Ok, so Ive been trying different things to troubleshoot my low WOT RPM/power and backfire issues....I replaced the plugs, cap, rotor, fuel water filter and carb filter. I did NOT replace the wires because the store I went to did not have them in stock and they checked out ok. I tested each one with a multimeter. I dont remember exactly what it was but somewhere around 9-11K ohms on each one. I had also checked timing and attempted to check fuel pressure but didn't have the right fittings for the pressure gauge I rented today. My original thread is here discussing this along with some other issues.
http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/4-3-backfires-above-2300-rpm-just-put-new-exhaust-manifold-fuel-issue-643928.html
Anyway....today I had the engine running on muffs and even tho I had previously checked the plug wires I decided on a whim to yank one while the engine was running...TO my surprise the idle speed did not change much at all. I began to systematically check each wire. What I found was any of the wires on the starboard side of the engine (2,4,6) could be pulled off the distributor cap with little to no effect on idle speed. To be sure I SWAPPED WIRES from one side to the other..(changed both plug and dist. ends of course to maintain proper firing order) I could actually pull all three off the starboard side and it will still idle. The RPM seemed to increase but it still ran.
If I pull a single wire off the port side. (1,3 or 5) The idle drops and runs rough. (er?) If I pull another one the engine dies. Its like the engine is only running off the port side.
I took an old plug and plugged into 4 and then 6 and held it to a ground and saw a spark....It did look rather weak but so did the other side (cylinder 3) and it was one of the old plugs. Bad coil maybe but wont explain why it only seems to produce power on 1, 3 and 5?
What could be the issue with this? Cant be normal? Seems like that whole side of the engine is not grounded but that cant be possible? There is a different brand of exhaust manifold, riser than the port side but I cant see how that would have anything to do with it.
Could this engine even run on only 3 cylinders? That would certainly cause loss of power/backfire and makes me think its something really simple.
Thanks in advance for any help and ideas!
http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/4-3-backfires-above-2300-rpm-just-put-new-exhaust-manifold-fuel-issue-643928.html
Anyway....today I had the engine running on muffs and even tho I had previously checked the plug wires I decided on a whim to yank one while the engine was running...TO my surprise the idle speed did not change much at all. I began to systematically check each wire. What I found was any of the wires on the starboard side of the engine (2,4,6) could be pulled off the distributor cap with little to no effect on idle speed. To be sure I SWAPPED WIRES from one side to the other..(changed both plug and dist. ends of course to maintain proper firing order) I could actually pull all three off the starboard side and it will still idle. The RPM seemed to increase but it still ran.
If I pull a single wire off the port side. (1,3 or 5) The idle drops and runs rough. (er?) If I pull another one the engine dies. Its like the engine is only running off the port side.
I took an old plug and plugged into 4 and then 6 and held it to a ground and saw a spark....It did look rather weak but so did the other side (cylinder 3) and it was one of the old plugs. Bad coil maybe but wont explain why it only seems to produce power on 1, 3 and 5?
What could be the issue with this? Cant be normal? Seems like that whole side of the engine is not grounded but that cant be possible? There is a different brand of exhaust manifold, riser than the port side but I cant see how that would have anything to do with it.
Could this engine even run on only 3 cylinders? That would certainly cause loss of power/backfire and makes me think its something really simple.
Thanks in advance for any help and ideas!
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