Fuel Pumps on Dual Tanks 1990 4.9L
07-23-2012, 03:20 PM
#1
Fuel Pumps on Dual Tanks 1990 4.9L
Each time I start the engine I have to turn the switch on and let the fuel pump (does this on both tanks) run for a short period of time before the engine will start. If over night it may take 2 mins. before starting, if less than and hour since the engine was stopped maybe 10 seconds. It seems as if the pump has to fill the fuel line before it the engine will start. Once the the engine starts no problem with acceleration. Has a little engine miss when first started.
08-21-2012, 04:07 AM
#4
The fuel pump is suppose to kick on for 3-5 seconds when the ignition is switched. when you hear the pumps kick on how do they sound easy to hear, or do they sound weak? The only thing i could think is the pump is wearing out but it seems unlikley that they would go at the same time. it takes 2 minutes to build pressure in the lines on either tank after sitting overnight?
08-21-2012, 09:16 AM
#5
check the wiring to the pump, my buddies truck had the same issue. It had corroded terminals and wiring. He had to splice in a foot of wire on all of the fittings, and he covered them in dielectric grease
08-22-2012, 07:48 AM
#6
I was thinking that the fuel pressure regulator might be getting bad -or- if there's a check valve on the return line somewhere, that might need to be replaced. Could be the high pressure fuel pump or the wiring to it is going bad.
Just to be on the safe side ... change the fuel filter to rule that out ... if you haven't done so already.
There's a pressure relief valve up on the frame rail. The reason it's there is so that you can relieve the system pressure before doing work on the fuel system.
Check it and see what the pressure is with the motor running.
Check it with engine off.
Restart the engine, shut it off, and check the pressure a couple hours later.
Do the same thing after it's been sitting overnight.
It might point to a problem somewhere other than the low pressure pumps on the fuel tanks.
Just to be on the safe side ... change the fuel filter to rule that out ... if you haven't done so already.
There's a pressure relief valve up on the frame rail. The reason it's there is so that you can relieve the system pressure before doing work on the fuel system.
Check it and see what the pressure is with the motor running.
Check it with engine off.
Restart the engine, shut it off, and check the pressure a couple hours later.
Do the same thing after it's been sitting overnight.
It might point to a problem somewhere other than the low pressure pumps on the fuel tanks.