OK guys this car is driving me nut.!!!!its a 5.0 with a carb on it..it has new cam bearings mains and rod bearings..after doing all this 4 and 6 would not fire and had low compression in them 2 holes i pulled the motor apart and put new rings in put it all back together same **** 4 and 6 will not fire..ok it has to be valves send the head to the shop and he tells me i have 1 bent valve and 2 that are leaking he tells me that he fixed them and he re surfaced the head.. i put it back together and same **** 4 and 6 will not fire it has new cap rotor plugs and wires no matter what i do they will not fire what it going on??

 

What about the lifters and cam lobes for those cylinders? Compression must be no less than 80psi.

 

won't fire or no compression ???? BIG difference !!

 

going to do another compression test tomorrow as for the cam lobes and lifters all looked well putting it back together i did run it today with the valve cover off all looks well its all moving right

 

well it did have low compression in hole 4 and 6 thats why i had the valve work done but its still not firing i will do another compression check

 

So is it a firing problem or not ???

do u get spark on those plugs or no ?????

I guess if u ran it , its ok now ???

what i am saying, u can leave the damn pistons out and it should fire if the ignition is working correct !!!

did u check for spark ???

 

i have spark to the plug

 

so what is it doing ?? running on 6 ?? or shaking ,,,is the timing right ,,,is the camsensor ( distributer modul ) ok ???

 

yes its only running on 6 no change if you pull them 2 spark plug wires off if its running.. it has no computer in it so cant be camsensore timeing is right if it was a distributer modul it would be doing it on all 8 not just 2

 

sounds like the spark on those 2 is just not strong enuff...do u have a spark tester ?????

if u see spark, does not nessecarily (stupid word..lol) mean that it is fine !!!

 

ok guys this is what i got today..

i only did one head the other i know to be ok.. hole 2 dry test was 160psi hole 2 wet test was 165psi..hole 4 dry test 140psi hole 4 wet test 160psi..hole 6 dry test 140psi.. hole 4 wet test 145.. hole 7 dry test 150psi hole 7 wet test 160psi...

just to recap its all new rod bearings mains cam bearings...new rings....after putting it together i had low compression in holes 4 and 6 it was like hole 4 was 95psi and hole 6 120psi..took the head in was told i had a bent valve and a few leaking got that fixed put it all back together and it still seams like 4 and 6 are not firing it has spark and fuel.if i pull the wires off the cap as its running 4 and 6 have no change at all..

wires are new cap is new rotor is new the only thing that is not new is the coil i did not change this because if its not working all hole would not be firing?? i need help I'm lost my bud how is a mechanic is lost

 

did u try..and i am going way out of wack..lol, to change the sparkplugs from 2 other cyl to those ??? i mean, something is just not ading up. U have compr. u have spark..maybe weak..but u have spark..i would also change 2 wires ..just to make shure.

there is realy nothing else that can cause this !!!!
Wires and plugs !!!!.....or a bad cap..very unlikeley tho !!!!

 

yes i have moved plugs around and wires its always the same

 

Then change the coil and the cap !!! other then that i can not think of anything .

got to be something simple and stupid for shure.

 

Hello vangogh4560!!

When you pull a plug on #4 or #6, is it covered with fuel??

Did something accidently get stuffed into your intake tract to those two cylinders, during your rebuild?



P.S. Is everything aligned properly, ie cam/crank/dizzy?

 

just took my carb off and i see nothing in the way..

are 4 and 6 covered in fuel no they look normal

I'm sure its all aligned properly.. could something in the distributor be doing this?? just keeping 4 and 6 from not firing? its just the hole side by side thing that is bugging me OTHER THAN IT NOT FIRING

 

Hello vangogh4560!!

Correct me if I'm wrong, but usually, the spark plugs that are not firing due to lack of spark are covered with fuel that's not getting burned........so, you already said it was getting spark, and you checked to see if there was any blockage internally in the intake, and that was okay........how do you know that it's not firing on those two cylinders?



P.S. How did the valves on that cylinder head get bent in the first place?

 

Have you checked your firing order? 18436572

 

i know that #4 and 6 are not firing from pulling the wires off the cap you can hear a change in how the motor runs ..its a old school trick.. also with a heat gun my header tubes are over 500d on 2 and 8.. 4 and 6 are like 350d..1 3 5 7 are all over 500D i think i just had a few burnt valves the shop told me i had one that was bent BUT it did not look like the head had a new valve in it..at this point I'm thinking my edelbrock, manifold my have a crack in it this is the only thing i can think of what do you think maybe a crack in the runners for them 2 holes?

