #22.
https://www.landyzone.co.uk/land-rover/td5-air-bleed-valve-in-fuel-filter.140965/

CharlesY said:

Well I can tell you right now, my TD5 Disco does NOT have one of those valves. It just is not there!

Is it possible to buy one?

Click to expand...

Sorry, I do not understand your "front" reference, is this in vehicle line? as the air bleed valve is at the rear outside connection on the filter housing. Maybe changing the nomenclature would be better Rear Outside etc.

discomania said:

The front left union is the where air is meant to go,

Click to expand...

attaching the drawing to make sense of it , from how you descibe it.


Cheers

This is the TB for the defender TD5.

Cheers

neilly said:

FYI,

from Mar 14th 2011 this is what CharlesY wrote, stating he did not have a NRV in his filter head. See posts #19 and #22.
https://www.landyzone.co.uk/land-rover/td5-air-bleed-valve-in-fuel-filter.140965/



Sorry, I do not understand your "front" reference, is this in vehicle line? as the air bleed valve is at the rear outside connection on the filter housing. Maybe changing the nomenclature would be better Rear Outside etc.


attaching the drawing to make sense of it , from how you descibe it.
View attachment 129916View attachment 129916

Cheers

Click to expand...

Correct, because he looked where it SHOULD be and it wasn't there - the original posts even states the pipe from union 7 which is the LP feed.

Neilly... really? Lets not fall out here - from your first reply you have been negative, unhelpfully really, I am doing my best to discuss with you. Your car works, why don't you stop muddying the waters and let this be what it is.

Regarding my identification of unions, my nomenclature will work just fine and given it was used from the first post of my thread we will just stick with it thanks; it is based on looking at the filter head from where any normal person would want to stand/kneel and look at it and how it appears on the diagram(s).

So Neilly, if I put a fuel filter down in front of you, back/mounting plate furthest away from you and the front/unions towards you and said point to the left what would you do?

So left would be nearest the back of the car and right would be nearest the front of the car, back would be nearest the chassis and front would be nearest you.

So you know where the bleed valve is meant to go and I know where the bleed valve it meant to go and I said "The front left union is the where air is meant to go". Which if you look on all the diagrams is to no. 9. I am sorry it confused you, but had you looked at it and realised we were looking at the same union my naming convention would have made sense!

discomania said:

Also by adding this check valve to later engines does suggest that LR thought, "Hey, maybe we need a check valve here to stop diesel run back". Another thought I will propose is that did the 10P engine fuel senders have a full tank depth air bleed pipe? If so then the system was closed and unless there was a leak no air could get into the system. Did they then work out it was 5p cheaper to put a halfpenny silicone duck bill valve into a union rather than have a piece of pipe 300mm long?

Click to expand...

IMO as long as there's no leak along the system it's no reason for the fuel to run back or if it is a leak that check valve won't help much, AFAIK there's no difference between fuel pumps fitted to 10P or later engines, i think that the air bleed valve is there to bleed the air mixed in the fuel while driving when the tank is shaked by the movements as to keep "aerated" fuel from getting into the HP feed

I hear you say that once it's started, it runs great, but when you turn it off, it doesn't want to start again. But does it rev up and pull well?

I'm just curious as maybe it's not a fuel issue and maybe its a compression issue? Have you tried starting with a small amount of easy start etc, may work if it starts with a pull start.

Also, have you checked that the crank position sensor is being picked up correctly? This can sometimes be the cause of a crappy start. Best to check this with nanocom to see if a fault has been logged, but I would either try a new/good one first or if you have one, put a scope on it.

Simon098 said:

I hear you say that once it's started, it runs great, but when you turn it off, it doesn't want to start again. But does it rev up and pull well?

I'm just curious as maybe it's not a fuel issue and maybe its a compression issue? Have you tried starting with a small amount of easy start etc, may work if it starts with a pull start.

Also, have you checked that the crank position sensor is being picked up correctly? This can sometimes be the cause of a crappy start. Best to check this with nanocom to see if a fault has been logged, but I would either try a new/good one first or if you have one, put a scope on it.

Click to expand...

As said it has done this sort of thing since it was 2 years old. Not only does it go when started but it goes like stink (remapped). It will start fine again once started within say an hour or so, overnight not a chance in hell.

It is fuel, we know this 100%. No doubt about it.

I'd read the post above fully, the story explains it all really, a skim read will not furnish you with the full picture.