B4 Starts then dies. Then starts hard.

Ever since Monday this week my 96 Passat TDI has been being crabby in the morning... It just started getting colder, so I'm sure that has something to do with the issue.

When I first go to start it, I wait for the glow plugs to warm up and it starts up perfectly.

It runs great for about 5 seconds then stumbles to a stop. When I attempt to restart, I have to crank it over for almost a minute while feathering the throttle and it stumbles/creates a sizable cloud of smoke out of the tailpipe. Once I get the engine firing (roughly) at 1500 RPM or greater it runs beautifully again.

My initial thought was that I had bad glow plug(s) but that would not explain the perfect initial start.

After doing some research, I'm thinking I could have a pressure leak that is allowing fuel to bleed back into the tank thus leaving air in the lines. My pump does show signs of leaking around the underside, and I do have the stink of fresh diesel fuel under the hood.

Should I attempt replacing the fuel filter and plastic fitting on the top?

Off the top of my head:

Verify that all of the GPs are working - multimeter is best (unless you have replaced them recently)

Where is your injection timing? do you have VCDS? (not knowing is just guessing)

Is there any air in the clear line leading to the pump?

How is the air filter?


Changing the fuel filter never hurts, but it's better to diagnose the problem.

If you smell raw diesel under the hood, you better address that issue first. I had to replace the IP seals on my 96. I did not experience the Fuel Filter leak that others have.

@Windex. is there an acceptable amount of air bubbles in the fuel line?

Windex said:

Off the top of my head:
Where is your injection timing? do you have VCDS? (not knowing is just guessing)

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I'll look into this tonight. The issue has only recently cropped up though and I can't see this as being the problem.

Windex said:

Is there any air in the clear line leading to the pump?

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I only thought to check for this after I had it started this morning. I will make sure to check before attempting to start tomorrow. Could leaking seals in the IP cause this or is the valve atop the fuel filter a more common failure point?

Windex said:

How is the air filter?

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It's about 18 months old. Who knows though, there could be a mouse nest in there!

Classic air intrusion symptom. The IP and lines are full of diesel and it starts up, once it runs it's gets that big air bubble in there, and the IP can't push the air out the lines effectively. Lots of cranking later the air is eventually pushed out, diesel gets tonthe injectors, and it fires.

The car has been sitting since 8:30am. I just took a look at it and sure enough, there are bubbles appearing in the filter to IP line...

I suppose this would constitute an IP rebuild/replacement huh?

Quit likely the fuel filter, or "t", is where leak is. If the ip is the issue, you would have fuel leakage.

rdkern said:

Quit likely the fuel filter, or "t", is where leak is. If the ip is the issue, you would have fuel leakage.

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So the pump is definitely seeping but I wouldn't say 'leaking'. If the filter side of the system is always low pressure (vacuum while running) it could potentially let air in without letting fuel out right?

Here are pics of the pump:

Hanicus said:

If the filter side of the system is always low pressure (vacuum while running) it could potentially let air in without letting fuel out right?

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Right!

If the pump were full of air, I would think it would be hard starting from the get-go. I think you're drawing in the air from the filter, causing a "gulp", then purging it out.

I agree.

Feathering the throttle while starting does nothing since it's controlled electronically. The fuel pedal only starts working once it's running.

Also, to avoid future problems, remove the plastic collar at the end of the injection pump (IP) wires, nearest the IP. There are three wires in the bundle, as shown in your picture, and they go to the IP connector. The plastic collar wears through the wire insulation, specifically the black/white wire that controls the IP solenoid, which shuts your car off.

Here is what it does, these are all from different cars.

Abacus said:

I agree.

Feathering the throttle while starting does nothing since it's controlled electronically. The fuel pedal only starts working once it's running.

Also, to avoid future problems, remove the plastic collar at the end of the injection pump (IP) wires, nearest the IP. There are three wires in the bundle, as shown in your picture, and they go to the IP connector. The plastic collar wears through the wire insulation, specifically the black/white wire that controls the IP solenoid, which shuts your car off.

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Thank you for the info! I had not realized that the throttle would function until the car was running... which makes sense now.

I think I may have found the issue this morning. First, I decided to be a little more diligent this time and examine the amount of bubbles in the line. They were minimal, and it started right up.

Near the filter:


Near the IP:


After about 5 seconds of running it stumbled to a stop and I quickly rechecked the lines to find a lot of bubbles zooming around:



At this point I am imagining that for how long it was initially running there must be a decent amount of fuel in the filter. And, for the amount of air getting into the system, there must be a noticeable amount of fuel leaking somewhere between the filter and the tank.

Sure enough:

Sometimes the filter can empty through suction if there is an air leak - and you never see the fuel.

Do you need a new "T", or need to replace hoses?

Well I put the car on the lift today and there are no signs of leaking fuel other than the IP

I guess that's what I get for running additive in attempt to compensate for old clogged injectors.

Anyone have an Injection Pump for sale?

Just reseal it, the instructions are on this site.

Abacus said:

Just reseal it, the instructions are on this site.

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I spent the better part of the weekend doing research and things make a lot more sense now... I'm sure hundreds of noobs like me have posted all the same stuff fishing for advice on how to fix the same issue .

It's obvious to me now that the pump head is leaking pretty significantly and I was extremely relieved to find that you can replace the seal without removing the pump or messing with timing.

Parts have been ordered

Just be very careful replacing the seals since there is a small shim that can fall into the pump if you pull the head out far enough, and then you're FUBAR and have to pull the pump.

The previous owner of my wagon had the pump replaced because it was leaking, cost almost $2K rather than the $14.28 for a new seal kit. Of course, that doesn't include the IP socket or the Vag-Com, but even buying those and a new computer would still be cheaper.

So this is odd... When I was having this issue I was down to the last 2-3 gallons of my tank.

After filling my tank again the other day the morning hard-start issue went away completely...

Is it possible that the additive was not mixed well in the tank causing over saturation towards the end of the tank? Maybe the solvent in the additive had an easier time seeping past the seals causing air to get into the lines?

More likely the return line in the tank was not in the fuel.

Yep, common problem. My wagon does this when it gets between the bottom two red marks on the gauge. I'll fix it at some point. The sedans I can run to the very last mark before they'll stop picking up the fuel.