New to the forum although I've been watching posts for a year or so now. I have a 78 F-150 Ranger Custom 4x4 with the 400. I absolutely love this truck and bought it with the intent to restore in in the next couple of years but right now its my daily driver.
Anyway, on to the problem. A couple of weeks ago it got down to about -10 which I thought no big deal. Went out to start my truck and it started like it normally does so I hit the gas to kick it down off high cam and let it warm up on high idle and it died and would not restart. Tried the next day, no start. So I added some Heet to the tank and the carb and let it sit. Next day go out and try to start it....get it running by basically holding the gas pedal to the floor and cranking. Then I had to hold it there for it to stay running. After a while of doing that it smoothed out and idled just fine...so I took it for a drive and there was no power whatsoever....like it was starving for fuel or I fouled the plugs or like maybe there was some condensation under the cap.
It's been two weeks, I've replaced the plugs and cap and rotor and also the fuel filter just to eliminate the easy stuff. Plugs were black ( I know it runs rich) the rotor had a green corrosion on it and the cap looked pretty bad. The fuel filter had never been replaced....but it still is doing the same thing.
Basically I can go out and set the choke and it will act like it wants to start once then just crank and crank until I hold the pedal to the floor. Then it will start and run really rough, eventually smooth out and idle but have no power. It almost sounds like its not running on all cylinders but doesn't idle rough once I let it warm up.
What are some things I need to be looking at. I was planning on checking the pump and looking for vacuum leaks....but this is my first carbed vehicle and my first Ford so I'm kind of in unfamiliar water.
Sorry for the long winded message. Any ideas are greatly appreciated. You all have some great information here and look forward to chatting with you more in the future.
im running a 351m with a big cam and thats exaclty what it does except it has great power before 3k rpm. when cold it even back fires, but after warm it runs great, im thinkning its defenitly a vacuum leak cus those are sympthoms of a low vacuum rise at manifold at low rpms....and it could be two things ata time, the vacuum leak and something causing the lose of power...
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Last edited by hollenjoe : 02-03-2008 at 07:07 PM.
Another note is to check your PVC valve. Sometimes with a buildup of condensate it can freeze up in the cold and not recirculate the crankcase gases.
I would also really check that choke closely some more...
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Mark in FL
restoretherepublic.com
Well I went out tonight after work to mess with it some more and tried to lay across the engine bay and pump the throttle to see if I could see or hear a good shot of fuel getting into it but couldn't really see anything. I'm kind of getting to the point that I am wanting to pull the carb off and just clean it out good and do a rebuild on it....this truck's 30 years old and never had anything done to it but a tune up (mainly just plugs and wires and stuff) and a brake job other than me installing a new transfer case. Is it worth the time and effort or should I really be trying to figure out exactly whats wrong?
I think that you should pull the carb and replace the needle and seat as well as cleaning the carb. Check the needle valve for contamination. The accelerator pump is another item to look at and replace. That's probably most of the parts in a rebuild kit anyway.
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Yeah, I think that's what I'm gonna do. I know the accelerator pump diaphragm is leaking and also there is a leak somewhere under the front of the carb so new seals never hurt anything. Wish I would have done this sooner, supposed to get 10 inches of snow tonight.
Took my carb off this evening and pulled the top off. There was a hole in the gasket between the upper section and the main carb body right over the float bowl. Haven't dug into it too far yet. Do I need to replace the external valves (i.e. dashpot, choke valves) or do those really cause problems. This will be my first carb rebuilt and I want to do it right.
Ok an update, rebuilt the carb last night which went really easily. Installed it today and started cranking. Did like it normally does where it acted like it wanted to start then didn't. Had to hold the pedal to the floor and it fired and ran rough for a while then kind of smoothed out and ran on its own on choke. So I let it warm up for a while and seemed to be ok then I tried revving it and it was still stumbling. Kit it down to normal idle and it was worse with trying to give it gas. I checked the float level and that seems to be good. Checked fuel, and its definitely getting to the carb. I had a buddy crank it while I looked at the fuel line and two big gushes came shooting out.
So where to turn next? I had a suggestion from a guy at work that builds stock car engines that said these trucks have a really cheap crossover pipe off the manifold that can collapse on itself and he really sounded like he thought this was the problem. He says if its running rich I should be seeing black smoke, which I'm not. But would this make it hard to start? My other option would be to check compression. What do you guys think? Thanks for the help.
I know nothing about anything 'cheap' on these engines. There is nothing to 'collapse' in them.
Try pumping the fuel through the fuel pump into a can while cranking the engine and see how the fuel flows. If you can, try also to borrow a carb from someone, or buy one from the junkyard that looks fairly clean. I think things are too lean.
The problem might not even be fuel related, but possibly a timing issue, vacuum, etc. Check with timing light with advance disconnected, then pull with vacuum and see where timing goes.
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Mark in FL
restoretherepublic.com
When you depress the gas pedal, you are not giving it Gas, you are giving it more air. The gas comes from the air flow through the carb. It sounds like it will idle OK, but when you come off idle and increase the air it will stumble. A motor needs three things to run, air, fuel in the right ratio, and spark at the right time. We can assume that it gets air, and we think that it's getting fuel in the right amount, that leaves the spark. As Mark said check the timing and vacuum, but also check the spark. A weak spark can cause all of those problems. Check the coil wire for resistance. Check for a fat spark at the plug wires.
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I am curious to see what will fix this problem. I had a very similar problem myself that started on a cold day and now after rebilding the stock carb,a new carb, intake, ignition module, coil, wires, cap, button, plugs, battery, and solenoid it still isn't running. I tried to replace the pick up coil in the distributor but broke the reluctor or armature I just decided to install an new Performance distributors DUI in it(ordering tomarrow). It did seem that my spark was weak but I didn't know if that was the problem since it did have a spark and all the other new stuff. Now after the distributor and the timing is checked hopefully it will run.
I didn't really help I don't think but similar situation and this is all I have checked with mine so far and nothing until the distributor comes in.
Well I went out tonight to check the timing and couldn't get it to start at all. It acted like it might start like it has been and then nothing. I looked down into my distributor to see if there was any play and if everything was lining up correctly. Seems as though I can move the rotor around by hand a little bit, probably a good 1/4 inch or so which seems to me that should not be (atleast with my chevy there was no play in the dist as far as moving the rotor) so my first thought would be that I started to shear the pin on the dist. gear.
Pitbull, let me know what happens once you get that new distributor in.
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