Capt Saveahoe

[TreeClimber]

Before you go tearing into the motor, please verify you have a good tank of fuel.

This wouldn't be the first time someone was chasing ghosts, only to later find out there was some water, diesel, sugar, dirt, or some other non-combustable fuel contamination.

 

[SnoFalls]

Just a thought ... that vintage 4.3 is notorious for having problems with the CPI injection "spider".

Pull the upper plenum and look to see if there are clean spots where fuel is squirting out from the injector assembly or poppets. Pretty simple to confirm or rule out it as an issue ...

 

[Hip]

It's the same. Fireing order is 165432 so number 4 TDC exhaust is the same as number 1 TDC compression. I'm fairly sure you still need the light on number 1.
It's up to you but I wouldn't take the front apart with the compression you have the chain can't be that bad.
You didn't put the distributor in with the rotor pointing at number 4 TDC exhaust stroke did you? 180 out?

no i havent pulled the dist yet without a valid timing mark i cant even find out if anything has slipped or jumped a tooth. when i pull the harmonic balancer i will look closely at it to see if it is damaged in any way.

i need to know where base time is before i pull the distributer.

im kinda thinking the base time is ok chain and sprocket wise but i need to verify where the mark should be, then i can pull the dist and swap in a known runner to see if the issues are there.

 

[Binder]

no i havent pulled the dist yet without a valid timing mark i cant even find out if anything has slipped or jumped a tooth. when i pull the harmonic balancer i will look closely at it to see if it is damaged in any way.

i need to know where base time is before i pull the distributer.

im kinda thinking the base time is ok chain and sprocket wise but i need to verify where the mark should be, then i can pull the dist and swap in a known runner to see if the issues are there.

After you varify nothing is broken.............
Line up the mark on the damper with the mark on the cover then see what piston is TDC compression stroke. If it aligns then time that cylinder. If things don't line up then the damper is slipped so choose a cylinder you want to time, typically number one. Use a screw in piston stop and turn it over by hand til it stops. Mark the damper. Now turn it over the other way and mark the damper. Center between these two marks is TDC of that cylinder. Use this new mark to time this cylinder and you know you are good regardless of what any book says.:awesomework:
Now given this.......You know if the engine runs crappy for any reason where it can't maintain a constant RPM at idle once you plug the timing bypass wire back in the timing will jump all over as the timing curve is per RPM. In other words your problem could still be non ignition related....Like maybe bad fuel?

 

[Binder]

BTW when you changed out the TPS you did set it right?

 

[Hip]

the harmonic balancer has spun, explains the disappearing timing mark. fawker feels tight and no visible damage but when held up to another one its definately way off.

ok so tomorrow ill start over.

Rick no i didnt set the tps when a swapped it out? ill look that up. thanks.

swapped out the dist though while apart so i can visually see everything.

set it like the book on number 4 tdc.on compression stroke, timing marks at 6 and 12. dist points ar no 4. roll everything around till timing marks line up with mark on pulley, gear marks at 12 and 12, and dist points to no 1 on compression stroke.:awesomework:

 

[Hip]

all back together and it still runs like crap.

it will drive down the road but at less than WOT it pops and backfires some?

i have swapped out all smog control items.

so when the CPI unit starts going what are the symptoms?

or have i been chasing bad gas for a week as someone suggested? ARCO and the tank is full...

 

[crash2]

If the tps is adjustable (not all of them are) its not going to produce the symptoms you are explaining. There is only a variance of like .3volts adjustment if it is.

 

[zukkev]

all back together and it still runs like crap.

it will drive down the road but at less than WOT it pops and backfires some?

i have swapped out all smog control items.

so when the CPI unit starts going what are the symptoms?

or have i been chasing bad gas for a week as someone suggested? ARCO and the tank is full...

IS the firing order correct??? ask Maverick26 about this!:redneck:

 

[SnoFalls]

so when the CPI unit starts going what are the symptoms?

backfires, "rich" smelling exhaust, stumbling during acceleration ...

Checkout http://www.blazerforum.com/forum/showthread.php?t=1374
note in post 4 the pictures with the "clean side" ... that's a leaking FPR. If the other side was "clean" then it would be a leaking CPI.

In your first post you mentioned that the fuel pressure was 60psi (good) and "does not drop drastically at all" ... it should hold steady for quite a while if the FPR isn't leaking.

 

[Binder]

If the tps is adjustable (not all of them are) its not going to produce the symptoms you are explaining. There is only a variance of like .3volts adjustment if it is.

I know Mike that you're familliar with what it would run like with an out of adjustment TPS but why would he not adjust it? Hip has told us what it's running like but it's hard to get the exact message across in writing so maybe.........On some models the computer can learn where idle is and some can't. That's why the ones that can't, have an adjustable TPS.....
Just saying make sure what work is done is correct so it doesn't cause more issues.

 

[dove'd85]

the tps on this blazer is not adjustable

 

[crash2]

I know Mike that you're familliar with what it would run like with an out of adjustment TPS but why would he not adjust it? Hip has told us what it's running like but it's hard to get the exact message across in writing so maybe.........On some models the computer can learn where idle is and some can't. That's why the ones that can't, have an adjustable TPS.....
Just saying make sure what work is done is correct so it doesn't cause more issues.

I don't think I recall ever seeing one adjustable on the cpi and Scpi motors unlike the tbi versions.

 

[Hip]

backfires, "rich" smelling exhaust, stumbling during acceleration ...

Checkout http://www.blazerforum.com/forum/showthread.php?t=1374
note in post 4 the pictures with the "clean side" ... that's a leaking FPR. If the other side was "clean" then it would be a leaking CPI.

In your first post you mentioned that the fuel pressure was 60psi (good) and "does not drop drastically at all" ... it should hold steady for quite a while if the FPR isn't leaking.

sounds like my issues exactly. thanks for the link...

 

[Maverick26]

IS the firing order correct??? ask Maverick26 about this!:redneck:

:redneck: Thanks Kevin again for skoolin me :redneck: It runs good now.

Hip: I have an injector cluster that works if you are interested in trying that... I hear they can get plugged up with old gas if the motor sits for a year or 2. Let me know.