jay745
What Would Glenn Danzig Do
Youve sure trusted me with a ton of work on your various cars over the years for having very little faith in me
6
Jay's 13' Wolfsburg Track Car Build
- Thread starter jay745
- Start date
riceburner
Autocross Champion
Oh stop, i got mad faith in you bro. I just want there to be an easy fix for your odd predicament
king1138
Go Kart Champion
Did all of this start to happen after a fuel up? I've seen a few times where a reputable gas station gets the wrong fuel delivered, or the wrong fuel put into a tank. It can cause all manner of problems like this. I once worked on a Mustang that ran like dog shit that I spent far too long trying to diagnose before pulling a fuel sample only to discover about a half tank worth of pink agriculture diesel. The owner had fueled up at a Sinclair (I think) that had the wrong fuel put in their premium tank. The gas station ended paying for the repairs.Well, I'm not out of the water yet. It's been starting up strong, idling fine. Today I got both new relays delivered, put them in, started up fine and idled fine for 20 min. I took it out, reversed fine down the driveway, in first as soon as I hit 2300 rpm it fell on its face like it wasn't getting fuel. I limped it home and parked it. Started up and idled fine after I got it home as well. No codes
jay745
What Would Glenn Danzig Do
There was a moment I was thinking bad gas, but no I was driving for several days after filling up
king1138
Go Kart Champion
Hmm. I suppose it could have taken a few days for symptoms to present, but it seems unlikely. If it were me, however, I think I'd want a tank full of known good before pushing too much farther.
jay745
What Would Glenn Danzig Do
It's shell 93, and both of my other cars were filled up at the same station within a day or so. Bad gas wouldn't have caused the relay to blow out like it did.
king1138
Go Kart Champion
Well it sounds like the probably almost certainly isn't bad gas. But, bad fuel (especially with water or diesel contamination) could cause the pumps to work harder, and an increase in electrical load could burn up the relay. Not trying to argue, because it sounds like you've already ruled it out, but I've seen some weird shit as a tech.
jay745
What Would Glenn Danzig Do
Absolutely and I do appreciate the reply. I'm not arguing either, I'm a part time tech as well and this is the first time in years I've been stumped like this. I'm still leaning towards crankshaft position sensor or cam position sensor.
uglybastard
Autocross Champion
Can scans for soft codes confirm any of these before you spend money or take stuff apart?
Sspcivic31
Drag Race Newbie
what is the fuel pressure in the rail as reported by vcds? i have seen the contacts in the 2 pin connector on the hpfp control valve fail. this will cause the rail pressure to be low. i do not rember if you only see 4-5 bar from lpfp or you get around 40 like its at idle. but it will be stuck. thats enough to drive around on light throttle but the car wont like it/accelerate. the contacts vw uses are only rated for like 5-10 mate /de-mate cylcles over the life of the contact. the contacts have a little spring finger in the center of the contact the fails and makes intermittent contact. pull the connector from the ecu side of the harness under the cowl, stick a dmm set to measure resistance across the 2 contacts for the hpfp at the ecu connector, then wiggle the wiring at the hpfp 2 pin connector. if they are bad the resistance will jump around and go open on the dmm. i have also seen several burned up underhood fuse blocks. those typically cause weird issues with the lighting, and rolling bulb out messages on the dash. there is a 30 amp fuse in there that will be melted usually for that.
Last edited:
zrickety
The Fixer
You've thrown so many parts at it, I'm stumped too. A sensor would be nice, but you'd think there would be a code.
I'm also wondering about fuel pressure, throw a gauge on there.
I'll look in the service manual tomorrow...did you get one yet?
king1138
Go Kart Champion
A cam sensor could potentially cause your fault, but would almost always set a code. I don't think the crank sensor would cause it, as their most common symptom of failure is a no start. Do you have a boost gauge setup? If it falls on its face at 2300 RPM, you may not be building boost. Perhaps a stuck wastegate flapper?
Roadrunner_GTI
Drag Racing Champion
Can you just start logging in VCDS? Lambda, rail pressure, misfires, timing, fuel trims, etc. I’m not a huge fanboi of Cobb AP but I will say it’s ability to easily log makes it nice for troubleshooting.
MrFancypants
Autocross Champion
Exactly how does it behave when it hits 2300 RPM? Does it stumble and misfire? Does it even try to build boost? When you open the door does the fuel pump prime?
When my car’s wiring harness plug to the throttle body started to go bad it showed some really bizarre behavior, but it didn’t cause relays to fail. This problem feels like a wiring issue because you’ve already replaced the parts that could cause the electrical surge that would blow the relay. If it’s not blowing anymore relays my money is on one of the wiring harness ends being damaged and not allowing enough voltage to flow to the pump to tell it to push more juice to the engine.
When my car’s wiring harness plug to the throttle body started to go bad it showed some really bizarre behavior, but it didn’t cause relays to fail. This problem feels like a wiring issue because you’ve already replaced the parts that could cause the electrical surge that would blow the relay. If it’s not blowing anymore relays my money is on one of the wiring harness ends being damaged and not allowing enough voltage to flow to the pump to tell it to push more juice to the engine.