No start I've got 12psi fuel pressure?

1991 CHEVROLET S-10
200,000 MILES • 4.3L • 4WD • AUTOMATIC
Avatar
VIPERKING75
  • MEMBER
  • 58 POSTS
1991 s10 blazer. I've got 12psi fuel pressure, compression test is good (approximately 145 on all cylinders) exhaust is clear. Fuel return line is clear. Spark is good. System seems to be flooding. Will barely start with one injector unplugged and at full throttle. Coolant temp sensor is reading proper resistance. Starting fluid kills the engine. Im at a loss right now
May 26, 2026 at 2:34 AM
Advertisement
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,832 POSTS
  • ASE Certified Mechanic
Yep, it will flood like this if one of the fuel injectors is shorted or the PCM is bad due to a bad injector driver inside the PCM. Here is how to test the fuel injectors.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector/

Also, check the main engine wiring grounds, (near thermostat housing). Also, I have seen a bad MAP sensor cause this issue as well, so please check the vacuum supply to the sensor. You might want to remove it and see if it is clogged. And I would try unplugging the coolant sensor to see if that makes a difference. Please go over this guide and get back to me.
May 27, 2026 at 3:49 PM
Avatar
VIPERKING75
  • MEMBER
  • 58 POSTS
Injectors are working, spray pattern isn't the best, but they are functional. Unplugging the temp sensor makes no difference. Ground to intake, engine, and body all read between 0.0-0.1 ohms of resistance. Map vacuum line is clear as well
May 27, 2026 at 4:12 PM
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,832 POSTS
  • ASE Certified Mechanic
Did you test the injectors like in the guide? They can test different when in operation. You must test the operation not just the resistance.
May 27, 2026 at 6:30 PM
Avatar
VIPERKING75
  • MEMBER
  • 58 POSTS
Yes I tested in operation. They are both working, I don't have a way to test duration of the pulses though
May 27, 2026 at 6:59 PM
Avatar
STRAILER
  • ✓ASE Certified Mechanic
  • 54,832 POSTS
  • ASE Certified Mechanic
Bad injectors or a bad ECM are the only things I have seen hold the injectors open like that if the ECM grounds are good. Can I ask if the spark is working correctly? Please check out this video.

https://www.youtube.com/watch?v=lXLJbuAZ4CE

Please go over this guide and get back to me.

May 28, 2026 at 4:45 PM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.