[Monty.Starkey]

Hey guys , gotta pick your brains since I'm stumped. I have a dodge B300 sportsman RV with the 360 in it. It currently runs very very rough, like shaking and making hellacious noises. However at idle it's smooth, but will die unless i can keep it chugging along till it's warmed up. I would assume a misfire but it would have to be half the engine for this kinda noise. I've replaced the plug wires, plugs, distributor cap, rotor and have checked the vacuum when it does idle smooth. It sits at around 18Hg till it starts shaking and being really rough then it's erratic..like the rpms. The timing is at TDC as per the valve cover and once it dies, it takes a monumental effort to get it running again. Since I've ruled out vaccum could fuel pressure do this? I'm unsure of the current pump . Or would the carb be creating an odd fueling scenario since it's been about 6 years since I last rebuilt it.

Is there anything with this information that one of you could create a possible issue? I'm having troubles finding info on this type of engine behavior.

It's a bone stock 360 with the Holley 2 barrel up top.

Thank you all very much for any information provided.

 

[dana44]

Welcome to the forum.

Rough running until warm can be several things, from distributor being worn, so check the shaft play there, choke not coming off properly, carboned up crossover in the intake manifold under the carb, and as you said, the carb itself. Make sure all the linkage is functioning properly, might even pull the top off when it runs rough, see if the fuel level is high or low, or out of fuel (squirter can give an indication, if it squirts smoothly good, if not, carb rebuild), and running good after she warms up, still looks like carb issue, possible fuel pump if it does sputter a bit when warmed up.

 

[Monty.Starkey]

Even at warm up it is erratic beyond idle, The choke seems to be functioning properly. Would any of those things create a very monstrous misfire that shudders the whole engine ? Even with the carb bowls filled and the carb squirting down both sides evenly it shudders like you would not believe ( or would ). But I will look into rebuilding the carb as I already have the kit, and i was planning on an electric pump. See where this takes me. The distributor has very small amounts of play on it. It doesn't so much sputter , itshake and feel like it's firing on half the cylinders, unless it get it to idle, then its smooth no noises.

 

[ImperialCrown]

Are the plug tips getting black from carbon fouling? This may indicate a rich mixture. If the engine smoothes out by introducing a vacuum leak (added air) by pulling an intake manifold vacuum hose, it may be running rich.
If a shot of carb cleaner solvent mist over the carburetor while it's running seems to smooth it out, then the added mixture may indicate that it's running lean.
If the vehicle sat over the season or the inside of the fuel tank is contaminated with old fuel deposits, that could cause issues. If the fuel pump diaphragm and internal check valves were allowed to dry and then re-wetted with fuel, they may not pump or seal very well. If the diaphragm ruptures on an old pump, fuel can enter the crankcase and mix with the oil. You might smell this on the dipstick and the oil will be thin. Measured fuel pressure should be 3-7 psi. A fairly accurate means of checking the fuel pump is to have the hose end pump fuel into a clear plastic soda bottle. The pump has to move fuel upwards about 2 feet to the carb and you should see good spurts while cranking. Use safe practices when handling raw fuel with rags to soak up any spills and no open spark or flame in the vicinity.
Carburetors can be trouble as paper gaskets shrink when allowed to dry if the vehicle sits and won't seal well when re-wetted. Rubber o-rings harden and won't reseal when re-wetted.
RV's seem to be mainly affected by these kinds of fuel system problems because of sitting for periods of time with old fuel in them.

 

[dana44]

Additionally, double check your firing order to make sure a couple wires didn't get swapped at the pairs of sparkplugs.
1-8-4-3-6-5-7-2. it's on the intake manifold somewhere, including rotation, which should be clockwise.

 

[Monty.Starkey]

Thanks guys I'll have to check and see those options. I'll get back with more updated info.

 

[Monty.Starkey]

Well narrowed it down to my Vacuum advance, now this is odd. If i remove my vacuum advance and plug it off the engine runs great, no mid range power of course . If i re install my Vacuum it goes straight to hell. The diaphram is holding just fine and if i pull the dist. cap off i can create enough vacuum with my mightyvac to advance it. My question is, what does this mean? i seriously seem to be missing something here if a good working diaphram and advance mechanism is screwing up my engine so bad it sounds like the worst misfire ever.

Off topic, is there supposed to be a return spring on the brake pedal?

 

[dana44]

Change out the vacuum hose itself, see if there is a leak in it. Also, make sure the vacuum port is ported and not manifold vacuum, so off the bottom of the throttle blades.

Some have a return spring, some don't, and if the pedal doesn't return high enough to keep the brake lights from being on all the time, put a heavy spring on it.

 

[Monty.Starkey]

Hose is good but I'll change over ports, see what happens I'm certain that's the only thing I didn't check lol

 

[Monty.Starkey]

Well both ports on the holley 2bbl are pulling manifold vacuum so I'm gonna check into that after a bit. However back to the brake pedal, it's very very stiff and difficult to push in or pull so i tore it down to just the swing arm and it alone is causing issues. Does anyone know a good way to remove it completely? I've removed the nut on the side but i cant seem to tap it out any direction. I've soaked it in lubricant in case it's just rusted but still seems to be very very hard to push. Any suggestions? And i honestly appreciate all the inputs, this knowledge is good to keep passing on.

 

[ImperialCrown]

Is there a vacuum hose routing diagram label still under the hood? It may have peeled off and blown away years ago. Is this the correct carburetor?
The m/cyl linkage bellcrank nut is a one-time use nut and I can't remember the last time that I serviced one of these. They can bind and I don't think that parts are easy to get for these anymore. You might try freeing it up with penetrant and oil. If not, disassembly may be the answer.
http://www.factorychryslerparts.com/showAssembly.aspx?ukey_assembly=544566&ukey_product=4280302
If you don't have a factory service manual, it may pay for itself quickly.