Mysterious Problem with the 944
06-13-2013, 04:18 PM
#1
Intermediate
Thread Starter
Mysterious Problem with the 944
So, Larry Tech Racing went to the ChumpCar race at Gingerman this past weekend. The car ran great thoughout the first day, and then, 15 minutes from the end of the saturday race, the car just stopped, and wouldn't restart.... We tried for hours to figure out the problem, but eventually gave up. Here's a list of everything we tried, can anyone here point us in the right direction?
-Filled it full of fuel (we had been having a fuel pickup problem, where the car would stutter after right hand corners on less than half a tank
-Checked the reference sensors, confirmed good resistance on them, and then swapped them for our spares
-Confirmed that spark was getting to all the plugs. Also replaced the plugs and all plug wires.
-Swapped to our spare ECU
-Confirmed that all the injectors were firing, by cranking it and having them spray into individual cups (it was noted that it looked like they MAY have been spraying more than usual)
-Confirmed that the fuel pump was working
-Confirmed that the return line wasn't plugged
-Pulled apart the DME and jammed some cardboard in the contactors to keep them closed
-Tried two other fuel pressure regulators (though not the EXACT one for the car)
-Made sure the timing was correct
We ended up with a situation where the car would crank and start on starter fluid, and ONLY IF the fuel pump fuse was unplugged. As soon as the pump was connected, the car would die. We even ran the pump off a second battery, completely external to the car, in case the pump was grounding out the ECU, or something weird, but still had the same symptoms....
I'm tempted to thing it's getting too much fuel flow, like the pressure regulator is bad, but I'd like to get your thoughts.....
Here's some pretty pics from the race, though:
-Filled it full of fuel (we had been having a fuel pickup problem, where the car would stutter after right hand corners on less than half a tank
-Checked the reference sensors, confirmed good resistance on them, and then swapped them for our spares
-Confirmed that spark was getting to all the plugs. Also replaced the plugs and all plug wires.
-Swapped to our spare ECU
-Confirmed that all the injectors were firing, by cranking it and having them spray into individual cups (it was noted that it looked like they MAY have been spraying more than usual)
-Confirmed that the fuel pump was working
-Confirmed that the return line wasn't plugged
-Pulled apart the DME and jammed some cardboard in the contactors to keep them closed
-Tried two other fuel pressure regulators (though not the EXACT one for the car)
-Made sure the timing was correct
We ended up with a situation where the car would crank and start on starter fluid, and ONLY IF the fuel pump fuse was unplugged. As soon as the pump was connected, the car would die. We even ran the pump off a second battery, completely external to the car, in case the pump was grounding out the ECU, or something weird, but still had the same symptoms....
I'm tempted to thing it's getting too much fuel flow, like the pressure regulator is bad, but I'd like to get your thoughts.....
Here's some pretty pics from the race, though:
06-13-2013, 05:15 PM
#2
Rennlist Member
Not sure if you checked ignition timing or valve timing. Whichever you checked, be sure to check the other. Did you look to see if the rotor bolt backed out -- it the rotor spins on the end of the cam you'll have spark at random unhelpful times. If starter fluid gets it going though, also check the air flow meter signal. If its way off, it can flood or starve the motor.
