dying when I hit 55mph

Hey I have a 1978 Ford Bronco with a 351m in it and it was recently rebuilt. I have a problem with acceleration, it dies when you stomp it to the floor, Also easing in on the gas you can accelerate to around 55mph when it acts like it runs out of gas, you can then let up off the gas and then you can get it back up to 55 and then wham it does it again. I put a brand new fuel pump on it so I know that aint the problem. I wouldnt think it would be the motor or tranny as I just had them both rebuilt. I talked to an old mechanic that said I probably had a rusted gas tank and he said rust probably got into my carb(which is the stock motorcraft) and that it more than likely busted my power valve which is ont he bottom of the carb. It will sit and idle perfectly too, it has no misses. Has anyone else ever heard of this problem. ( I have noticed that my gas tank has been leaking so and is awful rusty so I figured this guy might be right.) Any opinions will be greatly appreciated. you can post your answers here or email me at [email protected]





http://www.superford.org/registry/vehicles/index.php?vID=884

Check your accelerator pump as well. Also, are you sure it is not a distributor problem. I was having acceleration problems after installing my msd ignition, found out the stock distributor could not handle the spark an MSD puts out. It was burning up the stator in the distributor. You might also check your fuel lines themselves. However, it does sound like garbage in the tank is a likely source. My only question is if you are running a quality fuel filter, how did it get to your carb?

Quote:

found out the stock distributor could not handle the spark an MSD puts out. It was burning up the stator in the distributor.

That's a new one. Ford makes one (if not the) best stock distributors.
Did you have the TFI type? Or the Duraspark II with the module on the fenderwell?

I agree, Jason, it sounds like you got "debris" in the fuel lines.
I've never heard of foreign particles "blowing" a power valve.
That's usually a symptom of back-fire.
Have you run a fuel pressure/volume test at the carb to confirm if there's "blockage" in the lines?

Not a problem, I was having the same problem one day, make sure you check your fuel filters (Note: Filters) not just filter, you should have one under the truck going to the carb and one in the inlet of the carb, if dual feed do both or take them out, this solved my problem - found that the filters on both inlets of my carb got pluged quick, so what I did was put to filters inline from the gas tank - you can also make sure you us 93 octane, has less impurities in it.

Hope this works for you, it did for me.

You better check your wiring of that MSD - Duraspark II I can understand but TFI, No way everyone at the track is going to MSD and none of them are having that problem at all, Check your wiring - Read them direction carefully.

A friend got the Mallory Distributor - Said some very bad things about it and then came to me and he had it wired wrong, had to use two resistors, now his problems are gone but this was in the directions that came with the distributor.

The guys at the track use MSD and TFI all day long (Daily Drivers) and race like no tomarrow 3 days a week and have no problems at all.

Just would like to know - Why did you go Carb. ?.

It was a duraspark distributor, and I went thru three distributors before I got one that worked. And the MSD was profesionally installed, by a performance shop specializing in Fords. I went with a carb, because that is what was on it, and when I rebuilt the motor, did not have enough money to switch over to fuel injection. My next project will be to convert all the pulleys over to a single belt, instead of the five that are on there now. The way all those brackets and such are installed, was not one of Ford's "better ideas" hahahahahaha.

Man, that sounds familiar. I had a similar prob. with my 62. Mine was the fuel line that connects the metal line off of the tank, to the metal line in the frame. It was a 8" piece of rubber line that was weak enough that when I hit about 55 to 60 mph, the truck would choke out and want to dye. What it was doing was the line was soft enough at one end that the air from driving would push against the line and pinch off the fuel flow. It took me about four trips to figure it out. That might be something to thing about, if you don't find any debi in the tank or lines. If your tank is rusty on the outside and leaking, I would check and replace that first.

Sounds similar to the problem that I have had, my tank is rusted out as well, the pickup inside the tank was getting clogged with the rust particles, and was blocking the fuel flow to my electric fuel pump, there was some times that I couldn't barely accelerate, I'm running a Holley 225 lph EFI Inline fuel pump, along with 88 EFI 460, some was also getting through the sock on the pickup amd getting stuck at the screen in the intake of the pump also.

I finally found the Problem. Rust was no 1. Rust had ran its way through the filters on my bronco and found its way to the diaphram in the carb and busted it as well as the power valve. After replacing the tank, carb and blowing out the lines I was surprised to see it not run, but this was due to a vapor lock in the fuel lines. My bronco is once again running although not street legal.