95 4.3 back fire - S-10 Forum
 
LinkBack Thread Tools
post #1 of 8 Old 04-19-2017, 04:01 PM Thread Starter
Registered User
 
Join Date: Jun 2013
Age: 65
Posts: 34

User is: 954.3 is offline
95 4.3 back fire

I have a 95 blazer with a 4.3.
It ran fine but had a tapping sound. I found a rocker arm that wasn't lubing very good so I pulled it out and cleaned it, the oil hole was almost plugged. So I pulled all of them off and cleaned all the rockers and push rods, none of the others were plugged.
I put them all back together and tightened the lifter adjustment nut down until it bottomed out, run out of threads.

Is that what you do with positive stop adjustments?
I've never adjusted positive stop before, but from what I've been told that sounds like how to adjust them.

Anyway, now it won't start back up. It turns over fine but won't start.
It will backfire loud out the intake once in a while, but that's all. Doesn't even act like it is trying to fire off other than the backfire.

I hope someone can help me figure this out.

I do appreciate the help very much.
Thank you all

954.3 is offline  
Sponsored Links
Advertisement
 
post #2 of 8 Old 04-19-2017, 04:47 PM
Registered User
 
Join Date: May 2008
Posts: 434

User is: ala_frosty is offline
Re: 95 4.3 back fire

Triple-check check that you've got the spark plug wires all back on their correct positions and that the coil is firmly connected to the distributor properly.
ala_frosty is offline  
post #3 of 8 Old 04-19-2017, 05:11 PM Thread Starter
Registered User
 
Join Date: Jun 2013
Age: 65
Posts: 34

User is: 954.3 is offline
Re: 95 4.3 back fire

Thanks ala_frosty,
I never did unhook the distributor wires from the plugs or the distributor.
There still the same as they were when it ran fine before taking the rocker arms off. Other than the ticking it ran fine before I took the rocker arms off and cleaned them. It's really got me puzzled.

Am I adjusting the valves right?
I just tightened the nut down untill it bottomed out in the threads. Positive stop head. It's got the studs that screw in and have a bolt head for a socket down on the head.
954.3 is offline  
 
post #4 of 8 Old 04-20-2017, 12:56 AM
Registered User
 
oldeerslayer's Avatar
 
Join Date: Jan 2015
Location: SW Wisconsin
Posts: 683

User is: oldeerslayer is online now
Re: 95 4.3 back fire

Is it possible that some of the push rods weren't centered correctly on the lifters when you put the rockers back on? I'd pull them and make sure none are bent.
The more I think about this, the more I think Frosty is on the right track. Did you do both sides and not disconnect anything electrical?
oldeerslayer is online now  
post #5 of 8 Old 04-20-2017, 01:08 AM
Registered User
 
AWD V8's Avatar
 
Join Date: Jan 2009
Location: Surrey, BC, Canada
Age: 63
Posts: 6,765

User is: AWD V8 is offline
Re: 95 4.3 back fire

I don't know what year the engines changed rocker arm design, what do your rockers look like?

These you tighten right down, like a bolt.





These must be tightened a certain amount while the crankshaft is in the correct position. These are easy to mess up the adjustment.



Popping through the throttle body means an intake valve is not closing (bad adjustment), or that a cylinder is firing while an intake valve is open (Wrong firing order).

It is possible that a push rod wasn't centered in the lifter, that could bend the push rod, possibly bend a valve from opening it too far, but usually the push rod just slips into the lifter when the engine rotates and then the adjustment is too loose.

Check the firing order first, that's easy.
Let us know what style of rocker arms you have.
Then a compression check or pull the valve covers off, your choice. A compression test will tell you if you have a bent valve. Pulling the rockers again to check the valve assembly/adjustment.

Usually backfiring is simply a bad valve adjustment or firing order. Usually no harm done.

I'm not old, I'm ripe - My LS Jeep project
AWD V8 is offline  
post #6 of 8 Old 04-20-2017, 09:26 PM Thread Starter
Registered User
 
Join Date: Jun 2013
Age: 65
Posts: 34

User is: 954.3 is offline
Re: 95 4.3 back fire

Thanks everyone for all the help.

I think I know what is wrong, but it will be a couple days before I get time to try it. I'll let you know how it goes.

What I think is wrong is that the heads I have are not bottom stoppers. They are screw in studs but don't have the ledge on the stud for the rocker to bottom out on. So I got to readjust the lifters and try it.

They have the lifters like the bottom picture in AWD V8's post above, but I guess some of the 4.3's have that type of lifter with a ledge on the stud for bottom stop and some don't have the bottom stop, so you have to set them by doing the tdc approach.
But neither one had the lifters in the top picture in AWD V8's pictures above.

I found it out by looking at another 4.3 I have and it has the same looking rocker but has the ledge for the bottom stop.
The nut just tightens down until it stops plus 20lbs.

I'll let you know what I find out .

Thanks again.
954.3 is offline  
post #7 of 8 Old 04-21-2017, 07:58 AM
Registered User
 
oldeerslayer's Avatar
 
Join Date: Jan 2015
Location: SW Wisconsin
Posts: 683

User is: oldeerslayer is online now
Re: 95 4.3 back fire

Quote:
Originally Posted by 954.3 View Post

They have the lifters like the bottom picture in AWD V8's post above, but I guess some of the 4.3's have that type of lifter with a ledge on the stud for bottom stop and some don't have the bottom stop, so you have to set them by doing the tdc approach.
But neither one had the lifters in the top picture in AWD V8's pictures above.
If you have the lifters in the bottom picture that AWD posted, those are the venerable 1955-1995 plain old Chevy rocker arms. You have to do the traditional take out the slack +1 turn on each rocker using the TDC method. Personnaly I prefer to do them one cylinder at a time by adjusting one valve when it's opposite valve is open.
If you bottomed all them out thinking they were the newer style shown in the top picture, you need to pull and look at each pushrod to be sure they didn't get bent.
oldeerslayer is online now  
post #8 of 8 Old 04-21-2017, 11:41 AM Thread Starter
Registered User
 
Join Date: Jun 2013
Age: 65
Posts: 34

User is: 954.3 is offline
Re: 95 4.3 back fire

Thanks for the help oldeerslayer,
I pulled the push rods and they were all bent. so I got to replace all of them and hope it didn't bend any valves. It doesn't look like it watching them go up and down, but we'll see how it runs.

Thanks again everyone for the help. I'll get back with you in a couple days to let you know if that was the problem.
954.3 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the S-10 Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.


Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome