Hey everyone. New to this forum, just bought an F-100 about a week ago and everything was going fine until today. I spent most of the afternoon trying to diagnose the problem and track it down but to no avail so I thought I'd throw it out here and see if you guys have any answers or suggestions.

The Truck:

1975 F-100 4x4 w/ 360 FE (All Stock as far as I can tell)

The Problem:

Truck Idles fine but while driving it intermittently skips and stalls and then runs fine for a while then starts the whole skip and stall again. (A little background: This only started after the truck overheated on me this afternoon while I was sitting in the McDonalds drive through. I thought that maybe it would stop after it cooled down but did not.)

What I have done:

Before the problems started I gave it a basic tune up: Plugs, wires, dist. cap, rotor, fuel filter, air filter, oil change.

After the problem started I started trying to diagnose it and found that my fuel pump was acting up and replaced it. This helped somewhat.....but the problem is still there. I was getting spark, but I had a new coil just sitting there so on the off chance that it was the problem, I replaced it. Still the problem exists. I checked the carb out as best I could without removing it, the accelerator pump seems to be functioning ok, and the choke is open correctly (i say that because when I first put the air cleaner on the truck I accidently pinched the choke cable and spent an hour trying to figure out why the truck wouldn't run...duh)

Anyway, thats my problem, and where I'm at with it, hoping to get some thoughts or suggestions cause I'm stumped. The only other thing I can think of is water in the gas or maybe a vapor lock issue???

Like I said the truck runs fine at idle and runs ok most of the time while driving, but then it starts to cut in and out. Once it starts it will usually keep doing it until I pull over, shut the engine off, and start it back up again. Then it will run fine for a bit and the problems start all over again.

 

man you sound like me...
Mine turned out to be the condenser in dist.
But mine has breaker points also...75 probably has electronic ignition I think...

Does it seem like the gas pedal suddenly evaporates on you when driving at anyspeed and it just dies like you're running out of gas?
Sticky float needle and seat maybe?
my .02

 

Pretty much...

I've found that when it cuts out like that I can usually keep it running if i feather the gas pedal. Thought about the needle....maybe I should just rebuild the carb and eliminate it.

And yes it is electronic ignition.

 

A sticky float could also give engine starting trouble too. These problems that are erratic are hard to nail without eliminating one thing at a time. Mine would die going down the road and I would have to get out, take off the breather and gently tap on the carb bowl to release the float. Then months later it died going down the road (and in park) for a completely different reason...a bad condenser!
I know it will nickel and dime you, but it also won't hurt to keep eliminating potential culprits, although kinda sounds electronic to me.
Just food for thought for ya, good luck.

 

Thanks for your replies rusty. However, I think I found the problem.....

I pulled my gas tank today, because I thought that there was a strong possibility that I had either something was clogging my sending unit or I had a lot of water in the tank. Much to my surprise I found about 20 feet of rubber 1/2" ID rubber tubing in the tank. Looked like it had been in there for years and was in various states of decomposition. Here is what it looked like.....

CRAZY! ISN'T IT!

And that was only about a third of what was actually in the tank!

AHHHHHHHHHHHHHH! So glad I pulled the tank because I could have replaced the whole motor and not found that!

 

Damn wonder if someone was trying to siphon gas from your truck.

 

Thats about the only scenario I could come up with....I figure someone was in the middle of trying to siphon it...got interrupted and shoved the hose in the tank so as not to get caught.

 

Well, I installed a new gas tank and sending unit. Fired her up and...... same problem.

So, that leaves the carburetor, because I have checked everything else. I pulled my 2150 off and bolted on a 2100 I had laying around from a 72 F-350. Bingo. No more stalling.

However, when I tore my 2150 down to rebuild it last night I couldn't get the venturi cluster out of the carb housing. Fought with it for hours, soaked it in PB Blaster, soaked it in chem dip. Finally got the cluster out minus one of the brass tubes. Not Good. No rebuild for the 2150. So...back to Advance this morning. Luckily they had a rebuild kit for the 2100 in stock. This made me happy because the 2100 is a 351 cfm vs. the 2150 that was a 287 cfm.

So here is my Question...

Does anyone see a problem with running my old spacer with the EGR setup on it and not hooking up the EGR to a vacuum port? Or does anyone have a suggestion for eliminating the EGR completely? The reason I ask is because the 2100 carb only has one vacuum port and I need it for something else.