Wow, wish I had those numbers. My fpr pressure when key turned on hits 62 psi as well. Is 62 to high? What is the downside to 62 as opposed to 61 psi?

 

Gotta make sure we're talking apples to apples here. The CMFI spec is 55psi to 61psi, the CSFI spec is 60psi to 66psi.

62psi on a CMFI system might make it run borderline on the rich side. 62psi on a CSFI system is not a problem at all. The PCM, (on both systems) can compensate for fuel pressure variation by adjusting injector pulse width, as long as the pressure is within spec.

 

what do you mean by this sentence Write off your reading of 62psi to gauge error, and you're at the upper end of the spec. im concerned about my pressure while running at idle, i want to know if i can raise that from 54 to rite about 58 will be safe to do that? also another member from s10 forum has his pressure at 58 idling but primes with engine off at 62 to 64. can i achieve the same pressures?

 

The accuracy of your pressure tester may be off, who knows. The maximum allowable fuel pressure for your engine is 61psi, (with the engine OFF) you're at the maximum allowable pressure right now.

As I mentioned before, engine running fuel pressure is irrelavant, it is what it is. The fuel injector is either open or closed. The amount of time, in milliseconds, that the injector is open determines how much fuel is discharged from the injector. The longer it's open, the more fuel it discharges. The PCM is able to maintain the proper 14.7:1 fuel mixture as long as the fuel pressure is within specs. If you raise fuel pressure above spec, more fuel will be discharged and the engine will run too rich. The PCM can only lean the mixture a certain amount. If you lower fuel pressure below the spec, less fuel will be discharged and the engine will run too lean. This is why you get lean fuel mixture DTC's when the fuel pump begins to fail.


Again, engine running fuel pressure means nothing. For a CSFI system, (1996 & newer) 62psi to 64psi is fine. For your 1995 CMFI system, it's too high and it will cause problems. Your fuel pressure is perfect, not quite sure why you want to fool with perfect.

 

Is there a problem with how its running? Sounds like your truck is right within specifications. You will only lose power by increasing the pressure beyond where it should be, as well as possibly damaging other parts due to a rich condition.

 

yes, there seems to be 3 problems. ill list them. while running at idle if you turn on the A/C the motor has a slight stumble when the compressor kicks on. then on some days, more so when cold, when you first start it in the morning , it will start and run rough like as if 1 cylinder is not firing or something and smells a little rich. if you turn it off and wait 10 mins it will re-start as normal. and its not a clogged EGR since i know what that sounds like when its stuck. plus mine is new. then the third thing i notice is that sometimes throttle response right off idle is a tiny bit hesitant. that is why i was looking at fuel pressure. and i just put a new AC Delco pump in but it helped a little but the problems are still there. so that why. got any other ideas?

 

Does the check engine light work?
Does it come on or stay on while driving?
Are there any trouble codes in memory?
If so, what are they?
How many miles since the oxygen sensors were replaced?
How many miles since the last tune up using AC Delco parts?

 

engine light is off. it will come on only when the rough start is happening and it flashes, but then goes off under a normal re-start though and stays off...it never comes on while driving though.....the only intermit trouble codes stored in memory are 2 manufacture specific codes P700 and P1100....been there a long time. no one knows why or what they are....o2 sensors are original. we bought this truck brand new in 95...it has 62k orignal miles on it.....tune up done last year and only put 200-300 miles on it since.....so what you think?

 

Your 1995 uses OBD1.5 computer controls and it is not fully compliant with OBDII, (1996 & newer). As a result, some DTC's may be set eroneously. The P0700 has to do with the transmission. The P1100 indicates a problem with fuel air metering, usually referred to as "unmetered air". Neither of these will make the SES flash though. A flashing SES indicates a misfire and should set a DTC in memory, usually P0300 through P0306. The DTC will clear itself if the misfire is not detected for a certain number of drive cycles. Check the DTC's as soon as possible after you notice the flashing SES light.

 

your right, i have a OBD1 Computer in it but a obd2 plug under the dash. and i cannot use a regular obd2 scanner. i have to use a generic with a obd2 cable. i scanned it right away but no DTC'S were set. however i still have those 2 pending manufacture specific p700 and p1100 codes, why cant i get rid of them? i rebuilt the valve body too but the p700 is still there. could i have bad computers? and do i have 2 computers?