I did the valve lash job on my new 3.4 today and have three cylinders that won't fire. It's not due to plugs/wires/distributor/rotor as they're all brand new. Also, the injectors (2.8)are less than a year old. I've checked the wiring schematic and the connectors are correct. I'm getting spark to the plugs and the compression passes on all 6 cylinders

Is it possible I did something incorrectly with the valve lash? If so, I'm snatching the intake off (for the 3rd time in 2 days) tomorrow.. Please get back to me ASAP!!!

BTW, I already tried to "search" something up on the subject but found nothing...

Yes, if you set the valves too tight it would keep the cylinder from having compression, the valve would always be open. Likely what you did is compressed the lifter as you were tightening down the adjuster, then bottomed it out and turned it another half turn to set it. If you look at the threads sticking above the nut on the rocker you should have about the same amount showing on all of them. You likely have then way too tight.

well, he said he got good compression all around, so I'd expect the lashing went fine. more likely just got igntion wires mixed up. how do you know 3 arent firing? could it maybe be 3 arent getting gas? the injectors fire in banks of 3, maybe its just a loose connector for the injectors.

My car is in the shop as I type this getting the collasped lifter and cam replaced due to over tightening the valve lash. When the #5 exhaust lifter collasped, it was not allowing the valve to open so I was getting compression but it never ran right and it flattened out the cam lobe. As was pointed out to me after the fact, never tighten the rockers down any further than 1/2 to 3/4 turn after zero lash. I can tell you from my own experience that this is an expensive mistake if this happens.

------------------

Vini, Vidi, Velcro.
I came, I saw, I stuck around.
Latest addition to the addiction is an 84 SE 4cyl Auto.
AIM-jaxpac257

I didn't do the "turn and a half" recommended by the manual. It's just 3/4 turn or less. # 3,5, and 6 are firing at both the coil and the plug. Compression is (3) 132 (5) 147 (6) 145. It occurred to me that these #s may be a bit low but cyls 1,2 and 4 range between 140 and 153 w/o oil squirts in the plug holes.

Injectors are a heck of a lot easier to get to than valves. Maybe there's a short in the wires furthest from the connector. It's curious that the 3 injectors closest to the connector end of the harness are just fine.

Since injectors fire in banks of threes and all three dead cylinders are at the far left end of the fuel rail (although attached to different banks),it's been suggested that I pull the upper plenum and fuel rail, disconnect all but the suspect injectors, pull the coil wire and crank the car testing the injectors one at a time. If they spray, my problem is most likely the valve job....if they don't I've got a wiring screw-up.

Any other suggestions, guys?

[This message has been edited by Doni Hagan (edited 04-25-2003).]

I agree that, if compression is good, you don't have valve lash problems.

Easiest things to check at this point, are the fuses in the box under the dash. There are 2 fuses, think labelled "F INJ-1" & "F INJ-2," or some such.

Each fuse provides power to 3 injectors. Maybe a momentary short, blew one, in which case, I'd absolutely re-fuse . BTW, sorry if you already tried this.

I guess I would think that if the engine was running prior to the valve lash adjustment, then three cylinders went dead, they were probably not adjusted correctly. I suppose it is possible that if you took off the injector harness a wire could have come loose.
I adjust the valves to zero lash by moving the pushrod up and down untill it stops, then tighten 3/4 turn. If you use the twist the pushrod untill you can't twist anymore, you take the chance of screwing them down so tight you have no lift, because the oil could have drained out of the lifter. This is especially true on new builds or replacing lifters with new ones....Paul

Okay, I just pulled the fuel rail, disconnected the "good" injectors and tested the "bad" ones......they're spraying as suspected so it's not the fuses (which I checked at first / my father used to say always go for the easy fix), the harness or the injectors themselves. My next step is to re-do the valve lash on all 3 cyls. If that doesn't do it, I'll look at the lifters.

Here are my next questions...

(1) Considering that I didn't run the engine for longer than a few minutes (checking firing order, etc.)and the damn thing ran fine before I got my greasy little hands on it, it's unlikely I damaged the cam itself. However, could I have permanently damaged the lifters in the process and should I consider replacing them with new ones or just pulling the questionable ones and re-priming them with oil?

(2) I was considering rebuilding my 2.8 at one time and have a full set of new lifters & pushrods at hand. Will those lifters work on the 3.4?

(3) How can you determine if a particular lifter is collapsed?

Again, thanks for the input and PLEASE get back to me ASAP! After a full week of this, HERCULEAN frustration is beginning to set in! All because I thought I didn't have time to rebuild the old block!!

[This message has been edited by Doni Hagan (edited 04-25-2003).]

[This message has been edited by Doni Hagan (edited 04-25-2003).]

Thread Hijack!

