I'm working on a 1986 ram 3/4 ton with a 360 4bl carb. If left for a few days it takes 15-20 mins of cranking to start. once started it's fine. If left for 4-5 hours then takes about 5 min. to start. I know it's a fuel delivery problem. I've replaced all the fuel lines from tank to pump (rusted through). Between me and the prior owner there have been 3 new pumps. The presure at the carb when this problem occurs is 1 tneats right 1 pound, If I pinch the return line from the fuel filter (one line in and two out) The pressure goes up to 5 lbs.
It seems that once sittng all the fuel dissappeares from the carb and the lines! Why is ther a return from the fuel filter to the tank? and shouldn't the check valve in the carb filter hold the gas there?
How is the pump driven? Lobe on cam or is there a Cup bolted to the cam to drive the pump?
Thanks for any reply.
Joe

 

are you sure you have the fuel filter installed correctly? there is a lobe on the cam.

 

I don't have a whole lot of carb experience, but from what I have, I've never seen one with a return line. I thought that was a fuel injection feature.

 

both my trucks have return lines and both run good with them.

 

There is a bleed line off the fuel filter for vapor lock control that returns to the fuel tank, it is intact and the filter (new) is installed properly (Vertical). the filter in the 4bbl carb is new and also contains a check valve. all the lines have been replaced and the pump is new. The lobe or the cup that bolts to the front of the cam seems to be fine because pressure is needed to push the pump in place to start the bolts. Showing the arm on the pump is pushing against the cam....still if the truck sits for a day it must crank for at tleast 2-5 min to get fuel to the carb. once started, it starts repeadedly through the day fine. Just can't sit for more than a day.????????
Joe

 

Just for grins, since you know there's at least 1 check valve on the feed side, if you have a little needle nose vise-grip, I'd crimp the return line close to the carb overnight, and try to start the truck in the morning. If it starts "normally" then at least you know where in the system your problem is. To me it sounds like it's siphoning the lines back into the tank while it sits.

 

before you start your truck in the morning do pump the gas? if i don't pump the gas on my truck before i start it in the morning it will usually take a bit longer but she will not tick.

 

Well yeasterday we took off the filter and looked at the return tube on the filter
specs call for .060, about 1/16 but the hole was about 1/8 so we soldered up the tube and redrilled it to 1/32. this morning when my brother stared the truck . he pumped it a few times and cranked about10=15 sec and it started Phew!!!!
he adjusted the power sterring belt and now we need to fix that... the reservoir is leaking... Dam rust. Well keep all informed.
Thanks Joe

 

even if the gas in the in the line between the carb and filter was to empty back into the tank through the return line, there should be enough gas still in the float bowl to start the truck if you pump the gas. pumping the gas causes the accelerator pump to squirt a bit of gas into the engine and closes the choke at the same time which makes it easier for the engine to start when cold.

 

Hello all! New here. Found this thread in a google search for the problem I was having. This is exactly the symptom I had and I took y'alls advice and pinched off the return line from the fuel filter and waited 24 hours...hit the key and Varoom!!! Thanks mutch for the advice!!

My question now is, should I get a new stock style fuel filter and replace it (does it have a back flow valve?) or should I get a straight-through filter and bypass the return all-together? I'm inclination is to bypass it. Any experience or ramifications?

Thanks again for this thread! Y'all nailed it!