For those willing to look, 92 CPI 4.3 issues

[doughchvy1]

Colorado, I had a 95 that would do that. i put alot into mine trying to find the problem out and it ended up being the temp sensor along with the O2 sensor they were reading oppisite of each other which was throwing the timing all over the place.

[Colorado]

That's crazy . Well I hope just replacing the temp. sensor does the trick then. Far as I know the O2 sensor is factory.

[Squirell]

sounds like a fuel pump.....gf blazer did the same thing. changed the fuel pump and its fine now

[Colorado]

That would also be cool with me. Well the fuel pressure is about 42 and the compression is low. 90-120 most cylinders. Just put in new injectors and it still only starts on starting fluid and dies once ya touch the gas. Next step in coolant sensor. 

[Chevy Racer]

42 PSI?  Needs a little more than that.  I would go with a new pump.

[Colorado]

Ya priming it's about 60ish and running it bounces around 42. Really don't wanna do a pump but apparently that's the problem. Gotta see what the book says. Guess I'll try a coolant sensor too.

[xjs3667]

Imo  stop throwing parts at it and hoping one of them will work...very costly, unless you have the money then go ahead, but test the parts before you replace get a scanner hooked up to and see if cts is reading correctly, your fuel psi is low dont just assume its the pump, check filter and psi before filter, and also when you checked fuel pressure what was the pressure after pump primed with key on engine off. CTS could be throwing the timing off but then you need to find out about fuel psi problem

[xjs3667]

prime fuel psi key on Engine off-  60psi

Running psi- no less than 54 psi

clogged line, filter, or sock on pump can cause 10- 15 psi drop 

[Colorado]

To my knowledge you can't connect a scanner to OBD1. It had a code on and off this summer when running but it seems gone. I put on a new inline bottle type filter when I dropped the tank and tried to fix my lack of fuel gage issue. The intank sock filter didn't look plugged at all. Dunno how to check pressure BEFORE inline filter unless I put in a filter delete fuel line....but that one was new....

[Buck]

the spiders go bad in them  alot under the intake  check them 25 50 bucks at  junk yard

[xjs3667]

I have a scanner that hooks up and will control computer functions as well as read codes, but easy way to test cts pull it out and hook up volt/ohm meter to it, check for oem specs.   To check psi before filter- fuel pressure tester should have an adapter that will thread into fuel line or a quick connect, If not easy to make one, self explanatory.  

[Colorado]

the spiders go bad in them  alot under the intake  check them 25 50 bucks at  junk yard

I just installed brand new injector poppets and put in new spider lines (both) this summer. With a newer used regulator.

My question is, does the computer read the cts in open(I think it is)  loop (a day of not running)

[xjs3667]

O2 senosor is read in open/ closed loop

Cts is not its consntly read and adjust fuel rate per temp reading it sends to computer   its kinda like a choke on a carb   its the only way for fuel injection to choke engine     ie cts is broke and is telling computer engine is 800 degrees when its actually 45degrees it would adjust fuel and timing to be crazy lean and vice versa

[Colorado]

Well this morning I tested the pressure on our 98 Safari and the fuel pressure never goes below 57-8 and never over 62 so everyone who said 60 is right. So guess F.P. is my issue.  I have a buddy who still says it's timing but this shows itself..   

[Colorado]

Replaced the fuel pump with a Ebay special and it runs great now. everyone.  

[Jthomas]

idk if this is your prob, but it happend to me.

on the fuel pump there is a bag filter that goes on the end of it. well the bag filter came appart and got sucked up in to the pump. it didnt completly stop the pump, but stopped the flow, a lot. so i would backfire under load, and just ran like .

hope this is your problem, its an easy fix. wish ya luck.

[Jjay78]

did you check the distributer gear? wear or damage is fairly common and will make it run like   if you didn't already check plugs and wires too.

did you check the dizzy gear?? neighbor had a late 90's 4.3 in an extended cab that ran great till one morning we was heading to pick up his old lady when her car died on her, well 1/4 mile down the road he blew off a couple teeth on the dizzy gear and we were walking

[Colorado]

JThomas :I replaced the sock filter with the new one that came with the new pump and I checked to make sure it was snug and on all the way.

Jay: I checked all that and it's nice and tight.

[Dirt Worm]

Mass air flow or map sensor would cause same symptoms, sounds like same thing my 97 jimmy was doin

[xjs3667]

looks like no one reads thru the thread.........

good to hear you got it runnin good colorado.

glad I could help