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90 olds Cutlass losing injector pulse


mustang42782
12-02-2007, 10:15 PM
got a 90 olds cutlass supreme international in trade for some vehicle work. It has the 3.1 in it, po said it needed a fuel pump. Bench tested the pump as it was removed by po and it ran fine. Placed pump in bucket of fuel, hooked it up and turned key to run. Had 2 second pump prime run, 40 psi to rail.
Started car up and it idled, then went to rev it up and it died, would not restart. Had previously checked injector pulse and it was present. Now have very weak to no injector pulse. Started where I had a feeling the problem may exist as i found an old rail and some injectors laying in the trunk. Found bare wires (green) in the main engine harness to the back 3 injectors so I cut the bad section out and re soldered in new piece. Buttoned up everything and tried again. Good spark, good fuel pressure, no injector pulse. Engine will try to fire intermittently and flash a momentary pulse but goes back to nothing.
Have read about the crank position sensor but from what I take it this only controls spark from the DIS. Does this also time the injectors as well?
Or am I looking at something else? BTW I am a CCT certified tech, and am very knowledgeable so let me have what your thinking !

maxwedge
12-03-2007, 07:39 AM
Welcome to AF. CPS controls spark and injector pulse thru the icm, both are common sources of this symptom. The icm can be tested at Napa , or Autozone, the crank sensor is tougher, you could test the resistance, or if you had a scope this would be the best way. Rarely the pcm can cause this also.

mustang42782
12-03-2007, 07:59 AM
Thanks Max. Im more of a chassis guy and hadnt messed with the fuel systems much. That and it has been 8 years since i worked the dealerships LOL . Ill ohm the CPS tonight along with the injectors as these injector types are prone to shorting

mustang42782
12-09-2007, 12:27 PM
I found one injector at 4.6 ohms the rest were at 11.8 to 12.4. Replaced the 4.6 ohmer and took the ignition module to orilleys to have it checked. No response from the PIP so the module is bad. Hopefully this is it! Went ahead and replaced the CPS as it was eAsy to do and cheap.

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