Stuck on the Side of the Road. Any ideas?
05-20-2018, 03:13 PM
#46
Race Car
Thread Starter
I'm 99% sure it is but yeah, fingers still crossed.
Good to know. My relay spares count is now up to 3, starter, fuel pump, and fuel injection. I will get this car back and forth across the US one of these years!
Thanks! I just finished using it on a flight test for work and thought there was a big probability I'd breakdown before getting home. Just glad I caught it on tape.
It'd be cool to have live on board video monitoring of all the critical systems. But with much smaller cameras. Nano cameras would be sweet!
Thanks for the link Bill. The FP relay is new in my car and seems to be doing its job. The one in the video was the fuel injection relay. Made in West Germany, so likely the original or at least very old. It also has a ffth post which I assume also triggers from TDC signal.
Yup, I keep 2 new spares in the trunk tool box along with the switched jumper. Its the only on-road failure I've had, twice now with 2 different relays. First was at a gas station 2 hours from home and the other was at the end of my driveway after an extended wide open throttle pass of my wife in her 997 on the long straightaway of the state highway before our neighborhood turn off.
Thanks! I just finished using it on a flight test for work and thought there was a big probability I'd breakdown before getting home. Just glad I caught it on tape.
It'd be cool to have live on board video monitoring of all the critical systems. But with much smaller cameras. Nano cameras would be sweet!
Hi Nate...
Clever way to monitor that relay!
Check this link for some more info on the fuel pump relay. See post 6 and 7. If I understand correctly, the FP relay gets its power from the ignition circuit (key position 1, relay terminal 15), ground through terminal 31, and control via 31b. When the key is turned to position1, the relay closes the contacts for a second or two. After that, it relies on a signal from the ignition module on 31b that tells it whether the engine is cranking/running. I think it connects to the module terminal that tells the coil to fire (and probably runs the tach). If that signal goes away, the FP relay opens and stops the fuel pump.
Since that's an electronic circuit inside the relay, it can (and apparently often does) fail and replacing the relay solves the problem. If a new relay doesn't solve the problem, then I think the next step is chasing down the signal to 31b. I think if you jumpered 30 and 87 and it still stalled, that would mean either the module stopped sending the coil firing voltage pulse, or the wiring between gains too much resistance over time or heat. At that point you could run a separate wire between the module and the relay which would prove/disprove that circuit.
Clever way to monitor that relay!
Check this link for some more info on the fuel pump relay. See post 6 and 7. If I understand correctly, the FP relay gets its power from the ignition circuit (key position 1, relay terminal 15), ground through terminal 31, and control via 31b. When the key is turned to position1, the relay closes the contacts for a second or two. After that, it relies on a signal from the ignition module on 31b that tells it whether the engine is cranking/running. I think it connects to the module terminal that tells the coil to fire (and probably runs the tach). If that signal goes away, the FP relay opens and stops the fuel pump.
Since that's an electronic circuit inside the relay, it can (and apparently often does) fail and replacing the relay solves the problem. If a new relay doesn't solve the problem, then I think the next step is chasing down the signal to 31b. I think if you jumpered 30 and 87 and it still stalled, that would mean either the module stopped sending the coil firing voltage pulse, or the wiring between gains too much resistance over time or heat. At that point you could run a separate wire between the module and the relay which would prove/disprove that circuit.
