Fueling issue NEED HELP IM LOST

[Bear601]

Ok prob something easy but I'm at a loss once again I'm new to carb engines so here it go's this past Dec I purchased a 1985 c10 swb w/ 305 v8 w/262 cam it ran like dog ____ found out carb was all jacked up and headers were leaking so I replaced the 750cfm edelbrock with a new summit 600cfm strip/street carb and replaced the whole exhaust with new summit long tubes, new exhaust with a H-pipe and new mufflers. I also put new 8.5mm wires and new plugs. Then I purchased a msd cap and rotor kit and installed that. Truck was showing improvement so then radiator sprang a leak so replaced it and went back with elec. Fans wired to the ignition then I noticed my fuel filter was empty so I replaced the mechanical pump and clear plastic filter ran great then 1 month later blam filter was empty while running so I started watching it and when it's cold or warm at idle filter is full but the sec I drive the truck and then stop somewhere I can pop the hood and empty filter until I let it completely cool down and for the life of me I can't figure out why so please please please someone help me before I stick a for sale in it or have a really big camp fire with it lol I'm LOST and can't figure it out

 

[austinado16]

Clear filters always look empty when the engine is running. The fact that the engine is running....is proof that it IS getting sufficient fuel.

 

[Bear601]

Clear filters always look empty when the engine is running. The fact that the engine is running....is proof that it IS getting sufficient fuel.

I understand that but it is clearly empty because you can see the small amount of fuel squirting into the filter instead of filling up the filter and it runs great while idling but runs horrible when under a load/driving and after driving

 

[austinado16]

Have you replaced the fuel pump? Made sure the fuel lines have no cracks?

 

[yevgenievich]

Just to rule out fuel supply, figure out amount of fuel in the bowl of the carb when running bad, move the throttle while looking down the bore of the carb when the issue is present. It should spray fuel if the bowl is full of fuel. Also can just take the top plate of thr carb off and see if it is full(edelbrock style)

 

[Georgeb]

I recommend you go over the lines on the suction side of the pump for leaks where it could suck air in. Also for anywhere the fuel line comes close to the exhaust for any reason.

 

[wallerus]

#1 I don't like Edelbrock carbs.
#2 I don't like Holley carbs.
If I have to run a carb I find Holley to be more adjustable and better fuel mileage.

DID YOU REPLACE THE FUEL FILTER?

I am leaning towards the fuel pump not being the problem. To check it do the following.
"DO NOT SMOKE AROUND OPEN FUEL SYSTEM"
Remove air cleaner. Open choke by hand and operate the throttle lever. A healthy spray of fuel should shoot out.
No fuel, weak fuel, Could be carb or fuel pump.
Good spray move on to pump.
The fuel system needs 4-7 psi of pressure to operate properly. Check the pressure idling and under load. DO NOT MOUNT A FUEL GAUGE INSIDE THE PASSENGER COMPARTMENT OF THE VEHICLE.
Too much you can overpower the needle and seat, too little and it runs out of fuel at acceleration and high load.

Remove fuel line from carb.
"DO NOT USE FLEXIBLE OR RUBBER HOSE FROM THE FUEL PUMP TO THE CARB, HARD LINE ONLY. HOSE CLAMPS ENGINE COMPARTMENT HEAT DAMAGE FUEL HOSE AND CAUSE LEAKS."
For this test only run a rubber line from fitting to a bucket or pan. Crank engine, a good strong line of fuel should come out.
Good fuel then System is ok and you have other problems.
Bad fuel, move on.
If you have not already, replace any rubber lines from the truck frame to the pump. They may look fine but can be damaged internally. Check for kinks in all fuel and return lines from the tank forward.
Don't forget tank vent lines and canister lines.

Reassemble fuel line to carb. CLEAN ANY SPILLED FUEL FROM ENGINE COMPARTMENT.
Start and drive truck for 15 min. Turn of engine and immediately remove fuel cap. Any pressure or heavy vacuum (the canister purge system will create a very small vacuum during running) means your vent / purge system is compromised and needs repair. High vacuum in the tank with damaged vent / purge can pull all the fuel from the fuel line causing hard starts. You can also try running it with a loose fuel cap to check the vent system. DO NOT RUN THIS WAY EXCEPT FOR TESTING.

DO NOT DISABLE ANY EMISSIONS RELATED EQUIPMENT.

If all these items check good your problem is in the carb (not uncommon with your current brand "from my experience") or in the the ignition / timing system.

One other item. Run the electric fan from a thermostat controlled system, painless makes them for a reasonable price. Running the fan all the time can cause hot and cold soak problems. The engine needs to warm up and stay there. With the fan running all the time the cooling system opens and closed the thermostat constantly and fuel mileage / driveablity will be affected.

 

[Bear601]

well looked under the truck this morning and theres only one metal line for fuel going to the engine so I plan on replacing the metal line from the tank to the engine with a 3/8 rubber fuel hose today when I get off work today unless someone thinks replacing the metal line with a rubber one is not a good idea. plus I dont have a return line theres is only one line from engine to tank or tank to engine how ever you want to look at it could that have anything to do with anything

 

[Bear601]

well when its warmed up the fuel bowls are empty almost and I dont have a return line and as far as the vent on the tank I havent dropped the tank due to it having 3/4 of a tank. removing the bed to get a better look tonight

 

[MikeB]

I understand that but it is clearly empty because you can see the small amount of fuel squirting into the filter instead of filling up the filter and it runs great while idling but runs horrible when under a load/driving and after driving

I wouldn't worry about how much fuel you can see in the filter at idle. Running horribly under load could point to a variety of things. However, make sure there's not another filter installed somewhere else, like close to the tank.

And by "under load", do you mean when accelerating, or at a constant speed going up a hill? Does it bog (blaaaah) or hesitate/surge/stumble?

How many turns out from seated are the idle mixture screws when you adjust them for max vacuum at idle? And what is that max vacuum reading?

Have you checked all your vacuum lines for leaks, as well the distributor and brake booster (by sucking on the respective hoses)?

I think all Summit carbs are square bore. Is yours installed on a square bore or spread bore manifold? If it's a spread bore manifold, sometimes a square bore carb will seal OK, other times it requires a sealing plate like this: http://www.summitracing.com/parts/edl-2732/overview/

What is your initial ignition timing at idle with the vacuum advance line plugged?

 

[MikeB]

#1 I don't like Edelbrock carbs.
#2 I don't like Holley carbs.

Help me to understand what that comment adds to this thread. I suspect hundreds of thousands of us run those carbs with zero issues. Each has its pros and cons.

 

[austinado16]

well looked under the truck this morning and theres only one metal line for fuel going to the engine so I plan on replacing the metal line from the tank to the engine with a 3/8 rubber fuel hose today when I get off work today unless someone thinks replacing the metal line with a rubber one is not a good idea. plus I dont have a return line theres is only one line from engine to tank or tank to engine how ever you want to look at it could that have anything to do with anything

You'll want to verify function, rather than just keep guessing and throwing parts at this thing. For example, if the metal fuel line leaked, you'd have an obvious fuel leak. Verify fuel pump output, via an actual output test of the pump.

 

[Georgeb]

You'll want to verify function, rather than just keep guessing and throwing parts at this thing. For example, if the metal fuel line leaked, you'd have an obvious fuel leak. Verify fuel pump output, via an actual output test of the pump.

This^^