Having fuel problems need a direction to head in

[Turnburn720]

Alright fellers I have an 83 f150 with a carburated 300 six here. It died twice when going uphill within 2 days, and then refused to start again. It will run (roughly) for a second or two when I pour a little gas into the carb, then die. I figured it was the fuel pump, so I replaced the mechanical fuel pump, the fuel filter, and blew out the line in between them. Still no fuel, the starter will turn it but it won't run.

The rubber hose going to the tank was empty when I pulled it off the old pump, but it was sitting for a while, so I figured it drained back to the tank. I poured a little gas in the rubber hose thinking it might prime it up a little bit I got nothing. I also noticed that the choke plate was fully closed when I took the air filter housing off, and if I reset it by hand, when the throttle cable pulls it shut completely again. Is this normal? I'm a total novice to carburetors so if anyone's got any advice or insight I'd love to hear it.

I was thinking that my next step would be to replace the rubber hose between the pump and the hard line running back to the tank, in case the ethanol swelled it up or something. The gas gauge doesn't work, but to my knowledge it has at least a few gallons in the tank. If the hose replacement doesn't make any difference, which direction do I head? Do I look at the carburator, or do I begin the process of removing the bed to look at the tank?

Edit: Replaced the rubber hoses, they turned out to be 5/16"

[Gary Lewis]

If the engine hasn't been run in an hour or so the choke should be closed.

But if you aren't getting fuel then the problem is between the tank and the pump.  There's a rubber hose from the tank to the hard line, and if you have two tanks there's another hose from the hard line to the switching valve, then another from the valve to the hard line.  And then the hose from the hard line to the fuel pump that you mentioned.

The original material does NOT like ethanol.  When I got Dad's truck one of those hoses dripped fuel when the truck was off.  The line didn't really have a hole in it, it had just turned to sponge.  When I pulled it off I mashed it into a ball and it stayed!

But if they can leak fuel out they'll leak air in, and that air can kill the vacuum that the pump creates to move fuel.  So I'd replace all of the hoses.

However, I also had one that wouldn't prime, so I pressurized the fuel fill to the tank with just a few psi of air.  That got fuel to the pump and after that all was good, it never failed again.

[Turnburn720]

Ok thanks. A guy I was talking to said something about the pickup in the tank, but I thought that the fuel line basically goes into a sock in the tank, there wasn't any valves or anything in there?

I'll replace the rubber hoses, is that just 3/8 fuel line?

[Gary Lewis]

You need to get ethanol-proof hose.  Modern fuel hose is.  And I do think it is 3/8".

But, there is a sock in the tank and it can get plugged.  The old mechanic's trick is to put air pressure on the line going in and blow the sock off.  It is more like a strainer than a filter and it might catch flys, but not much more.

However, pull the cap off the tank when you do that.

[Turnburn720]

Thanks a lot if the rubber hoses don't work, then I'll give er a good blowin

[1986F150Six]

If you blow the sock off, be sure to add an inline fuel filter between the hard line and the fuel pump.

[Turnburn720]

Yeah that's a good idea

[Gary Lewis]

Yes!!!  I should have said that.  And, you can do it even if you don't blow the sock off.

[Frank Wyatt]

I have a '81 with the 300/4.9 and Carter YFA carb and all my fuel lines are 5/16 from the tanks all the way to the carb.

[Gary Lewis]

Frank - That's good to know.  This is something that is frequently asked, and somehow we need to determine what the size(s) are.  However, the screen grabs below are from the MPC, with "9324" being the base part # for fuel line.

So, what do we make of this?  I see both 5/16" and 3/8" used.  

[Turnburn720]

Is the 3/8 for the hose and the 5/16 for the tube? I think the hose would have to be a diameter larger in order to slide over the tube and clamp onto it.

[Gary Lewis]

Good question, and one for which I didn't know the answer.  But a bit of Googling tells me that which the tubing OD is accurately represented, the hose ID isn't quite.  MercRacing has the table shown below.

The easiest row to look at is the 2nd one with 7/16-20 thread size.  The tubing size is 1/4" but the actual hose size is .22".  But I think the hose will actually say it is 1/4" hose.  So apparently hose sizing is slightly smaller in OD than the "size" shown on it so it'll tightly fit the tube.


 

[Angelo Voltura]

Gary Lewis wrote

Good question, and one for which I didn't know the answer.  But a bit of Googling tells me that which the tubing OD is accurately represented, the hose ID isn't quite.  MercRacing has the table shown below.

The easiest row to look at is the 2nd one with 7/16-20 thread size.  The tubing size is 1/4" but the actual hose size is .22".  But I think the hose will actually say it is 1/4" hose.  So apparently hose sizing is slightly smaller in OD than the "size" shown on it so it'll tightly fit the tube.

Gary that is a fantastic chart, any way we can integrate that into the forum database?

[Gary Lewis]

Sure.  But where?  Ideas?  Thoughts?

[Gary Lewis]

I wonder if we need a new section.  Maybe called "Reference"?  A place where we could collect details we want to get back to, like hose sizes or bolt torque spec's.  Things that we may need to know and just need a place to keep them for future use?

Thoughts?

[Angelo Voltura]

That would be my best guess, a reference section. That would be a really neat idea especially when it comes to engine rebuilds, I can go through my Haynes and get torque specs for a lot of things as well. Since paper manuals are going away (working for Advance about a year ago we threw them all out), specs for things are going to become harder to get ahold of.

[Gary Lewis]

Please don't go to Haynes for torque spec's!  They almost ruined a Kawi 900 for me decades ago, so I don't believe a word they say.  Having said that, the 1995 factory shop manual has errors as well.

No, what I meant was standard torque specs for a given bolt.  There's a spec for every bolt and nut, so if we had that and couldn't find the right one in the factory shop manual, most of which we have on the site, then we could use the standard spec.  Or, if we had a question about something in the FSM would could check the standard spec - which is what I did recently and proved the '95 FSM wrong.

[Angelo Voltura]

Ah, ok I follow what you are saying now. That would be a fantastic reference to have.