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Discussion Starter #1
Dear fellow T4 owners,

I own an AAB 2.4 T4 from 1991 and although I am happy with it, it has never been easy to start up. I first thought it would be a problem with the glow plugs. Although it was a hell of a job, I managed to change them all but things didnt get any better (I tested the plugs outside, and all of them seemed to be in normal operation).
I have then noticed there is air on the diesel circuit. On the transparent tube that comes our of the pump, a few seconds after I crank apears an air bubble wich is about 2cm long. It then settles.
I changed all return pipes (the rubber ones) and also bought a new fuel filter valve (the one that goes on top of the fuel filter) with no sucess. Right now the engine is a non starter, and I wonder where does this air come from... should I change the remaining rubber hoses (the transparent and the other)? Should I remove the passenger seat to get to the tank sensor?
Could this simply be a low compression problem on the engine? It has 270.000km but apart from very hard to start, it has enough strenght to cruise at 100km/h with no problem...

Any help would be really good as I am starting to get out of ideas:..

Best regards,

Sergio
 

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did you change the small blank off cap on your first injector, when you changed the leak off pipes, these have a habit of going soft over a period of time and starting to leak and when your using the throttle they tend to suck in air, which eventually ends up in your clear fuel line, I had the same problem with mine, so I changed it, the van runs like a dream now,try it it might work for you. Regards bighookT:T:T:T:T:
 

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Discussion Starter #3
Hi bighook,

actually the first was the only one i did not replace... I only have open tubes for replacement. Can I make a end tube with normal tube?

Best,

Sergio

did you change the small blank off cap on your first injector, when you changed the leak off pipes, these have a habit of going soft over a period of time and starting to leak and when your using the throttle they tend to suck in air, which eventually ends up in your clear fuel line, I had the same problem with mine, so I changed it, the van runs like a dream now,try it it might work for you. Regards bighookT:T:T:T:T:
 

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Hey Sergio I have the same problem at the moment.

It takes a few times to get it running, I have replaced all the rubber breather lines on the injectors as I had a leak from one of them before. I get air in the clear line to the fuel pump. Mine happens when it has sat there for more then 24 hours. I also have found that if it sits on level ground it is worse and aslo if it is parked facing up hill. It is much easier to start when facing down a slope as I gues the bubbles will go back to the tank.

I have checked all the connections on the fuel filter and they seem ok but it could be coming from the fuel tank, or possibly a perished seal in the fuel pump but then again you would think there would be a diesel leak when it's parked.

Have you tried bleeding the air out the system by loosening the nuts on the injectors one by one and let fuel come out? You will need some one to turn the ignition for you while you do this, maybe 5 seconds or so on each injector. This will get you running so you can get it to a mechanic.

I have thought about fitting a diesel hand primer after the problem is resolved, just for piece of mind. I'm taking it to a diesel specialist this Thursday which probabaly won't be cheap.

I will let you know what happens.

Jerry
 

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Discussion Starter #5
Thanks for the reply Jerry, I am almost giving up on this... changed all rubber tubes, changed the transparent tube, checked up if there was a leak where the tubes leave the tank, the air is always there, and no matter how much I crank, it won't start :(
 

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I've got air bubbles for the moment, too.
To start it without crank it to death, I undo the banjo on the return pipe (not the clear one) on top of the injection pump, and fill the pump with diesel with a pipette.
Then my engine starts in less than 3 seconds.
If I don't do that I can crank it until the battery dies and still doesn't start.
 

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I've had same kind of problem some time ago with my other car Mercedes 190 when running it on SVO.
When running my Merc on diesel it was starting without problems.
When filling it up with SVO, there were air bubbles.
Someone mentioned me that diesel being less viscous and more fluid was flowing easier to the fuel pump.
But the SVO being more viscous, it was flowing harder to the pump, and so the pump was sucking some air from a tiny hole ...who knows where....????
To avoid dismantling your whole fuel system and look for a tiny little hole, he suggested me to install a fuel pump in the tank or near the tank.
That pump will push fuel in the lines, unlike our injection pumps which are sucking fuel from the lines.

Someone else suggested to create some pressure inside the tank and see where the fuel drips....and fix the hole.

I haven't done it, as I got rid of the car.
But in case I can't fix my van, I'll try that.

Before trying any of these, change your fuel filter....maybe being old and full of gunk, it stops fuel from flowing easily to the pump, and the pump sucks air from somewhere.
 

