Excess fuel return dilemma

Hi All,
Came across a bit of an abnormality with this TDI 200 engine (ex Disco) where there seems to be a fair pressure build up in the return line from the top of the pump back to the tank. Enough to cause a fuel leak at the fittings.

You can remove the return hose from the tank end and drain it into a container and no probs. You can also put a bit of hose on the return line where it goes back into the tank and it will blow through alright, so doesn't appear to be any obstruction.

The tank is off a Mazda E3000 Diesel which has a NON vented screw type cap with a rubber seal. There is an additional vent line built into the tank which has a small nylon sliding ball in it, which is some sort of safety device to stop fuel escaping in case of a roll-over.

Funny thing is, when the tank only had about two inches of fuel in it, didn't leak. Filled the tank to about halfway up and I'm surmising that the extra weight of fuel is stopping the return line from operating correctly. I've had the fuel sender out to fit a new one and shown a torch in, the return line is roughly the same height above the bottom of the tank as the pick up line.

Wondering if it may be a combination of the original Range Rover fuel tank return fuel line just vented straight into the TOP of the tank and also the original may have had a vented cap. Often seen tanks where an excess fuel line returns to the filler neck and then returns to mix with the cooler fuel.
I don't run it for very long the way it is.
Seems to start almost instantly the few times I have started it lately, don't need the glow plugs as yet in this weather.
I did notice last time I started the engine that it seemed a bit "smoky" at idle. If the return fuel line is not doing it's job as it was designed, could be building up TOO much pressure at the engine?

I was going to try swapping the lines for the return line and the vent line so the fuel returns straight to the top and leave the cap off so it vents to the atmosphere. As it's not yet on the road, can tinker a bit, but obviously have to have some sort of vent into a charcoal canister affair for eventual registration.
Bloke on another forum reckons it is probably sucking air in on the lift pump side, if so, wouldn't have thought it would start and run so easily.
Any thoughts?
Dave_64

Dave
This might be your problem.

I have just had a leak from my fuel filler cap - searched a few message boards last night and found a story about the boost diaphragm (on the fuel injection pump) - I have a 1987 2.5td (the old leaky cav19j) anyway I was actually expecting to find a whole load of tips about the fuel cap and how to un block the pressure vacuum release valve - instead I was reading that there was a common fault which required a rubber diaphragm changing in the FIP, this was fiddley but took about an hour tonight - thats right within 24hrs of reading a post I was able to order the part (fremantle fuel injection $64) and fit it - and guess what - it only worked a treat. Last night I could remove the fuel cap and hear a loud hiss as the pressure was being released - put it back on and drive five minutes only for the same amount of pressure to be produced, and I dont mean a little bit this is some major pressure build up guys and no wonder the diesel was leaking out- I thought it was heat and expansion - turns out it was the pipe from the turbo which is connected to the FIP - the reason for the connnection is that when the turbo is on boost the pressure from this pipe actuates a part of the pump to get extra fuel in - only problem is that there is a rubber diaphragm and when it fails the air goes down the spill return pipe and tries to blow up the fuel tank - hence the over pressure - here is a link to the pictures which explain how to change one - it was actually quite easy and she started first time. Even the guy I picked the part up from today had not heard of this happening - but I promise you I have just carried out the exact process below and it has worked - and as soon as I got the old rubber out it was split exactly as shown in the pictures - I just had to tell someone.
redirect.viglink.com/?format=go&jsonp=vg...Land%20Rover%20Forum


The cap might be a problem too. Looks like the Landrover has quite a complex fuel system tied in with the fuel cap which judges the pressure to restrict emissions while stopping over pressure or a vacuum blockage. Maybe your engine still has some sensors requiring the cap input?

Here is a bit on the cap.



