Just finished install - no fuel pump signal from ECU

[BarryV]

So I spent this past weekend putting a Vortech V1 on my 1992 GLI.


The car had an OBDII VR6 swapped in from a 1998 Passat, and the motor was fairly stock, with the exception of EGR and SAI, which were gone, and programmed into the existing GIAC software.

Here is the current configuration:

stock compression
288 cams
42 lb Bosch green top injectors
4" MAF
Vortech V1 with 8 lb pulley
C2 42 lb race profile software - OBD II
Walbro inline 255 LPH fuel pump, relayed off of mkII intank pump.

We basically spent all afternoon yesterday trying to chase down an issue with the motor not getting fuel, only to figure out that the connection we were tapping into for the inline pump was corroded.

I wired in a 30 AMP relay, using the factory harness going to the mkII in line pump assembly as the signal source. The fuse and relay are mounted in the fuel pump well with the Walbro pump.

We got the car running pretty well last night at the shop with a little help from the Vagcom and mostly just a lot of going over things and making sure everything was tight.

Here's the idle video



I let the car cycle through two cooling cycles and ran it up and down the back street behind the shop, to make sure everything was good to go.

Drive it home - 20 minute drive, and 2 blocks from my house, the car cuts out.

I checked the relay and fuse... both under the car, and under the dash, and all were good. The ECU is not sending the signal to the fuel pump to turn on.

Where do I go!? This is driving me to drink!

Car in question:

[bonesaw]

Is stock pump turning on? Check to see that ecu is seeing rpm signal when cranking. The crank position sensors are notorious for going bad, especially becoming intermittent once they warm up.

[BarryV]

Is stock pump turning on? Check to see that ecu is seeing rpm signal when cranking. The crank position sensors are notorious for going bad, especially becoming intermittent once they warm up.

The stock pump is not getting a signal when cranking.


If the tach sees the RPM, that is being sent from the CPS?

Or do I need the Vagcom again?

[Scurvy Bandit]

Is this like the older VW's where the tach and the fuel pump get the signal from the (-) side of the coil? Good luck man.

[BarryV]

Is this like the older VW's where the tach and the fuel pump get the signal from the (-) side of the coil? Good luck man.

Dont believe so. I think it all comes from the CPS.

Which... correct me if I am wrong, if the CPS is bad, I wouldnt have spark. I am definitely getting spark - confirmed that with the plug and wire.


It should be mentioned - The car turns over, and tries to start. I will spin up to 1K but dies before it gets to idle.

[xpalendocious]

chip fell out of the ecu? ive seen it many times

[BarryV]

chip fell out of the ecu? ive seen it many times

I didn't check that, but I guess anything is possible. The chip was very snug, going into the socket on the ECU board.


I drew out a quick current diagram, and the yellow X signifies where I don't have the 12V I should.



Mind you, that was at a factory harness plug, behind the rear seat. There is a lot of harness in between the factory in dash relay and that plug.

I feel like, and hope the factory relay in the dash went out. I can feel it click, when I turn the ignition key on, but that doesn't mean it is electronically passing current through. I am going to check the pins on the fuse block for the relay, for the 12V, ground and signal in tonight.

[Smokestack]

You can try using a jumper across the pins on the relay to give the circuit a test. If they kick on then the issue is either the relay(s) or the signal wire from the ECU. It's also possible that the supply for the in dash relay blew a fuse.

[BarryV]

You can try using a jumper across the pins on the relay to give the circuit a test. If they kick on then the issue is either the relay(s) or the signal wire from the ECU. It's also possible that the supply for the in dash relay blew a fuse.

Chris! I need your phone number dude. You are my long lost mad scientist.


I am buying a new relay today after work. Cant hurt to have a mkII relay on the shelf, with 2 mkII's in the garage, amirite?

Jake - the guy that owns the shop we used to put the charger in suggested running a "stand alone" signal feed to the factory in dash relay, fed from the ignition switch. I think if all else fails, and the new relay doesn't solve my problem, I am going to just run with that idea for now. At least until I can get an ECU sent off to United, for a new tune.

[steveo27]

Barry, like I posted on Facebook, mine did this a while back. I ended up just jumping the FP relay with a toggle switch to drive the car. It drove me nuts for the LONGEST time. I traced everything and tested everything. I ended up finding the ground pin on the FP relay wasnt grounding. I ran a ground jump to that pin and it worked. I replaced the fuseblock and it worked like it was supposed to. My fuseblocked ended up going bad somewhere inside and it caused all the problems.

Just some food for thought

[xpalendocious]

fp relay trigger is a ground signal from the ecu. feeding the signal wire +12v ign won't trigger the relay.

[xpalendocious]

position 12 on your ce2 fusebox pinout

12 Fuel Pump Relay (80, 67 or 167)

1 Main Fusebox Starter Power (not used)
2 Main Fusebox Start/Run Power
3 To ECU (Fuel Pump Turn-On)
4 To Fuse 18, Fuel Pump, Oxygen Sensor Heater
5 G2/6 (not used)
6 Main Fusebox Battery Power From 30B
7 G2/7, T1 (not used)
8 Main Fusebox Ground (not used)
9 M/4, U1/8, G2/5 (not used)

[xpalendocious]

On the engine wiring harness going to the fusebox

G1/03 ECU- Fuel Pump Relay Turn-On (gas) - Fuel Pump Relay Power - Red/Yellow (gas),

[BarryV]

Barry, like I posted on Facebook, mine did this a while back. I ended up just jumping the FP relay with a toggle switch to drive the car. It drove me nuts for the LONGEST time. I traced everything and tested everything. I ended up finding the ground pin on the FP relay wasnt grounding. I ran a ground jump to that pin and it worked. I replaced the fuseblock and it worked like it was supposed to. My fuseblocked ended up going bad somewhere inside and it caused all the problems.

Just some food for thought

fp relay trigger is a ground signal from the ecu. feeding the signal wire +12v ign won't trigger the relay.

position 12 on your ce2 fusebox pinout

12 Fuel Pump Relay (80, 67 or 167)

1 Main Fusebox Starter Power (not used)
2 Main Fusebox Start/Run Power
3 To ECU (Fuel Pump Turn-On)
4 To Fuse 18, Fuel Pump, Oxygen Sensor Heater
5 G2/6 (not used)
6 Main Fusebox Battery Power From 30B
7 G2/7, T1 (not used)
8 Main Fusebox Ground (not used)
9 M/4, U1/8, G2/5 (not used)

On the engine wiring harness going to the fusebox

G1/03 ECU- Fuel Pump Relay Turn-On (gas) - Fuel Pump Relay Power - Red/Yellow (gas),

Well... thats amazing info!

Steve... I saw your spot on FB. I started setting up to trouble shoot and then passed out on the couch after dinner. Guess I saved myself a lot of trouble.

Thanks guys, for the great advice. I will be looking at the ground now.

[BarryV]

So I feel like a complete dumbass.


I guess the fuel pump relay circuit has a slight delay in it.

Troubleshooting with everything back together, and a buddy cranking the car, I found 12 V sitting on the Walbro, and the pump was actually turning on.


Car would start, sputter, and then die. WTF


Takes a closer look, and MAF coupler had fallen off the intake tube, inside the inner fender, below the frame rail.


Wow.

Ok... so T-bolting the intake couplers today and re-assembling tonight.