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Hi all -
I'm in the process of some diagnostic work on a no fuel situation in my S4 Motronic Spider. The engine just shut off today on the road, coasted to the curb, got towed home. No bang, no bump, just cruising along fine as usual and it shut off - all other electrics working fine. As of now, the fuel pumps aren't turning on - however, when direct voltage is applied via a battery, they both work fine. So here's what I've done.
1) Checked grounds/connections/tubing/fuses and relays. All work fine.
2) Confirmed good, fresh gas in tank. No air leaks.
3) Confirmed strong spark from plugs and coil.
3) Car cranks, RPM tach moves, no fuel on plugs. Gauges work.
4) Squirted starter fluid in open TPS, car started, died.
5) Jumpered fuel pump relay pins 30-87, still no dice.
6) Battery is good, voltage is fine.
7) No ECU codes.
8) ECU and relays click when ignition is turned "on". No noise from pumps during cranking.
9) Rotor and dist. and wires are fine.
Wish I'd had my voltmeter with me, as well as my shop manual, but alas. I would have liked to confirm voltages. As of now, I don't believe I'm getting power to the fuel pumps. No whine from the pumps or anything (unless I connect a battery directly to them). RPM timing sensor is hooked up. Nothing obviously loose or disconnected. I keep things neat and clean. Relays all were checked in the horn relay position. Checked out OK. Fuses near the ECU swapped out too. All connections there tight and clean.
A few years back I had an ECU issue that resulted in no voltage to the ignition coil. The last thing we suspected was the ECU, but I'm curious if this is another ECU problem, except this time it is killing voltage to the pumps. Again, nice fat sparks from coil. I'm following the same troubleshooting path I did a few years ago. Agh.
I'm perusing my S4 shop manual, hoping to come with some ideas. Dammit, why can't I ever get off easy - like an in-tank pump or something??? I'm just so jaded to this process already. Murphy's Law is in full effect on me this week!
Thanks in advance for your ideas.
I'm in the process of some diagnostic work on a no fuel situation in my S4 Motronic Spider. The engine just shut off today on the road, coasted to the curb, got towed home. No bang, no bump, just cruising along fine as usual and it shut off - all other electrics working fine. As of now, the fuel pumps aren't turning on - however, when direct voltage is applied via a battery, they both work fine. So here's what I've done.
1) Checked grounds/connections/tubing/fuses and relays. All work fine.
2) Confirmed good, fresh gas in tank. No air leaks.
3) Confirmed strong spark from plugs and coil.
3) Car cranks, RPM tach moves, no fuel on plugs. Gauges work.
4) Squirted starter fluid in open TPS, car started, died.
5) Jumpered fuel pump relay pins 30-87, still no dice.
6) Battery is good, voltage is fine.
7) No ECU codes.
8) ECU and relays click when ignition is turned "on". No noise from pumps during cranking.
9) Rotor and dist. and wires are fine.
Wish I'd had my voltmeter with me, as well as my shop manual, but alas. I would have liked to confirm voltages. As of now, I don't believe I'm getting power to the fuel pumps. No whine from the pumps or anything (unless I connect a battery directly to them). RPM timing sensor is hooked up. Nothing obviously loose or disconnected. I keep things neat and clean. Relays all were checked in the horn relay position. Checked out OK. Fuses near the ECU swapped out too. All connections there tight and clean.
A few years back I had an ECU issue that resulted in no voltage to the ignition coil. The last thing we suspected was the ECU, but I'm curious if this is another ECU problem, except this time it is killing voltage to the pumps. Again, nice fat sparks from coil. I'm following the same troubleshooting path I did a few years ago. Agh.
I'm perusing my S4 shop manual, hoping to come with some ideas. Dammit, why can't I ever get off easy - like an in-tank pump or something??? I'm just so jaded to this process already. Murphy's Law is in full effect on me this week!
Thanks in advance for your ideas.