1980 Seville Injector Problem(s) second post

[Ron Draper]

Sorry for the delay - age and weather (on me ).

Timing is okay.  This is my forth injector so it must be something I am doing wrong.

But backing up to 1st injector replacement - not as much gas coming as original injector but lots of back firing.  Well it seems that this injector is allowing way too much gas thru. 

I get another rebuilt and put it in and it at least it starts but still too much gas - runs better on the one original injector than with the rebuilt but will not run on just the rebuilt injector. 

I get a third injector and it is better yet but still too much gas - will run with the one original injector but not with the one rebuilt. 

The forth injector is only slightly better that the third injector. 

Fuel pressure is a steady 10 pounds at idle and thru various open throttle points and the book says 9 to 12 is okay. 

What have I over looked?  Can I adjust the injector (Middle screw between the leads?)?  Is the fuel pressure too low for the blended fuel of today?  Should I monkey with the one "good" injector? 

I can't pop open the accelerator as it bogs down and some cases dies but I can ease open the throttle and it speeds up but does not run smoothly.  Plugs have been cleaned and regapped.

No codes being set unless I force one (disconnect vac line or switch).

Thanks for your help.

Ron

[TJ Hopland]

Have you tried both new/rebuilt injectors at the same time?  Maybe the 'good' one is actually faulty and happens to be the side with the o2 sensor on it so its cranking up the fuel to compensate?  o2 shouldnt be 'online' during warm up so that does not explain it all unless you also have a faulty coolant temp sensor.   Amount of fuel is primarily based on rpm and intake manifold pressure.  I dont really see the rpm signal being messed up but you could have a bad map sensor.  Could be as simple as a bad hose causing a leak or a kink or somehow plugged?  Low vac would make computer think engine was under load and give it more fuel.   

Before you dump much more money into parts it may be time to get a computer hooked to that thing and see what various sensors are reading.   It may be pretty obvious.  GM OBDI scan tools often can be had fairly cheap on craigs list and or ebay.  Since they quit making cars that used that system in 95 you dont really have to worry about software updates.   I had a nice OTC one that would read obd1 and early obd2.  I paid $75 for it and sold it for $75 2 years later when I got rid of my obd1 cars and bought an 05 that required something more advanced.

[CaddyShackPA]

FWIW, on my '80 Seville 368 I once had a running-rich problem that was not in fact the one visibly fat injector but instead a bad output transistor circuit in the computer. I was able to inexpensively (amazingly) replace the whole ECU with one from Advance - no more problems. I think I had to swap the calibration modules, keeping the chip from the original. Pay careful attention to the ECU grounding and static concerns if you swap it out. Also, a failed injector (low impedance) can kill the ECU, so don't connect a good ECU to a bad injector...

Regards,
Jeff #23864