300tdi misfire

hi i have posted this somewhere else on this site but cant find it lol.
my 95 disco 300 tdi has a misfire starting at about 1500 rpm.
its new to me so i have done the following as its a keeper
change oil fuel and air filters
had injectors cleaned refurbed
new set of glow plugs
checked tappet clearance
new delphi lift pump
found the rear fuel filter but its been bypassed
replaced cambelt and front cover
temp fitted a boost gauge its about 5 lb at 1500 10 at about 2000 and 15 at 3500
i havent got a compression tester so cant check that

i am left thinking its a fuel pump problem but a setup /repair of pump is 300 quid plus vat so was hoping someone might be able to point me in the direction of something i have missed
many thanks kev

Have you checked the fuel pipes at the diesel tank?

Open the boot, lift the carpets and remove the round cover, 6 screws. The pipe connectors are sealed into nylon fittings which seem to harden and eventually crack, letting air in, but very little diesel out! Only real fix is replacement!

I'd also have a look at the turbo. 1500 rpm is getting towards the (usually 1800rpm) point where the turbo kicks in, if there's damaged blades or other issues here they won't be helping.

As @Paul D says above - corrosion at the tank outlet can be an issue - relatively easy fix as access thru the boot floor is pretty good.

moorsman61 said:

fitted a boost gauge its about 5 lb at 1500 10 at about 2000 and 15 at 3500

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to agree with post #2 again - this isn't right - have you Got any pictures of how you have fitted this, and, if you can tell me how you're testing it - the boost will only come up on load.

Confirm manual or auto too please

moorsman61 said:

found the rear fuel filter but its been bypassed

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IMHO put this back in - it's there for a very good reason - to keep water out of the rest of the fuel system!! ( its called a sedimenter by the way )

Paul D said:

Have you checked the fuel pipes at the diesel tank?

Open the boot, lift the carpets and remove the round cover, 6 screws. The pipe connectors are sealed into nylon fittings which seem to harden and eventually crack, letting air in, but very little diesel out! Only real fix is replacement!

I'd also have a look at the turbo. 1500 rpm is getting towards the (usually 1800rpm) point where the turbo kicks in, if there's damaged blades or other issues here they won't be helping.

Click to expand...

hi no i haventy checked tank end of pipes yet but the lift pump is drawing plenty of fuel but i think you are sugesting it might be drawing air as well?

Disco1BFG said:

As @Paul D says above - corrosion at the tank outlet can be an issue - relatively easy fix as access thru the boot floor is pretty good.


to agree with post #2 again - this isn't right - have you Got any pictures of how you have fitted this, and, if you can tell me how you're testing it - the boost will only come up on load.

Confirm manual or auto too please



IMHO put this back in - it's there for a very good reason - to keep water out of the rest of the fuel system!! ( its called a sedimenter by the way )

Click to expand...

no i havent bypassed the sedimenter it had already been done quite agree its there for a purpose and i will re-instate it asap
testing boost with a gauge teed off the pipe leading to the fuel pump

Disco1BFG said:

As @Paul D says above - corrosion at the tank outlet can be an issue - relatively easy fix as access thru the boot floor is pretty good.


to agree with post #2 again - this isn't right - have you Got any pictures of how you have fitted this, and, if you can tell me how you're testing it - the boost will only come up on load.

Confirm manual or auto too please



IMHO put this back in - it's there for a very good reason - to keep water out of the rest of the fuel system!! ( its called a sedimenter by the way )

Click to expand...

sorry missed that its an auto

moorsman61 said:

no i havent bypassed the sedimenter it had already been done quite agree its there for a purpose and i will re-instate it asap

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Cool

moorsman61 said:

testing boost with a gauge teed off the pipe leading to the fuel pump

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Ok - just seen your other post - so is it EDC or not ? - There's a blanked boss in the rear of the inlet plenum ( used on the EDC autos) - which will take a banjo bolt and a pipe to give an accurate reading of the actual boost pressure in the system.

no its not EDC i dont think is that what the electrical system is called this has only the single wire connection to the fuel pump stop soleniod
also no blanked off boss at inlet plenum.
i intend when i get it running right to fit a pipe from the inlet plenum to the gauge and wastegate actuator but as is gives a good indication that the turbo is doing roughly what it should
given the state of rest of mechanics on car i would expect it to have had all sorts of crap fuel in the past so am worried about poss damage done to fuel pump

just been and checked pipes where they go into the tank all looks very good pulled sender out and looking into the tank once again all looks clean
was suprised tho that when i undid the fuel pipe unions neither pipe was full of fuel i was expecting to recieve a diesel hand wash??

moorsman61 said:

also no blanked off boss at inlet plenum.

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http://www.allbrit.de/UNI.cfm?PAGE=801360&SPRACHE=EN

Have a look at part number 2 in the diag linked above....

moorsman61 said:

just been and checked pipes where they go into the tank all looks very good pulled sender out and looking into the tank once again all looks clean
was suprised tho that when i undid the fuel pipe unions neither pipe was full of fuel i was expecting to recieve a diesel hand wash??

