Hi All,

I am a Ford rookie and proud new owner of a 78 F250 with a poorly running 351M, Holley 4412, 4 speed. I am experiencing some severe hesitation at high speeds and especially going up hills (feels almost like running out of gas). Engine also gets kinda hot at high speeds (normal at idle). It idles so so but will stay running. Was pinging a bit but octane booster cured it (need to retard timing? pleas confirm). Any suggestions would be helpful. Sorry if this is redundant.

 

Check your fuel system.

 

I replaced the fuel filter plugs cap rotor and wires. fuel pump is new too. Timing set to~12btdc. runs strong except at prolonged high speeds and up hills. someone please help. Im going to head for carb next if no one has any advice.

 

There is more info here and in the fuel system forum if you use the search function. You may have a problem with fuel tank venting or pickup tube filter if so equiped. There may be rust in the tank or lines also.

 

Really sound like fuel delivery not keeping up. Low float level, plugged up filter intank, pin hole in rubber hose comming out of tank or it collapsing.

When does it ping?

 

The timing adj cured the pinging part. Thanks, I will look through the fuel system archives.

 

In addition, this morning it got much worse it started out in the usual manner only bucking at high speeds then started barely idling and was undrivable. The only way I could keep it running (barely with a lot of backfire) was to repeatedly pump the throttle. When I replaced the fuel pump no gas came out of the line from the tank. This is my first ford but with the other three fuel pumps I've done the gas came a squirtin out. If this is a tell tale sign of something please let me know. It seems like a pickup tube filter clogged would cause this. I will check the lines and pickup filter. Any other suggestions would help. Thanks again for all the input.

 

I you have compressed air you could try blowing back through the line to clear (temporarily) the tank sock. Loosen the gas cap and don't let anyone stand near it. If you blow the sock off you may get gas out the filler. If it's clogged it's no good any way but the junk will fill up your inline filter till it gets used up.

 

I blew out the line back through the tank and sure enough it cured the problem (temporarily). Can anyone give me some background on removing these tank socks? Will I have to drop the tanks? Any advice would be helpful. Thanks again.

 

Either the sock is blocked, or the carb needle/seat/float is worn or out of adjustment, or the passages in the carb are blocked, or you have a big time vacuum leak, or the EGR valve is sticking open and leaning out the engine big time (definitely disconnect it, I bought a stalling Saturn very cheap once from a school teacher, I disconnnected the EGR, and it ran fine and no longer stalled, ended rolling that car's odometer up to 222,000 miles before selling it.)

You can run without the sock in fuel tank, just make sure you use a fuel filter at the carb. If it still does it, then you know it's not the sock. Most socks just press on, or bolt on, or clip on the pickup tube in tank. You also may have a bent or crimped fuel line or hose.

Hard to exactly diagnose without seeing the truck myself. If the fuel system checks don't help, start looking at ignition, like a coil.

 

To get the sock off you have to drop the tank enough to pull out the sending unit. The sock is on the end of the pick-up tube. It's a very fine steel type mesh that plugs easily with rust. Just take a pair of wire cutters to it. Then make sure you have plenty of fuel filters because you wil go through them like mad. While you're at it throw away the factory fuel filter at the front of the carb. They plug up way too fast when you have garbage in the tanks. Just screw in a piece of pipe, or drive a screwdriver through the screen and run another type of filter after the pump. I use one at the tank, even though I've been told that this is a bad practice. It catches the junk before it gets to my fuel pump and plugs something up.

Good luck and have fun with your new ride. Wish I still had mine.

 

Removed tank sock added large inline filter downstream of pump. Still runs like crap. Very intermittent. To get it to idle I either have to pump the gas like crazy or choke it. Sometimes it idles fine but consistently at high speeds bucks and hesitates. Should I tear into the carb? Please help. I am thinking its not the ignition because I can choke it and it idles ok. Maybe I'm wrong. Again, my first Ford. As always any advice would be helpful.

Thanks

Sean R

 

OK, if you can choke it and it stays running, but won't run unchoked, it sounds like a fuel problem.

Did you disconnect the vacuum line to the EGR valve yet ?? If you didn't, DO IT NOW. It's can weird hat-looking thing directly behind the carb, towards the firewall, with a vacuum hose going to it. Pull the vacuum hose off, and plug it with a screw.

You have to follow the fuel line from the tank, all the way to the carb, CLOSELY, to make sure there are no crimps, breaks, or rust-through spots. If that checks OK, then look at fuel pump. What really must be done, is a fuel pump volume and pressure test to make sure you have the volume/pressure you need at the pump.

If that is OK, look for a VACUUM LEAK. Perhaps the EGR plate under the carb has burned through around the edge. You can permatex it shut. Also check closely the large vacuum hoses to the POWER BRAKES and PCV valve. Also the vacuum to the DIST. VAC. ADVANCE, and any others you may see.

Now, if all these factors are OK, then you need a carb rebuild, MOST LIKELY.

Again, you fellas posting these "won't run right" questions have to realize, a V-8 engine is a very complicated machine. It's not so simple that you can just post a question on a net message board, and get the instant diagosed answer right off, that will "fix" it. If it was THAT easy, everyone would be doing it and fixing their own trucks, and that's not happening. We have to actually SEE and WORK ON the engine, to really properly diagnose and fix it, cuz it can be a multitude of things wrong. For all we know, someone dumped sand or water in the gas tank- see what I mean ?? Working on this stuff is a learned skill over a lifetime. Let me give an example:

I worked at a diesel/truck repair garage. A tractor came in that wouldn't start, but had just been rebuilt by another garage, diesel engine. My boss, the shop owner, had us crank it over, while he shot starting fluid in the intake. No start. He took one look at us, and said "that engine has the wrong crankshaft in it". We tore it down, guess what, it had a shorter stroke crank in it, that would not let the diesel engine start, wasn't building enough compression. (diesels fire off heat of compression and are fuel timed) The piston at TDC was down in the hole a long way, no where near the deck, due to the shorter stroke of the wrong crankshaft.

That kind of skill only comes with LOTS of experience (my boss was 56 years old, worked in diesels since age 16, he could tell by LISTENING to it). You can't just post a message on the net and get that result, we have to see it.

 

I realize that it is very difficult to diagnose things over the web. However, I am just looking for practical advice from experienced ford owners. I have built VW based off road cars for many years and know a lot about them and have been able to give a few pointers to some rookies based on my own experience. That is what I'm looking for here. I do not expect someone to tell me exactly what is wrong with my truck but was hoping for some advice on common failures in Fords. I have received many helpful tips thus far and am very appreciative of the help that you all have given. If posts of this nature are not welcome or considered annoying please let me (and other newbies to Ford and/or this website) know. Thanks again for all of your help.