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  #1  
Old 12-23-2012, 05:32 AM
Boots Boots is offline
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Question IP air leak

Hi All,

Just recently, my IP has started letting air into the system - but only when the engine isn't running!

I've had the shaft seal go a couple of years ago and that just caused it to suck air all the time - you pretty much couldn't run the engine at all.

The current symptoms are that after stopping the engine, you can see the fuel drain back down the clear tube to the filter and actually hear the air getting drawn in at the pump!

The battery's taking a bit of a hammering and it runs rough for the first 2-3 seconds but apart from that, once it's away, there is no sign whatsoever of air ingress. You can keep your toe in the carpet as long as you like and it won't draw air...

Before I go pulling the pump again to do the shaft seal, has anyone known the cut-off solenoid to leak air in? I'm wondering if it only leaks in the de-energised position and that's why it runs ok once started.

It'd be really nice if a new solenoid sorted it as I was hoping to get more than 20,000 miles out of the seal!

There's no sign of fuel getting out at all and the spill pipes and return hoses are in good shape.

If I do have to get the shaft seal done, my local shop says there is now a double-lipped version for this pump aimed at making the seal last longer I presume - anyone heard of this?

If anyone has any other ideas as to a possible cause of the problem, please let me know...

It's gonna have to manage until after xmas for financial reasons and the battery seems to be holding up for now but I don't really like the idea of the pump not being full of fuel while it's stopped and, if it is the shaft seal, I daresay it'll get worse and quit on me altogether, like it did before!

Boots.
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  #2  
Old 12-23-2012, 11:58 AM
ngoma ngoma is offline
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Worn bushings can cause early shaft seal failure, allows the shaft to wobble more than the seal was designed for. Might want to check shaft runout.

As a troubleshooting aid: Since you can hear the air ingress, what about using mechanics stethoscope to verify the leak location via the sound?
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Old 12-23-2012, 03:20 PM
Boots Boots is offline
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Great idea, cheers mate. Should have thought of it myself really!

If it's been the car's companion all its life, the pump's done 170k miles so I expect it's probably time for a rebuild. Looks like 2013's gonna be a learning year...
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Old 12-23-2012, 10:28 PM
ngoma ngoma is offline
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Should have added that excessive tension on the IP belt can wear the IP shaft bushings oblong. Did yours have that condition?

One other idea: If the IP shaft had (varnish) buildup on it where the new seal rode, that would tear up the new seal sooner than normal.
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  #5  
Old 12-25-2012, 05:06 PM
745 TurboGreasel 745 TurboGreasel is offline
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Quote:
Originally Posted by Boots View Post
The current symptoms are that after stopping the engine, you can see the fuel drain back down the clear tube to the filter and actually hear the air getting drawn in at the pump!


Before I go pulling the pump again to do the shaft seal, has anyone known the cut-off solenoid to leak air in? I'm wondering if it only leaks in the de-energised position and that's why it runs ok once started.

It
Pressurize the system with an external pump, and you should be able to see fuel piss out the leak.

I've changed the shaft seal on the engine out of the car, and I think it could be done on car if you are patient and creative. Might only be worth it if you didn't have timing tools.
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Old 02-12-2013, 11:36 AM
Boots Boots is offline
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Unhappy

Thanks for your input everyone.

ngoma, I didn't do the seal myself last time so I didn't get to see how the old one had worn/failed.

The IP belt was refitted by a local garage after head gasket replacement last year but it doesn't feel excessively tight. About 1/2" deflection available mid-way with moderate pressure.

I don't have a stethoscope yet but I think it must be the shaft seal. (Sound is definitely coming from that end.)

I clamped off the return hose today and applied an airline to the filter feed pipe. Started out real gentle at first - 0.5 bar or less - to see if I could get some fuel to come out the leak. No joy. With the return clamped, the darn thing was air/fuel tight to 3 bar.

Whatever path the air is taking to get in and allow the fuel to drain back, it's a one-way path. Most likely applying positive pressure, as I did today, is causing the shaft seal lip to re-seal against the shaft. Only other reason I can think of for the case to be airtight to positive pressure but leaky enough under vacuum that gravity and a few grams of fuel will pull air in is that one of the pump components is effectively acting as a one-way valve between the fuel inlet union and the leak. Maybe the pressure reg valve - I'll have to remind myself of the exact layout of the pump internals...

It is very odd that there is no sign of air ingress when the engine is running.

I eliminated the stop solenoid by applying power just after the engine had stopped - the air still got in as before.

(Annoyingly thought of this logical test AFTER buying a new solenoid.)

I was going to change the solenoid anyway but it seems to me you have to remove the injector lines to get a spanner on it. Went to do that and found that one of the delivery valve housings was loose in the pump head and so turning the gland nut on the pipe was just loosening the valve housing out of the pump rather than the injector line from the valve. Nightmare!
Of course, it had to be the most tucked away one at the bottom and on the motor side. I don't really understand how it wasn't leaking fuel here or mis-firing. The delivery valve housing was properly waggling about. I was running out of time and the solenoid had been pretty much exonerated anyway so I admitted defeat and simply carefully tightened the whole thing back into the pump. No sign of twisting the pipe so that little problem will have to wait until the pump comes off.

Which it's looking more and more like it's going to have to. I can't afford the dial gauge to time it back up at the moment but I think that's the next step. Depending on the price a seal/bushings kit and LP pump paddles etc., I might even have a go at a rebuild...

Just at the moment, the pump is making me curse a fair bit but I have to remember all the distributors, HT leads, spark plugs, MAF sensors, vacuum lines and ECUs I'm NOT having to deal with thanks to its existence

745TG, were you thinking I could lock the pump with a pin and lock the cam somehow to be able to pop the belt and sprocket and not need a dial gauge?
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Old 02-12-2013, 11:36 PM
745 TurboGreasel 745 TurboGreasel is offline
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I've done it with clothespins holding the belt to both pullies, engine at TDCby flywheel, pop the pump gear off, and note the direction of the keyway on the pump....also make a witness mark pump-bracket if you will be removing the pump.
You can't pin the pump and remove the pulley, and do not move the crank, cam,or cam gear but you can return the pulley to the pump without it ever leaving contact with the belt.
lisle seal tool #58430 worked good for me.

Removing the pump obviously adds opportunity for potentially compounding error, but by the belt only method you will easily be close enough to run, if not spot on. The engine I did it on was on a stand, was real easy, and it fires perfectly at 33F. Probably colder, that's about as cold as it gets here. You could undo the tranny mount, and jack the tail up for a hair of extra space.

Last edited by 745 TurboGreasel; 02-12-2013 at 11:40 PM.
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Old 02-13-2013, 12:01 PM
Boots Boots is offline
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Blimey, I think you must be braver than I am!

I'd be bound to let one or other of the shafts turn whilst they weren't connected, knowing me.

I'll pop along to my local vw dealer and see if I can persuade them to lend me a DTI clock and holder for a deposit...

Thanks for the tip about the seal puller. I've been a bit more heathen about fetching lip seals out in the past - whack in something pointy but strong and lever the critter out - but in this case damaging the shaft would be bad so I'd better get hold of a puller and do it the civilised way, I suppose!
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  #9  
Old 02-13-2013, 02:08 PM
745 TurboGreasel 745 TurboGreasel is offline
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Not that brave, the only consequence of failure is I'd have to get out my pins and dial.

The other shafts aren't inclined to turn, as they are all connected together by the timing belt.

I was going to make a copy of the VW seal puller, but I decided it was cheaper just to buy this puller, and I will use it on other seals too. No regrets.
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