Fuel Problem I Think

Disco1BFG · Jun 19, 2020

mick 1986 said:
Just got back from @border

The fuel problem is still present. When I turned up, lift pump #2 was fitted. This had a piece of hard plastic nylon from the lift pump upto the fuel filter housing. It had signs of air in it, large bubbles as shown in the video uploaded earlier in the thread. I checked the unions on lift pump #2, these were slightly loose, so nipped them up. This appeared to fix the problem instantly. That was until we turned the engine off, and left it a few minutes, then started it, only to find as much air as before I nipped the unions.

At this point, I placed a piece of clear tube where the hard nylon one was, fearing the air could be brought in by the nylon having a less than perfect seal. This didn’t make any difference. I then placed a piece of clear pipe just next to the pickup pipe, this showed no signs of air. Next was to place a piece of clear tube on the inlet to the lift pump, this didn’t show any signs of air at this point.

So at this point in the diagnosis, clear plastic pipe was at 3 points, fuel pick up, lift pump inlet, and lift pump to fuel filter. Only the lift pump to fuel filter had air, so I suspected the lift pump to be faulty. Off we go to a local motor factors to purchase a new lift pump, a Bearmach branded pump, lift pump #3.

Fitted lift pump #3, same as before, only this lift pump was struggling to draw fuel from the fuel tank. It wasn’t drawing air into the fuel line, as the clear pipe at the pickup was full of fuel and no air was present. It was trying to push fuel out as you could see bits spluttering up the clear plastic to the fuel filter housing. Wondering if this was caused by an airlock inside the lift pump, we removed the clear plastic from the lift pump output and placed it into a Jerry can. This ran the engine perfectly, fuel was drawn from the tank upto and out of the lift pump spurting towards the bulkhead. Quickly moved the fuel line from the jerrycan and back onto the lift pump, started the engine again, same as before. Struggling to draw fuel from the tank.

At this point I realised the fuel line from the filter to the FIP had a join in it, so replaced that piece for clear plastic. This didn’t do anything to the fault.

The final trial was to put the fuel lift pump pickup pipe into the Jerry can to see if it could draw from that. It didn’t draw any fuel through that pipe.

The original lift pump, #1, was old and showed no signs of pumping at all, this was replaced before I arrived. Lift pump #2 & #3 both show signs of pumping when off the vehicle. If you pump the lever and cover the inlet, it sucks and appears to work as it should. Apart from replacing the lift pump again, I’m out of ideas.

Firstly, good on you for helping out

Sounds like spill pipes are fubar - they are a known issue - are they all ship shape ? I've had them fail more than once over the years - once, quite expensively - MPG went down

Regarding the spacer on the LP - some 300's appear to have them, others don't

IIRC, Mike at Britannic resto's mentions this occasionally ..... I'm guessing it depends on the size of the lobe on the cam - therefore some need said spacer, and some don't ....

border · Jun 19, 2020

Big Thank You to Mick 1986 for coming over to help me, Really Appreciate it. This is a mystery tried almost everything.
Just looked on my Disco 300tdi , It does Not have Spacer. Saying that about the size of Lobe, when I took lift pump off the other day, as soon as it came away from block a few mil I remember trying and there was some resistance there as if it was working, but when fitted and bolted in there is Nothing there At All, this is with one bought brand new in February and another Today, Cant be that unlucky can I

jamesmartin · Jun 19, 2020

mick 1986 said:
No. It’s a 300tdi. I didn’t think they had one, do they?

spacer is built in to the ali side cover

jamesmartin · Jun 19, 2020

air appearing when you turn engine off can be leak off pipes as disco mentioned not when running though

border · Jun 19, 2020

jamesmartin said:
air appearing when you turn engine off can be leak off pipes as disco mentioned not when running though

These have been mentioned a few times now, never really looked at them as they are new , but think I will take them off tomorrow and check them over, as a last resort.
This has got my head really done in now.

Disco1BFG · Jun 19, 2020

Spills are a pain - fail when they like - I got an advisory on my last MOT for one leaking - BUT, the little sh*t had only failed on the way to the bl@@dy MOT station !

Main failure point I see is the drain from #1 inj back to the FIP - two different pipe sizes anorl

.....

Hicap phill · Jun 19, 2020

Sometimes that cotton weave covers any cracks.

have you got an electric fuel pump? Like a facet ? This will apply positive pressure up to the FP

mick 1986 · Jun 19, 2020

border said:
These have been mentioned a few times now, never really looked at them as they are new , but think I will take them off tomorrow and check them over, as a last resort.
This has got my head really done in now.

Thinking about other things now too. I would try and remove the two unions on the lift pump, and put the fuel pipes straight on to the two metal pipes of the lift pump. That will remove any possible air coming into the threads or olives.

