# 2010 Jetta 2.5 hard starting



## Gordonmcds (Jul 30, 2018)

Bought a used Jetta. The day after bringing it home, it began being difficult to start. After talking to a friend, he told me to cycle the key a few times to test the fuel pump. I hear the pump run and then stop after about 2 seconds. When I cycle 2 or three times it almost always starts right away. Fuel pump? Or could it be the crankshaft sensor (I don't know if this car has one). Could it be a weak battery (no indication of that but I haven't tested it)? Could it be a weak key fob battery(smart chip not getting enough power)? I'm spitballing but would like to get it figured out.

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## Ichabod0525 (Feb 11, 2018)

Based on your observation when cycling the key before starting successfully I'd have a peek at the fuel pressure through the whole cycle in suspicion of a leaking injector. You could also pull each plug to see if you have one that is wet with fuel after shutdown and cool. Smell of fuel in the oil is also a giveaway. You can rent the TOOLS necessary for the pressure test at little to no cost. Do you have fuel trim figures?


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## Gordonmcds (Jul 30, 2018)

No, I have no clue what the pressures should be. I haven't pulled plugs yet either, something I plan to do. Wouldn't a leaky injector throw a code for a vacuum leak? I've scanned already and zero codes. I was told that the pumps have a check valve and when that goes bad, it allows the fuel to seep back to the tank. 

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## Ichabod0525 (Feb 11, 2018)

Yes good call it could be the fuel pressure regulator as well, your term check valve. I do not have the exact spec but the residual pressure should be in the 35-38psi ballpark.


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## Gordonmcds (Jul 30, 2018)

So, check fuel pressure, before starting, then start, run for a bit, turn off and watch for pressure drop? Then that would mean a fuel pump, correct?

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## Ichabod0525 (Feb 11, 2018)

No that's where the fun starts. That will only give you some numbers to aid in troubleshooting the problem. Low residual? somethings leaking. Low running pressure? Pump, filter maybe another cause. It's a multi step process.


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## Gordonmcds (Jul 30, 2018)

Where is the filter? Is it inline or part of the tank/pump assembly

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## AlAmir (Aug 13, 2018)

*filter*

the filter should be ini front of the rear passenger tire. if you are getting it off for the first time it is a pain but after you figure it out it wont be a big deal. there are also a bunch of how to videos on youtube detailing the process. https://www.youtube.com/watch?v=wfK2OBeZK80 
did you ever resolve the issue?


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## Gordonmcds (Jul 30, 2018)

No, still haven't resolved it. I will admit that this car replaces a prius, so I'm not 100% sure its all the cars fault. But it does crank a long time after sitting. Then the next time I turn the ignition, it fires right up. 

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## AlAmir (Aug 13, 2018)

from what i read the check valve should be integrated into the fuel pump. if i were you i would do the normal maintenance on it first. if you will keep this car for a while it cant hurt to do the maintenance because it will also help eliminate the causes. I would check or change the spark plugs, air filter, oil and filter, fuel filter, check the battery. i would do all of that before changing sensors. would a weak battery in the fob stop it from running? i would think if the chip in the key failed to send a signal then the dash light for the immobilizer would illuminate. do you hear a difference in the engine rotation when cranking. if its slower than usual then it might be the battery being weak or starter might be going. if there if not difference in rotation and the car starts but only after priming the pump a few time then i would think there is a problem with the check valve. there should be a constant sitting pressure at the rail attached to the injectors. the only way to find out is to attach a fuel gauge to the rail. autozone loans one out with a $150 or so deposit. but atleast you would know if your getting pressure and what it drops down to. hope this helps


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## Ronny Bensys (Apr 17, 2014)

Gordonmcds said:


> No, still haven't resolved it. I will admit that this car replaces a prius, so I'm not 100% sure its all the cars fault. But it does crank a long time after sitting. Then the next time I turn the ignition, it fires right up.


The fuel line loses the pressure it should normally maintain for a long time. Do you smell fuel after a long time sit when you try to start up and fail?


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## Ronny Bensys (Apr 17, 2014)

There are 2 fuel filters. One is a serviced one located under right rear passenger, just right to the fuel tank.

The other one is inside the pump assembly. It gets clogged over the time, after say 100-150k miles.


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## Ronny Bensys (Apr 17, 2014)

We have at least one check valve, if not an other one inside the pump. The check valve that we are familiar with is inside the fuel filter. It prevents the fuel from flowing back and maintains the pressure.
Start with normal service works like AlAmir explained. Fuel filter, plugs, air filter and battery. Consider your milage too. Review the service records if you got it when you purchased the car.


