Hey guys, looking for some help with my buddy’s Talon. We first started having this issue last summer. The car was running perfectly fine and then one day it suddenly started acting up. The issue is that the car will attempt to start, fire up for a second, and then immediately die.

So far we’ve tried the following:

1. Replaced the fuel pressure regulator with a brand new one and set base pressure correctly
2. Replaced the CAS with a brand new unit
3. Swapped in a new coil pack
4. Changed the MPI relay with a known good relay
5. Swapped ECUs using known good ECUs with two different ECMLink chips
6. Verified spark on all cylinders
7. Swapped spark plugs

Not necessarily in that exact order, but all of the above has been done with the same result every time.

I’ll post videos below, but today another issue started happening that wasn’t present before. With the key in the ignition position, the MPI relay intermittently clicks and the fuel pump cycles on and off. Sometimes it stays on, sometimes it stays off. At the same time, it also sounds like the injectors are getting power on and off along with everything else.

We checked all the visible grounds and nothing immediately stood out as wrong.

Any help or ideas would be greatly appreciated. The car is running speed density.

datalog it. Look for anything that feeds ECU info that would shut the car off or drastically change fueling, CAS, crank sensor, and coolant temp come to mind. Or it's a huge vacuum leak but given the clicking etc I kind of doubt that. I'd look at the ECU harness also particularly if it has been cut/abused/tampered etc over the years.