My wife drove her 96 Cabrio a few days ago. When she got ready to drive home, it wouldn't start. I called a tow and had it returned to my garage. It is a 2.0L ABA OBDII with auto transmission. No "Check Engine" light. The light works when starting the engine. It would crank, but not start.

1. I checked for spark. Have strong spark from the coil to the distributor. Also, I stuck an old spark plug into #4 plug wire and tossed it on top of the intake manifold. Cranked it and had spark there, too.
2. I next pulled the fuel supply line from the fuel rail and expected to find fuel squirt out under pressure. Nope!
3. I stuck the same hose in a soda bottle and cranked the engine. No fuel in the bottle!
4. I listened to see if I could hear the fuel pump. Nope! (but it's pretty quiet normally)
5. I then checked the 20A fuel pump fuse, according to the diagram in my Bentley manual. It tested good.
6. Following the Bentley manual for testing the fuel system, I made a fused, switched jumper wire.
7. I then pulled the fuel pump relay and connected the jumper to the battery B+ terminal and to terminal 87 on the relay panel and bypassed everything except a direct path from the battery to the fuel pump, through the fuse panel and factory wiring. Pump did not run.
8. While I had the relay out, I read the schematic on the side of the relay and used jumpers to wire it to the battery. The relay clicked and a test light showed voltage coming out of the correct terminal.
9. Returning to the Bentley manual, I used a digital volt-ohm meter to check for the ground (trigger signal from the ECU) on terminal 85 of the relay socket. The Bentley manual says there should be a momentary signal here when the key is turned "on". I found a constant ground after giving it a few seconds. Also, a constant ground when the key was turned to "start".
10. The Bentley manual states if there is a ground signal, the relay may be bad. I replaced the fuel pump relay. No help.
11. I got in the trunk and uncovered the fuel pump. I unplugged it and inspected the connections. They looked good. Also verified, with a helper listening, the pump isn't running by jumpering the battery to the relay terminal 87.
12. I hooked up the jumper again to the battery B+ and terminal 87 in the relay socket and used a test light to check for voltage at the fuel pump plug. No voltage!
13. Finally, I used the VOM to determine which wire in the fuel pump plug was the ground. Then, I ran the jumper from the battery to the power side of the fuel pump and a ground wire jumper to the trunk latch. When I flipped the switch, the fuel pump ran!

At this point, I am assuming there is a problem with the chassis wiring from the relay to the fuel pump. And that's where I have a problem, trying to decipher the wiring diagrams and not knowing where the wiring harness runs.

 

Which wiring diagram are you using?

You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing. You can investigate more components with VAG-COM\VCDS.


If you have a 109 relay you can crank it all day and it will never start, its the main power feed to the ecu.

https://volkswagenforum.com/forum/ne...gnature-34185/

 

I am using the Bentley manual for testing and wiring diagrams. I don't have or have access to VAG-COM. But, I do have a OBDII scan tool that can reset codes. It shows no codes stored at this time. I do not have relay 109.


In my original post, I mentioned in item #9, the Bentley test said I should have an intermittent ground signal from the ECU to pin 85 on the fuel pump relay. When I turned the key "on", the signal was steady for at least 30 seconds.


Last evening, I had my wife sit in the seat while I hooked up a jumper wire from the battery (B+) to the fuel pump. The pump ran and I could hear fuel sloshing through the pump hoses. Probably air that was introduced when I pulled the fuel supply line from the fuel rail during initial testing. I had her try to start the car. On the first attempt, it sounded like a cylinder or two fired. The next two attempts.....nothing.


Multiple problems, or am I overlooking something?