Air Leak Points Please

[frank rabbets]

That looks horribly identical to the one I got off ebay from another supplier. Perhaps they come in different strengths. I'm in Birmingham tomorrow so I'll call in and suck a few. If I cannot get a weak one I'll take you up on your kind offer.

It is the atmospheric pressure,circa 14 psi, on the fuel in the tank that supplies the engine. The pump on the engine just moves fuel out of the way and pressurises it for the injector pump and spill line. I think there must be a relief valve somewhere to supply the spill pipe. Clearly with the engine not running air must be able to get into the pump or injectors area on a healthy vehicle so atmospheric pressure is working at both ends and the supply pipe forms a "U" tube with the tank so both levels in the tank and pipe are the same. Hence the need for the non return valve. It would be much easier with tank on the roof.

I think that makes sense.

Thanks
Frank

 

[adrianr]

Once helped someone do a roof get me home with a jerry can and some tubing. Useful thing gravity.

Let me know if you get stuck, happy to help. Mine came from a hydraulic parts and service company. Hydraulic transmissions services ltd.

 

[Towpack]

Clearly with the engine not running air must be able to get into the pump or injectors area on a healthy vehicle so atmospheric pressure is working at both ends and the supply pipe forms a "U" tube with the tank so both levels in the tank and pipe are the same. Hence the need for the non return valve. It would be much easier with tank on the roof.

I think that makes sense.

Thanks
Frank

I just don't see why air should be able to get into the IP or injectors on a healthy engine with the engine stopped. Looking at exploded and sectional diagrams of the IP seems to confirm the system is 'sealed'. If air was to get into the injector lines they would need 'bleeding' before every start and you certainly would not get the instant 'start on first turn of the key' which you do normally. There is a regulator valve in the feed pump which I'm assuming bleeds off excess fuel into the overflow/return pipe, back to the tank along with excess fuel from the injectors.

It's unclear from the diagrams/manuals whether the fuel return pipe feeds the top or bottom of the tank but, assuming it feeds fuel back into the top the ONLY way I can see air getting into the system is IF:

The one way valve in the filter housing is failing AND the regulator valve in the feed pump is leaking slightly due to age/mailes or whatever. In this situation, especially on an upward facing slope, air could be drawn from the tank, down the return pipe and through the leaking regulator and non return valves in the IP and filter housing but this air would not get to the injectors.

 

[frank rabbets]

With a healthy engine there is still a non return valve fitted as standard in the filter housing. If air could not get in I wonder why they fit this valve. As I said I've taken off the whole filter assy with pipes and it holds vacuum and pressure on the bench but when I connect it to the engine fuel level in the substitute clear plastic pipe drops quickly back into the tank.

I've just thought... if there was no valve the fuel primer pump would not work. Perhaps this is it's main reason for being there and I have another fault. Time to push it into a swimming pool and put the airline on the IP to see where bubbles come out.

Frank

 

[Chris]

My understand was that there is a diaphragm in there which develops pin holes. This allows air in somehow which then allows fuel to drain back into the tank. However, it must also somehow form a siphon so that fuel is also pulled through the filter and the IP.

I find it difficult to believe that this is possible, rather thinking that the fuel on the IP side of the filter would stay put allowing the engine to start. Mine was bone dry every time. Fitting the simple in line check valve cured it instantly.

Chris

 

[frank rabbets]

Hi Chris. You might be right. My air is being introduced through a part of the system which is not under pressure with the engine running. Otherwise I would have a fuel leak with it running. If the hole was in the IP lift pump then this would syphon back to the tank emptying the filter body. I think the standard valve in filter body is just so the priming pump works so if it leaks a bit it doesn't matter once all the air has been purged back to the tank through the spill pipe. In fact when I prime mine I can hear bubbles coming up through the fuel in the tank so the spill pipe must enter below fuel level.

All this happened after I adjusted the tappets. I did take off the nozzle leakage pipe from the 6 injector tops to get at the adjusting nuts on the tappets but I remember checking the 6 banjo bolts very carefully. I wonder if air can get in here or somewhere else that I've disturbed?

I'm sure your valve will work but I don't lie doing fixes when i don't really understand what is happening .

Thanks for the support.

Frank

 

[Chris]

Frank, I think you may have nailed it there. Hadn't considered the leak being in the lift pump. Of course. That would make sense now. Yes, the one way valve is probably just for primer pumping, but mine didn't do that either so I figured that was the issue and stopped there.

