Passat TDI starting issues.

[stefan]

I've been getting this worked on for a few weeks at the dealership, of and on, and nothing yet. I started a thread at tdiclub here, which has brought up a new idea.

Heres my original post:
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My 2005 Passat wagon doesn't always start properly. It's not cold start related thing, as I have noticed it between 0 and 25 degrees Celsius. It does seem to be starved of fuel. So far, if I turn the key a few times to cycle the rear lift pump a few times, it will start no problem. The other odd thing is that I often hear bubble sounds from under the hood when the rear pump first runs, before starting the car as though air is in the fuel lines. My thought is that fuel is running back to the tank somehow when the car isn't running.

Things I have tried so far:
-New fuel filter
-New plastic return T that fits in to filter
-new o-rings on T
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Since this post, the dealership has also replaced the fuel sender unit and some fuel lines. SCFC has been really pretty helpful in the whole thing, and had a loaner for me when they kept my car, which was nice. Unfortunately, they can't find the issue. Right now their theory is that it is related to the crappy glow plug recall that my car has had done, but this doesn't really make sense because I have start issues even with a hot engine, and in warm weather (20 degrees outside).

The tandem fuel pump issue that was posted on TDI club seems like a possibility.

SCFC also said they expect a VW Canada rep to be in in November to review the glow plug issues, but no promises on a new recall.

So I'm not sure where to go from here. I think right now my best bet is to wait for this rep to come and go and see if he has anything to say, and then start over with diagnosing.

If my car is having start issues with a warm engine, and also on nice sunny +20 days, is it reasonable to think this is not a glow plug thing? Also, you Passat TDI guys, do you ever get any loud 'bubble' type noises when your fuel system primes right when you turn the key, before you crank the engine over? It's pretty loud. I should have showed you guys when we had the meet up here in Creekside.

[Vulcan]

Re: Passat TDI starting issues.

I thought that at +20 the glow plugs didn't even come on. It sounds like you may have a pin hole in the fuel line.

[stefan]

Re: Passat TDI starting issues.

I thought that at +20 the glow plugs didn't even come on. It sounds like you may have a pin hole in the fuel line.

That's my thought on the glow plugs too. I have had the sender unit pump, various fuel lines, as well as the filter and return T replaced, so a leak in the tandem pump isn't all that unlikely. There is no visible leaks anywhere. The dealer just cleaned out my engine bay really well, so anything resembling a leak should show up. I'll keep an eye on it all.

[Benjamin]

Re: Passat TDI starting issues.

Diesels need compression+Fuel+air

Most likely not the air, so the other two are what you have left.

Compression test + leak down test?

Cam shaft I would have them take a quick look at here as well.

Tandem pump and injectors are the next steps in the fuel fuel system, but of course the other 2 tests above will be a lot cheaper and eliminate the entire compression side of the problem.

I don't think glow plugs are your problem here yet, -10`c and yes I would go that route, but its warmer then that.

Since the dealer is throwing parts at this left right and center, maybe have them do the balanceshaft assembly at the same time. It must be sounding a little louder by now, just something else that could pop up.

Anyhow, let us know how this turns out.

Benjamin

[stefan]

Re: Passat TDI starting issues.

the noises it makes when priming still have me leaning toward the fuel system. Without hearing it, its hard to describe, but it is quite loud, and I'm sure it's not normal.

On the upside, SCFC is a 10 min walk from my office. I'll have to take it in again and get them away from glow plugs as a cause. It just doesn't make sense.

I'm not sure what a balance shaft should sound like... I don't think anything there sounds off yet.

[Benjamin]

Re: Passat TDI starting issues.

Balanceshaft issue, well if you get it covered under warranty and get it dealt with and out of the way cost to you is $0.
If you wait and do it yourself and bring it into a dealer and pay your self for VW's engineering mistake probably around if not more then $4000. Half of that being parts, and the other half what VW gives for the job in terms of time.

In terms of the fuel system, well here is how the starting sequence goes. Open the door, glow plugs start warming up if needed. Turn the key Glow plugs continue warming and the glow plug light turns off when it figures it is warm enough to start the car. During this period though the fuel pump in the tank is turned on and primes the system for start.

Key is turned, tandem pump does not start until the engine is turned over as it sits where the old ALH vacuum pump used to sit. Fuel reaches the injectors which are electric and inject fuel at the proper time to start the car.

Now saying all that, how long does it take for the fuel pump to prime from the tank? Do you start the car before that is completed, or do you wait?

Next, how fast does the engine turn over? The Tandem pump probably needs a certain RPM to function correctly and if this can not be attained by the starter/battery then that could cause problems as well.