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## AlAmir (Aug 13, 2018)

If it takes you a couple of attempts to start your car i would guess your losing pressure somewhere. as you initiate the starting process you your pump would prime and pressurize your lines. i am guessing they dont want too high of pressure sitting in you lines when the car isn't used. more pressure might lead to more problems with leaks. so you check valve to maintain enough pressure in you lines but for initial start it would go up. if your going to keep this car for a while i would change the fuel filter first. and dont get it at autozone or the stealer ship. go to deutsche auto parts online or ECS tuning. plus after starting it if you dont have the issue until it sits for extended time then the leak maybe s tiny if any. check your battery at autozone for cold cranking amps


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## Gordonmcds (Jul 30, 2018)

Looks like I will start with the external fuel filter. Already changed oil, filter, and air filter. Spark plugs next. I don't smell fuel after it has sat for an extended time period. I'll check the battery as well. 

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## Ronny Bensys (Apr 17, 2014)

AlAmir said:


> i am guessing they dont want too high of pressure sitting in you lines when the car isn't used. more pressure might lead to more problems with leaks. so you check valve to maintain enough pressure in you lines but for initial start it would go up.


The 2.5L is not designed that way. We don't have pressure relief valve and fuel pressure regulator. No return line as well. On the other hand, we have a leak detection pump to ensure that the system is maintaining the built pressure.

The setup is pretty simple.

Fuel tank ---> Pump ---> Fuel filter ---> Fuel rail
<-------------------------------------


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## Gordonmcds (Jul 30, 2018)

What's the spark plug to buy? Just went to Autozone and the only type they have for my car is the Autolite double platinum. I usually use Bosch. They do not carry a Bosch for my car, except the Iridium plug which they say is not recommended for my car.

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## Ronny Bensys (Apr 17, 2014)

Buy OEM. They cost $10 per plug. Bosch is for the CBTA engine.
Other good alternatives are NGK ZFR5E-11 and newly listed NGK ZFR6T-11G. Both are perfect replacement for Bosch standard nickel plugs.

Buy 4 bar fuel filter, OEM or Mann or Hengst. 
OEM p/n is 6Q0201051J.


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## TheDiamondOreo (Aug 19, 2018)

I have a 2007 Rabbit 2.5L with the same exact issue you are describing in your original post. I purchased the car in February 2018 with 104,000 miles and it currently has 112,000 miles on it now. The issue has been present since I bought the car. When the car sits for any extended amount of time, an attempt to start the car leads to a hard start but not a slow rotation. A couple extra primes of the fuel pump leads to it starting no problem-just as you said. 

From what I am gathering from all of the information in this thread and from other sources around the internet, this is an issue that is common but also very difficult to locate and fix. Is the general idea currently to perform general maintenance and go down the list to see if that fixes the issue? The car has a battery less than a year old and a recent oil change. I will attempt to change the external fuel filter soon and see where that leads me to. Thank you all for the helpful information!


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## Ronny Bensys (Apr 17, 2014)

TheDiamondOreo said:


> I have a 2007 Rabbit 2.5L!


Has the previous owner ever changed the fuel filter?

The manufacture date on the filter will help guess when last time it was serviced.


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## TheDiamondOreo (Aug 19, 2018)

Ronny Bensys said:


> Has the previous owner ever changed the fuel filter?
> 
> The manufacture date on the filter will help guess when last time it was serviced.


I did not see any mention of a fuel filter being replaced on the service records when I purchased the car. I’ll look at the fuel filter when I replace it for any dates. 


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## Ronny Bensys (Apr 17, 2014)

TheDiamondOreo said:


> I did not see any mention of a fuel filter being replaced on the service records when I purchased the car. I’ll look at the fuel filter when I replace it for any dates


Ok. Please keep us posted.


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## Gordonmcds (Jul 30, 2018)

Just received my fuel filter today, plan to change it tomorrow, more to come...


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## Ronny Bensys (Apr 17, 2014)

Gordonmcds said:


> Just received my fuel filter today, plan to change it tomorrow, more to come...


Please check the manufacture date on your old filter when you remove it.


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## Gordonmcds (Jul 30, 2018)

Changed it out. Looks like the original filter which has about 117k miles on it. After figuring out how the clips worked it was easy enough to change out. About 1/2 cup of fuel spilled so make sure to have a spill cloth under your work area.









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## Gordonmcds (Jul 30, 2018)

Ok, since I changed the fuel filter so far so good. It takes about 1-1.5 seconds when the ignition is turned before starting right up after sitting overnight. No need to cycle the key to prime the fuel system. Hopefully that $30 part was all I needed, I didn't really want to buy a $300 fuel pump. Spark plugs are next. 

