Leaky Injectors

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johnneale

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I get a slight mist from the joint between the injector pipes and injectors when the engine is running. They have been loosened & tightened up many times and presently are done up bar tight with dry joints,

/forums/images/graemlins/confused.gifI don't want to change the pipes/injectors - is there any way of making a leak thru joint here ??? I have been told that it is possible to use gas tape (the white stuff) but surely that would dissolve - anybody got any other ideas.
 
gas tape would be useless. It eventually disolves in diesel and allows the joint to leak again. You could try lockseal (available from a motor factor) but its possible that the high pressure wil be too much for this, in which case replacement may be the only viable option, so its worth a try.
 
Normally there would be a copper washer below and above the feed pipe union. If these are missing or damaged, you'll almost certainly get a leak. You shouldn't need to use any kind of sealing compound.
They must be copper (rather than steel) otherwise they won't squish down and seal properly. As Talbot says, tape would be useless.
 
Is the leak on the injector pipe or the dribble pipe?
If it's the dribble pipe then copper washers have "work hardened" just replace them with new ones and all should be ok.
Technically you should replace them every time you release the joint. If however it's on the injector feed pipe then it means the swayged end is no longer seating correctly and you may have to replace the pipes.
 
I understood you should not use copper washers - they are too hard.

White lead washers are much softer and crush with less torque applied to the fixings. They're much softer than even annealed copper.

Certainly on my Volvo engine, the use of a copper washer caused a sheared bolt when trying to nip the B****** up (Its all I had at the time) /forums/images/graemlins/frown.gif and it does have lead washers as standard.
 
[ QUOTE ]
. They have been loosened & tightened up many times and presently are done up bar tight with dry joints,


[/ QUOTE ]

... and that is why you are having trouble, which will only get worse. Like any metal component threads and seatings wear and deform if overtightened, and after a while no longer work properly. Overtightening - as in 'bar tight' actually makes the problem a great deal worse as the seatings are being damaged more every time you do it. I doubt very much if any compound or tape will repair the seal now, so replacement is the only option. You may also find the seatings and threads on the injectors are damaged if you have been overtightening them. There has to be sound metal to metal contact to seal against the extreme pressures present in injector pipes, and any sealing compound will simply be blown out very quickly. Injector pipes locking nuts need to be tightened securely, usually around 30NM, but not forced down to cure leaks. Forcing them will simply do further damage to the fittings.
 
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I understood you should not use copper washers - they are too hard.

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Having had 3 Volvos, I question this statement. All 3, one of them was brand new, had copper washers on every banjo fitting! It is sometimes said that copper washers should not be used under the injector inside the sleeve and this is correct even thogh they are sometimes supplied when injectors are serviced.
 
If you want to be really tight or you're stuck for hetting hold of them you can anneal the copper washers. You heat them up in the flame of a gas blowlamp or gas stove until cherry red and drop into cold water. You can lap flat them by working them on wet and dry placed on a flat surface.
 
Dropping red hot metal into water etc actually hardens the metal, not soften it.

Get it red hot then let it cool on its own. Annealed copper is plenty soft enough for high pressure lines.
 
[ QUOTE ]
Dropping red hot metal into water etc actually hardens the metal, not soften it.

Get it red hot then let it cool on its own. Annealed copper is plenty soft enough for high pressure lines.

[/ QUOTE ]
Well it doesn't. Have a look at web page
 
[ QUOTE ]
Dropping red hot metal into water etc actually hardens the metal, not soften it.

[/ QUOTE ]Not quite true, it depends on the metal in question. Some, like copper, are not hardened by heating and quenching. One benefit of quenching copper is to reduce the amount of oxidation that would otherwise take place if aircooled.
Quenching Annealled Copper is not required.
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"Artificial intelligence is no match for natural stupidity"
 
Well, there you go - savageseadog gives us a website that says you should quench hot copper to soften it. Cliff says it doesn't make any difference to hardness if you quench or not.

When I did my apprenticeship in the dark ages I was taught to heat and let cool to soften copper. Admitted it is many moons since I worked on engines for a living but for many other moons I worked on overhauling very big to gi-normous diesel engines. To soften and re-use the copper sealing washers I always did as I was taught and, more to the point, never had a problem.
 
Original poster said he had a leak between the injector and the pipe no copper washer there, lots of people do not read the question properly, hence the drift from the topic,
 
[ QUOTE ]
Well, there you go - savageseadog gives us a website that says you should quench hot copper to soften it. Cliff says it doesn't make any difference to hardness if you quench or not.

When I did my apprenticeship in the dark ages I was taught to heat and let cool to soften copper. Admitted it is many moons since I worked on engines for a living but for many other moons I worked on overhauling very big to gi-normous diesel engines. To soften and re-use the copper sealing washers I always did as I was taught and, more to the point, never had a problem.

[/ QUOTE ]Slow down there that is not what I said. Raising the temperature to "red heat" anneals the copper or in layman's terms, softens the copper. Subsequent quenching will not harden the copper again although it will minimize oxidation of the surface.

The crystal structure of Copper is FCC (Face Center Cubic) or in modern speak, CCP (cubic close-packed). Metals with this structure do not harden on quenching e.g. Aluminium.

To recap, heating to a sufficiently high temperature anneals the material by allowing the crystal structure to realign itself and crystal faults such as twinning planes to realign themselves. It can also allow for grain growth. (larger grains > softer/weaker materials).

For the purposes of recovering copper washers etc any subsequent quench is of no benefit in maintaining the softness of the material but nor will it harden it again.

Materials that do harden on quenching from elevated temperatures include steels and some alloys do so through various mechanisms which are too complex and varied to go into here such as the formation of martensitic phases or precipitation of inter-metallics such as carbides or nitrides for example.

One very interesting thing about copper is the ancient Egyptians had copper tools for carving the stone for the pyramids and other buildings but no one has figured out how they managed to harden them. Many of the old copper tools have been found (soft) but the stones show tool marks from hard cutting edges. /forums/images/graemlins/confused.gif

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"Artificial intelligence is no match for natural stupidity"
 
Well - that got a lot of answers .... The very fine mist (which is not visible, but only detected with loo paper) doesnt come out of the top of the injectors on the return line (copper washers there are doing their job), but between the delivery pipe from the injector pump to the injector which is a dry metal joint. I agree that ideally I should renew the pipes and injectors, but thats a lot of money, the boat is in greece - and it hasn't been a major problem

So Gas tape is out, anybody tried lockseal or any other sealing agent ???
 
The pressures involved with fuel injection are such that as suggested above direct metal to metal contact is neccesary. You may be correct about the source of the leak being an overtightened injection nut having caused the coned end of the pipe to deform itself and flare out the injector connection. If so injector pipes need not be a fortune they are made up as a matter of course by injection specialists. New nuts and pipe may well be sufficient to solve the problem without a new injector union. Pipe lengths are supposed to be the same length to keep the injection timing the same on each cylinder.

Due to the pulsing nature of the injection and the high pressures it is common for parts of the pipes to crack and you may find with close examination that the problem is a tiny crack.

If price is a problem try the scrap yard and bend what is available to suit your engine.
 
. Pipe lengths are supposed to be the same length to keep the injection timing the same on each cylinder.

First iv heard about this...be interested to know a bit more !.....
 
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