The fuel spill rails didn’t all look perfect, but none of them looked like they were perished and possible leak areas. Check the banjo bolt you replaced, and make sure it’s tight, and has a sealing washer on both sides.

mick 1986 · Jun 19, 2020

jamesmartin said:
spacer is built in to the ali side cover

I thought it was on the 300, but wasn’t certain.

mick 1986 · Jun 19, 2020

jamesmartin said:
air appearing when you turn engine off can be leak off pipes as disco mentioned not when running though

I wasn’t too sure if that could cause it. It wasn’t a slow return to the tank, and it didn’t appear to flow from the filter back to the lift pump, just from the lift pump back to the tank. It was quite confusing to be honest.

jamesmartin · Jun 19, 2020

mick 1986 said:
I wasn’t too sure if that could cause it. It wasn’t a slow return to the tank, and it didn’t appear to flow from the filter back to the lift pump, just from the lift pump back to the tank. It was quite confusing to be honest.

it can flow back through inj pump to filter then lift pump and further if lift pump valves are fully seated

mick 1986 · Jun 19, 2020

jamesmartin said:
it can flow back through inj pump to filter then lift pump and further if lift pump valves are fully seated

Im not sure I understand that, or I may have confused things. There didn’t appear to be any flow from the filter at all, either to the FIP or LP, but it did appear to flow from the LP back to the tank (back down the fuel supply line, from tank pickup).

neilly · Jun 19, 2020

mick 1986 said:
Im not sure I understand that, or I may have confused things. There didn’t appear to be any flow from the filter at all, either to the FIP or LP, but it did appear to flow from the LP back to the tank (back down the fuel supply line, from tank pickup).

Stupid question, does the lift pump have the removeable top on it with the filter? was this screwed down tight?
this was the third?? LP changed, so the fittings were replaced for the LP side of the pipes. Only things not changed are the pipes / connections on the vehicle.

Cheers

border · Jun 19, 2020

Ive put it back to the way we had it Mick, with the clear pipes everywhere,. Will take a couple of Vids tomorrow,
It is Very Confusing , got to be a Solution somewhere along these bloody Lines though,

jamesmartin · Jun 19, 2020

mick 1986 said:
Im not sure I understand that, or I may have confused things. There didn’t appear to be any flow from the filter at all, either to the FIP or LP, but it did appear to flow from the LP back to the tank (back down the fuel supply line, from tank pickup).

im just saying when you turn engine of and when its stood air can seep back into the system, in theory lift pump vales should stop any air or fuel leaking back to the tank,depends were your air was coming from,thats a matter of elimination

Hicap phill · Jun 19, 2020

Just a thought....
Run the engine & when you switch off if you remove the lift pump to filter pipe at the highest point(fuel filter) leave fo a bit.
Could This show if the fuel is syphoning back to tank ?

mick 1986 · Jun 19, 2020

neilly said:
Stupid question, does the lift pump have the removeable top on it with the filter? was this screwed down tight?
this was the third?? LP changed, so the fittings were replaced for the LP side of the pipes. Only things not changed are the pipes / connections on the vehicle.

Cheers

I don’t think it has any sort of removable filter on it, it certainly appeared to be a pressed and sealed construction.

Yes third lift pump fitted today. The second gave similar, but not identical, issues. I don’t know what the symptoms/reason for change of the original was, but it was almost certainly not working. I couldn’t get it pump in my hand, but can get both lift pump #2 & #3 to pump in my hand.

The olives and unions were changed, but thinking about things after the event, I should have put the fuel lines directly onto the lift pump pipes for lift pump #3. That would have eliminated another 2 possible causes.

mick 1986 · Jun 19, 2020

Hicap phill said:
Just a thought....
Run the engine & when you switch off if you remove the lift pump to filter pipe at the highest point(fuel filter) leave fo a bit.
Could This show if the fuel is syphoning back to tank ?

Im not sure that will show anything. There was fuel and air in the pipe from the lift pump to the filter. This level didn’t drop while the fuel drained back towards the tank from the lift pump. I assumed the air allowing the fuel to drain back, must be coming into the lift pump itself, but not sure that assumption is correct.

mick 1986 · Jun 19, 2020

jamesmartin said:
im just saying when you turn engine of and when its stood air can seep back into the system, in theory lift pump vales should stop any air or fuel leaking back to the tank,depends were your air was coming from,thats a matter of elimination

That was what I failed to find tonight. Logically, I think removing the unions and olives from the lift pump, and the fuel return spill lines should be next. If all of that is done, the only other thing that could be causing it is the main line from the tank. I can’t see how that’s possible though, as no air bubbles were seen at either end of the feed line.

I didn’t check the main return from the FIP back to the tank. Could that cause issues too?

jamesmartin · Jun 19, 2020

mick 1986 said:
That was what I failed to find tonight. Logically, I think removing the unions and olives from the lift pump, and the fuel return spill lines should be next. If all of that is done, the only other thing that could be causing it is the main line from the tank. I can’t see how that’s possible though, as no air bubbles were seen at either end of the feed line.

I didn’t check the main return from the FIP back to the tank. Could that cause issues too?

the main return is just open to the top of the tank,if it runs bubble free when running thats all that matters, if you have clear plastic before lp and then between filter and inj pump that should show something

Fuel Problem I Think

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