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DerAlex Guest
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05-05-2002, 23:58 Subject: Air Pollution: Diesel Alternatives Now |
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This morning, my TDI wouldn't start (Golf IV, 90 horsepower, ALH engine).
I first checked to see if there were any air bubbles in the fuel line. I thought there weren't any, but it turned out the entire hose was completely empty, filled only with air and no diesel.
I tried starting the engine for ages, but it wouldn't turn over.
I thought the filter might be completely clogged or a fuse might have blown, and the pump wasn't working at all.
The fuse was okay, so I went to the gas station, filled the reserve canister completely, and then poured it into the tank at home. After that, I filled the diesel filter until it overflowed.
Then, after a short time, the engine started.
Okay, my question is: Where can air 'leak' into the fuel system?
I've been having this problem with the blisters for about a month now, but I don't want to have to go through the procedure I described every month, especially not when I'm in a hurry.
Translated on 20-09-2026, 12:16.
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ulf Profi-Schrauber

Joined: 04/13/2002 Posts: 11058 Karma: +18 / -0 Location: Saarland 2023 MG ZS Premium Support
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06-05-2002, 16:23 Subject: Where Does Air Come From? |
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Written on: Sunday, May 5, 2002, 10:58 PM
Title: Air Instead of Diesel Again
"Die Sonne scheint hell, und die Vögel zwitschern fröhlich. Ein leichter Wind weht durch die BĂ€ume, und die BlĂ€tter rascheln leise. Es ist ein wunderschöner Tag, um drauĂen zu sein."
Hi Alex,
First, to avoid any misunderstandings: The ALH engine, like all VE-TDIs, draws fuel using the injection pump as soon as the engine starts to turn. Therefore, fuses are irrelevant in this process.
Quote: | | I first checked to see if there were any air bubbles in the fuel hose. I thought there weren't any, but it turned out the entire hose was completely empty, containing only air and no diesel. |
That's strange. How long had he been standing there before?
Quote: | So, my question is: Where can air "leak" into the fuel system???
I've been having this problem with the blisters for about a month now, but I don't want to have to go through the procedure I described every month, especially not when I'm in a hurry.
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Air can practically seep in through any leak. However, often the same hole that allows air to enter will also cause diesel fuel to leak, meaning you should be able to smell the leak.
Unless the hole is "somewhere up top," and the liquid drains back into the tank.
What surprises me is that you can drain about 100 ml of diesel from the ESP (in the AFN engine), and the remaining amount is still enough to allow the engine to start and draw in more fuel, without the engine stalling.
Therefore, your pump must have been completely empty, in my opinion.
Could it be leaking and draining when left standing for extended periods?
I'm afraid the only thing you can do to find out is to stop every few minutes and check where the air is leaking into the hose or where the diesel is dripping from. GruĂ Ulf
_________
MG4 Electric
Translated on 20-09-2026, 12:19.
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DerAlex Guest
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07-05-2002, 19:51 Subject: Air Pollution: Diesel Alternatives Now |
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My TDI was parked from 2 AM to 2 PM, which is 12 hours.
It must be because I'm standing on a slope (our driveway has a slight incline, max 5%).
If the car is parked on a flat surface or in the garage, this doesn't happen.
However, it seems like air is slowly leaking in, because a few days ago, when I refilled the cleaning solution, I noticed that there were some bubbles in the hose.
Then I guess I'll have to see if I can find any leaks.
Translated on 20-09-2026, 12:22.
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Mathias Guest
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08-05-2002, 14:29 Subject: Air Pollution: Diesel Alternatives Now |
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'Doesn't the car have a check valve? If so, maybe it's broken. But it's still strange, because the fuel draining should create a vacuum.'
Translated on 20-09-2026, 12:23.
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eike Guest
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08-05-2002, 20:59 Subject: Air Pollution: Diesel Alternatives & Solutions |
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Hello,
'My car once sucked in air because the return line wasn't properly connected to the diesel filter. As a result, it sucked in air while driving, creating bubbles in the hose.'
Perhaps a new gasket needs to be installed there. My diesel filter had to be replaced after only 15,000 km because it was drawing air in at that specific location. It seems to be a problematic area.
However, that didn't cause him to run out of money.
Regards,
Eike.
Translated on 20-09-2026, 12:24.
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wilhelm busch Guest
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18-05-2002, 9:48 Subject: Air Pollution: Diesel Alternatives & Solutions |
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[quote='DerAlex']This morning, my TDI wouldn't start (Golf IV 90PS ALH).
I first checked to see if there were any air bubbles in the fuel line. I thought there weren't any, but it turned out the entire hose was completely empty, filled only with air and no diesel.
I tried starting the engine for ages, but it wouldn't turn over.
I thought the filter might be completely clogged or a fuse might have blown, and the pump wasn't working at all.
The fuse was okay, so I went to the gas station, filled the reserve canister completely, and then poured it into the tank at home. After that, I filled the diesel filter until it overflowed.
Then, after a short time, the engine started.
Okay, my question is: Where can air 'leak' into the fuel system?
I had this problem with the blisters about a month ago, but I don't want to go through the procedure described above every month, especially not when I'm in a hurry.[/quote]
Hello Alex,
It's a known phenomenon that, due to an empty or nearly empty fuel tank and parking on a hill (uphill), the fuel lines can drain.
Sure, here is the translation of the text from German to English:
'Gr. W.' translates to 'Large size.'
Translated on 20-09-2026, 12:26.
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DerAlex Guest
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23-05-2002, 11:59 Subject: Air Pollution: Diesel Alternatives Now |
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Thank you for the answers.
Then I'll probably try to avoid letting the car run out of gas and get stuck on a hill.
By the way, is 30 euros a reasonable price for the diesel filter?
I couldn't find any leaks anywhere, and I also checked all the connections and tightened the screws. The filter hasn't been changed in a long time, maybe that's the problem.
Translated on 20-09-2026, 12:28.
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