The pusher pump by the way has been tremendous. Car feels very different. Bit like having a pacemaker fitted. All the IP has to do now is squirt the injectors.

Chris

 

[frank rabbets]

Here we go again! Just ordered a 0.8 psi one way valve. The lowest I could find. I was tempted yesterday to kiss goodby to the problem by buying a new T filter housing for £145 but of course it may not have cured the problem because in itself it is not the cause.
Congrats on the fuel pump. If you have no fuel leaks all should be well. Do you think your engine was being starved of fuel because of your air ingress?

Thanks
Frank

 

[Chris]

Frank, it was my old 80 that was leaking, not this one. I have one the mod A) because I could and b) in anticipation of the same problem plaguing this truck in the future. I just think that they are big old trucks that get tired IPs.

Chris

 

[frank rabbets]

Hi chaps
Think I might have found something. When I did the tappets I disconnected the injector leakage pipe from the rubber hose, then reconnected it. This hose is very hard and cracked. I disconnected it again and used the primer pump and fuel came out of it so it is defo connected to the supply side of the lift pump on the IP pump. She drained down again overnight so I shall put a new hose on tomorrow and also play about a bit.
I shall put a see through hose on the spill pipe and see if there is any air being sucked in. I hesitate to put a one way valve, especially a strong one as the lift pump may suck too much air in. A better idea would be to fit an electric fuel switch/tap if there is such a thing. This could be wired to the ignition or a separate switch for added thief confusion.

Frank

 

[frank rabbets]

B..L..O..O..D..Y
H..E..L..L

My theory about the injector leakage pipe is now far out in front of all the others.
I have massive increase in fuel consumption together with an engine full of diesel. I thought the oil pressure was dropping. I'll take the cam cover off and run the engine to see where the diesel is leaking.
I thought I better check the oil level just in case and bingo. No damage thank god.

Frank

 

[adrianr]

 

[frank rabbets]

Oh well cured it. All 6 injector tops were leaking from their banjo fittings due to me using the old aluminium washers. Problem is that the top of the injectors are very small squares with sharp edges and dig into the washers. Not round like I'm used to. The test is to put a polythene pipe on the leakage pipe coming out of the front side of the cylinder head and suck. You should be able to hang it from your tongue indefinitely. I could almost breathe through mine but it is now secure with new washers. At least I had the moral support of my wife through all this...." I hope you've learned your lesson now and stop messing about with things you don't understand".

Frank

 

[adrianr]

Glad its fixed, well isolated, and that you are in receipt of such sound moral support and sage advice from her who must be obeyed!!

From your experience of this I've realised again that if a fault appears its worth thinking back to see if I first did something just prior to its occurrence. So thank you for that.

I often wonder how are you supposed to understand something until your first realise you dont understand it, dive in and have a play?

After all:
- Success comes from good judgement
- Good judgement comes from experience
- Experience comes from poor judgement



It might still be worth sticking in the one way valve when it arrives?

 

[Chris]

I was told that I must put new banjo washers on there when I changed my injectors. In fact my 'jector bloke gave me some. They were just plain copper, nothing special.

Hope that cracks it Frank.

Chris

Competency is about understanding when to stop and head back. Few people drown on the outward leg of their swim.

 

[frank rabbets]

Thanks each. I do not think I will put the one way valve in. I do not think I will have drain back probs now. Chris I have put plain round washers in; not the "C" section ones that Toyota use. Did you just use plain round ones? I wondered if the Toyota shaped ones were to help the banjo bolts from coming undone. They were certainly difficult to release. I was thinking of putting Toyota ones in but if yours have not come undone I may not bother.

I'm glad I did not fit the one way valve and forget all about it.

Frank

 

[adrianr]

It always pays to trust your instincts and intuition.

 

[Chris]

Deff round copper washers Frank certainly not c washers or circlips etc. std copper

Chris

 

[frank rabbets]

I took the sump plug out and it drained overnight. Over 3 gallons of fluid; so it was with some trepidation that I started it up this a.m. All good news. It had not drained down overnight and started on first cylinder. Also pressure gauge went up to 2/3 so everything OK. I had only just changed the oil and with over 1/3 diesel in there it's certainly given the engine a good flush. In fact the oil is now so clean you cannot see it on the 'stick. Thanks for the support.

Frank
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