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## TheDiamondOreo (Aug 19, 2018)

Ordered my OEM fuel filter on ECS. Should be here next week. Been ridiculously busy now that college started again. Hopefully get around to it then, will keep you guys posted. Good to hear so far that the issue hasn't come back, Gordon! Still good so far?


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## Gordonmcds (Jul 30, 2018)

TheDiamondOreo said:


> Ordered my OEM fuel filter on ECS. Should be here next week. Been ridiculously busy now that college started again. Hopefully get around to it then, will keep you guys posted. Good to hear so far that the issue hasn't come back, Gordon! Still good so far?


After about two weeks it started happening again, only not everytime I try to start it. Mainly after sitting overnight. I'm going to take it to a mechanic to get a diagnosis done. May also be the crankshaft sensor. Still have to change the plugs before a trip to the mechanic though..

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## le0n (Jun 12, 2013)

haven't been on in a while and just saw you post.

i can't see anywhere if someone mentioned the purge valve being faulty.

*hard start symptoms on the 2.5 almost always point to a bad or failing n80 purge valve.*

they're cheap and easy to replace; and they are easily damaged if mistreated.

you can clamp shut the intake-side hose that comes off of the purge valve to see if the engine starts on the first try.

if so, then swap the valve (less than $25)

if it does start easier, remember to remove the clamp to not cause a mil.


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## Gordonmcds (Jul 30, 2018)

le0n said:


> haven't been on in a while and just saw you post.
> 
> i can't see anywhere if someone mentioned the purge valve being faulty.
> 
> ...


Purge valve? Is that like an egr valve?

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## Gordonmcds (Jul 30, 2018)

I meant PCV valve..

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## TheDiamondOreo (Aug 19, 2018)

Gordonmcds said:


> I meant PCV valve..
> 
> Sent from my SM-G950U using Tapatalk


I had a code for a purge valve when I bought my car. Had it replaced and CEL went off and the hard starting issue was never fixed for me.


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## Ronny Bensys (Apr 17, 2014)

Did you test your fuel system if it can build up and hold the pressure?


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## TheDiamondOreo (Aug 19, 2018)

I did not check my fuel pressure. Never done this before and have no idea how to do this  Still waiting for my fuel filter to come in the mail. Hopefully Gordon comes back and let’s us know what his mechanic said - I would love to know and would greatly appreciate it! 


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## le0n (Jun 12, 2013)

TheDiamondOreo said:


> I had a code for a purge valve when I bought my car. Had it replaced and CEL went off and the hard starting issue was never fixed for me.


no, it's not like a pcv.

it allows vapors from your fuel tank to be burned in the combustion process (as needed). it cycles on command from the ecm. if it is stuck open, it is a vacuum leak that will cause hard-start conditions on the 2.5.

it's free to test if you read my previous post.

if you don't have a clamp method, just remove the intake side hose and stick a bolt in the hose for a temporary plug.

if you had this n80 valve replaced before, did you in fact blow out the vapor line that leads to the tank? if debris was left in there, it could immediately cause the new valve to malfunction (vacuum leak).


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## TheDiamondOreo (Aug 19, 2018)

le0n said:


> no, it's not like a pcv.
> 
> it allows vapors from your fuel tank to be burned in the combustion process (as needed). it cycles on command from the ecm. if it is stuck open, it is a vacuum leak that will cause hard-start conditions on the 2.5.
> 
> ...


The code for the purge valve came on probably a few days after I bought my car, so the dealership I bought it from had it repaired at one of their shops. So no idea if they did it correctly or not (hope they did!) I will look back to your posts and try your test, thanks!!!


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## Gordonmcds (Jul 30, 2018)

Hey everyone. A little update. I have not taken my car to the mechanic yet. What I did do was change the spark plugs. I was shocked when I went to loosen them up. They were not tight at all! I probably could've loosened them with a screwdriver instead of a ratchet. After putting in the new ones, the hard start has stopped. Plugs were changed on Saturday and not a single long crank start since the change. This morning, cranked for about 1.5 seconds and started right up. Maybe the plugs being lose allowed compression to leak out when starting. Anyways, I will update in about a week. Hopefully, $48 worth of plugs was all I needed. 

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## Gordonmcds (Jul 30, 2018)

Not sure if anyone is still reading this post but the issue returned with the hard starting. I ended up replacing the fuel pump. It was not as difficult as it sounded and now my car starts right up. Another note, after talking with a friend, when you turn the ignition to the on position, wait for all the lights to go off, then start the car. Starts right up every time now with the replaced fuel pump. Car had 178000 miles on it at the time of replacement so it was mostly likely way overdue.


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