351M down to half power and missing
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Laughing Gas
Joined: Apr 2001
Posts: 1,191
Likes: 4
From: West Union, OH USA
351M down to half power and missing
my grandpa got in his 78 F-150 with a 351M and tried to start it. it backfired and died. it wouldn't start after that so i put a new fuel pump on it and would start but runs bad. it will barely pull itself. so whats wrong. the same thing happened to his 81 f-100 with a 300-6 after i put a new fuel pump on it. except it never ran bad before and it ran good for a day or two.
Senior User
Joined: Sep 2001
Posts: 118
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From: Bothell USA
351M down to half power and missing
[updated:LAST EDITED ON 02-Jul-02 AT 04:40 PM (EST)]If you haven't already replace all the fuel filters just a thoght but it's happend to me before. Also make sure all of the plug wires are connected. Good luck!
1979 F-150 4x4 351M
2001 Ranger 2.5L
1979 F-150 4x4 351M
2001 Ranger 2.5L
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Laughing Gas
Joined: Apr 2001
Posts: 1,191
Likes: 4
From: West Union, OH USA
351M down to half power and missing
i was thinking it was something with the timing too. like maybe it jumped time or something. it doesn't really matter i was just curious. we've got other trucks to use around the farm so it will probably just sit, but the 81 is the one my grandpa drives and he wouldn't let me tear it apart until i knew what was wrong with it.
Posting Guru
Joined: Jun 1999
Posts: 2,415
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From: Comox Valley, Canada
351M down to half power and missing
Just a thought but how about bad fuel???? Have seen that before, affected each vehicle different for some reason 
Some ran rough, some wouldnt run and some never missed a beat.
Sparky
Some ran rough, some wouldnt run and some never missed a beat.Sparky
New User
Joined: Feb 2002
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351M down to half power and missing
Try checking the timing. It sounds to me like it jumped a couple of teeth. To do that without running the engine, turn the engine over by hand until the 10 deg. BTDC timing mark on the bottom pulley is in line with the timing pointer on the block. Take the distributor cap off and see if the rotor button is pointing towards the #1 plug wire on the dis. cap. This is the wire going to the front sparkplug on the passenger side. If the rotor button is in the opposite direction, turn the engine over one complete turn and check the rottor button's location again. If it is not pointing to the #1 wire. It has jumped its timing. This is an easy and accurate way to check it.
I hope this is helpfull. Let us know how you make out. GOOD LUCK
79 F150 4X4 351m
I hope this is helpfull. Let us know how you make out. GOOD LUCK
79 F150 4X4 351m
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Laughing Gas
Joined: Apr 2001
Posts: 1,191
Likes: 4
From: West Union, OH USA
351M down to half power and missing
well, the 81 is fixed. just tightened up the fuel pump and rerouted the fuel line. for the 78 i'll try to check the timing and see what happens, thanks
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Laughing Gas
Joined: Apr 2001
Posts: 1,191
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From: West Union, OH USA
351M down to half power and missing
[updated:LAST EDITED ON 05-Jul-02 AT 07:57 PM (EST)]ALMOST STOCK, where are the marks on the harmonic balancer to tell when its a TDC? is it a notch or what?
and i checked the oil and its overfilled. that could do something bad too but i dont know what
and i checked the oil and its overfilled. that could do something bad too but i dont know what
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Joined: Feb 2002
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351M down to half power and missing
Fordguy76
The marks on the balancer are engraved ( ATDC 30,20,10,0,10,20,30 BTDC ). ATDC is after top dead center, 0 is top dead center, BTDC is before top dead center. The marks are engraved on the outer circumfrence of the balancer. Some times they are hard to see. If you use a cleaner and steel wool it may help. Sorry it took so long for my reply but I was on vacation. Let me know if I can be of any help in the future.
Good Luck.
The marks on the balancer are engraved ( ATDC 30,20,10,0,10,20,30 BTDC ). ATDC is after top dead center, 0 is top dead center, BTDC is before top dead center. The marks are engraved on the outer circumfrence of the balancer. Some times they are hard to see. If you use a cleaner and steel wool it may help. Sorry it took so long for my reply but I was on vacation. Let me know if I can be of any help in the future.
Good Luck.
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Laughing Gas
Joined: Apr 2001
Posts: 1,191
Likes: 4
From: West Union, OH USA
351M down to half power and missing
thanks man. thats okay about it taking so long, im in no hurry. i have other stuff to play with and havent even looked at that truck in awhile. i'll try to see what i can do and give you an update
Cargo Master
Joined: Apr 2001
Posts: 2,364
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From: Eustis FL
351M down to half power and missing
Oil overfilled? Does it smell like gas? Could be that the fuel pump ruptured, pumping fuel into the crankcase. That could cause a combustion cycle from the underside of the pistons, making it run like garbage!
Change the oil now that you changed the pump. That might do it.
My 71 Torino GT had the internally ruptured pump and the oil got higher everytime I checked it!
Mark
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=5362&.jpg
Ford started it; Ford will finish it!
Change the oil now that you changed the pump. That might do it.
My 71 Torino GT had the internally ruptured pump and the oil got higher everytime I checked it!
Mark
https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=5362&.jpg
Ford started it; Ford will finish it!
Freshman User
Joined: Jun 2002
Posts: 45
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From: USA
351M down to half power and missing
How long has it sat? I have a 79, that sat ofr some 5 years without being driven, it not only had bad gas(still woould run, but like garbage) but the carb was terrible. Water everywhere. Once I rebuilt the carb, and put good gas in, runs like a charm. This was only like 60 days ago tops! I also had to adjust the timing, I just did it by ear, then drove it, the retimed it, and so on. I made it some 500 hundred miles a month after on a camping trip, over 2 moutain passes, and it did awesome.
Just some thoughts!
Timothy Taylor
1979 F 150 Custom
64K all original 302
Just some thoughts!
Timothy Taylor
1979 F 150 Custom
64K all original 302
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