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I'm wondering if anyone can help me with an odd issue with my 2002 b5.5 1.8 FWD.

My vehicle, when cold, will not start on the first attempt. I can hold the key on, it cranks great but does not fire/start. I can then turn the key to the off position and try again, where the car will usually start fine (sometimes I will have to put the peddle down, which seems to help). The second attempt will sometimes have a rough Idle for a second or two, but once it catches, the car runs great - no issues at any point during travel. Also, if I stop running the vehicle and only leave it for a few minutes, it will start right back up, no problem. It's only when it sits for 10+ minutes or cold that It takes a few attempts.

I'm stumped. I replaced the battery, fuel filter, air filter to no avail.

What I think it could be:

  • failing fuel pump.
  • dirty throttle actuator/ angle sensor (I did get a fault of sensor 1 and 2 getting a bad signal a few months ago (which led to no turbo/boost), but I haven't had this happen since. I feel like this is not causing the starting issue, but I could be totally wrong here).
  • a leak in the fuel system.
  • injectors.
To me, it feels like the car is not getting enough fuel/air. I really don't want to start replacing things that I don't need, so if anyone has some insight that would be a huge help.

Thanks!
 

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It seems to me your issue is more related to fuel delivery mechanism.

1) Take out TB and decarbonize it.

2) Take out the fuel injectors and clean them.

3) If you haven't done so, replace the fuel filter.

4) Test the fuel pump and make sure it's not working intermittently.

5) Test the fuel regulator and make sure it works properly and replace if needed.
 

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That would be my assumption as well. It should hold fuel line pressure at the very least overnight. Mine still holds after weeks. The pump only comes on for a second in the accessory position to prime the lines up to operating pressure before cranking. If the lines do not have residual pressure and have bled back into the tank through that faulty valve, it takes a while for the pump to fill and pressurize the line with fuel.
 
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OP, does your driver door open switch work, i.e. does the puddle light come on and inside lights? Likewise, does Driver Door Open indicate on the instrument cluster?

The fuel pump runs for a couple of seconds after the driver's door is opened (to prime). If that switch (and communication to the CCM, which controls the dome light) doesn't work, the pump won't prime. In a quiet environment, you can hear the fuel pump run.
 

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OP, does your driver door open switch work, i.e. does the puddle light come on and inside lights? Likewise, does Driver Door Open indicate on the instrument cluster?

The fuel pump runs for a couple of seconds after the driver's door is opened (to prime). If that switch (and communication to the CCM, which controls the dome light) doesn't work, the pump won't prime. In a quiet environment, you can hear the fuel pump run.
That door switch or the door open/closed, has nothing to do with FP priming.
The FP primes when the key is turned to ON, regardless of the door open or closed.
 

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Will be following this with great interest. Have had the same issue over several years. Kind of a nuisance and working on many other projects so has not been a priority. If it does start the first try the engine stumbles for a moment which is annoying so I have gotten in the habit of doing a "pre-start". Will crank it for 2 seconds but then turn the ignition off before the engine catches. Wait a second and then it will start perfectly for me like there is no issue. Only happens when engine is cold.

Have done some major work on the engine recently (replaced piston rings with engine in) and at the same time went through the entire vacuum again including replacement of all the check valves (even though I did not see a problem with any of them) and it made no difference. I did add a small check valve to the fuel pump outlet and that seemed to have helped maybe a little but still did not fix it.

In the middle of another project that maybe could be related. I have had a leak in the brake booster for a while and it is fine driving but once I stop the engine the brake pedal will go hard pretty quickly. So maybe the additional un-metered air coming into the system from the booster on startup may be messing up the fuel mixture during cold start. Wanted to change the booster anyway before the leak gets worse and impacts brake performance so will see if it makes a difference. Probably not but I grasping at this point. Took it out two weeks ago and maybe will have a chance this weekend to put a different one in and bleed the brakes.
 

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Will be following this with great interest. Have had the same issue over several years. Kind of a nuisance and working on many other projects so has not been a priority. If it does start the first try the engine stumbles for a moment which is annoying so I have gotten in the habit of doing a "pre-start". Will crank it for 2 seconds but then turn the ignition off before the engine catches. Wait a second and then it will start perfectly for me like there is no issue. Only happens when engine is cold.

Have done some major work on the engine recently (replaced piston rings with engine in) and at the same time went through the entire vacuum again including replacement of all the check valves (even though I did not see a problem with any of them) and it made no difference. I did add a small check valve to the fuel pump outlet and that seemed to have helped maybe a little but still did not fix it.

In the middle of another project that maybe could be related. I have had a leak in the brake booster for a while and it is fine driving but once I stop the engine the brake pedal will go hard pretty quickly. So maybe the additional un-metered air coming into the system from the booster on startup may be messing up the fuel mixture during cold start. Wanted to change the booster anyway before the leak gets worse and impacts brake performance so will see if it makes a difference. Probably not but I grasping at this point. Took it out two weeks ago and maybe will have a chance this weekend to put a different one in and bleed the brakes.
It's the low vacuum that causes your starting issue. I've had it on nearly every Passat I've worked on after the vacuum system (reservoir or brake booster) has been opened. The unmetered air from the leak just makes it worse.
 
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Instead of cranking twice to start, try this:...
Turn the key ON for 2 seconds then OFF, 2 or 3 times before cranking.
Note: No point to go over 3 times as it can only prime 3 times between starts.
 

