1985-345 fuel pump problem

[Newty]

Hey guys, first time posting on here and hoping to get some insight on an issue I’m having with the fuel pump after the old went bad. I replaced the electric fuel pump at the tank with a holly Mfr. #: 12-801-1 because that’s what the Manuel stated as replacement for the P-30 Chasis but now when I crank it it only runs for about 15sec and then starves for fuel and cuts off. The new fuel pump is rated at 97gph and the old one was 110gph.
Could that be the issue ?

Thanks for any help!

[Waipio Rim]

If you still have the original carburetor setup there is also a mechanical fuel pump on the motor.

[WayneG]

Hopefully your pickup tube screen in the tank is not full of "rust dust".
When I dropped the tank in my 84, I found about half a cup of loose rust particles in the tank.

When that stuff gets swirled up in the gas, it will get into your fuel pumps and clog filters (Hopefully you have one before the pump)

[bobmiller1]

I agree with Wayne, if it only runs for 15 seconds I would take the pressure side off the pump and run a long hose into a 5 gallon jug, turn the ignition switch on and check the flow, your problem is either the new pump or your suction side is blocked. For diagnostic Purposes if you find the suction side blocked, disconnect the suction side from the new pump and with a rubber tip blow gun, blow backwards into the fuel tank, if your problem is then solved I recommend dropping the tank, although that is a pain in the ass you may have got a bad tank of gas recently........Regards, Bob

[Boom Sounds]

May as well replace the filter on the frame rail which is a cheap and prudent fix and can rule that out

[HowieE]

If the flow tests mentioned above check out OK I would check to see if the engine also has the standard mechanical pump mounted on the lower front of the engine block.


GM mounts that pump at the lowest point in the fuel system and water collects below the diaphragm. I had to remove one once for lack of flow at road speeds. I mud below the diaphragm and the edge of the diaphragm cracked and not making a complete seal.



I replaced the mechanical pump with a Carter electric and placed a mechanical pump cover plate on the engine block to cover the opening.

[alantbird]

I agree that there’s one at the engine. The elec one is just there to get the fuel to the engine pump due to a long trip from the tank.

[Waipio Rim]

there is also a screen in the carburetor where the fuel line connects that can get fouled.

[Grosspoluter]

I had a similar problem But I had NO electric pump at the tank, just the mechanical pump on the engine, that set up only gave me only 2-3 psi at the carb.
After i installed the electric pump at the tank the psi at the carb. went up to 5-8 and drivability went way up
I still run with both pumps

[Voltair]

Hi Newty,
Fuel supply in these long vehicles can cause issues, some sensible tricks once your'v cleared your current pos blockage, as has been stated befor, that the steel gas tank can start to lose its electro plating on its interior, as condensation inside will ocure, so will rust! To leason this get hold off a large Base Speaker, donut shaped magnet and attatchet beneath the pickup position on the tanks bottom. This will collect all the metal rust n stuff. Untill someone wonders what i'st doing there an removes it.
You want both an electrical pickup pump so fuel is forced under preasure to the engines mechanical pump so in the event off electrical failure your not left sitting in the middle lane.
Also these benifit from a fuel regulator to maintain a 5 psi at carburettor, otherwise thoes two pumps at times will pump up to unhealthy presures thus flooding fuel into the engine, cost plus rough running particularly at idlle.
All the above after filter changes are done, should be good to go...
Rus

[Newty]

Originally Posted by Waipio Rim

there is also a screen in the carburetor where the fuel line connects that can get fouled.

I'm going to check this....

[bkahler]

Originally Posted by Newty

I'm going to check this....

Actually it's a small filter that is fitted inside the carburetor right where the gas line connects.

[edmelik]

My 1985 airstream 3450 motor home sat for few years in the hot Needles California sun. I drained the old gas and started and it ran fine. After few days, when I tried starting it, it won't stop flooding the carburetor. I replaced with the brand new Quad Edelbrock carb and this problems still persist. I am told that there's a pressure cutout relay for fuel pressure issue. I looked and looked I can't find such a relay. What could be the issue with this really bad situation? Thanks

[davejay]

Hey
If you have an electric fuel pump back by the tank. Make sure its not a high pressure pump. They look very similar. When I put my fuel injection on I had to buy a new pump. They are identical. One has a black ring around it the other is a red ring. The low pressure pump puts out 13 pounds the high pressure pump puts out 65 pounds. If you got the high pressure pump on a stock carb with no regulator it will overpower the needle valve in the carb. Thus flooding. If you got dirt in the line it can flood. When you put the new carb on did you put a new filter on too. Close to the carb.
Stalling in 15 seconds sounds like the bowl is emptying but not filling back up. I'd be looking at the block fuel pump. It will pump fuel up. But not enough to keep it running. Gas today is really hRd on the diaphragms in the old fuel pump. That would be my guess on the starvation problem . Could also be a coil problem. But thats pretty obscure. When it starts to die. Crack the throttle a little. A little you should see a squirt of fuel . Don't trounce on the throttle. Back fires are hard on the eyebrows when your looking down into the carb. If you don't see fuel she's starving out. If you see fuel its either flooding or something else is causing it to die. Maybe coil related. To my knowledge there is no relay for fuel . Unless you got a computer controlled fuel system. If its a quadrajet carb with a block mounted fuel pump. Then you got a stock set up. Fuel filter fuel pump or blockage in fuel line. Dl