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Might be worth putting a piece of clear pipe in the output from the lift pump to the fuel filter to see if there is any air in the fuel....

Disco1BFG said:

http://www.allbrit.de/UNI.cfm?PAGE=801360&SPRACHE=EN

Have a look at part number 2 in the diag linked above....

Click to expand...

will have another feel around back there but i think there are just the two casting? lumps

Disco1BFG said:

Might be worth putting a piece of clear pipe in the output from the lift pump to the fuel filter to see if there is any air in the fuel....

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yes that makes sense or should i put it after the filter and just before the injection pump?

moorsman61 said:

yes that makes sense or should i put it after the filter and just before the injection pump?

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I'd be putting it 'tween the LP and the filter... filter housing in unlikely to give any trouble IME. The other good place to look for air is from #1 injector spill to the FIP.... ANY air is a leak somewhere, and whilst the Bosch VE FIP is very tolerant of it, it seems to reach a point where it simply can't cope.....

moorsman61 said:

will have another feel around back there but i think there are just the two casting? lumps

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Aye, the "lump" nearest the engine should have a blanking plug in.... IIRC, its 17mm AF M12 fine - same size as the fuel banjos....

ok will have a go tomorrow leak off pipes are all new and v tight

YEEEHAA fixed it whoopee took timing cover off again today to check timing as i had convinced myself it was a problem with the timing (cam or inj pump)
went through everything with utmost care put it all back together and fired it up NO BL%%DY DIFFERENT
BUT my long suffering wife affectionally know as the tea bitch came down with a fresh brew and a sympathetic ear and....as i revved it to the point of misfire she pointed out that the hose from the intercooler to plenum was sucking itself flat.
so pulled intercooler out again and blew into it but no resistance however decided to wash it out again to make sure
had to use petrol as i knocked over the brake cleaner can
after swilling some about for a while i poured it out fairly oily
in went some fresh and a further swilling about it looked fairly clean so poured it out and voila some 2p sized bits of plastic floating around
looked like bits of a black bin liner.
put the turbo output pipe onto the int out pipe and revved it with hand loosely over the other end of int caught about 150 sq mm of plastic bag bits
did this a couple of times then all bacxk together and NO MISFIRE
OUT FOR A TEST DRIVE 1ST BIG HILL FOOT HARD DOWN AND PICKING UP WELL THEN HUUUUGE CLOUD OF BLACK SMOKE
after a few moments exhaust cleared and it pulls like a train
after turning round back down hill and i could clearly see about 10 ft of sooty mark on road oops
anyway all good now thanks for all your helpfull suggestions
next job is to mod the wastegate actuator pipe so it only opens when plenum gets 1 bar
ps i found the plug in plenum will take it out and tap it for the above mod
once again many thanks
especially to my tea bitch technician number 1
regards kev

Tea bitch?? You'll be glad it's fixed so you can get to a&e quicker

moorsman61 said:

YEEEHAA fixed it whoopee took timing cover off again today to check timing as i had convinced myself it was a problem with the timing (cam or inj pump)
went through everything with utmost care put it all back together and fired it up NO BL%%DY DIFFERENT
BUT my long suffering wife affectionally know as the tea bitch came down with a fresh brew and a sympathetic ear and....as i revved it to the point of misfire she pointed out that the hose from the intercooler to plenum was sucking itself flat.
so pulled intercooler out again and blew into it but no resistance however decided to wash it out again to make sure
had to use petrol as i knocked over the brake cleaner can
after swilling some about for a while i poured it out fairly oily
in went some fresh and a further swilling about it looked fairly clean so poured it out and voila some 2p sized bits of plastic floating around
looked like bits of a black bin liner.
put the turbo output pipe onto the int out pipe and revved it with hand loosely over the other end of int caught about 150 sq mm of plastic bag bits
did this a couple of times then all bacxk together and NO MISFIRE
OUT FOR A TEST DRIVE 1ST BIG HILL FOOT HARD DOWN AND PICKING UP WELL THEN HUUUUGE CLOUD OF BLACK SMOKE
after a few moments exhaust cleared and it pulls like a train
after turning round back down hill and i could clearly see about 10 ft of sooty mark on road oops
anyway all good now thanks for all your helpfull suggestions
next job is to mod the wastegate actuator pipe so it only opens when plenum gets 1 bar
ps i found the plug in plenum will take it out and tap it for the above mod
once again many thanks
especially to my tea bitch technician number 1
regards kev

Click to expand...

Just be sure it wasn't the inner lining of that pipe, a slight tear and sheets of the stuff come away.

Buy a new pipe and while your out a bunch of flowers for the bitch. cos you'd still be there otherwise.

oh yes i am being super nice i think i should elevate her too TEA QUEEN lol
top int/c pipe is new i am going to order all others as well
but its got me thinking..... if the partially blocked int/c made such a difference should i be ordering a nice alisport or similair uprated int/c