Fuel pump or ECU ground?

[neinnein_nein69]

I recently pulled the fuse panel of my 1991 tintop to rewire my interior lights and radio power (B11 and B12) for a aux battery installation. haven't cut the wires yet and suddenly, this is happening:

- when the key is in, the door chime is erratic, sometimes it's on, sometimes not, and it will be triggered on and off by jiggling around the big spaghetti of wires

- with key in run, fuel pump will not kick on, but sometimes it will again if I jiggle the fuse box spaghetti. the van starts beautifully also, but it dies as soon as the spaghetti moves.

I looked at the ground trees, everything seems solid and plugged in there. I get power to the ECU through pin D23 (formerly D15), there's also power at the ECU and fuel pump relays in the engine bay, but something somewhere is loose, but it's not visually obvious.

does that ring a bell in anyone's mind re: which connection I should look at specifically?

thank you!

ps: trying to upload and post specific photos but it's not working for some reason so here's a random photo of my van

[crazyvwvanman]

None of the dash area grounds are needed for the engine to run.

There is only 1 wire coming from the dash area needed to run the engine and that is the black wire from D15.

The dash power comes from the battery on the largest red wire of the P spades on the back of the fuse/relay panel.
From there it comes out another P spade red wire and goes to the ignition switch.
The ignition switch then puts it on a black wire to pin A8 of the panel.
The panel feeds it to pin D15 (D23) where a black wire feeds it back to the ignition coil.

Mark

[neinnein_nein69]

that is very great info thank you, I'll follow that path closely and look for problems.

[neinnein_nein69]

after checking the whole signal path, I think I found the problem, the ignition switch?

when i push the key in harder, fuel pump engages and van starts great. I changed the IS last year, are they that fragile?
I did change the ignition lock cylinder a few months back when i lost my key and then put the original back in when i found it again, maybe I hurt it, who knows.

[Wildthings]

OEM switches tend to last a long time and traditionally don't cost much. Aftermarket switches are just the opposite undependable and comparatively expensive expensive. Sadly it can be hard to come by OEM switches.

[neinnein_nein69]

sorry, bumping this after issues resurfaced. been reading this thread attentively, my issue sounds very similar:
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

my D15/D23 is fine and the black wire going from dash to relays in the engine compartment has 12.6v

replaced fuel and ecu power relays (van is 91 so they are both 4 pins, no mods neede), ecu one clicks in run and fuel pump one briefly closes as if to prime the pump but the pump doesn't prime. ISV valves buzzes the whole time key is in run. Have not tested for spark or resistance across components yet but will do tonight using Kam's improved Digifant training manual which is great.

Just a quick question:

I remember sticking a screwdriver across terminals of the fuel pump relay to test the pump when I broke down on the side of the road recently and remember seeing sparks and smoke, which makes me think I might have damaged the ECU. If I understand correctly, the only way to know is to swap for a known good one, correct?

I opened it out of curiosity just now and some areas look a little toasted.

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[crazyvwvanman]

The only thing that clicks the fuel pump relay on is the ECU.
If FP relay clicks on and off to prime each time the key is turned to run then that part of the ECU is working for that to happen.

Near the air cleaner, along the firewall, there is a 2 pin connector that has the power and ground wire for the fuel pump.

Mark

[DanHoug]

those look to be previous repairs... the blobs of solder are not factory and the scortched areas may merely be the conformal coating that got melted in the process of the repair. would need to see the topside.