Not running on all 8 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1984Silverado4x4 · 11-10-2007, 08:16 PM

Can anyone come up with any ideas why my 305 wouldnt run on all 8 cyl with new plugs wires cap rotor and good compression?

No the wires are NOT crossed. They are all where they should be

xtreme80 · 11-10-2007, 08:44 PM

I'm going to assume you already checked for spark, so I won't go into that.

Second thing would be to pull the plugs and re-gap them. They can get pretty tempermental if they aren't gapped correctly.

Next I would check to see that your dist. cap is put on correctly and sits flush on the distributor. I've had one incident where the cap didnt seat correctly and wouldn't make contact with one or two of the brass terminals as the rotor spun.

If you checked all that and still have nothing, go through each wire and find out which one doesn't have spark. If you don't have a tool to do this, take a rubber handled screwdriver and stick it in the spark plug boot, hold the handle, then get the remaining edge of the screwdriver very close to a ground. Crank the engine and you should see the spark jump. If no spark, that one is your problem. Then you've probably narrowed it down to either a bad wire or a bad cap.

Hope this helps.

spudz · 11-10-2007, 08:50 PM

Did you check for spark on all 8?? If you have spark on most but not 8, odds are you need a new cap.. First step is to find out what cyl/s ain't firring. Then go from there.. Once you find out what cyl isn't firing, Ohm the plug wire or swap with a known good one.. Just cause its new doesn't mean its good. Then if that is OK, swap plugs with a known good one.. If that doesn't do it.. check compression.. if thats good... THEN.......you need to make sure your valves are adjusted and push rods ain't bent....THEN its real bad... if all that is good.... you may need a new camshaft........hope this helps...

Thumpin455 · 11-10-2007, 09:24 PM

Plug wires should have less than 18 ohms resistance in them. If all your plugs are firing then its time to check a couple other things. On some of the early ECM controlled vehicles, even up to 90, there was a problem with the reluctor wheel in the distributor. Its the gold colored one way under the rotor in the bottom of the distributor. They would crack and cause an intermittent, or constant tough to find miss. The year I have seen the most of that is 87, for some reason they crack often.

Barring that, check the compression in each cylinder and make sure the rockers are all moving a like amount. You could have a flat lobe on the cam or a bent pushrod. If it isnt electrical, start looking at mechanical sources.

spudz · 11-10-2007, 09:36 PM

[QUOTE=Thumpin455;2440362]Plug wires should have less than 18 ohms resistance in them. QUOTE]

Ya know I never remember that... What I usually do if I can't remember, is just compare it to the others.. if one is way off, then he's the bad guy.. And thats cool info on the relucter wheel.. never knew.. I grew up on the fuel injected side of things.. so dizzys and carbs is something I NEVER have in the dealership.. All of the info I have on them is self taught.

1984Silverado4x4 · 11-11-2007, 10:13 AM

Quote:

Originally Posted by xtreme80

Second thing would be to pull the plugs and re-gap them. They can get pretty tempermental if they aren't gapped correctly.
Hope this helps.

Wow. Gapping the plugs made a huge difference that I noticed as soon as I started driving it again. The gap wasnt even that far off either.

xtreme80 · 11-11-2007, 12:53 PM

Quote:

Originally Posted by 1984Silverado4x4

Wow. Gapping the plugs made a huge difference that I noticed as soon as I started driving it again. The gap wasnt even that far off either.

Yeah these engines can get pretty picky with plugs. Your engine will run BEST on Delco plugs. You're gonna pay twice as much, but they're worth it. The Delco plugs made the difference in me passing emissions or not.

Thumpin455 · 11-11-2007, 01:24 PM

Agree on the AC Delco.. Other than NGK I dont run anything else. NGK plugs are in my race car and the LS1, everything else gets AC

Malo83 · 11-11-2007, 03:09 PM

Agree also on the AC plugs, I run the AC Rapidfires and also replaced the stock HEI coil with a Power Coil from HYPERTECH, this really improved the performance of the little small block

www.hypertech.com

11-10-2007, 08:16 PM	#1
1984Silverado4x4 Registered User Join Date: Jul 2007 Location: Mount Horeb WI Posts: 179	Not running on all 8 Can anyone come up with any ideas why my 305 wouldnt run on all 8 cyl with new plugs wires cap rotor and good compression? No the wires are NOT crossed. They are all where they should be __________________ Its no disgrace being poor. Its just inconvenient. Last edited by 1984Silverado4x4; 11-10-2007 at 08:17 PM.

