Hello. I have a 1985 F-150. I replaced the carb with a new one. The truck idles great and has good power. Engine is a 300 CI 6cyc. The truck will run for like 5 to 10 minutes then act like it is running out of gas or like running on 3 cyclinders. Do you think maybe some dirt got into the new carb? The fuel filters are new also. I also put a new EGR valve on but don't think that has anything to do with the problem. What do you think? Need help!!!! PLEASE!!!! Thanks. Greg.

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1985 F-150 with 300 CI 6 cyc. Black with black int, fiberglass cap and bedliner, all black. aluminum mag wheels with BF Goodrich tires.

 

You might want to check the float level.

 

nunu726,
Just because it is a "new" carburetor does not mean it is "perfect" I went through three of them on an '83LTD i was using as a daily driver. On my '83, I tried 3 different cabs, and 2 mechanics. The 2nd mechanic rebuilt it, and literally ran like it was new (well, almost).

If you can't afford to find an ethical mechanic (I was lucky and did!), Here are some options:
A) fuel pump or tank pickup problem.
B) It sounds like the float level that was mentioned previously or a stuck/clogged needle and seat.
C) take it back, they should give you another. Keep in mind that you may have to do this several times and may wind up with several different problems associated with each carb. along the way.
D) Rebuild it veeryyy carefully yourself, and be sure each and every passage is clean.
E) Ask around your Town/city/neighborhood for a reputable mechanic.

Hope this helps. Let us know what fixes it.

Tony


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97 F150, 5.4l, E4OD, Towing Package, and every option except leather seats

 

nunu, you need to give us a bit more detail.

When you say the trouble starts up 5 to 10 minutes after you start it, is that while you're driving or while just idling?

If it happens while driving, does the problem go away? If so, what are the conditions that makes it go away? i.e., did you slow down, restart the engine, let it cool off first, etc?

You say 5 to 10 minutes. How fast are you driving when it starts in 5 minutes and how fast when in 10 minutes.

The problem could be a bunch of things. It could be the float level, fuel supply problem, faulty iginition coil, or other things.

The more information you give the better we can help you.

 

OK, a little bit more precise info, I start the truck and drive to work about a 10 minute drive. I stay at about 25 miles per hour the whole drive. When the problem starts, a couple times, when im driving, I reved the engine and it went away. A couple other times I parked the truck let it cool off then start it again. When I start it up it runs fine. One person mentioned the carb gasket might be the problem. It sounds like the carb to me. When I had the old carb on this never happened once. The old carb caused very rough idle and adjusting the lean/rich mixture screw had no effect on the engine. This is why I replaced it. But with the new one comes this strange problem. Im running the 93 octane gas and the spark plugs and wires are 2 months old. Hope this info helps. Thanks. Greg.

 

When you hit the bottom of the diagnostics list -- try opening the fuel tank and listen for vacuum -- the time is about right for a plugged tank vent.

 

My step father had a similar problem with an '85 F-150 with the 6. It turned out after going to 2 dealers that there was a TSB out on it. (probably went by "snail mail" back then) They had to install a spacer between the fuel line and a manifold (I think) anyway the truck's fuel was boiling in the line (vapor lock) and the engine couldn't get enough fuel. The little spacer worked.

May not be your problem, but symtoms seem the same and I'm sure they had fuel lines disturbed while installing the new carb. Worth a look-see at least.

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all4chem@aol.com
Y2K XLT Supercab Flareside, Oxford White, Medium Graphite, Captains Chairs, 6-Disc, 5.4L, 3.55LS, Tow Pkg, Block Heater, Sliding Glass, Remote and Keyless Entry, 5-Spoke Al Wheels, P235/70R-16 OWL Tires, Clear Corner Lenses, Eaglite Plasma Headlights, Al Striker Plates for the rear doors, Oxford White Lund Interceptor, Line-X Liner, and White Faced Gauges.
Ordered: 01-17-00
Built: 02-23-00
Delivered: 03-13-00

 

Sounds like a bad choke, when it warms
up(5 or 10 minutes)it stays engaged making the mixture to rich and causes the engine to stumble. I don't know if you can adjust electric chokes,it's been awhile since I had one. Is there any black smoke coming out the tailpipe when this happens?

 

From the further info, I doubt that it's the floater. If it was the float level, it would happen a lot sooner and it would be consistant.

Like Y2K says, it could be a plugged fuel tank vent, but even that would be a consistant and revving the engine would not clear it up.

I'm with 98SCREAMER. Sounds more like a poorly functioning automatic choke. I bet it's sticking and when you hit the gas to rev the engine, it "breaks" free and opens up fully.

Look at how the choke works and see if you can figure out how to open it fully without having to take the air cleaner off. In fact, if you can figure out the butterfly position from the position of the linkages, even better. Next time the engine starts missing and loses power, pull over and check the position of the choke and see if it's fully open.

I'd bet it's sticking in the partially closed position.

I've had a sticky choke butterfly on a carb once. Turned out the butterly was catching in the throat. It was hardly sticking, but once in a while, it would get hung up. Judicious use of a file cleared up that particular problem.

 

Well more bad news. I replaced the carb with another one and now the truck barely runs. I noticed the choke was staying almost fully closed, when I opened it up the truck ran better but now feels like it is running on 3 cyclinders. Well it's back to the parts store for carb number 3 tommorrow and im going to watch the choke on that one. I think Dennis is right on this one. I'll let everyone know what happens tommorrow. Thanks everyone! Hopefully I,ll get this problem fixed. Greg.

 

Now I know this is going to sound stupid but like a guy said a few posts ago, Sometimes it is better to rebuild what you have than to put new on. I too had the same problem not with a ford but a "c" truck.
I put a new carb on and it ran worse with the new one on. I put the old one back on tried it and then removed it again, got the kit and rebuilt it and it didn't run perfect but a lot better than before and MUCH better than with the new.
like the other guys were saying check the choke, see if it's sticking, the float could be stuck and flooding it.
Does your idle seem like it's at a normal "hot" idle speed? Is the timming set correctly?
it could be a few things.

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96 F150 XL,special
Air/PS/PB/AM-FM-Cass/
Light Package/300 I6/
5 SP Man/...
Nothing fancy just my little baby

 

Hello all! Well it looks like the choke was the major problem. Carb number 3 went on this morning and I made sure the choke was adjusted so it would open all the way. I took the truck out for a 1 hour ride. It idles smooth, maybe a hair low but thats easy to fix, good acceleration, for a 300 CI 6, and no weird problems like carb number 1 was giving me. I think on carb-1 I should of adjusted the choke before returning but thats all done now. I didn't think replacing a carburator was such a headach. Well thanks everyone with your help! Any more problems I'll be back. Thanks again. Greg.