Lang

Lang,
thanks for the link to the L/R forum. I had posed the same query on there, but no-one came up with that.
Mine is the 12L engine, which has a slightly different pump set-up which can be seen from the attached photos. As can be seen, it has a similar sort of housing only it is upright and easy to get to, so just looking at the indentations on the cover, it probably has a similar diaphragm.
Reading from what you have written and also what that bloke says on your link, the symptoms are very similar, so reckon you could be onto something.
Bloke who gave me the engine, told me he had had the injector pump done quite some time ago, but had never done the injectors. Why he didn't do both, I'm not sure. When asked he said it was getting hard to start and his mechanic reckoned it was the pump, so they reworked it and seemed to cure it.
The engine had been sitting in my shed for quite some time without being started, so possibly if it is the diaphragm, may have simply dried out.
I did notice that once the engine was in the chassis and the pump and filters changed and bled, it started very easily although did blow quite a bit of smoke until the engine had been warmed up. Haven't run the engine under any sort of load, or for any length of time since so may just need a good run to clean the cobwebs out.
I had cleaned the fuel tank out before mounting it and refilled it with fresh diesel from our local servo who sells a lot of it (diesel) and has just recently had new underground tanks put in, so I'm reasonably confident that it is not a fuel issue. Also changed all the filters at the same time.
I don't know if this had anything to do with it, but when I took the return fuel line off this morning, it was very "spongy" and obviously not the right type of line. Have a new line to go on when I get back out the shed. Tank to fuel filter is the proper braided line.
Dave

Done something wrong, photos should have been turned one quarter turn to the right.
Dave

Dave,
Easy to check, back off the 4 screws on top. Before you pull the diaphragm mark the housing and diaphragm so it can go back in the same place. Same set up as my Cummins. There should be a spring and spacer washer under the diaphragm.
Cheers Steve

Hi Dave,

Just in case this is an oversight, it might be wise putting a lock nut of some sort on the all thread. Otherwise, it'll probably shift around.

jd

Fitted a new excess return fuel line today, looks like it has stopped leaking at least.
Gave it a big bootful of revs momentarily, just about couldn't see the back wall of the shed for the smoke!
Ran out of time to take the cover of that diaphragm housing, but just reading what that bloke wrote about the 19J engine and what you blokes put up here, will suss it out before I start it next time, sounds like that may be the reason why it seems to be over-fuelling.
Had a boost pressure gauge here I fitted also, 0-30psi, just on flight revs went up to about 8psi so, an engine that was under virtually no load, dunno!
One forum reckons they should be pumping out around 12-14 psi, but would think that would be when the vehicle is under load and the turbo working to capacity.
Dave.

Dave ,
If the diaphragm is stuffed it will not smoke. If the pump is set up the same as mine there is a tapered pin attached to the diaphragm that controls the amount of fuel., as boost come up it pushs the pin down allow more fuel.
Under the cap on top of that cover should be an adjustment screw, this sets the initial pin position and controls smoke until the boost come up. Below the diaphragm there will be a spring and an adjustment wheel to add or remove spring pressure. This controls how much boost is required before it starts adding more fuel.
Looking at the top cap it does not appear to have been played with.
The only other place that could cause problems is there is a cross pin that rides on the fuel pin, they have been known to stick.
With the pin out and you move the throttle the cross pin should move out and should push back in easily with a small screwdriver. A couple of drops of oil on it will not hurt.
You will not see much boost without a load on it.
Will be a bit busy tomorrow but can get some pic's if it will help. Will dig up a couple of links to similar pumps.
Cheers Steve

This is mostly about upping the power on the Cummins 6 but the pumps are very similar and operate the same
dodgeram.org/tech/dsl/more_power/Power_ve.htm
There are a couple of others but with the Photo*ucket site mess the pic's are not there now.

Blackduck59,
Thanks for that Steve,
Yes, until it actually gets out on a road and has a good workout, boost figures are not going to mean much, I understand that.
Although the engine had been sitting on the floor for some time, it would be lucky to have had any more than probably 2 hours running since being installed in the chassis. Not just idling away, but have varied RPM whilst testing things like oil pressure, whether the gauges are working, Alt output, action of the clutch and so on.
Probably have to wait until it actually (if ever!) gets on the road and put under some sort of load.
Suppose it wouldn't hurt to just lift the cover on that boost compensator and have a look at the diaphragm, may not be the reason for what I would call excessive smoke. You would think that when the bloke had the pump worked on, they would have replaced that, but you'd never know.
Can't understand why he (previous owner of the engine) had the pump done but not the squirters, would have thought they would have been done first. Told me that that is what his mechanic told him to do, because of hard starting issues.
Dave

All injector pumps I have fiddled when starting start on full fuel and as they start the governor pulls the fuel rack back so it idles

This may explain your smoke, or maybe not

Paul