 

yes its right

 

Hello vangogh4560!!

I know the old school trick, however, you did say that the plugs are not soaked with fuel, which leads me to that they are sparking to burn off the fuel.........you do have a unique problem, it seems!!

What do the #4 and #6 plugs look like when they are pulled?

Black sooty, black wet, white glazed, tan/gray ???

Replace the two plugs with two new ones of the proper type/heat rating, run the motor, remove the two plugs, and tell me what they look like!!



P.S. Have you checked the two offending plugs for a broken/cracked insulator? You did say that you have spark to the plug, but I don't see you saying that the plugs are sparking!!



Non sparking plugs with fuel running to them will smell "gassy" once removed!!

 

its been raining for the last 2 days so i have not got to look at it

 

If your intake would be cracked, u would have a bunch of fuel in the oil !!!!
if u would have a cracked head u more likeley have water in the oil...but i dont think it would cause the cyl not to fire !

Its hard to tell over the web..lol

definatly is a absured problem u are having...and i think its actually something simple we dont think about !!! MOST OF THE TIME IT IS

 

Hello DAREDEVIL 1!!

Something like spark plug gap............

 

i have checked that its not that

what sucks is i work for a mechanics shop have every tool none to man have the brain of 4 others and all data and Identifix and still dont know whats going on

 

I GOT IT !!!!!!!!!!!!!


It is a V6 and your trying to fool us , look a V6 can never be a V8 its a fact ,,,,live with it ...


maybe not, still dont know !

 

If this is a true statement then apply it to this one:
Pulling a spark plug wire from a working cylinder will cause a change in the engine, if it doesn't the cylinder is dead.

 

Hello vangogh4560!!

Try this, on the two cylinders that are not firing, switch the plug wires at the spark plug (ie) plug wire from #4 on plug #6, and plug wire from #6 on plug #4 !!

Maybe they are firing, but at the wrong time........!!!





Is there a possibility that you have something stuck in the cylinder head, preventing fuel flow to those two plugs???

Misalinged intake manifold gasket???

 

Hello vangogh4560!!

Any luck???

 

Is it possible you put a 4.3L distributor in it instead of the v8 one? I know you would think it would only have 6 post up top but you could have put a v8 cap on it.

 

im thinking it is something with the distributor as well

 

Sorry to say that, but this would be halarious !!!!!!!

 

Hello All!!

I hate to burst the laugh bubble, but isn't the cap a different size??!!





It would be funny though!!

 

mmhhh, u shure ??????

 

Hello DAREDEVIL 1!!

Yeah, I'm pretty sure, I checked out the pictures of the two caps in question on the AC Delco Parts site, and I'm pretty sure the caps are different sizes!!

I also checked out the rotor that's used for the both engines, and the rotors are different, and different sizes also!!

Why use a different rotor.........because the cap is a different size??!!

The two engines that I compared are (small cap) 5.0L 1987 Code F, and 2.8L 1987 Code S!!



Without really having the two caps side by side, it's still a judgement call, and I'm not saying that I'm fully convinced either way, but I'd have to go with them being different sizes!!

I do think this requires some more RE

 

To be honest, i think the caps from a MSD 6 versus 8 cyl...bolt right up since there distributer has the same diameter and bolt/claw locations.

But i am also not 100% shure on this, i will check in the shop tomorrow.

 

Vangogh, What was it???
Was reading through this post like a script and the writer stopped at the climax. Please post update, inquiring minds want to know.

 

Hello DAREDEVIL 1!!

The caps are different, the 5.0L small cap has the two screws in line with two locating pins, and the 2.8L has the two screws slightly off line from the two mounting pins!!

The ignition control module is the same, and if you check out how that mounts, you'll see that caps are a different size!!

NAPA online!!

Check out the pictures, it's quite evident in the pictures!!

 

Hello jac113!!

I hate when that happens............right on the edge and BAM........no update!!!



Your right though, inquiring minds want to know!!



Especially since I've suggested a whole bunch of things, I'd like to know if any worked!!!

 

Hello DAREDEVIL 1!!

Did you check out those dizzy caps???

Did you hear anything from the OP as to the solution???

 

NO, sorry..was to bussy with other stuff....mhhhh

and no , did not hear a damn thing !!!! WOULD LOVE TO KNOW WHAT IT IS/WAS !!!!!!

 

Hello vangogh4560!!!

Calling vangogh4560, you've left all of us with a cliffhanger ending, what was it?????