DME actually does not prime pump for 3-second. So don’t worry about that if it doesn’t happen.
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Originally Posted by roypreston
put the new fuel pump on. Now have fuel to rail but still no start and no tach bounce. Will start while spray into intake but only runs while spraying. Maybe DME problem? Wish I had a know good one to try but I'm in Arkansas and not too many 944's around me. May just send mine off somewhere to rebuild.
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Seems like you’ve replaced lots of parts with brand-new parts, but haven’t actually measured and tested to confirm they were defective in first place. This can get costly as there’s hundreds more parts you haven’t replaced yet. There are easily 20 areas which can cause no-fuel condition. You’ll want to test and measure them all.
1. Don’t assume speed/ref sensor spacing is correct, especially with no tach bounce. That may have been original problem and is culprit in 99.99% of no-start issues. Until you measure and confirm peak-voltage output waveforms, your speed/ref sensor signals are still suspect. Also figure-8 spacer often gets lost. Note these measurements are done at DME connector to verify wiring in between as well. Doesn't matter one bit if your new sensors are working fine, but if their signals never get to DME properly, it's useless.
One of recent no-start cases had found bad spacing resulted in insufficient sensor output and adjusting it gave better signal and car started right away (along with new battery).
2. Measure supply and start-signal voltage to DME when cranking
3. Measure voltage output to fuel-pump while cranking. Measure resistance of fuse#34. Is pump being turned on? DME only turns on fuel-pump when it sees engine spinning.
4. Pull fuel-rail with injectors attached. Place little cups under each. Do you get fuel-spray when crankjng?
5. Also need to verify yes/no to getting injection pulses. Short in injector harness can prevent injectors from opening. Test at DME output pin AND at injector connectors to verify wiring in between is good.
6. Disconnect all injectors and measure voltage at each connector's 2 terminals (key ON). What is voltage measured for each one?
7. Search for “DME KLR test plan” for troubleshooting flowchart (ignore KLR tests). Follow steps in order and some part of that flowchart will pinpoint your exact problem. Do all sensor tests, especially ECT (NCT-II). Out-of-range values will prevent starting.