11-10-2007, 08:44 PM	#2
xtreme80 Wishin' I had more money! Join Date: Feb 2007 Location: Eugene, OR Posts: 1,242	Re: Not running on all 8 I'm going to assume you already checked for spark, so I won't go into that. Second thing would be to pull the plugs and re-gap them. They can get pretty tempermental if they aren't gapped correctly. Next I would check to see that your dist. cap is put on correctly and sits flush on the distributor. I've had one incident where the cap didnt seat correctly and wouldn't make contact with one or two of the brass terminals as the rotor spun. If you checked all that and still have nothing, go through each wire and find out which one doesn't have spark. If you don't have a tool to do this, take a rubber handled screwdriver and stick it in the spark plug boot, hold the handle, then get the remaining edge of the screwdriver very close to a ground. Crank the engine and you should see the spark jump. If no spark, that one is your problem. Then you've probably narrowed it down to either a bad wire or a bad cap. Hope this helps.

11-10-2007, 08:50 PM	#3
spudz Registered User Join Date: Oct 2005 Location: Branchville SC Posts: 1,647	Re: Not running on all 8 Did you check for spark on all 8?? If you have spark on most but not 8, odds are you need a new cap.. First step is to find out what cyl/s ain't firring. Then go from there.. Once you find out what cyl isn't firing, Ohm the plug wire or swap with a known good one.. Just cause its new doesn't mean its good. Then if that is OK, swap plugs with a known good one.. If that doesn't do it.. check compression.. if thats good... THEN.......you need to make sure your valves are adjusted and push rods ain't bent....THEN its real bad... if all that is good.... you may need a new camshaft........hope this helps... __________________ 2004 z71, 96 z71 on 38s, 88 Chevy k5 blazer, 4in lift. 84 swb project, 82 SWB project , 84 chevy 4x4 lwb project, 88 Jimmy beater/highschool ride. 79 c30. 99 tahoe 4x4 project. and a bunch of parts trucks.. Last edited by spudz; 11-10-2007 at 09:37 PM.

11-10-2007, 09:24 PM	#4
Thumpin455 My truck is an alcoholic Join Date: Nov 2007 Location: Marquette Mi Posts: 303	Re: Not running on all 8 Plug wires should have less than 18 ohms resistance in them. If all your plugs are firing then its time to check a couple other things. On some of the early ECM controlled vehicles, even up to 90, there was a problem with the reluctor wheel in the distributor. Its the gold colored one way under the rotor in the bottom of the distributor. They would crack and cause an intermittent, or constant tough to find miss. The year I have seen the most of that is 87, for some reason they crack often. Barring that, check the compression in each cylinder and make sure the rockers are all moving a like amount. You could have a flat lobe on the cam or a bent pushrod. If it isnt electrical, start looking at mechanical sources. __________________ Too much stuff, too many projects to list everything. my 454 urged 76 swb beater

11-10-2007, 09:36 PM	#5
spudz Registered User Join Date: Oct 2005 Location: Branchville SC Posts: 1,647	Re: Not running on all 8 [QUOTE=Thumpin455;2440362]Plug wires should have less than 18 ohms resistance in them. QUOTE] Ya know I never remember that... What I usually do if I can't remember, is just compare it to the others.. if one is way off, then he's the bad guy.. And thats cool info on the relucter wheel.. never knew.. I grew up on the fuel injected side of things.. so dizzys and carbs is something I NEVER have in the dealership.. All of the info I have on them is self taught. __________________ 2004 z71, 96 z71 on 38s, 88 Chevy k5 blazer, 4in lift. 84 swb project, 82 SWB project , 84 chevy 4x4 lwb project, 88 Jimmy beater/highschool ride. 79 c30. 99 tahoe 4x4 project. and a bunch of parts trucks..

11-11-2007, 01:24 PM	#8
Thumpin455 My truck is an alcoholic Join Date: Nov 2007 Location: Marquette Mi Posts: 303	Re: Not running on all 8 Agree on the AC Delco.. Other than NGK I dont run anything else. NGK plugs are in my race car and the LS1, everything else gets AC __________________ Too much stuff, too many projects to list everything. my 454 urged 76 swb beater

11-11-2007, 03:09 PM	#9
Malo83 Cruzzzn' Vet Join Date: Jan 2005 Location: Porterville,Ca. Posts: 1,918	Re: Not running on all 8 Agree also on the AC plugs, I run the AC Rapidfires and also replaced the stock HEI coil with a Power Coil from HYPERTECH, this really improved the performance of the little small block www.hypertech.com



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