fuel problem
Thread Starter
AudiWorld Member
Joined: Jun 2023
Posts: 68
Likes: 18
From: Atlanta, Ga.
fuel problem
I've had this car pretty well sorted now and I'm really enjoying it. Lately, the last 4 or so cold starts the car will not fire until I use the key to re - pressurize the fuel system. The 3rd time I turned the key to on without cranking, back off, and then cranked and the car fires right up. Once warm, this goes away.
I'm thinking something is leaking down in the fuel system. I've replaced the filter but have not yet replaced the pump. Outside of this issue the motor runs beautifully right up to redline. Would this likely be the pump or fuel pressure regulator? Other ideas? Car is a 2003 S8.
Additionally, from time to time I can smell an odor which seems like a crankcase odor. There are no oil leaks of any kind that I can detect, driveline or valve covers.
I'm thinking something is leaking down in the fuel system. I've replaced the filter but have not yet replaced the pump. Outside of this issue the motor runs beautifully right up to redline. Would this likely be the pump or fuel pressure regulator? Other ideas? Car is a 2003 S8.
Additionally, from time to time I can smell an odor which seems like a crankcase odor. There are no oil leaks of any kind that I can detect, driveline or valve covers.
Last edited by oldscool; Mar 3, 2025 at 11:05 AM.
Thread Starter
AudiWorld Member
Joined: Jun 2023
Posts: 68
Likes: 18
From: Atlanta, Ga.
I've done additional reading since posting this. It seems the issue will be leaking injector (I believe less likely), leaking regulator, leak in hard/soft line, or pump. I had a bit of trouble getting the filter lines to seal initially, so I'll have a look there first.
If anyone has thoughts on common crankcase ventilation parts that commonly fail on these cars, I would be interested to hear.
Also, upon purchase of the car I bought a Continental fuel pump (made in Germany) in anticipation of changing it out. I am reading older posts about only using VDO Siemens pumps. Thoughts?
If anyone has thoughts on common crankcase ventilation parts that commonly fail on these cars, I would be interested to hear.
Also, upon purchase of the car I bought a Continental fuel pump (made in Germany) in anticipation of changing it out. I am reading older posts about only using VDO Siemens pumps. Thoughts?
Last edited by oldscool; Mar 4, 2025 at 06:33 AM.
AudiWorld Senior Member
Joined: Apr 2001
Posts: 1,912
Likes: 39
It really sounds like you have fuel pressure leaking down.
There are a couple common culprits.
One is the pump itself as it has a built-in check valve.
Another source is the fuel line between the pump and the top of the fuel pump housing assembly.
Also, the fuel filter as you previously stated.
Really the only thing I can offer over the internet is for you to investigate a little more thoroughly.
I had one car that had similar issues and we ended up replacing the fuel line between the pump and the top of the housing. This resolved the issue.
Please note that if you replace the fuel line from the pump you must source submersible fuel line I purchased mine from Bel-metric..
https://belmetric.com/cohline-series...?sku=RH7.3TANK
-Richard
There are a couple common culprits.
One is the pump itself as it has a built-in check valve.
Another source is the fuel line between the pump and the top of the fuel pump housing assembly.
Also, the fuel filter as you previously stated.
Really the only thing I can offer over the internet is for you to investigate a little more thoroughly.
I had one car that had similar issues and we ended up replacing the fuel line between the pump and the top of the housing. This resolved the issue.
Please note that if you replace the fuel line from the pump you must source submersible fuel line I purchased mine from Bel-metric..
https://belmetric.com/cohline-series...?sku=RH7.3TANK
-Richard
Last edited by audinutt; Mar 5, 2025 at 07:21 AM.
Thread Starter
AudiWorld Member
Joined: Jun 2023
Posts: 68
Likes: 18
From: Atlanta, Ga.
Thanks for your response. As I thought more about the latest drive I remembered a slight whiff of gas at one point. Not being that familiar with the system yet, I thought it may have been from the housing as a smoke test by a technician early on found some leakage there. I now think the smell may have been from the filter I had trouble with sealing. I'll have to put the car back on the lift to verify.
I'm just going to R&R the pump and housing soon for peace of mind. Thanks for the link. Not sure if that hose comes with the reproduction housing, I ordered the other day.
I'm just going to R&R the pump and housing soon for peace of mind. Thanks for the link. Not sure if that hose comes with the reproduction housing, I ordered the other day.
Thread Starter
AudiWorld Member
Joined: Jun 2023
Posts: 68
Likes: 18
From: Atlanta, Ga.
Following up, the long crank problem has never returned, even after days of sitting. It makes no difference how much fuel is in the tank either. So, with the new pump and housing in my inventory I'll just continue to enjoy the car for now.
I removed the PCV valve and found a tear in the diaphragm about 1 inch long. Repaired it with some silicone and cleaned everything well. I've not smelled the crankcase odor since. Ironically, this smell was what prompted me to replace driveline seals initially, some leaky, some not. From my experience with this, a faulty PCV valve can produce a very noticeable odor in these cars. I've never experienced this in any of the many cars I've owned.
I removed the PCV valve and found a tear in the diaphragm about 1 inch long. Repaired it with some silicone and cleaned everything well. I've not smelled the crankcase odor since. Ironically, this smell was what prompted me to replace driveline seals initially, some leaky, some not. From my experience with this, a faulty PCV valve can produce a very noticeable odor in these cars. I've never experienced this in any of the many cars I've owned.
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