MKIV Jetta Runs Great w/ Fuel Tank Bypassed...Now What?

I just bought this Jetta ('00 5-speed) and I'm working through a no-start issue.


Previous owner said it runs a couple miles down the road then dies and won't re-start. I've confirmed this multiple times.
The dealer told him it needed a $3900 IP.

I replaced the fuel filter and it started right up and ran for a couple miles before losing power and dying. Will not re-start and I see a lot of air between the fuel filter and IP.

Yesterday I rigged up a fuel bottle to the fuel filter and went on a 15mi ride through the country. It ran awesome!!

Issue seems to be the supply line from the tank or maybe something inside the tank??

I'm down to about 1/4 tank of fuel. I thought about filling it up to see if that effects the way it runs. If it runs awesome on a full tank, that means the issue is in the tank, right?

Looking for some guidance...the next steps in troubleshooting.

Sometimes, I wish I had been a boy scout!


Thanks guys,
-Jason

Love the Rube Goldberg set up.
Congrats on the buy!
Since your down to 1/4 tank of fuel I'd pop the cover off the tank and see what's going on in there.
You can inspect the sender unit really well or better yet pick a new one up, they are not that expensive, check to see what the venders on here have them going for.
At least you know you starting with some thing good.

The air you see in the clear line is probably coming from the thermostatic tee fitting. Did you replace the orings on it when you replaced the filter?

I've eliminated the possibility of the issue being with the fuel filter assembly.
My jug-o-diesel connects to the fuel filter.
The issue is somewhere in the tank or fuel line before the fuel filter.
Thank you,
-Jason

There is a check valve in the sender that can get plugged , or the pickup tube develope a crack when low on fuel in the tank.
Easiest thing to,do as I said is pull the sender while you low on fuel and either take a look at it or just replace it with a new unit and report back,on what you find.

You got it!!
Thank you Steve,
-Jason

If the tank being below 1/4 is allowing it to draw air, could it be that someone reversed the supply and return hoses at the fuel filter?

I'm not sure where the return hose ends in the tank on our MK4 cars, but on my old MB diesel, it was far enough down that a full tank would allow the engine to run, but it would suck air when below about half.

Pull sending unit, test with multimeter the wires to it and the amp draw on the pump, its probably bad and or the lines are leaking and or check valves need replacing.

My recommendation is to delete the in tank pump, mod the sending unit to pick up with baffle, buy a walbro pump and some fittings with new check valves all aluminum from amazon and rock and roll with an upgraded and better fuel pump that will never leave you stranded even if it dies, Walbro's wont restrict fuel flow when off or failed leaving you with enough power that the IP will draw on its own and keep you on the road.

Mongler98 said:

Pull sending unit, test with multimeter the wires to it and the amp draw on the pump...

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Mongler98 said:

MY recommendation is to delete the in tank pump...

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The OP has an '00 Jetta with an ALH. There is no "in tank pump". It is just a fuel pick up and sending unit for the gauge.

well then, half the work is already done!

This is NUTS!!!

Backstory: I bought this off the 2nd owner who was having trouble with it stalling periodically. When this would happen he couldn't get it to re-start, so he'd have it towed to the dealer where it was always serviced. I have all the records...this 1 dealer did all the work.

Tonight I went out there to swap the sending unit from my donor car into the non-running Jetta and immediately I could tell the sending unit cover and ring had been off recently. I pulled the sending unit out of the tank and there was a small paper bag clogging the sending unit. I cleaned out the mess, reassembled everything and went for a 30 minute, trouble free drive.

Could someone have really put a paper bag in this guy's fuel tank?!

Crazy

nomorotors said:

This is NUTS!!!......
I pulled the sending unit out of the tank and there was a small paper bag clogging the sending unit. I cleaned out the mess, reassembled everything and went for a 30 minute, trouble free drive.
Could someone have really put a paper bag in this guy's fuel tank?!
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False economy... putting a NON-VW-SPEC paper bag in the fuel tank...

Are you sure it was a paper bag? It’s kind of difficult to tell from the pics. Could the sending unit have been previously replaced and some type of packaging left around it?

and this is why we dont let anyone but ourselves or trusted TDI guys touch our cars.
well, easy fix!

Tdijarhead said:

Are you sure it was a paper bag? It’s kind of difficult to tell from the pics. Could the sending unit have been previously replaced and some type of packaging left around it?

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Looked to me like a small paper bag. It's a brown paper something that appears to have been put into the tank intentionally.

I spoke with the previous owner yesterday and he said VW was the only one to ever service his car and he hadn't had an issue involving the tank or sending unit.

I offered it back to him because it looks like someone sabotaged his Jetta. He certainly would not have sold it had this not happened.

-Jason

Soon....only criminals will have paper bags!!

"I offered it back to him because it looks like someone sabotaged his Jetta. He certainly would not have sold it had this not happened."-Damn OP, you are one amazing guy! Very very few people would do that! God Bless you!!!!

Kids are always bragging about "bagging" their cars!

I'm glad it was an easy fix!

csstevej said:

I'm glad it was an easy fix!

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It's "in the bag"

MY SIDES! make it stop, please!

Looks like you bagged yourself a cheapride!

VincenzaV said:

"I offered it back to him because it looks like someone sabotaged his Jetta. He certainly would not have sold it had this not happened."-OP, you are one amazing guy! Very very few people would do that! God Bless you!!!!

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It's not me. The seller is a VW enthusiast who loved his Jetta. He was very kind to me during the sale...I was simply returning the favor.

More backstory:
He was asking $1000 for his Jetta. When I showed up, we hit it off and talked VW's for quite some time. Come time to talk price on the TDI, he told me I could have his Jetta for a 6-pack of Coke and $250. I was shocked!

Once I figured out what had been done to his beloved Jetta, I told him I had zero dollars invested and about an hour of my time. (In an efford to out-do his kindness) I offered it back to him for a 6-pack of Coke. We talked yesterday and he said he'd already replaced the car otherwise, he'd take me up on my offer.

The whole thing has been a bazaar deal.

-Jason

ill give you 24 packs of coke and $250.00 for it!
JK, wow, karma will come back around for the both of you guys for sure.

Looks a bit like chicken skin that can form from a very bad and wet batch of WVO or biodiesel...

ytk said:

Looks a bit like chicken skin that can form from a very bad and wet batch of WVO or biodiesel...

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It looks like a lot of things that it's not.
I have the previous owner's fuel log from the past 10yrs. He didn't burn WVO, biodiesel or chickens. Grief.

-Jason

I was going to bet it was the chickens too... Integrity is something the world is getting short on; God bless you for being honest. And btw, Dang!, what a deal on that car.

You sir have just been bestowed a lifetime of good luck. I applaud your integrity.

I'm not a believer of luck or karma.
What I own is not important. What's important is who I am and how I treat others.
Always be content with what you have. Never be content with who you are.
God's blessed us all with more than we deserve.

-Jason

You may not believe in karma...... but karma believes in you.