I have two problems that might be related to valve lash. I replaced the head gasket. I used the tighten till you can't twist then back off method to adjust the lash. Now it runs lower on oil pressure than it did before I worked on it, and it seems to have an exhaust leak (due to noice). Any chance this is valve lash related or should I look at the typical causes for these problems?

quote Originally posted by Doni Hagan: Okay, I just pulled the fuel rail, disconnected the "good" injectors and tested the "bad" ones......they're spraying as suspected so it's not the fuses (which I checked at first / my father used to say always go for the easy fix), the harness or the injectors themselves. My next step is to re-do the valve lash on all 3 cyls. If that doesn't do it, I'll look at the lifters. Here are my next questions... (1) Considering that I didn't run the engine for longer than a few minutes (checking firing order, etc.)and the damn thing ran fine before I got my greasy little hands on it, it's unlikely I damaged the cam itself. However, could I have permanently damaged the lifters in the process and should I consider replacing them with new ones or just pulling the questionable ones and re-priming them with oil? (2) I was considering rebuilding my 2.8 at one time and have a full set of new lifters & pushrods at hand. Will those lifters work on the 3.4? (3) How can you determine if a particular lifter is collapsed? Again, thanks for the input and PLEASE get back to me ASAP! After a full week of this, HERCULEAN frustration is beginning to set in! All because I thought I didn't have time to rebuild the old block!! [This message has been edited by Doni Hagan (edited 04-25-2003).] [This message has been edited by Doni Hagan (edited 04-25-2003).]

1) I would replace them.
2) Call your local parts store (someone who knows what they are doing) and see if the lifters for the 2.8 and 3.4 are the same part numbers (unless someone else knows).
3) Don't know, but why take the chance, sounds like you are running out of patience. BTW, put assembly lube on the new lifters, and look at the cam lobes on the cylinders in question for any scoring etc....Paul

Guys,

Thanks for the input. Really. I've got a concert tonight so I get to take out my frustrations on a drumset for a few hours. By tomorrow morning, I'll be ready to tear into this bugger again.

Paul, we've never spoken before....Thanks.

Doni.

AARRRGGG!!!

I redid the valve lash. I still have dead cylinders BUT THEY'RE DIFFERENT ONES!!!!

I've got a couple of new questions now...

(1) As I didn't change anything in the valve train (lifters/valves/cam/pushrods), what was the GM factory setting for the valves (not the rebuild manuals, THE FACTORY!)

(2) When I'm told to make sure the "lifter is compressed," what exactly does that mean? I was told to adjust the rocker's ball head until the pushrod was esentially extending slightly insde the lifter itself.

(3) Are the exhaust rods and intake rods different lengths on the 2.8 vs. the 3.4? Are they different lengths within the SAME engine?

These may seem like really dumb questions but I'm catching hell trying to resolve this "dead cylinder" problem and was to make sure I'm not overlooking anything at all. BTW, the last time I checked compression on all 6 cylinders, the numbers had leveled off to an average of 157.

Thanks.

Oh yeah, just in case anyone's interested....2.8 lifters and 3.4 lifters are the same part (according to Jegs, Summit and GM.)

[This message has been edited by Doni Hagan (edited 04-29-2003).]

To adjust the rockers you tighten the nut until the pushrod touches the lifter. As soon as the rocker will not "rattle" you are there. I think what you are doing is colapsing the lifter as you are tightening the rocker and not realizing it, it is easy to do. After you are there then tighten the rocker another half turn, this will push the bore in on the lifter. The manual says a turn and a half, almost all mechanics feel that is too far. You are making sure the cam is on the low side on the lobe, correct?

The intake and the exaust pushrods are the same on the 2.8

quote Originally posted by Paul Prince: How low on oil pressure? Do you have any cylinders missing? Is it very low on power? I suppose with the pushrods not filled with oil, or very little, you are not getting much upper valve train oiling. The exhaust leak? I don't see how it could be related, you may have a misaligned crossover pipe connection, or have cracked something during the teardown.....Paul

It is running about one or two notches above red line when idling and hot. When cold, it won't go below 40 when idling. When at speed and hot, it runs about 40 or so. No cylinders missing and the power seems to be as good as before. It is possible I cracked something, how do I test that without teardown?

quote Originally posted by Steve Normington: It is running about one or two notches above red line when idling and hot. When cold, it won't go below 40 when idling. When at speed and hot, it runs about 40 or so. No cylinders missing and the power seems to be as good as before. It is possible I cracked something, how do I test that without teardown?

