Howdy Fellers,

Okay, I got one. Just bought a very good 95 Ford - starting to put a wrench to it this weekend, but I've got an issue with the rear gas tank. So, before I start tearing into things, I thought I might ask you folks with more experience. So here it goes:

When I flip the switch from front to rear, the motor instantly dies. Okay, maybe a 1 second delay. But, if I put the switch back to front and turn the key, she'll fire right up. Now, when I bought the truck, the rear tank was bone dry and the cap was missing. I replaced the cap, put 10 gallons in it, checked for leaks and listened to see if the pump was coming on, flipped the switch and nothing.

Now am I confused or, do both lines come into a Y-junction and then flow through the same fuel filter? Cause if they do, then the engine shouldn't be dying right away cause there still should be some fuel in the main line.

Well, that's all I've got and I've just been fixin my own for the last couple years, so not very experienced and don't always understand shop-terms. 'Preciate any and all help, you guys and gals have a good day.

Thanks!

Matthew

 

The pump in your back tank is dead or it's not getting 12v. The fuel system in these trucks maintains 45psi at the fuel rail by pushing a whole lot more fuel volume than the motor can actually use most of the time, and the extra is just cycled back to the tank. This is why the engine dies immediately when you switch tanks, because fuel pressure immediately drops to zero.

 

Thanks Conanski.
Figured Id be swapin the pump,The current one comes on but must be sick.
Is there A method of checking for good pressure with out A gauge?

 

No there is not, any time the fuel pressure drops below 28 PSI the engine will die if it is a V8. It will not restart until it has 28+ PSI fuel pressure if it is a V8.
You did not say what engine you have.
The fuel pressure gauge do not cost that much and if you have a FI truck why not get one?

 

Hey Subford.
Well now,There are A lot of tools I need to get,That would be one of them,Just got A local job 3 weeks ago,Been OTR truck drivin for years,What self repair I get done is hit and miss and my repair degree is from the school of hard knocks -
I just bought this truck,Cant find any sticker info,it was listed as A 1995 ford F150 V8 only but the block looks larger than A 5.0 , Maybe 5.8 - Other than the tank I need to swap out

 

the sparks,wires,cap/core - hopefully I dont mess up too bad with distributer -New territory. .

 

I do not understand what you are trying to say.

 

if you block the truck up, on ramps or something, you can reach over the next to last cross member and get to the wires that connect to the tank. consulting a wiring diagram, glean which two supply power to the pump. Key off, engine off, connect a test light, switch to rear tank and have someone toggle the switch. should see a glow for fuel prime. if you do then suspect the pump.

not hard to get at the pump, however the tank now weighs 70lbs more than it did a little bit ago so suck out the gas.

if it was dry for some time and the cap was off, I would suspect the integrity of the tank....might be time for a new one, as well as the suspected faulty pump.

 

OTR - Over the road truck driving ,
The rest was just ramblins about my repair list , But I ran out of room and had to use A new window -

 

10 - 4 Thank You.

 

My case is overflow but when I hit the switch everything runs fine but the gauges.

What I am not sure if the low pressure pump is working or not.

My understanding (may not be correct) is the following.

Toggle switch to front tank = Low pressure pump on front tank starts pumping; actuating the fuel tank selector valve.

Toggle switch to rear tank = Low pressure pump on rear tank starts pumping; actuating the fuel tank selector valve.

Is that the ONLY function of those low pressure pumps?

 

No they also fill the fuel reservoir in the selector valve for the high pressure pump to use in when going to WOT. The engine also can die going up a hill or when the fuel tank is less than 1/2 to 1/4 tank full without them.

And of course thy prime the fuel lines from the tank they are in to the high pressure pump if you run out of fuel.