97 Jetta TDI

[97TDIGUYYY]

I traded for the car about a month ago. I replaced the clutch and rear main seal, changed the oil and oil filter, filled it up with diesel on my way home from my moms the other day, went out the next morning to start it and it won’t start. These cars don’t have a fuel pump so that’s not an issue, I’ve started it multiple times over the month and have drove it probably 5 times with around 45 minutes of drive time total. Any ideas would be greatly appreciated. I looked inside the fuel filter and there was no fuel in there, maybe sucking air?

 

[turbodieseldyke]

Sounds like the fuel drained back into the tank overnight. The check valve, where the fuel line leaves the tank, is supposed to prevent that.

 

[Lug_Nut]

Was this the first no-start of the 'multiple times over the month' since you got the car?
Was this the first time you've added fuel?
Had the car sat unused for some time prior to you getting it?
I'm inclined to suspect the fuel pick-up in the tank might be blocked or significantly restricted.
You're correct that they don't have a lift pump. They rely on the injector pump to function as a fuel'suck' to get fuel from the tank, past the check through the filter media. There's a reason later TDI have a lift pump to maintain prime.
If there were air bubbles from sucking past worn o rings or loose clamp fittings they be burped out in the tank. The thermal valve on top of the filter was likely warm enough to be open to return air-fuel to the tank. Overnight the bubbles could rise and form one large space on top of the filter media. The filter wouldn't drain empty overnight, there'd be fuel in it, even if the liquid is not covering the top of the media. But now the thermal valve has cooled and changed overnight to the re-circulate position. The air-fuel return gets right back into the injector pump instead of going back to the tank. Fuel gets consumed and air percentage in that closed-loop increases.

 

[97TDIGUYYY]

Yes this was the first no start of the the time I’ve owned it and yes it was the first time I added diesel as well. This car did sit for a little bit before I got it, no more than a month or two, which I know is too long. I replaced the pickup tube yesterday off the parts car I have and it seemed to be in better shape than the one that was in it for sure. I plan on replacing the fuel filter tomorrow when my part comes in. I’ve checked all clamps and they seem tight. I thought about adding an inline fuel pump and placing it on my firewall that way when I turn the ignition on I will be pumping fuel to my filter. What would you recommend on fixing my issue? I am new to the TDI world so anything is appreciated.

 

[Abacus]

A month or two sitting is not a long time at all for a diesel, I know some that started up great after sitting for years.

The most common issue with these is the fuel pump leaking. Do you have any wet spots around the pump or underneath?

Another thing I would check, and it's also fairly common, is to check the thermostatic T on the fuel filter. If it's loose and allows air into the fuel filter the filter will drain back to the tank, then the car has to crank over a lot to suck the fuel back into the filter to fill it up. I like to put a small dab of grease on the o-rings when installing a filter, to help it stay sealed. Also make sure the filter and T are correct for your car, the A4's used a different filter and the o-rings are on the T, not on the filter like our cars. Also make sure the retaining clip is in place to keep it down.

 

[garciapiano]

Your check valve might be sticking open. I had a similar issue after letting my car sit for a few months. It’s sort of a pain to get to, so your best bet might be to hook up a vacuum pump like a shop vac to your supply line, and flood your tank with diesel cleaning fluid, to loosen up any clogs you might have.
Once you’re able to get it started, you’ll probably need to run a few tanks of fuel before it gets unstuck. I’ve found the new renewable diesel works well as a fuel system cleaner.

 

[97TDIGUYYY]

I actually installed a new filter yesterday that I ordered from O’Reilly’s. Filled it up with diesel, was able to get fuel from my supply line that runs into the filter. Filled up the line that runs to the injector pump, and the thermostatic t was tight with the pin over the top of it. Still wouldn’t start I am hoping it’s not the injector pump. I feel it would have given me signs before like running bad or not trying to start but I haven’t had any issues until I filled it up with diesel for the first time. I am going to replace some of the fuel line around the filter and see if I can find any fuel leaks, but I am stumped on this one.

 

[97TDIGUYYY]

Your check valve might be sticking open. I had a similar issue after letting my car sit for a few months. It’s sort of a pain to get to, so your best bet might be to hook up a vacuum pump like a shop vac to your supply line, and flood your tank with diesel cleaning fluid, to loosen up any clogs you might have.
Once you’re able to get it started, you’ll probably need to run a few tanks of fuel before it gets unstuck. I’ve found the new renewable diesel works well as a fuel system cleaner.

So essentially even if that line was disconnected from the filter, as long as that valve isn’t stuck open there would still be fuel in my supply line from the tank, it wouldn’t drain back into my tank?

 

[garciapiano]

So essentially even if that line was disconnected from the filter, as long as that valve isn’t stuck open there would still be fuel in my supply line from the tank, it wouldn’t drain back into my tank?

the supply line will drain back to the tank since the check valve is at the tank.

 

[Abacus]

The check valve is at the tank so the fuel in the supply line won't drain back but the fuel in the return line will.

 

[turbodieseldyke]

The check valve is at the tank so the fuel in the supply line won't drain back but the fuel in the return line will.

If the supply check valve is stuck open, won't the fuel drain back?

 

[garciapiano]

If the supply check valve is stuck open, won't the fuel drain back?

yes, sorry that’s the point I was trying to make

 

[Abacus]

If the supply check valve is stuck open, won't the fuel drain back?

Yes, then it will drain back. I have seen some that are sticky so its entirely possible it's not acting properly. I keep a few around for just that reason.