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Old 10-26-2007, 11:28 AM   #1
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Default timing problems with 90 f150, 4.9

i recently purchased a 90 fi50 4.9 standard w/od. i noticed the problem when after the truck was warmed up on the freeway it would not handle any load, if going up a hill it would chatter and bog down until on the down side. i also noticed when hot it was hard to start, kicking back on the starter. i assumed the timing was too advanced so that when the computer tried to advance under load it was too fast. when i tried to set the timing i found the harmonic balancer has moved and the marks are off. so i put it at tdc on the compression stroke put a paint mark on the balancer and set it by that with a light. after that ran great but it still wont start when hot, like the timing is too fast, i retarded the timing and it will start but it runs crappy again.

any suggestions
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Old 10-26-2007, 01:26 PM   #2
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It would be interesting to understand how the harmonic balancer moved. It's been a long time, but I thought it was keyed?

Did you remove the SPOUT connector when setting the timing?

Hmm, or is the SPOUT connector there? Could be a problem for normal running if it's missing.
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Old 10-26-2007, 02:28 PM   #3
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i like you thought they harmonic balancer could not move, but when the piston is at tdc on the compression stroke the mark is almost 1/2 turn away. yes i did remove the spout connector
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Old 10-26-2007, 02:33 PM   #4
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Not sure how yours is set up, but is there any chance that the crankshaft pulley bolts onto the balancer, and that sometime in the past it was bolted on - eh, I guess 1/2 turn off?

I recall my Jeep had a similar problem, but the crank pulley was forced/wedged on over the balancer with a rubber strip joining the two - the rubber strip degraded and had allowed the pulley to slip in relation to the balancer - now that was a real joy.
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Old 10-26-2007, 02:42 PM   #5
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i'll have to look when i get home. Someone else told me he thought the balancers were pressed on over rubber. i guess i will soon find out. if this is the case, do i just try to set the timing by ear? how close do i have to get? if im close will the computer correct it?
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Old 10-26-2007, 03:11 PM   #6
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Depends on how good your ear is, I guess. Some guys can nail it, I've tried it and was nowhere close.

From my perspective, this is something where a couple of degrees can make a world of difference.

For example, how confident are you that the centerline of your hash mark is on the money and not two degrees one way or the other?

On the other hand, for the motor to be running this badly, if it's a timing related issue, suspect that it's more than just a couple of degrees off.

The computer needs to know what the 'baseline' timing is for its lookup tables and calculations. However far off the base timing is will relate to how far off the computer will be on its initial calculations.

It may be able to learn somewhat through the knock sensor and other feedback, but it's always going to be working in an offset mode that would be lost on a PCM reset or battery disconnection.

If you're confident that you've marked TDC accurately, don't know why that wouldn't be good enough. Otherwise, maybe junkyard another balancer?

*Edit* have you checked for any fault codes? While this timing thing is certainly an issue to resolve, wondering if there's another player contributing to the problem?
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Last edited by wde3477; 10-26-2007 at 03:15 PM. Reason: added another thought
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Old 10-27-2007, 03:20 PM   #7
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my check engine light has not come on so i dont thinki can get a fault code.

i went back to the basics, reset my timing with a light and the prev mark i hade made. set it to between 8 and 9 degrees before tdc, manual calls for 10 i was trying to be on the safe side in case my mark is off slightly. runs great now, but once again won't start when it'shot. i am going o try tochange the pos battery cable and the cable from the solenoid to starter, i'm hping my problem is a bad connection.

it seems backwards to me but is there any reason if i had a bad connection it would be harder to start hot? oh and i checked the battery it is not low tested 12+ volts
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Old 10-27-2007, 09:27 PM   #8
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you need to replace that balancer if it has slipped. I dont know about your particular motor but most older for v-8s will slip the outer ring throwing off timing marks. also that is the balance weight for the motor. are you having any vibration issues ? also not wanting to start when hot can be a sign that the base timing is still a tad hi. you definately do not want that balancer to seperate totaly. it could tear stuff up.
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Old 10-27-2007, 09:36 PM   #9
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Quote:
Originally Posted by TEDA View Post
i recently purchased a 90 fi50 4.9 standard w/od. i noticed the problem when after the truck was warmed up on the freeway it would not handle any load, if going up a hill it would chatter and bog down until on the down side. i also noticed when hot it was hard to start, kicking back on the starter. i assumed the timing was too advanced so that when the computer tried to advance under load it was too fast. when i tried to set the timing i found the harmonic balancer has moved and the marks are off. so i put it at tdc on the compression stroke put a paint mark on the balancer and set it by that with a light. after that ran great but it still wont start when hot, like the timing is too fast, i retarded the timing and it will start but it runs crappy again.

any suggestions
Well,if you have doubts to whether the outer ring has slipped on the inner ring of the harmonic balancer you could remove the #1 spark plug and make a piston stop.This is something that you would use to go down and contact the piston as it comes up to TDC.Make your mark on the balancer and then rotate the engine in the opposite direction until the piston stops again.The centerline between the two marks will be actual TDC.This is kind of the last resort,but you would rule out the possibility of slippage.I would check compression first.
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Old 10-27-2007, 09:47 PM   #10
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For your starting problem hot - does it turn over slower, or does it turn over 'unevenly'???

For slower, you might be onto something with the power / ground connection.

For unevenly, suggest there is something with the motor itself - timing, etc.
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