Dead cylinders 95 LT1
Thread Starter
Cruising
Joined: Dec 2010
Posts: 12
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From: McKenna WA
Dead cylinders 95 LT1
Need help,I was sitting at a red light when I felt my engine start to run with a miss , this was about two weeks after changing my optispark,plugs , wires and had my injectors cleaned and flow tested the number #3 and # 8 cylinders appear to have quit working. I pulled the plug wire to test which cylinders were dead, then did the same with injector wires. Both revealed that #3 & #8 were not working. Anyone had this happen ?
Last edited by jimlynn1; May 27, 2011 at 07:00 PM.
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Need help,I was sitting at a red light when I felt my engine start to run with a miss , this was about two weeks after changing my optispark,plugs , wires and had my injectors cleaned and flow tested the number #3 and # 8 cylinders appear to have quit working. I pulled the plug wire to test which cylinders were dead, then did the same with injector wires. Both revealed that #3 & #8 were not working. Anyone had this happen ?
Thread Starter
Cruising
Joined: Dec 2010
Posts: 12
Likes: 0
From: McKenna WA
Yes I pulled each plug wire and tested each one with an extra spark plug to make sure it was firing . I am thinking the signal from the PCM to injectors is failing or shorted. I don't know if the PCM can be checked for that ?
Safety Car
Joined: Apr 2011
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Also look at the harness bundle that is the trunk line for the inj harness sections....its mounted along the firewall behind the block. Wiggle that and see if ANYTHING changes. I've found that the splices from that trunk line will rot and break away from the main wire. They were never well protected and certainly NOT sealed by more than black tape from the factory. Very half-assed IMHO. My left bank inj went stupid with mixed signals, misfires that moved from 3 to 5 to 7....hard to figure out, but when I did, I had to chop out that inj harness section and resolder in new wire and I used new plugs for everything. Runs perfectly now. Right bank had no signs of deterioration or rot...strange.
Just idle the engine and wiggle that area of the harness, play with the throttle as you do it and see if that makes any difference. It's a place to start if the noid lite says all are getting a signal. next step is to see if they're getting the right signal. Check the wire inserted into the inj plugs also. The most important grounds (5) are spliced into this section of harness near the oil filter.
Just idle the engine and wiggle that area of the harness, play with the throttle as you do it and see if that makes any difference. It's a place to start if the noid lite says all are getting a signal. next step is to see if they're getting the right signal. Check the wire inserted into the inj plugs also. The most important grounds (5) are spliced into this section of harness near the oil filter.
Safety Car
Joined: Jun 2006
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From: FL
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Le Mans Master
Joined: Jan 2006
Posts: 5,621
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From: Orlando FL
The injectors should check 12 ohms. But this does not mean the injector valve is really working. If you did verify spark to the cylinders, then I would definitely check the drive from the PCM with the noid light as recommended. (The PCM grounds the low side of the injector to fire it.)
If you find no drive to the injectors, I would then start checking connections to the injector and the PCM connector.
You can also check to see if there is 12 volts on the pins of the injector. If there is no voltage the injector will not operate. Compair the good ones to the questionable ones. Don't need to run engine, just have key to ON.
If you find no drive to the injectors, I would then start checking connections to the injector and the PCM connector.
You can also check to see if there is 12 volts on the pins of the injector. If there is no voltage the injector will not operate. Compair the good ones to the questionable ones. Don't need to run engine, just have key to ON.
Thread Starter
Cruising
Joined: Dec 2010
Posts: 12
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From: McKenna WA
Miss firing 95 LT1
Guys I found the problem with my LT1 .The number 8 and number 3 spark plug wire were both split and arcing out . I replaced the BWD wires with MSD 8.5 mm super conductors , what a difference that made . Had to pull the supercharger off to replace the wires and thats not fun. Thanks
for the help.
for the help.
Race Director
Joined: Sep 2001
Posts: 14,682
Likes: 753
From: NEwhere Ohio
Guys I found the problem with my LT1 .The number 8 and number 3 spark plug wire were both split and arcing out . I replaced the BWD wires with MSD 8.5 mm super conductors , what a difference that made . Had to pull the supercharger off to replace the wires and thats not fun. Thanks
for the help.
for the help.
I had brand new MSD 8.5mm wires that spark arc'd (the optispark to igntion coil wire) against the water pump housing.
It was occurring at the junction of the boot/wire on the optispark side.
I had to wrap the junction in electrical tape to keep this from occurring.
Ive had much better luck with Taylor wires.
Le Mans Master
Joined: Aug 2004
Posts: 5,141
Likes: 7
From: Metairie Louisiana
When I first put my MSD 8.5's in I had problems with them arching to the headers. One boot eventual burned through and had to be replaced. Try some zipties for now to pull them away from anything and make sure they are not touching anywhere.
Thread Starter
Cruising
Joined: Dec 2010
Posts: 12
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From: McKenna WA
MSD Vs Taylor wires
Yes I've been told that MSD someimes have problems with arching . I will wait for Taylor wires next time . I have both banks in a Nomex tube and heat wrap where they come around the first header tube to keep the heat away.
