My blazer has the first year of the vortec intake, central port 4.3. The first issue was lack of power so I replaced the plenum fuel line and put in a newer fuel reguator. Then it became hard starting. It would
crank w/o firing. Well I have plugs that fire and injects gas fine. But now it will barely start on starting fluid. If it does it will idle fine, but sputter in gear then die before needing more fluid.
It's gotten to the point that it won't even rev without backfiring. I took the plenum off and starting fluid fires back out the intake tunnels. This said, I think the timing is done. Any idears?
Thank you for responding if you do. Ryan.
dont want sound dumb, but have u removed the cat. converter yet?
Not a dumb question. The cat was gone when I bought it. It's runnin straight piped exhaust with one muffler. It ran like p00 before the exhaust was done. I thought good exhaust would fix this since it was bad beforehand. The Y pipe has a realllly small leak but nothing horrible. I'm told it's timing. But ==dunno
how much fuel pressure? could be timing though
I don't know the fuel pressure but the backfiring I know has nothing to do with the pressure. Also, I'm told if the timing is fried then the motor needs rebuilding.
them pletums are known to go bad. but i doubt thats the problem, maybe try changing the EGR valve in there while you got it apart.
I don't remember it breaking but a tab on the EGR piece snapped so I gotta get another one.
check fuel pressure should be like 45 psi that will cause lean back fire
Quote from: mudbrat71 on December 23, 2011, 03:08:31 PM
check fuel pressure should be like 45 psi that will cause lean back fire
needs 62 to start and 59 i think to run? i could be wrong tho
Quote from: J.C. on December 23, 2011, 03:10:08 PM
Quote from: mudbrat71 on December 23, 2011, 03:08:31 PM
check fuel pressure should be like 45 psi that will cause lean back fire
needs 62 to start and 59 i think to run? i could be wrong tho
I'm thinking in the 60 PSI range too. Also I think I got an EGR that will work for ya. I'll look around. They are like $90 new. Ask me how I know that. LOL
did you check the distributer gear? wear or damage is fairly common and will make it run like p00 if you didn't already check plugs and wires too.
did you change the coil? rember how i riged that one on i at the mounds when the other one blew up? lol
Quote from: ProGrade on December 24, 2011, 05:57:17 AM
did you check the distributer gear? wear or damage is fairly common and will make it run like p00 if you didn't already check plugs and wires too.
check for slop or end play between the gear andend of it those 4.3 can be fussy on the timing being just right id think a fuel pressure issue is most likely trhe cause
Quote from: Chevy Racer on December 24, 2011, 01:18:51 AM
I'm thinking in the 60 PSI range too. Also I think I got an EGR that will work for ya. I'll look around. They are like $90 new. Ask me how I know that. LOL
So how do ya know that? loll I can even come get it from ya. (maybe cheaper?)
Quote from: ProGrade on December 24, 2011, 05:57:17 AM
did you check the distributer gear? wear or damage is fairly common and will make it run like p00 if you didn't already check plugs and wires too.
The distributor seemed to have no play this summer. It's got a tested good ICM, with new cap. Wires didn't look bad but I have to assume they are old.
Quote from: rangerwheelinmike on December 24, 2011, 06:00:36 AM
did you change the coil? rember how i riged that one on i at the mounds when the other one blew up? lol
It's still got the coil on that we rigged. It even tries to fire without being properly grounded.
And BIGFRANK, I think yer right. Next step is checking pressure. The pump is NOT new at all. I'm convinced the timing is shot which I'm told if that's the case the whole engine needs rebuilding = not worth it.
you need to ground that coil better its not even tight
needs 60 psi of fuel preasure to start and if its not there it will send you all over the place to find it check ya fuel preasure before ya do anything
It was grounded tightly and still didn't run mikey and yes I plan to do a compression AND fuel test after Christmas even though I'm also told fuel won't affect it.
==thanks everyone for the help.
fuel will affect it dude... it runs on gas ==roll
It sounds stupid but if its got a w vin code the temp sensor on the drivers side haed is bad it makes it hard to start and back fires because its not reading the right fuel pressure thru the computer i saw a couple of them at the shop do it If that helps
Funny you say that cuz I've never tried the temp. sensor AND I don't have a fuel (another story) or temp. reading..... TWO gage clusters later.
My opinion, 4.3's go forever pretty much and I can't picture the timing gone at (purchased miles of) 125k.
And I (still) agree Derik. Anything is poss. with engines.
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.
That's crazy p00. Well I hope just replacing the temp. sensor does the trick then. Far as I know the O2 sensor is factory.
==thanks
sounds like a fuel pump.....gf blazer did the same thing. changed the fuel pump and its fine now
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. :(
42 PSI? Needs a little more than that. I would go with a new pump.
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.
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
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
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....
the spiders go bad in them alot under the intake check them 25 50 bucks at junk yard
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. ;D
Quote from: Buck on January 16, 2012, 03:05:18 AM
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)???
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
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.. ==doh
Replaced the fuel pump with a Ebay special and it runs great now. ==thanks everyone.
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 p00.
hope this is your problem, its an easy fix. wish ya luck.
Quote from: ProGrade on December 24, 2011, 05:57:17 AM
did you check the distributer gear? wear or damage is fairly common and will make it run like p00 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
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.
Mass air flow or map sensor would cause same symptoms, sounds like same thing my 97 jimmy was doin
looks like no one reads thru the thread.........
good to hear you got it runnin good colorado.
glad I could help ;D