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| Ford PCM 351 nightmare continues..... |
| Author |
Message |
    
Larry P Smith
Member
Username: graphix
Post Number: 6
Registered: 08-2009
| | Posted on Sunday, August 09, 2009 - 09:24 pm: | 
|
I am having a problem with this motor. The engine runs like a champ up to about 1600 RPMs then labors and bucks, spits and hesitates at the 1600 RPM mark. I have totally rebuilt my holley 650 carb, totally drained the gas tank and wiped clean, replaced all filters and even hooked to a auxillary fuel tank in case there was a problem in the tank.After that I hooked up a electric fuel pump direct to the carb with a auxillary fuel tank. Checked for ignition "leaks" after dark. I Checked compression and fuel pump pressure. I've isolated the exhaust in case there was an obstruction. I pulled the distributor to check for end play and inspected the centrifical advance, which was all OK. New cap, rotor points, condenser, coil and ballast resistor, plug wires and plugs The results are always the same. It seems that the misfires above 1400 RPMs are on the right bank of cylinders. The plug tips are black and the new cap has black marks inside on the contacts and the rotor tip is black as well as if it has been arcing. I put a spark tester on one of the right bank cylinders and rechecked firing order. At 1200 RPMs I had nice hot blue spark at 1800 rpms the spark was erratic and somewhat weak. Next I went and bought a second new coil andchanged the ballast resistor. I acts to me as if it is starving for fuel, but I have about 7 pounds of fuel pressure at the pump. I put a vacuum gauge on it and the vacuum is normal at idle and drops like a rock as I try and accelerate. I advanced the timing manually as I watched the vacuum gauge to see if it would improve, but it does not. I am having a problem with this motor. The engine runs like a champ up to about 1600 RPMs then labors and bucks, spits and hesitates at the 1600 RPM mark. I have totally rebuilt my holley 650 carb, totally drained the gas tank and wiped clean, replaced all filters and even hooked to a auxillary fuel tank in case there was a problem in the tank.After that I hooked up a electric fuel pump direct to the carb with a auxillary fuel tank. Checked for ignition "leaks" after dark. I Checked compression and fuel pump pressure. I've isolated the exhaust in case there was an obstruction. I pulled the distributor to check for end play and inspected the centrifical advance, which was all OK. New cap, rotor points, condenser, coil and ballast resistor, plug wires and plugs The results are always the same. It seems that the misfires above 1400 RPMs are on the right bank of cylinders. The plug tips are black and the new cap has black marks inside on the contacts and the rotor tip is black as well as if it has been arcing. I put a spark tester on one of the right bank cylinders and rechecked firing order. At 1200 RPMs I had nice hot blue spark at 1800 rpms the spark was erratic and somewhat weak. Next I went and bought a second new coil andchanged the ballast resistor. I acts to me as if it is starving for fuel, but I have about 7 pounds of fuel pressure at the pump. I put a vacuum gauge on it and the vacuum is normal at idle and drops like a rock as I try and accelerate. I advanced the timing manually as I watched the vacuum gauge to see if it would improve, but it does not.This leads me to believe that the valves or lifters are at fault, but it doesn't backfire or pop as it would if that were the case. I am at my wits end and would greatly appreciate any help I recieve. Thanks in advance...... |
jeffrey smith
New member
Username: jeffrey1678
Post Number: 3
Registered: 07-2009
| | Posted on Monday, August 10, 2009 - 05:50 am: |
|
i wish i could help you but i am haveing the same promblem.mine goes up to 2600 rpm.i have put everything on it and it runs great up to that point and i have just about to give up on it and sell the boat.nobody can help me.i took it to a boat machanic and thay could not figure it out. |
makomark
Senior Member
Username: makomark
Post Number: 1119
Registered: 09-2008
| | Posted on Monday, August 10, 2009 - 11:33 am: |
|
Larry:
Check out this link - see if scenario 4 fits your case with the 'drops like a rock' reading.
What did the compression test show - any difference wet or dry? |
Michael Fry
Member
Username: mfry
Post Number: 12
Registered: 07-2009
| | Posted on Monday, August 10, 2009 - 04:32 pm: |
|
can't see the link |
makomark
Senior Member
Username: makomark
Post Number: 1125
Registered: 09-2008
| | Posted on Monday, August 10, 2009 - 05:54 pm: |
|
www.secondchancegarage.com/public/186.cfm
sorry about that. |
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