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Discussion Starter #8
Changed fuel filter, tried to fill once again the transparent tube and this happens: fuel flows very slowly inside the pump. It never stops, I poured about 1 liter.
No drops anywhere, so I must guess this fuel went to the tank?

Anyway, after two weeks os labor and frustration, I just closed the van and will ask a mechanic for help... there goes my $$$ for my vacations :(
 

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Is the fuel actually getting in to the injection pump?
Have you loosened the injector pipes to see if fuel sqirts out?
If fuel is not flowing through then you will not clear the air out either



Fuel stop solenoid
Ignition switch
Immobiliser
 

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Fuel wont always leak from the spindle bush/seal -- check phsically for play !! Also , try leaving for an extra 5-10 seconds , after the glo-plug lightgoes out , before cranking , I have to do this on another vehicle , or it just wont start . Leave for longer , instant life !!
 

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I've had same kind of problem some time ago with my other car Mercedes 190 when running it on SVO.
When running my Merc on diesel it was starting without problems.
When filling it up with SVO, there were air bubbles.
Someone mentioned me that diesel being less viscous and more fluid was flowing easier to the fuel pump.
But the SVO being more viscous, it was flowing harder to the pump, and so the pump was sucking some air from a tiny hole ...who knows where....????
To avoid dismantling your whole fuel system and look for a tiny little hole, he suggested me to install a fuel pump in the tank or near the tank.
That pump will push fuel in the lines, unlike our injection pumps which are sucking fuel from the lines.

Someone else suggested to create some pressure inside the tank and see where the fuel drips....and fix the hole.

I haven't done it, as I got rid of the car.
But in case I can't fix my van, I'll try that.

Before trying any of these, change your fuel filter....maybe being old and full of gunk, it stops fuel from flowing easily to the pump, and the pump sucks air from somewhere.
You should at the very least have used a heat exchanger to warm the Veg oil up, as you say the oil is alot thicker then diesel and you would have put strain on the IP trying to pump it. The heat exchanger will thin the viscosity of the oil down to the right amount for the IP T:
 

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The reason it won't start is due to the fact that the IP can't pump fuel with air bubbles in, and the van can't run on air either. Don't keep cranking it over continously or you will burn out the starter motor as they aren't meant to go for a long period of time.

Sergio- Replace the fuel filter valve which sits on top of the filter, I think (hope) this is where the air is getting in on mine as I dont see a seal on the bottom. Also like some one else suggested the rubber stop on the far left injector as you look at the engine. The local dealer here quoted me $50 AUD for the valve which is crazy when I can get it for 5 GBP and the rubber stop for GBP 0.68!! Get both from here if you can't get locally or don't want to pay horrendous dealer prices. Postage won't be much to you either. Theay also sell the injection pump shaft seal, have to check if it is for your pump or not though.

Good Luck mate.
 

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Forgot to say, try the valve and rubber stop first, they are cheap if that's all it takes before going to the mechanic, this is what I have now decided to do instead of paying some one to fault find it for me. If that fails I'm changing all the fuel lines from the tank all the way through to IP.

T:
 

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You should at the very least have used a heat exchanger to warm the Veg oil up, as you say the oil is alot thicker then diesel and you would have put strain on the IP trying to pump it. The heat exchanger will thin the viscosity of the oil down to the right amount for the IP T:
Oh, yeah, I know all about heat exchangers and SVO.....
only you don't know how lazy I am.....
 

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Discussion Starter #18
I bought a valve from VW (ouch!), new filter an new rubber stop.. this is why I am giving up. Have done most easy parts :(
 

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Discussion Starter #19
I guess it could also be compression, it burns quite a bit of oil, and has a smokey exhaust, but has always been able to handle highway speeds (100/120 km/h)... Can a low compression engine go that fast?
 

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Discussion Starter #20
Hi there! I am still fighting this one:

1- Inserted a one way valve on the transparent fuel tube and now i get no bubbles from the pump
2- Tried brake cleaner on the air intake with no success - nothing happened (tried both while someone was cranking and my self)
3- Can it be that after so much cranking the fuel injectors are too much dirty?
4- When the abttery is still fresh, it starts smoking and two or three cylinders seem to start firing, but that's it...
5- I changed all plugs, but when I use them, if I touch outside them they only seem warm (on the engine). I tested them outside and all of them glowed easily. Is this normal?
Should I remove all injectors and clean them? Soaking in brake cleaner or carb cleaner will work out? Why didn't brake cleaner on the intake do anything?

Best,

Sergio
 
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