camjeep3 Posted April 30 Share Posted April 30 Quick background. Truck was running fine until parked due to rear axle decided to explode. That was 10-12 years ago. I started tinkering on the truck put a fresh battery in and realized my fuel pump was dead. Went through the fuel system, new pump sending unit tank and regulator. Fuel to the rail. I get a crank but no start. Pulled a plug and I get a good spark whole cranking. Checked CPS at plug and voltage was low. Replace CPS. Nothing. Try another CPS. 0 voltage at plug with sensor isolated from truck wiring. I am going to do the cruiser checks but if I'm still confused. Should I see spark with a bad CPS? Link to comment Share on other sites More sharing options...
89 MJ Posted April 30 Share Posted April 30 You shouldn’t get spark with a bad CPS. Did you add fresh fuel or is it still the 10-12 year old fuel? Might need to drain the fuel system and add fresh gas. Link to comment Share on other sites More sharing options...
camjeep3 Posted April 30 Author Share Posted April 30 New tank. So fresh gas Link to comment Share on other sites More sharing options...
Eagle_SX4 Posted April 30 Share Posted April 30 If you have spark but no start you can always check the timing and make sure the distributor is properly indexed. Link to comment Share on other sites More sharing options...
camjeep3 Posted April 30 Author Share Posted April 30 Something I will definitely check. But I figured unlikely since it hasn't been touched and the truck was running. Link to comment Share on other sites More sharing options...
gvthnks Posted May 8 Share Posted May 8 I don't understand. If you had good spark at the spark plugs, then your CPS was working. 0 Voltage at plug with sensor isolated from the truck? You won't get voltage on the CPS harness side plug. The CPS generates voltage as the flywheel turns in close proximity to it. So to check it, the CPS has to be in its location, and you check the two wires coming off of it looking for AC voltage. I run the multimeter leads from the CPS up to my meter laying on my windshield and crank it over with the key while looking for AC voltage. We're looking for about .5 VAC here. Are the fuel injectors firing? I'd use starting fluid to see if it will fire while cranking it over. If it does, that's the easiest way to isolate it to a fuel issue. Link to comment Share on other sites More sharing options...
camjeep3 Posted May 13 Author Share Posted May 13 I don't understand either. I am checking CPS as you describe and get nothing. Maybe I need to try a different meter. But if no CPS signal means no spark then I have a different issue. I'll try starting fluid and work from there Link to comment Share on other sites More sharing options...
gvthnks Posted May 13 Share Posted May 13 Make sure your meter is set to measure AC voltage and not DC. Link to comment Share on other sites More sharing options...
camjeep3 Posted June 1 Author Share Posted June 1 Had a few mins and got a charger for the battery. With starting fluid it will fire up and die Link to comment Share on other sites More sharing options...
ratrapp Posted Monday at 01:50 AM Share Posted Monday at 01:50 AM if you have fuel pressure at the rail then the injectors have probably froze from sitting all those years. Link to comment Share on other sites More sharing options...
camjeep3 Posted Monday at 09:54 AM Author Share Posted Monday at 09:54 AM There is pressure at the rail. If I hit the valve it shoots fuel out. Any way to test the injectors before I buy new ones? Link to comment Share on other sites More sharing options...
TurboedMJ Posted Monday at 02:56 PM Share Posted Monday at 02:56 PM To make completely sure you have adequate fuel pressure, rent a fuel pressure test kit from AutoZone or the like and verify pressure. Read post #5 https://naxja.org/threads/87-renix-4-0l-auto-weak-vs-strong-fuel-pump-sound-when-cranking.1063540/#post-245350096 There may also be a way to test that the PCM is firing the injectors properly. Link to comment Share on other sites More sharing options...
ratrapp Posted Monday at 05:07 PM Share Posted Monday at 05:07 PM yeah i would get a noid light and see if the injectors are pulsing.if they are and you have adequate fuel pressure i bet the injectors have froze up from sitting.its not that uncommon. Link to comment Share on other sites More sharing options...
camjeep3 Posted Tuesday at 09:57 AM Author Share Posted Tuesday at 09:57 AM I had the rail apart and contemplated replacing the injectors. I put seals on instead... So I fully expect I'll end up having to replace injectors Thanks guys. I'll report back Link to comment Share on other sites More sharing options...
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