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Will be following this with great interest. Have had the same issue over several years. Kind of a nuisance and working on many other projects so has not been a priority. If it does start the first try the engine stumbles for a moment which is annoying so I have gotten in the habit of doing a "pre-start". Will crank it for 2 seconds but then turn the ignition off before the engine catches. Wait a second and then it will start perfectly for me like there is no issue. Only happens when engine is cold.

Have done some major work on the engine recently (replaced piston rings with engine in) and at the same time went through the entire vacuum again including replacement of all the check valves (even though I did not see a problem with any of them) and it made no difference. I did add a small check valve to the fuel pump outlet and that seemed to have helped maybe a little but still did not fix it.

In the middle of another project that maybe could be related. I have had a leak in the brake booster for a while and it is fine driving but once I stop the engine the brake pedal will go hard pretty quickly. So maybe the additional un-metered air coming into the system from the booster on startup may be messing up the fuel mixture during cold start. Wanted to change the booster anyway before the leak gets worse and impacts brake performance so will see if it makes a difference. Probably not but I grasping at this point. Took it out two weeks ago and maybe will have a chance this weekend to put a different one in and bleed the brakes.
I have gotten a code for a break booster leak in the past, so this is a good start...From reading other threads it sounds like it could be the Fuel Injection Pressure Regulator that can cause this issue (someone mentioned that after replacing it their problem went away). This is connected to the vacuum system so this might all be related.
 

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I'm wondering if anyone can help me with an odd issue with my 2002 b5.5 1.8 FWD.

My vehicle, when cold, will not start on the first attempt. I can hold the key on, it cranks great but does not fire/start. I can then turn the key to the off position and try again, where the car will usually start fine (sometimes I will have to put the peddle down, which seems to help). The second attempt will sometimes have a rough Idle for a second or two, but once it catches, the car runs great - no issues at any point during travel. Also, if I stop running the vehicle and only leave it for a few minutes, it will start right back up, no problem. It's only when it sits for 10+ minutes or cold that It takes a few attempts.

I'm stumped. I replaced the battery, fuel filter, air filter to no avail.

What I think it could be:

  • failing fuel pump.
  • dirty throttle actuator/ angle sensor (I did get a fault of sensor 1 and 2 getting a bad signal a few months ago (which led to no turbo/boost), but I haven't had this happen since. I feel like this is not causing the starting issue, but I could be totally wrong here).
  • a leak in the fuel system.
  • injectors.
To me, it feels like the car is not getting enough fuel/air. I really don't want to start replacing things that I don't need, so if anyone has some insight that would be a huge help.

Thanks!
Curious to see what it is as my b5.5 is having the same issue.

Checked vacuum lines, MAF, throttle, etc with no luck just yet.

Good luck!
 

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Some great suggestions in this thread and I will try to check over the next couple of weeks. I had promised an update but unfortunately it's pretty much a bust. Some diy jobs are great but some others feel like two steps backwards. I could not figure out how to bench bleed the master cylinder and not loose it all when re-installing it on the booster. So getting the air out of the system has been a process. I have both a Motive pressure bleeder and the help of my daughter. On top of that, one of the lines to the ABS unit was not sealing. There was a scratch on the aluminum block where the line seats. Tried several times and ended up having to use teflon tape. Each time I tried got more air into the system...

Brakes are still mushy now and should get new batch of brake fluid this weekend so will continue to try. Worst of all, brake pedal goes hard again after turning off the engine for a while. Have not driven it that much due to the mushy brakes but still seems to have a slow start as expected. At the same time, the weather is getting warmer so that may make it behave a little better than in the winter months.

When all is sorted out again, will try the check of the FPR and will try and prime the fuel pressure before starting to see if that makes a difference. I think there is a way to jump some power to the fuse of the fuel pump and make it run before trying to start.

The main purpose of this project was not to fix the slow start issue but to make sure the brake booster was not going to fail catastrophically and it looks like it was not the problem (even though it had a lot of paint damage from prior brake fluid leaks) so then it has to be the check valve (already replaced the washer previously). So will need to plan a junk yard trip to see if I can find that part (new close to $100).
 

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That is almost certainly a faulty anti-return valve at the fuel pump.
Another vote for this.

I had the exact same symptoms a year or so ago. I was able to test the CTS with VCDS and confirm it was fine. I rented a fuel pressure tester from AutoZone in an attempt to test the fuel pressure at the rail, but this kit was clearly designed for dumbestic only so no fittings worked. I finally had to disconnect the feed line from the fuel pump to fuel filter and rig the tester up there. I noticed fuel pressure immediately dropped to 0 after stopping the engine.

I also tried a way less scientific test. I would squeeze the rubber fuel line hose with my fingers while the engine was running and compare it to immediately after stopping the engine. There as a noticable decrease in firmness.
 

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Just for my case, replacing the CTS was one of the first easy things I tried but no difference. Pretty sure it's not the fuel pump either since I now have an in-line check valve and still no change. Could still be the FPR or injectors leaking. Will check those in a little. I think if I can figure out how to run the fuel pump briefly prior to starting and not have the problem, then it definitely would be a fuel pressure issue. If no difference, back to chasing vacuum issues.
 

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Just for my case, replacing the CTS was one of the first easy things I tried but no difference. Pretty sure it's not the fuel pump either since I now have an in-line check valve and still no change. Could still be the FPR or injectors leaking. Will check those in a little. I think if I can figure out how to run the fuel pump briefly prior to starting and not have the problem, then it definitely would be a fuel pressure issue. If no difference, back to chasing vacuum issues.
See post #9
 
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