78ford250

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  #1  
Old 04-23-08, 01:45 PM
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78ford250

Rebuilt the motor to my 78 3/4 ton 4x4 Ford last year and replaced the 2brl carb a short while ago. Was running great, but a few months ago, as I was merging onto the freeway, the drive shaft fell out.... from the front!
Repaired that, however, now, after that repair, whether related to the drive shaft incident or not, the truck does not have any power to accelerate past 30mph. Have had it in the shop 3mos now and they are baffled. Checked compression, checked fuel filter and pump, checked distributor and carb, checked lifters and timing chain (considered overrevving). It has become a mystery and they are about to just put it back together and return it to me. ANY IDEAS, anyone???????????? We're at wits end!
PS- idles fine!!!!!
 

Last edited by battletruck; 04-23-08 at 02:31 PM. Reason: added comment
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  #2  
Old 04-23-08, 03:29 PM
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Did that driveshaft by any chance hit your exhaust somewhere and collapse a pipe, choking off your exhaust? Try disconnecting exhaust up near manifold & see how it accelerates after that. Don't forget to check for a seized emergency brake cable that got hit, and is holding brakes on too. Does the engine rev out like it should, or just won't rev up?
 
  #3  
Old 04-23-08, 04:58 PM
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Actually, forgot to include that....taking off the exhaust was the first thing we did before taking it to the shop! It's not that the engine revs way up and there's no acceleration; the rpms kinda match the speed, but it just never kicks in to get going. Doesn't sputter and choke, really. Have noticed a rare backfire a couple times over the last year, tho, since it was rebuilt.
 
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Old 04-23-08, 06:27 PM
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Does it sound like the engine is under heavy load when trying to take off normally? Will it rev up as normal when in neutral?
 
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Old 04-23-08, 08:22 PM
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just to be sure try useing a old spark plug knock the center out and tap for a long bolt. then screw it into the no. 1 cyl and useing a breakover bar slowly turn the engine to tdc and then run the bolt down to the piston to stop the rotation. Mark your harmonic ballancer for tdc, then turn the engine backward to tdc and mark the ballancer and make sure that tdc is where it is supposed to be on the ballancer. I have seen on older vehicles the rubber go bad and the ballancer rotate so that when you set time you are not correct. if the marks do not bracket true TDC so that it is centered replace the harmonic balancer.
remember Murphy was an optimist
 
  #6  
Old 04-23-08, 09:33 PM
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It got to the point where they thought the timing chain had jumped a tooth 22 degrees- found the harmonic balancer WAS shifted, but the timing was okay ?????? Revs up normally at neutral, doesn't over rev trying to accelerate or seem to be under a heavy load- just won't get out of its own way.
 
  #7  
Old 04-24-08, 03:37 AM
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When the driveshaft fell out it might have damaged the rear end causing resistance.
 
  #8  
Old 04-24-08, 06:43 AM
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would it be to much to ask have you checked for brake drag (front and rear) or bearings in the diff being bad? I assume it is not full time 4wheel drive. My dad had a 76 dodge full time and it was a real dog.
Murphy was a optimist
 
  #9  
Old 04-24-08, 03:31 PM
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I'm pretty sure that while cking the exhaust system they cked all the rear "nuts & bolts" that may have gotten tweaked, but I'll make sure- gotta ck everywhere if it's not looking like an engine issue- thanks for all the ideas!
 
  #10  
Old 04-24-08, 03:41 PM
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Do your truck do have dual fuel tank ?? if so check the port fitting sometime you will suprised to find debries in there.

and also check the fuel line from the tank to the engine lift pump to make sure there is no hidden kink line and btw yes ford did have crossover fuel line on the 4X4 models check that under the front crossmember along with PS line.


if not the issue try get a vaccum gauge and hook up to one of the vaccum port [ unregulated port is the best] and when the engine at idle it should pull 18+ inch of vaccum and watch it and with idleing mode it should hold steady but if fall down or read low you have issue with either timming or exhaust one of the two.

Merci,Marc
 
  #11  
Old 04-25-08, 01:27 PM
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These may be a few specific areas they haven't looked, so I'll pass it along- I know when they pulled the line at the motor, the fuel was pumping out......exhaust & timing seem to have been eliminated, unless the shop is really missing something-
thanks for your posting!
 
  #12  
Old 04-27-08, 11:51 PM
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shop called Friday and they put the truck back together....actually, driving home, thought it wasn't doing all so badly, in fact, ran pretty well. Got in later, and before a mile had passed, it was starting all over again. The truck goes back in Monday-
 
  #13  
Old 04-29-08, 02:59 PM
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Took the truck back Monday...... they called an hour later, said they'd wrapped a plug wire poorly, and when I put it into park at home, it pulled off the wire!!!! So far so good, knock on wood, but still don't really know what was done. They put it all back together, ck'd the timing, the carb and the plugs again.......and so far running well-! All we can think is that they missed a small something taking it apart, and when they had to put it back together, it all got resolved???? Who knows!!!! Thanks for trying to help!
 
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