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EJ22 OBD-1: Strange Start Problem (Pt 3)

 

I gathered some more information this afternoon; I'm learning this start?sequence is a bit complex....

- Fuel Pressure test
Gauge tee-d in after the filter
Turning the key to 'Run'
IF the CEL?cycles (as I described?before) then the fuel pump doesn't come on until the CEL?becomes constant (this happens unpredictably, sometimes immediately, sometimes after a few s, sometimes it seems to just keep on cycling)
- Once CEL is constant, then the fuel pump turns?on for 2-3 s; pressure rises to ~32-34 psi (that seems about right?)
- Then pump turns off and pressure decays back to < 10 psi pretty fast (in < 10 s)
Going from 'Run' to 'Start' turns the fuel pump on again and the engine usually (but not always cleanly) fires up
Fuel pressure remains at 32 - 43 psi when the engine is running (higher when revving?the engine); that seems correct.

The rapid decay of fuel pressure once the pump turns off seems wrong; I would have expected it to stay high for 30 - 60s at least (that's what I'm used to on my L-Jetronic TR7s). If this indicates a leak, then I would think the only possible causes could be the pressure regulator or injectors - anything else?

Jason suggested the ignition switch may be at fault; that may be possible?so I'll?try that but I can't get any different result by any kind of pressure/wiggling of the key/switch

Thanks for reading my long missives and for all your ideas!

Fuel pressure regulator on order...
Spare injectors dug out of my parts stash; they need rebuilding first...

THANKS
Mike Hart
Paso Robles, CA
(650) 387-8957
 
Edited

I believe the ECU is grounded through the main engine ground to the intake manifold so you could check that.There are documented problems with poor ground connection there. The ECU supplies a ground path for ignition power to the FP relay, thereby enabling battery power to the fuel pump. Faulty ignition power? You really need a 12v test light and multimeter to be diagnosing this. With the two green test connectors connected and key turned to ON, the relays should be clicking and fuel pump cycling. The fuel pressure would cycle between 40 and 45 psi with no decay below 40 with a good regulator on my 02 2.5L. There are other tests to diagnose fuel pressure problems as well. The CELs you are getting is a concern. Maybe your ECU is going tits up or it's a ground to the ECU issue.
Edit: What CEL codes are you getting? If you don't know how to check look for YouTube videos on how to.
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