Fuel system

[peterara]

I had a few questions for anyone I have a 86  crewcab dually and having problems with fuel getting to carburetor. I have dual tanks. First I was having problems with it starving at the carb for fuel so I replaced the fuel pump.  After that it ran for a few days and had the same problem.  So I decided to drop the tanks and have them cleaned and also replaced the fuel sending unit on both tanks and still same problem.  Then I bypassed the electric switching valve and still the same problem. It doesn't seem to have any leaks along the fuel lines.  Any suggestions would be well appreciated.  Thanks

[jetmech]

I know it is a dumb question but I have to ask; did you replace the fuel filter? Also the rubber hoses tend to swell and get soft with todays gas. Did you replace rubber lines? You may have one closing down on the inlet side of the fuel pump.

[peterara]

Yes I did replace the fuel filter twice and all the rubber hoses from fuel sending units not the hoses from the fuel pump.

[frotosride]

I may be mistaken but there should be two fuel filters one in line and one on the carb..Also try disconnecting the line at the carb and switch the pump on. Just use a old hose and gas jug. Your supply line may be clogged..another dummy check. Make sure you put the filter in flowing the right direction. Wouldn't be the first time I've seen this. Did  you checked the pickup in the tank when you had them cleaned?

[peterara]

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[peterara]

Sorry I'm still trying to figure this thing out. Here is a quick pic of my 86 c30 with the fuel problem just thought I'd share it. Thanks for all the help. I'll try it again on Saturday

[LTZ C20]

Nice truck!

[jetmech]

It sounds like you have covered all the bases. My '85 crew 3/4 ton has only one fuel filter and it is in the carb. Not sure how you could check for wear on the camshaft fuel pump lobe. Also the possibility of a defective fuel pump. Most replacement fuel pumps are fairly cheap so it may be wise to try another new one and check push rod for wear while you are there. Trash in the carb needle and seat? Float level good? Was this the original problem that triggered all these repairs?

[fxrsrider]

Not sure how you could check for wear on the camshaft fuel pump lobe. Also the possibility of a defective fuel pump. Most replacement fuel pumps are fairly cheap so it may be wise to try another new one and check push rod for wear while you are there. Trash in the carb needle and seat? Float level good? Was this the original problem that triggered all these repairs?

I would run with Jetmech's line of questions, if I were you.  Sounds like you've replaced or repaired everything from the fuel fill door to the carb......so the carb is next.  If you've never rebuilt it, then it could use a rebuild.  If its "starving" for fuel, then the float bowl is suspect...personally, I'd rebuild the whole thing (actually I'd replace it with an aftermarket 4bbl....but that's just how I like to do things).  If your problem persists after the carb rebuild, then look at your intake, then the heads, then the cam (which you can see "virtually" by measuring the valve movement).

Quick afterthought.....does your problem persist if you open the throttle by hand directly at the carb?......pedal and linkage should be looked at too.

[peterara]

It's kind of weird but I will run the truck for about 30 minutes or so then it acts like it runs out of gas. Then I let it cool down and it starts back up then repeats itself. The carb is a little old so I'm thinking of replacing that next. If not the carb then I'm out of ideas. Also out of money. Lol. Luckily it started acting up right after It passed emissions. The fan clutch seems to be a little weak Idk if that might be an issue with vapor lock.

[BiggG74]

Could it be possible the floats are filling up with gas?

[fxrsrider]

Could it be possible the floats are filling up with gas?

a common problem with old carbs.  I'd check it out.

A carb rebuild kit isn't all that expensive.  Carbs are pretty simple devices.  Get yourself some PB Blaster/Carb Cleaner and a rebuild kit (change the floats while you're at it).....it won't hurt and may be your problem.  You don't have to get a new carb....though 4bbls are nice.

[frotosride]

Could it be possible the floats are filling up with gas?

Sounds like your fuel may be boiling.. check all the lines coming from the tank and make sure they are away from the exhaust and a heat shield for the places that have no choice but run close to the exhaust