85 f150
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85 f150
i have an 85 ford f150 that starts and idles fine but hesitates under load. i have rebuilt the carb, put on a new fuel pump and fuel filter, and new plugs. but when i put on a new distributor cap, rotor cap and plug wires it got drasticly worse. plug wires are correct. any ideas would be great!
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From: Northeast, OK
I've seen several harmonic balancers that have slipped. The rubber gets old and let's go and the outer ring slips and the timing marks are then wrong. I would suggest pulling the plugs, holding your thumb over #1 plug hole, and turn the engine over with a breaker bar. When you are coming up on #1 TDC you will feel pressure on your thumb. Stop there and insert a soda straw long enough it won't fall in. Continue cranking until the straw quits coming out and you are at TDC. Check the timing mark. If it isn't very close your balancer has slipped and needs to be replaced.
FTE Legend
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From: Northeast, OK
Most harmonic balances that have slipped look good. It is just that the marks or off that is the indicator. Having said that, I had one recently where the outer ring was cocked.
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FTE Legend
Joined: Jul 2010
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From: Northeast, OK
I would check it, for sure, by finding TDC. Pull the plugs, put your thumb over #1, and when you fell pressure stop. Put a straw in and slowly turn until the straw quits coming out. Check where the timing mark is.
Lead Driver
Joined: Jul 2009
Posts: 6,477
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From: Sheffield, AL
The timing of an original 1985 4.9L engine is controlled by the computer. Did you disconnect the spout wire to check the timing?
Regarding the harmonic balancer, listen to the previous posters. They know their stuff!
With the engine stopped, using chalk or a crayon, draw a line straight across the face of the balancer and then drive [if possible]. When you look at the balancer again, if the line is broken, it will indicate that the outer ring has shifted.
Looking at your 1st post made me think of this: since you state that after replacing distributer cap, rotor and plug wire, it ran "drastically worse", why not put each old part back on [one at a time] and see what is causing the worsening?
Regarding the harmonic balancer, listen to the previous posters. They know their stuff!
With the engine stopped, using chalk or a crayon, draw a line straight across the face of the balancer and then drive [if possible]. When you look at the balancer again, if the line is broken, it will indicate that the outer ring has shifted.
Looking at your 1st post made me think of this: since you state that after replacing distributer cap, rotor and plug wire, it ran "drastically worse", why not put each old part back on [one at a time] and see what is causing the worsening?
Last edited by 1986F150six; Jun 27, 2013 at 02:23 PM. Reason: Last paragraph.
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