I have a 1980 Scirocco 1.6 with a Neuspeed throttle body, Pertronix module an a Techtonics exhaust. Last week while driving home from work I noticed that when I let off the gas the tach needle would drop down to zero but would pop back up as soon as I reaccelerated. I can hear a click from the fusebox area under the dash when the needle pops back up. The tach needle doesn't drop every time I back off the gas. Most of the time it operates normally. Monday morning this started happening again. The car bucked a few times and then finally quit. I pulled to the side of the road and the car wouldn't fire. After a few minutes it fired up and I was able to make it the last few miles to town. I pulled the the fuel pump relay and it was very warm to the touch and one of the terminals has a bluish color. After sitting all day the car would not start. Yesterday I was able to start the car and drive it around a bit without any trouble. Any ideas?
Well... the fuel pump relay should be "watching" the ignition circuit to verify that the car is running... in other words it is looking for a tach signal... if the relay is bad and the tach terminal is intermittently grounding that could certainly cause the problem that you are describing. Sounds like a "chicken or the egg" thing though... a fault in the ignition circuit could also cause the problem (i.e. if you're intermittently getting a constant 12V on the circuit it will also kill your spark, tach and fuel pump relay) but anyway that's where I'd start looking
There was a big time problem like this with late '70s to early '80s cars. I sat at a drive-thru window once and part of the wiring harness smoked right in front of me. (This was with a '76 Scirocco.) If you have the same problem, the symptom is that the fuel pump is cutting on and off and that's the reason for the short stalls. Sort of like hiccups, if I remember correctly.
As I remember, the problem was that the wiring harness for the fuel pump relay was sized for the current requirements of the pump assuming that everything was running properly. The first deviation from "properly" is when the fuel filter starts getting a little dirty and the pump has to work harder and pulls more current.
There was a VW "fix" for this that involved removing the fuel pump relay, adding a new socket to the top of the fuse block (snaps in), and then an adjunct wiring harness from the new socket. IIRC, there's a connector that plugs into the old socket where the relay was and a separate (heavier gauge) wire that goes either to +12 or Ground (don't remember which).
If this is your problem, I'd suggest that the first thing you do is to change the fuel filter. I mean like RIGHT NOW! Do that and the current draw will go back to normal and that'll prevent it from getting worse. After that, you'll need to look at the fuel pump relay itself and see if it's heat damaged and then at the fuse block and the wiring harnesses that plug into the back of it. Again, it's been a long time ago, but I remember that one of the harnesses has a single wire that's carrying all of the current for the pump. If you're facing the fuse block, I think it's one of the harnesses that plugs into either the right or left corner. If you unplug it and look at each side, you'll most likely find that it shows signs of excessive heat. Look on the outside of the connector for any discoloration. The plug housing is probably white, so it'll be reasonably obvious.
Any good (old) VW mechanic will probably remember this problem and should be able to help you and dealers' may still stock the replacement wiring harness.
Yeah early Scirocco's and MK1 volkswagens in general have a big problem with corrosion at the fuse box. That clicking noise at the fuse box was more than likely the fuel pump relay switching when it lost the tack signal.. I have seen bad relays, also bad hall senders in the distributor.
Thanks for the advice. I will change the filter tomorrow. Hopefully that will cure it! Have any of you had a Pertronix unit go bad? I've had one in my '80 4000 for years with no problems, but i suppose it's possible.
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