Thread a mechanical oil pressure gauge in where the electric oil pressure sender is. Check the oil pressure on the mechanical gauge. If it is still low, then it could be contaminated oil (coolant, gasoline) excessive main bearing clearance, oil pump. You could also try a straight oil like SAE 30. If it is a bearing, or oil pump, it will probably just be a matter of time.....Paul

quote Originally posted by Doni Hagan: AARRRGGG!!! I redid the valve lash. I still have dead cylinders BUT THEY'RE DIFFERENT ONES!!!! I've got a couple of new questions now... (1) As I didn't change anything in the valve train (lifters/valves/cam/pushrods), what was the GM factory setting for the valves (not the rebuild manuals, THE FACTORY!) (2) When I'm told to make sure the "lifter is compressed," what exactly does that mean? I was told to adjust the rocker's ball head until the pushrod was esentially extending slightly insde the lifter itself. (3) Are the exhaust rods and intake rods different lengths on the 2.8 vs. the 3.4? Are they different lengths within the SAME engine? These may seem like really dumb questions but I'm catching hell trying to resolve this "dead cylinder" problem and was to make sure I'm not overlooking anything at all. BTW, the last time I checked compression on all 6 cylinders, the numbers had leveled off to an average of 157. Thanks. Oh yeah, just in case anyone's interested....2.8 lifters and 3.4 lifters are the same part (according to Jegs, Summit and GM.) [This message has been edited by Doni Hagan (edited 04-29-2003).]

1> not sure of the "factory" setting for the valve lash, but the books say 1-1/2 turn after zero lash. everyone agrees a turn and a half is to much, and they mean one half turn.
2> the lifters have a little spirng loaded piston that the rod sets on. you'll see 2 little wires holding in from popping out the top. if its collapsed, it wont be against the two little wires, and/or be real easy to push in.
3> the entire valve train (cam, lifters, rods, rockers, valves, etc.) is the same for the 2.8, 3.1, & 3.4

when you say cylinders arent firing, how do you know which ones arent firing? even with a horrible lash job, collapsed lifters, wrecked cam, etc., they'll still fire. with a over lash, they might backfire thru the intake or exhaust, but they'll still fire, and with under lash, they'll rattle & tick, but still fire. check the bottom of the lifters on the offending cyl's and make sure its nice smooth & flat. if theres any bowl shape to it, the lifters & cam are wrecked (see my thread...i'm wrecking cams....)

edit - anyways, I still think its an ignition or fuel problem, not a lashing problem. by turning the crank by wrench and watching the lifter/rockers go you can see if its working right.

[This message has been edited by Pyrthian (edited 04-30-2003).]

quote Originally posted by Pyrthian: 1> not sure of the "factory" setting for the valve lash, but the books say 1-1/2 turn after zero lash. everyone agrees a turn and a half is to much, and they mean one half turn. 2> the lifters have a little spirng loaded piston that the rod sets on. you'll see 2 little wires holding in from popping out the top. if its collapsed, it wont be against the two little wires, and/or be real easy to push in. 3> the entire valve train (cam, lifters, rods, rockers, valves, etc.) is the same for the 2.8, 3.1, & 3.4 when you say cylinders arent firing, how do you know which ones arent firing? even with a horrible lash job, collapsed lifters, wrecked cam, etc., they'll still fire. with a over lash, they might backfire thru the intake or exhaust, but they'll still fire, and with under lash, they'll rattle & tick, but still fire. check the bottom of the lifters on the offending cyl's and make sure its nice smooth & flat. if theres any bowl shape to it, the lifters & cam are wrecked (see my thread...i'm wrecking cams....) edit - anyways, I still think its an ignition or fuel problem, not a lashing problem. by turning the crank by wrench and watching the lifter/rockers go you can see if its working right. [This message has been edited by Pyrthian (edited 04-30-2003).]

I guess my point was he said he adjusted the valves and then 3 cylinders wouldn't fire, but they were firing before. And if the intake valve is not opening at all, it will not fire. I would think you would have to screw them babys down pretty tight.
I had an intake valve pushrod break (the tip) a few years ago and the cylinder was dead........Paul

yeah, I see what ya mean. If the intake is not opening at all, then its not tightened at all. that would be noisy as hell. overtightened it would never close all the way. I was wondering how he could tell which cyl wasnt firing?

I determined which cylinders weren't firing by getting the engine to run (a feat in itself) and disconnecting plug wires from the distributor until the engine either sputtered or cut off. If you pull a wire and absolutely NOTHIN' happens to the way the car is running, there's a problem there. At one point, the engine was running on 2 cylinders!

I'm gonna tear into it again and inspect the cam lobes. I already checked the lifter feet and not only were they not concaved but were as smooth as a baby's behind.

when you adjust your lifters you have to make sure that they are on the lowest part of the cam lobe. You can see this when the pair of lifters are both down in their bores, this is when both valves are shut and the correct position to adjust them. Crane Cams has a good technical article on adjusting the valve lash on their website. WWW.cranecams.com you just have to look for it.

I checked the "Crane" site....Excellent resource!!
I know a lot more about lifters than I did before and hopefully the info will come in handy adjusting this beast!

Thanks.

quote Originally posted by avengador1: Crane Cams has a good technical article on adjusting the valve lash on their website. WWW.cranecams.com you just have to look for it.

I looked and Looked... Where on the website is it?? sorry for the stupid question...

Try this smoooooth. http://www.cranecams.com/master/adjustvt.htm