Tandem pump, well if the seals are not good well this could cause issues, I would think the issues would almost be felt while driving as well as starting, but again could be the issue.

Injectors, well these now are all electric, so they need to have the proper power delivered to them so that they can dump the proper amount of fuel into the cylinders at the specified PSI for the correct duration.

Now saying all this where do you start, well if you are sticking to the fuel system there is one common element between most of the above. That would be the battery as it plays a key role in everything. Your car is 5 years old now, original battery's typically are normally near the end of their life span.
I don't know how the dealer checks battery's these days. Back when I was in the industry snapon had their high end cart testers, and the cheap hand held ones. The hand held ones were pretty much useless at checking anything but a voltage on these. The voltage The cart testers would put a massive load on the battery and test after that which was a way better test.

Saying all that I don't have a definite answer or one that I could confidently point you in the right direction. It could be what I mentioned, it could be something else like a MAF or something related to that. Honestly if the dealer wants to save some coin and not replace thousands in parts they should put those fancy scan tools to work. Capture as many readings at a bad start as you can, MAF, RPM, Voltage, ect. You can eliminate a lot pretty quickly if you can verify all the values are where they are suppose to be.

Just more fuel for the fire.

Ben

[stefan]

Re: Passat TDI starting issues.

Now saying all that, how long does it take for the fuel pump to prime from the tank? Do you start the car before that is completed, or do you wait?

Ben

For best starting, I cycle the pump until I stop hearing bubbles in the fuel lines, then crank. Engine turns over pretty fast. If I cycle it a few times, the car typically starts fine.

Bad start example would be just waiting for plug light to go of then crank, or you run in the a store for 10 mins, come out to a car that is still hot, turn key until plug light goes off, crank. Basically ambient temp and engine temp seem to not make a lot of difference.

Battery likely is original, so 5 years. I believe it was tested. I have to read the invoice again. Based purely on cranking speed, I would say the battery isn't garbage quite yet.

As far as balance shaft, I don't think the dealer will go there at all unless something sounds particularly bad. I suppose I can ask them to check it, but if there is nothing obvious wrong, I'll just get hit with an hour for diagnostics that isn't warranty.

[luunta]

Re: Passat TDI starting issues.

This is the new Passat you just picked up recently? (New to you)

I really hope this stuff doesn't turn up on my jetta. :(

[stefan]

Re: Passat TDI starting issues.

This is the new Passat you just picked up recently? (New to you)

I really hope this stuff doesn't turn up on my jetta. :(

New to me, yeah.

[luunta]

Re: Passat TDI starting issues.

:(

[Vulcan]

Re: Passat TDI starting issues.

I don't think you should be hearing these bubble sounds....on my Jetta I hear the lift pump in the tank buzz for a second when I turn the key on but that is it for noise until I crank the engine.

[VWSM]

Re: Passat TDI starting issues.

It might be in your best interest to have them pull off the cover and have them take a look for abnormal wear.Documentation is your best friend.

As for the bubbling noise and waitng for the pump i would suspect fuel draining back to the tank.Cheap route to go is buy an MKII Diesel check valve and install it on the fuel delivery side just before your filter.

[stefan]

Re: Passat TDI starting issues.

As for the bubbling noise and waitng for the pump i would suspect fuel draining back to the tank.Cheap route to go is buy an MKII Diesel check valve and install it on the fuel delivery side just before your filter.

hmm, that would isolate the issue at least.

*Where can i find said valve?

[Benjamin]

Re: Passat TDI starting issues.

Here is my one opposition to the leak theory. The system is pressurized from the pump in the tank. That would mean a leak would be happening when ever the car is running due to the pressure.
The only other place air could get in then is the pickup, which was replaced already.
Diesel does not evaporate, so any leak would be noticeable.

Try the check valve, hopefully that will fix things.

Benjamin

[stefan]

Re: Passat TDI starting issues.

Here is my one opposition to the leak theory. The system is pressurized from the pump in the tank. That would mean a leak would be happening when ever the car is running due to the pressure.
The only other place air could get in then is the pickup, which was replaced already.
Diesel does not evaporate, so any leak would be noticeable.

Try the check valve, hopefully that will fix things.

Benjamin

i'm 99% sure there is air in the system when I start it. How it is getting there, I'm not sure. I've seen a system seal under pressure and leak under vacuum, but it wouldn't be a pinhole or anything in this case (or fuel would be leaking out), it would more likely be a gasket or mechanical component. Apparently there is a non-return valve of sorts in the tandem pump, according to that TDIclub link.

I was ruling out the tank to since they replaced most of the stuff back there. The only weird thing there is that it seems to not have the problem with a full tank. I have to drive a little more to confirm this though. I just filled up on Sunday and it has started fine since. May just be coincidence.