4.3 TBI cranking issues

[R Q]

Pretty sure I have a compression tester you can use. (I wonder where that is?) (But I'm sure I can find it) I am totally slammed with a time sensitive project and wife is out of town for the the weekend or I would come help. I'll be here from noon tomorrow and most all of the weekend

 

[a_kelley]

Well it wasn’t that easy. Counted the wires 3x and am positive that it is timed correctly 612345.

You meant to say 165432, I hope.

It’s a 91, pre Vortec. I have adjustable rockers. They way I’ve always done them is to tighten them down so you can barely spin the pushrod then another half turn. There is little to no movement in them at all. So too tight or too loose?

that may yield too tight, simply because you're putting pressure on the pushrod/lifter when it won't turn, but that's subject to what you define "barely turn" as. Compression test will show if they are too tight. Also if they are too loose and you tighten them down and don't wait 20-30 minutes the lifters can hold the valves open if they are fully pumped up... That caught me off guard on a 4.0 I was having trouble with valves sealing and thought it got shaved too much, so I backed off the rockers, had compression, tightened and lost compression until it sat with pressure on the lifter to bleed it down.. Also would definitely be too tight if you set it that way with the lifters not pumped up. But you'd know if it was hanging open - it'd turn somewhat freely.

 

[paulevans76]

I've had to play with my rockers on my 2.8 and 3.4 engines (60* GM v6, but goes together and runs pretty much the same) many times. The rocker adjustment is crucial,too tight would not let it run worth a turd if at all. All the manuals for these (60*) motors give directions that will overtighten the the rockers, so we've all been through the dance multiple times.

I'm not sure on the torque spec for the 4.3, but for ours its essentially take it down to zero lash and then a half-3/4 turn - but that is dependent on the thread pitch so I'd look into what the spec is on the 4.3. In the case of our motors, you have to rotate the assembly to one position to adjust one half of the rockers, and another position to adjust the other half.

 

[upnover]

Few questions.
How old is the fuel?
What kinda fuel pressure do you have? If you have more than it can handle, the excess fuel should be pushed back to the tank.
I am posting a vid, this is how I used to set the valve lash when I built an engine, had the heads off, or replaced a cam. If you have put in new lifters, same deal. but you may need to readjust once the lifters get pumped up.
Have you checked the spark plug gap?
If and when you check the compression, and it's bad. Could be as simple as dirty valves. "If" you can get it running, and it's rough, and everything else is right, you can pour a small stream of water down the TB, and it may clean off the valves and get it running better. (I have done this many times in past years and it has worked wonders. You do have to idle it up and don't pour so much down the engine that it stalls it. If this is one of the issues, you will have a lot of crud come out the exhaust.
Check again, that you have it wired correctly(spark plug wires)
You mentioned another fuel pump that was pushing too much fuel down the engine. Check your oil, smell it, it may have a good bit of gas in it!
After you have tried to crank it, pull a plug, make sure it's not like you dipped it in gas
If you have it wired right, If you are in time, If there is nothing causing the valves not to close, if you have spark at each plug, there is no reason for it not to fire.

 

[justjeepin86]

You need to actually test the fuel pressure with a gage. You have the return going to the tank, correct? A higher volume pump should have just sent more fuel back to the tank. How long has this thing sat now, a couple years? If you have the plug wires, spark, timing, and fuel pressure, my vote is bad injectors. I haven't looked at your build thread in a while, so forgive me if I've missed something.

 

[YJJPWrangler]

Injectors look good. I have a solid cone of fuel being sprayed by both of them. I'm borrowing a friends compression tester tomorrow to check compression. It will also let me know once and for all if I am at TDC on the compression stroke for cylinder 1. Fuel is new. @justjeepin86 , return is going to the tank. Last time I tried cranking it, it felt like it immediately flooded. Pulled spark plugs and they were soaked with fuel.

 

[a_kelley]

Pulled spark plugs and they were soaked with fuel.

if you unplug the injectors, do they still deliver fuel? You can try to manually pulse them to see if they are hanging open after they are supposed to close too.

 

[YJJPWrangler]

Yes, injectors unplugged will not deliver fuel. I relashed the rocker arms per the manual. I borrowed a bore snake camera and a compression tester from a friend. Compression tester yielded no compression at all at cylinder 1. I used the camera to look into the cylinder and noticed that the intake valve was not closing completely. I snaked a couple more cylinders and noticed the same thing. I got this motor second hand from a member on this board and the motor had set for a couple years. On initial teardown, I noticed a decent amount of oil sitting in the cylinders. I suspect that I have a some carbon buildup on some of the valves and its preventing them from closing completely. Decided to bite the bullet and pulled the heads. Got both of them pulled off. This is one of the heads. Driver side, cylinder 1 is the far left.

I did notice a lot of gunk buildup in the water jackets of the heads and I found some metal shavings floating around as well. Cylinder walls aren't scored so I don't know exactly where they are coming from. Next step is to pull the valves and take a look at them and see what I find.

 

[R Q]

I have your cure on an engine stand in my shop...PM sent.