Stalling / Update
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Stalling
Hello, I was wondering if anyone might be able to give me some input through past experience. I have a 76 with a 390 in it. This is the original engine with all factory spec parts. (the truck itself only has 170,000 miles). After sitting the winter (It was winterized, and I've gone through about 10 tanks running each to near-empty) the truck will stall at any speed. It is almost like it is starved for gas. It simply continually loses power until dead. Once dead however it starts right up and away I go. This problem is extremely random. It matters not what speed I am going, or what RPM the motor is at. All that really seems to matter is that it only does it when the motor has warmed up. I would think that it was vapor lock, but the motor is pretty cool running and has a sound cooling system. Also if it is vapor lock, why now and not last summer when it was 110 degrees out and I live at 2600 feet? This is the most perplexing situation that this vehicle has given me. I would appreciate ANY input whatsoever... I like my old beast and would like to keep it happily running. Thanks!
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Posting Guru
Joined: Feb 2004
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From: Saratoga, NY
there was a guy with this same problem a week ago, and it turned out to be the fuel filter. It would die and start right up, once the engine died the pump not pumping would allow junk to fall free and 'unclog' the filter until it got plugged up again when it was re-started.
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From: Washington
Besides fuel filters it could be the needle valve at the carbureator gummed up from sitting so long or the float sticking for the same reason. also it could be a fuel pump. If the diaprahm gets a pinhole in it; it can work for awhile and then lose presure until you shut down and relax it and then it would start working again for awhile. Check all fuel lines for cracks and loose fittings all the way back from the tank. If it starts sucking air, well you know.
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O.K. then, since the consensus says fuel filter, I will try changing it during my lunch hour today... The only reason I didn't change it earlier is I took it off and blew through it and it seemed fine. I will try this and let you know this afternoon! I will double check the fuel lines for breaks/cracks/loose fittings. Also I thought it might be the fuel pump, so I went ahead and spent $40 to change it (small price to pay for peice of mind) and that changed nothing.
If it IS a needle valve or float in the carb... how does one go about fixing that? Do I attempt to rebuild the stock carb, or do I buy a new one? If so, does it make a difference what brand? I think the original factory equip. is a Rochester right?? (heard they are hard to work on)..
I'll check in later, thanks!
If it IS a needle valve or float in the carb... how does one go about fixing that? Do I attempt to rebuild the stock carb, or do I buy a new one? If so, does it make a difference what brand? I think the original factory equip. is a Rochester right?? (heard they are hard to work on)..
I'll check in later, thanks!
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From: Washington
There's only about 5 screw's that hold down the top plate of the carbeurator, lift it off and you can see the float. If the bowl is full and float goes up and down easly you can cross off the float
and needle valve. While your checking, make sure that the bowl is clear of water. If there is any water in there at all you probably have water in your tank. It will condence in there from just sitting for prolonged periods.
Also make sure that all of your vacum lines are hooked up and no cracks.
A long shot could be a weak coil breaking down when it gets hot but it sure sounds like it's a fuel problem.
Good luck.
and needle valve. While your checking, make sure that the bowl is clear of water. If there is any water in there at all you probably have water in your tank. It will condence in there from just sitting for prolonged periods.
Also make sure that all of your vacum lines are hooked up and no cracks.
A long shot could be a weak coil breaking down when it gets hot but it sure sounds like it's a fuel problem.
Good luck.
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From: SD
Originally posted by 76Explorer
Do I attempt to rebuild the stock carb, or do I buy a new one? If so, does it make a difference what brand? I think the original factory equip. is a Rochester right?? (heard they are hard to work on)..
Do I attempt to rebuild the stock carb, or do I buy a new one? If so, does it make a difference what brand? I think the original factory equip. is a Rochester right?? (heard they are hard to work on)..
Marty
Post Fiend
Joined: Jan 2003
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From: Montana Territory
Well, you can rebuild it yourself in 2.5 hours for $23, or buy a rebuilt one for $180 and spend that 2.5 hours trying to set it right.
These are extremely easy carbs to rebuild yourself.
These are extremely easy carbs to rebuild yourself.
Postmaster
Joined: Feb 2003
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I'm guessing that you have a 4bbl on that 390. If so, original equipment was a holley and Pony Power's procedure above is not the correct one to use on that carb. Holleys have the floats in the bowls at each end of the carb. I think it's 4 screws that hold the bowl on. When you take it off the contents will spill, so be aware of possible fire hazards.
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Joined: Jan 2004
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From: Franklin, GA
I think the key to diagnosing your problem was when you mentioned that this only occurs when the engine is completely warmed up. In my experiences, I would swap the electronic ignition control module for a new one. The fuel filter shouldn't be temperature related to produce a clog. Maybe not a bad idea to replace it anyway, especially if it has been a while since it's last service.
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Thank You hdgapeach, however can you explain why it gratually decreases in RPM until dead? I have never experienced spark that decresed in power until the truck eventually dies... BTW The module on the fender was replaced about 5,000 miles ago. Like I said... It's 'like' vapor lock... only it starts right up afterward.
I replaced the fuel filter as most in the forum have suggested, and the truck didn't do it on the way to work this morning, so... I'll give it a few days. I looked into the carb, and it is a stock Motorcraft 2 barrel. IF I have to go the carb route, is there an advantage to moving to a 4 barrel other than HP gain? and what sort of HP might I be looking at if I switch?
I replaced the fuel filter as most in the forum have suggested, and the truck didn't do it on the way to work this morning, so... I'll give it a few days. I looked into the carb, and it is a stock Motorcraft 2 barrel. IF I have to go the carb route, is there an advantage to moving to a 4 barrel other than HP gain? and what sort of HP might I be looking at if I switch?
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Thanks Mattsbox, that answers another question I had. BTW the truck didn't do it again at lunch (I have a 25 mile trip home each way), so for now I'm assuming it is fixed. Thank you all for your thoughts on the matter. For those interested, and for future people searching the forums for this particular problem, I will post when I know for sure it is fixed and what did the trick. Thanks again.