Odd problem, 85 F250
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Elder User
Joined: Oct 2007
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Odd problem, 85 F250
Well, starting yesterday, I first noticed this issue. Driving the interstate, after about 20-30 minutes, the truck was acting like it was running out of fuel, even though there was fuel in the tank. Since that first occurrence, it has happened a couple more times. I have replaced the 4180 carb with an 1850, and have adjusted the floats, idle circuit, and idle speed. I'm not positive what the timing is set at exactly, but setting it by the mark on the balancer makes it run like crap. The only other work I've done to it recently was installation of an Accel coil, B&M shift kit, and a transmission cooler. The fuel pump is newer, I replaced it about 4 months ago, and I can't find any leaks in the fuel lines. I'm kind of at a loss as to what could be the issue. Driving around town there seems to be no problem, but during or immediately following highway driving speeds this problem shows itself.
Senior User
Joined: Sep 2007
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From: Indiana Cornfields
May be you ignition control module. In my 1980 it would start to cut out and act like it was running out of fuel once I had been driving it for about 10min. But if I kept it under 30 and stopped quite often it ran ok. Replaced it and now it runs like a champ. This may not be your problem, but it may be something to look at.
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Elder User
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Yes, I've replaced everything except the hard lines, because they all appear to be in very good shape. The symptoms, to me, really mimick running out of gas. If I let off the accelerator, and coast for a few seconds, it's again fine. I'm going to try, just because I have spare parts, swapping out the floats and seeing what happens. I need to have this truck "right" again by tomorrow morning, because I'm supposed to go pick up a junk van with it tomorrow.
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Joined: Sep 2007
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From: Indiana Cornfields
Is it backfiring any more than normal? And does it seem like it is getting enough fuel into the carb when you rev it up while in park?
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From: Denver Metro Area, CO
This happened to me on my 1981 with a mechanical fuel pump; I had replaced the rear tank with a used one that had on its sending unit an electric fuel pump. The mechanical pump was able to pull only so much fuel through it, up to approx 3,000 or so RPMs. I would suggest checking the pressure & flow rate of the fuel being delivered to your carb. I know you say your pump is new but defects occur and it can't hurt to verify. Go from there.
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Posting Guru
Joined: May 2004
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From: Billings Montana
I have two thoughts.
1. How new is the 1850 carb? Is it possible that the accelerator pump is going to poo on you?
2. You *may* be a victim of vapor lock. I don't know how cold it is where you are, but if you have a fuel line near your exhaust, the fuel might be starting to boil in the line.
1. How new is the 1850 carb? Is it possible that the accelerator pump is going to poo on you?
2. You *may* be a victim of vapor lock. I don't know how cold it is where you are, but if you have a fuel line near your exhaust, the fuel might be starting to boil in the line.
Postmaster
Joined: Feb 2008
Posts: 2,658
Likes: 5
From: Out of here
I have two thoughts.
1. How new is the 1850 carb? Is it possible that the accelerator pump is going to poo on you?
2. You *may* be a victim of vapor lock. I don't know how cold it is where you are, but if you have a fuel line near your exhaust, the fuel might be starting to boil in the line.
1. How new is the 1850 carb? Is it possible that the accelerator pump is going to poo on you?
2. You *may* be a victim of vapor lock. I don't know how cold it is where you are, but if you have a fuel line near your exhaust, the fuel might be starting to boil in the line.
I was just thinking the same thing.
Also, just because your fuel pump is only 4 months old doesn't necessarily mean it's still good.
Maybe it's on it's way out too. Was it a good pump or a "right off the boat" brand?
Fleet Mechanic
Joined: Apr 2007
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From: patricia ab canada
i have had the problem to,but in my car.i put on an open air filter new carb and fuel pump.my carb ices up.last time this happened i took off the air cleaner and the venturies were coated in ice.the rush of cold moist air freezes to the metalin the carb and chokes off the fuel. ww2 pilots had the same problem in the planes.thats why the factory has stove pipes off the snorkel on the factory air cleaner. good luck
Posting Guru
Joined: May 2004
Posts: 2,223
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From: Billings Montana
i have had the problem to,but in my car.i put on an open air filter new carb and fuel pump.my carb ices up.last time this happened i took off the air cleaner and the venturies were coated in ice.the rush of cold moist air freezes to the metalin the carb and chokes off the fuel. ww2 pilots had the same problem in the planes.thats why the factory has stove pipes off the snorkel on the factory air cleaner. good luck
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Elder User
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The carb is "brand new"; it was bought in 1971. It was left in the box on the shelf ever since. I put a new power valve in, checked the floats, replaced the transfer tube O-rings with the bigger, better seals, and after tonight, will be replacing the front fuel bowl and metering block gasket.
How likely am I to be icing in roughly 70 degree temps? I'm not being a smartass, I'm asking seriously.
If I'm going down the highway, say, 50-60mph, within a few minutes, it starts choking off. If I let off the skinny pedal for a few seconds, everything goes back to normal, but only for a few minutes.
The pump I just installed, unrestricted, is now giving me 7-8 psi, the fuel lines are fairly distant from the exhaust pipes as well. I'm not getting ANY back firing, and just around town, it's fine, even if I get into the throttle hard. It seems to be only while at a steady cruising speed.
How likely am I to be icing in roughly 70 degree temps? I'm not being a smartass, I'm asking seriously.
If I'm going down the highway, say, 50-60mph, within a few minutes, it starts choking off. If I let off the skinny pedal for a few seconds, everything goes back to normal, but only for a few minutes.
The pump I just installed, unrestricted, is now giving me 7-8 psi, the fuel lines are fairly distant from the exhaust pipes as well. I'm not getting ANY back firing, and just around town, it's fine, even if I get into the throttle hard. It seems to be only while at a steady cruising speed.
Post Fiend
Joined: Jul 2004
Posts: 8,786
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From: Northern California
It's a possibility, though may not be your problem, that your carb is icing.
High air flow over gasoline can give off an "Air conditioner" effect.
Simular like to a can of pressurized air for cleaning electronics.
Without the choke heat riser tube, and air cleaner heat riser, etc, my carb on my 4.9 will ice up at 68 degrees and below. Gasoline made today does not have fuel antifreeze in it like it did when these trucks were new. Put a bottle of "heet" fuel line antifreeze in your fuel and see if that helps.
High air flow over gasoline can give off an "Air conditioner" effect.
Simular like to a can of pressurized air for cleaning electronics.
Without the choke heat riser tube, and air cleaner heat riser, etc, my carb on my 4.9 will ice up at 68 degrees and below. Gasoline made today does not have fuel antifreeze in it like it did when these trucks were new. Put a bottle of "heet" fuel line antifreeze in your fuel and see if that helps.