Fuel cut-outs in hot weather

2007 GTI w/approx. 74k miles. DSG transmission.

Last Thursday, I drove out from Phoenix to Vegas for a convention. About 50 miles outside of Vegas, I started getting these intermittent fuel cuts (about once every couple of minutes, it seemed). The fuel delivery would completely die out and not return for 2-3 seconds. Eventually, the car threw a CEL.

So, I left the car parked at my hotel after I arrived in town and it sat for the whole weekend. I drove it around the following Monday to run some errands in Henderson. The CEL was gone and the car drove just fine, as if nothing ever happened. But, I was only out for about an hour for that trip...

The next day, I drove back to Phoenix. About 3-4 hours into the trip on the I-93, the fuel cuts returned and they progressively worsened as I got closer to town. They eventually got so bad that the fuel delivery would cut out mid-turn at intersections (scary stuff)... This has all been in 100+ degree weather.

Early this morning (about 7:30AM and 80 or so degrees), again, the CEL vanished and the car was driving like normal around the neighborhood.

So I did some searching around on this problem, and I'm gathering that I most likely have a bad low-pressure fuel pump (as in, it's overheating, thus causing the intermittent fuel delivery in hot weather). I've read that other possible problems could be the camshaft follower, HPFP thrust sensor, coil packs, etc., but somehow I'm kind of doubting those things. This car is on its third set of coil packs (both sets replaced under recall) and its second set of plugs. I'm going to head to O'Reilly's or AutoZone and get it scanned to see what codes it's been throwing and I'll report back.

Any thoughts? Thanks in advance!

Without any codes, its hard to tell.

I had an issue once on a real hot day with fuel cuts. I went home and scanned my car and the issue was my HPFP thrust sensor. I would try replacing that before you start messing with your fuel pumps.

http://www.golfmkv.com/forums/showthread.php?t=145695
http://www.golfmkv.com/forums/showthread.php?t=133155

fuel pump control module was overheating. Happens alot. Im working on a relocation harness for them

eurocars said:

fuel pump control module was overheating. Happens alot. Im working on a relocation harness for them

Click to expand...

Or the LPFP itself is dying. Not overheating, just no longer cutting the mustard. Gasoline expands as it heats, which makes it thinner, which means it's harder to pump.

Same thing was happening to me all through WUSTE. Replaced the LPFP w/ the help of a local vegas dubber and have had 1500+ miles of trouble free driving since.

Plug in VCDS and measure block 106. 106.2 is the LPFP duty cycle. On a hot day after a good drive (heat up the gas tank) you want it under 70% at idle.

Mine was pegged at 91.8% under those conditions.

Used pump with 40k miles on it? 63.1%.

Timpanogos Slim said:

Or the LPFP itself is dying. Not overheating, just no longer cutting the mustard. Gasoline expands as it heats, which makes it thinner, which means it's harder to pump.

Same thing was happening to me all through WUSTE. Replaced the LPFP w/ the help of a local vegas dubber and have had 1500+ miles of trouble free driving since.

Plug in VCDS and measure block 106. 106.2 is the LPFP duty cycle. On a hot day after a good drive (heat up the gas tank) you want it under 70% at idle.

Mine was pegged at 91.8% under those conditions.

Used pump with 40k miles on it? 63.1%.

Click to expand...

could be, but the fuel pump control module overheating seems to be more common. The fuel pump is atleast submerged in fuel in a returnless system so it shouldnt be getting that hot. The fuel pump control module is sandwiched between carpet and the rear seat foam which insulates the heat inside of it. Last time mine overheated, it was too hot to touch with my bare hands. ripped up the seat cover, limped it to a gas station, got a bag with ice to put on top of it and it drove fine antother 300 miles home (coming back from a car show in tennessee)

eurocars said:

could be, but the fuel pump control module overheating seems to be more common. The fuel pump is atleast submerged in fuel in a returnless system so it shouldnt be getting that hot. The fuel pump control module is sandwiched between carpet and the rear seat foam which insulates the heat inside of it. Last time mine overheated, it was too hot to touch with my bare hands. ripped up the seat cover, limped it to a gas station, got a bag with ice to put on top of it and it drove fine antother 300 miles home (coming back from a car show in tennessee)

Click to expand...

It's not about a hot fuel pump. It's about a weak fuel pump and thin fuel. The problem doesn't manifest on cold days because the fuel is denser.

AFAIK, as implied by ross-tech wiki anyway, the overheated control module is a defective control module.

And that should be way easy to diagnose. Yank up the back seat and use the shoulder belts to hold it up. Drive around and see if the module gets hot. Mine was no warmer than any other part of the car in 100 degree vegas weather when i removed it to get to my LPFP, despite the 40 minute drive into Boulder City i'd just completed.

Diagnosing a weak pump unfortunately requires a vcds license.

If the OP lived in the wasatch front i would absolutely plug in and measure that block for free. But he don't.

There must be someone in the greater phoenix area with micro-can or hex+can that can measure that block for a minute and get an idea what is going on.

It's most likely a problem with the low pressure fuel pump. Several members have encountered this including me. Bostonaudi reported problems running in hot track weather and a newer revision fuel pump fixed it. Happens most often in 100+ degree weather and long distance driving.

In any case, see if you can grab a hold of someone with a VAGCOM cable and check out the pump pressure.

This video from ross-tech explains it pretty well:

http://www.youtube.com/watch?v=jThQVzYFbVo

but yeah, find someone with a micro-can or hex+can.

Try the regional forums here and on the vortex.

Thanks for all the replies, guys. The CEL was gone when I started the car early this morning like I previously stated and hasn't returned all day, though I haven't been driving the car enough today to warrant the behavior it's been displaying. Since the CEL was gone, the AutoZone guys didn't see a code come up.

All I know right now is that if the car is out in the heat for an extended trip (like on my weekend road trip to Vegas), eventually I start getting the fuel cuts that progressively worsen over time until I stop and let the car sit for a few hours. It seems inevitable at this point that I'll either have to get the car diagnosed at the dealer or find someone in my area with a VAG-COM scanner.

I'll report back as I find out more. Thanks guys!

one question about this topic... block 106, fuel pump, on full throttle at 6000 till 7000 rpm, its on 91.8%. Is that mean it working well, or its on limit/needs change lpfp?

anyone?

Thats the max limit for ecm control.

This is an old thread, so main fuel delivery problem has likely been solved. But don't forget there is also a fuel filter that might benefit from an occasional replacement. As I recall, it's located under the car, right rear area.

Thanks. I have it (6.6 bar) and will change it. Just was suprised that I see that high % at wot

>has exact same issue that makes oir car undriveable

>says will check in

>never does...