Won't start after new vacuum pump

Are you sure you it was not air being returned to the tank that you were hearing? How is the engine running?
 
The engine is ok but not great, it's hard to start (again) also. My friend used a manual pump at the inlet hose by the vacuum pump on the side of the engine. I'm guessing it couldn't be air returned to the tank since the return shouldn't be affected. Or could it still be affected somehow? Could air be going into the vacuum pump, since a hose is let lose, and then travel to the tank? I figured as long as the vacuum pump isn't forced to turn there would be no air entering the return hose.
 
Where did you get your new in tank pump from? I bought a new Bosch in tank pump for my S2 18months ago and it failed after less than 2k. I bought it from a previously trusted ebay seller but I strongly suspect it's a Chinese copy.
 
Tractor Dave said:
Where did you get your new in tank pump from? I bought a new Bosch in tank pump for my S2 18months ago and it failed after less than 2k. I bought it from a previously trusted ebay seller but I strongly suspect it's a Chinese copy.
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I bought it from a German Audi site, I had to become a member in some club. Not sure how I did it since most of it was in German but it seemed legit. But of course, the new pump could be failing, although 've only had it for three months.
 
Have you taken the car for a good drive yet? That should get any remaining trapped air out. Make sure the fuel hoses especially on the tandem are good condition and not cracked and tight onto the tandem.
 
By a strange coincidence, just done a tandem pump on an A3 tdi today.
Slightly different issue. Oil in the fuel filter. Internal seal in the pump had failed.
On re assembly, there was no priming necessary. Engine fired straight up no issues.

Another thing to check is that your screen in the tank isn't blocked. Did you change the in tank pump?
 
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Took if for a semi-good drive recently, should have been enough to clean air out though. I'll check the hoses again, thanks.
 
Tractor Dave said:
By a strange coincidence, just done a tandem pump on an A3 tdi today.
Slightly different issue. Oil in the fuel filter. Internal seal in the pump had failed.
On re assembly, there was no priming necessary. Engine fired straight up no issues.

Another thing to check is that your screen in the tank isn't blocked. Did you change the in tank pump?
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Hmm, I needed a lot of cranking to get mine fired up after I changed the tandem. Probably not a good sign. Do you think it's possible that a new tandem pump could draw in air where the old one was to weak to do it? I
I changed the in tank pump three months ago, I haven't done anything with it today other than double check that the hoses were connected properly.
 
And are you sure you got all the pipes on correctly? Any damage to the pipes on removal? (easily done as they seem to set in position).
 
It's the only time I've changed an in tank pump so I can't be sure but it all seemed OK. There's only two lines and then the electrical connection. They're not leaking in any way.
 
So when you turn the ignition on you hear the tank pump run? That will pressure feed fuel up to the tandem and back down the return line to the tank. When the engine is started the tandem pressure feeds the injectors with the extra fuel still returning to the tank. This set up should self bleed out any air. Are you getting fuel without air bubbles to the tandem? What tandem did you fit?
Later cars only have the tandem and are very capable of dragging the fuel from the tank. Is there trapped air in the fuel filter? All connections correct on the fuel filter?
 
I haven't done an in tank pump on an A2 but have done a few on the S2. If they are similar, the pump sits in a cradle which is held in place in a cage. The whole cage is removed by twisting anti clockwise. You then get to the filter screen at the bottom which is often blocked up with crud. There is another screen on the bottom of the pump. To do the job properly, you need to drain the tank and clean out all the crud in the bottom before replacing everything after a good clean. This might cure everything you are experiencing.
 
audifan said:
So when you turn the ignition on you hear the tank pump run? That will pressure feed fuel up to the tandem and back down the return line to the tank. When the engine is started the tandem pressure feeds the injectors with the extra fuel still returning to the tank. This set up should self bleed out any air. Are you getting fuel without air bubbles to the tandem? What tandem did you fit?
Later cars only have the tandem and are very capable of dragging the fuel from the tank. Is there trapped air in the fuel filter? All connections correct on the fuel filter?
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Yes, I hear the pump when I turn on the ignition. No, there's bubbles in the fuel when I pump/prime manually at the inlet hose by the tandem pump, not a lot but a always a few. But from what you said earlier I'm now wondering if this could be due to air entering the return hose while I've disconnected the inlet hose. Could this be possible?

I filled up the filer to the brim and have double checked all hoses, it should be fine.
 
I would recheck the fuel filter.There could still be air in the filter or leaking connections. The return line is also under pressure back to the tank, but any loose connection or degraded pipe will allow air into the system.
 
Tractor Dave said:
I haven't done an in tank pump on an A2 but have done a few on the S2. If they are similar, the pump sits in a cradle which is held in place in a cage. The whole cage is removed by twisting anti clockwise. You then get to the filter screen at the bottom which is often blocked up with crud. There is another screen on the bottom of the pump. To do the job properly, you need to drain the tank and clean out all the crud in the bottom before replacing everything after a good clean. This might cure everything you are experiencing.
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This is the in tank pump:
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Fuel pump AUDI A2 (8Z0) 1.4 TDI 2850617 | B-Parts

Buy Online Fuel pump for AUDI A2 (8Z0) 1.4 TDI 2850617 and enjoy ✓ Fast Shipping ✓ Warranty ✓ Original Used Parts.
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No cage or anything, just took if out and put in the new one. When you're talking about cleaning it do you mean you just bought the inside pump and not the white plastic thingy around it? I bought the whole thing and just put it straight into the tank.
 
That used pump has done a lot of Kms. Are you sure the 1.2 and 1.4 pumps are the same? So what was wrong with your pump?
 
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