psychic mechanic wanted....
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More Turbo
Joined: Nov 2004
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From: colorado
psychic mechanic wanted....
My 79 F100 that I have lent to a friend is acting possessed - I haven't looked at it yet, so all I have to go on is his description of the problem. So with very little info and no truck to look at- I'm making this appeal to all you psychic Ford fans to name that issue! It is a 351M with a older looking cast iron Edelbrok intake and a Holley 4 barrel ( it's a 4160) Two months ago it was coughing and sputtering, wouldn't idle and kept dying. I rebuilt the carb, changed oil, cap, rotor, plug wires, plugs and fuel filter... and it ran fine. I wish now I would have done one thing at a time to see what made the difference. Any way, a day ago it was running fine for my friend, he stopped somewhere and when he came back and started it it was doing the same old trick - won't stay running won't idle. ---I'm thinking either a plugged fuel filter or a sticking float. What does your magic ball say?
Thanks in advance for any help!!
Thanks in advance for any help!!
Posting Guru
Joined: May 2003
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From: Oak Harbor WA
When I got my 79 it was very temper mental for the first few months. I still have nightmares. Hard to keep it running, wanted to die, took 10 minutes to start. Ended up replacing the carburetor with an Edelbrock and it fixed it.
Very possible its the fuel filter in your case, any kind of crud in the tank could have come loose and plugged it. Its the first thing I would check before ripping the truck apart.
Very possible its the fuel filter in your case, any kind of crud in the tank could have come loose and plugged it. Its the first thing I would check before ripping the truck apart.
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From: colorado
Originally Posted by Mil1ion
What's up with not posting in the 73-79 forum?
Tempermental Ignition Module is my guess
Tempermental Ignition Module is my guess
I know....I thought of posting there later too... I did run a duplicate in the 351 engine forum though! I'm blaming it on too long of a day at work! So the ignition module would make it act like that? Also, I did have the gas tank out a couple of months ago so maybe I stirred up some gunk that plugged up the new filter...
Posting Guru
Joined: Mar 2005
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From: western montana
it takes a bit to plug a new filter. You have a single tank I take it with no switch for a second...i had a dual set up with one tank...but it got switched to the 2nd and acted the same way...very weird that it pulled enough to run for a bit at a time.
If ignition it could be anywhere from the harness connections under the hood to the module. Recently had to splice past a connector. It would be good to test electrics when not running...see if you have fire then work way back to coil, module etc if you don't. original modules do not allow much for cooling...place washers between module and inner fender so air can circulate better and heat is not reflected back. Some parts stores can test modules but not sure they can adequately test a tempermental unit.
Basics....fire and fuel...if you have fire when it won't run you know it's fuel and vice-versa.
If ignition it could be anywhere from the harness connections under the hood to the module. Recently had to splice past a connector. It would be good to test electrics when not running...see if you have fire then work way back to coil, module etc if you don't. original modules do not allow much for cooling...place washers between module and inner fender so air can circulate better and heat is not reflected back. Some parts stores can test modules but not sure they can adequately test a tempermental unit.
Basics....fire and fuel...if you have fire when it won't run you know it's fuel and vice-versa.
Post Fiend
Joined: Jul 2006
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I like the carb adjustment theory. A stuck / mis-adjusted float is usually an easy fix, and an easily overlooked problem.
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Joined: Sep 2000
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From: Beachville, Ontario
Does it have EGR? I had problems with a chunk of carbon coming loose in the EGR and it wouldn't close properly. No idle or low speed driveability, had to 2-foot it across town.
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When it's running bad, shut it off, pull off the fuel line from the filter (after eliminating the filter as the problem) and blow into the line toward the gas tank. Reattach and crank her up. If she runs good then, you got junk in the line/tank.
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Joined: Nov 2006
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From: Simi Valley, CA
Originally Posted by Mil1ion
What's up with not posting in the 73-79 forum?
Tempermental Ignition Module is my guess
Tempermental Ignition Module is my guess
I second the motion. Replace the pickup coil (stator) in the distributor, also.Use ONLY new MOTORCRAFT parts, the gypo aftermarket modules are made in China and are crappola.
--------------------------------------------------------------------------
btw...
>> Fuel filters, there's more than one type...
On the pickup tube of the fuel sending unit, is a plastic meshed filter screen (exc. in-cab tank). Since it rarely gets replaced, can you imagine what it looks like after 30 years?
D1AZ-9A011-A .. Filter Screen
C0AF-9276-A .. Fuel Sending Unit "O" Ring Gasket
Last edited by NumberDummy; Jul 26, 2007 at 12:46 PM.
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Joined: Jan 2008
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Originally Posted by rhw
I know....I thought of posting there later too... I did run a duplicate in the 351 engine forum though! I'm blaming it on too long of a day at work! So the ignition module would make it act like that? Also, I did have the gas tank out a couple of months ago so maybe I stirred up some gunk that plugged up the new filter...
ie:NON-Ford Trucks or Cars,Generic,Large Trucks type topics.
FTE used to frown upon the MUlti-posting of threads as well.
IMO> It is better to Post ONCE in the proper forum and if no one replies, keep bumping it to the top of the page.
This 73-79 forum is the Best Place for this topic.
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More Turbo
Joined: Nov 2004
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From: colorado
Okay... finally got time to poke at the truck! I was a big fan of the ignition module idea so I put in a new Motorcraft one and there was no difference. So I went ti the carb and double checked my float levels. Seemed fine. Tried to start it and it coughs and chokes and wont idle. It is also blowing out huge billowing clouds of black smoke. (neighborers came down from two doors up to see what was going on) I put on a different Holley carb I had sitting in the shed and it acted the exact same way. I'm thinking timing or heads?
Postmaster
Joined: Apr 2002
Posts: 3,613
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From: Coal country
Black smoke is still a carb problem.
Check the power valve - my money is on that it has popped, and is dumping too much extra fuel down the intake.
My second guess is fuel pump pressure too high.
Check the power valve - my money is on that it has popped, and is dumping too much extra fuel down the intake.
My second guess is fuel pump pressure too high.
Junior User
Joined: Jan 2007
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my 77 was running rough and had similar problems as yours. but when i put flowtech headers on it i realized not all of the cylinders were firing. so I changed plug wires and i was deffinately getting good spark. so i pulled a valve cover off and realized i had a bent pushrod and broken lifter that was for the intake. so i replaced them and shot it with a timing light and i had some plug wires on the wrong cylinders so my uncle labeled them. but when I went to put the plugs back on he had labeled the wires with two 3's but anyways my 400 runs alot smoother