An odd question for an odd situation! Please help!

[S10-CRUSHER]

Hey guys,

I have a 99 Ranger, 4.0 with an automatic.

I have an odd question that I would THINK that I would know the answer to, but...here it goes:

When checking the voltage at the ACTUAL fuel pump, what voltage should I see on my meter?

I won't get into what's goin on too much, but basically when I first turn the key on/engine off, I'm getting 11.59 volts. IMMEDIATELY after I see the 11.59 volts, it falls down to 6.65 volts.

Is this normal?

Any help is most appreciated!

-TNT

 

[IlovemybroncII]

Hey crusher I dont know but my thinking is it would have full power at start up to pressure the fuel line then shut off or power down and as you drive it powers up to spin motor a little faster to keep up with presure lost as you use fuel just my thinking hope it helps with your ?

 

[dogboy]

The voltage decreasing, makes sense to me, except I would think the voltage would drop all together.
When you turn the key, the pump pressurized the system, then since the system is pressurized, it no longer needs to run.

 

[S10-CRUSHER]

Hey thank you guys. I appreciate your information.

The thing is, since 2007, I've gone through 3 fuel pumps. I figured when I replaced the first one in 2007, it was because of the age of the pump. At that time, I replaced the fuel filter and then the fuel pump relay went out. So...I replaced it.

This time, I took the pump out and noticed the pump sock is almost BLACK verses the normal "fuel yellow" or off-white. With the pump out of the truck, I submerge the pump in a can of fuel, connect the + and - to the battery directly and the pump works but the fuel shoots only about 6 inches away from the pump. The "kick" that it had before isn't there. I'm thinking that there's something in the tank that's clogging the pumps. However, I'd like to rule out this 6.65 volts...CRAP from being the problem. I'd hate to drop the tank if I don't have to.

I need to be positive this 6.65 volts...thing...is ok.

Thank you again for your help on this.

-TNT

 

[89jeeper]

Im surprised there arent more people are offering advice for you TNT? Sure would be nice to hear about why your Ranger is going threw so many fuel pumps huh?

 

[masterbrenden]

i just don't know
maybe the cuase of your problems the brand of the pumps your getting
i know airtech pumps hate the high pressure needed to run the 3.0l

 

[BRUTUS_T_HOG]

the pickup sock in the tank is a water separator, they get clogged by having too much moisture in the tank and/or too much sediment. do you have any EVAP codes or check engine light? check the fuel tank vent, also what is the fuel pressure? a bad regulator will cause failure by running it at max output all the time. check the fuel pump ground too.

try filling up at a different station and using a fuel dryer additive like red HEET

i would also recommend NOT replacing a fuel pump with a remanufactured.. ever, they take used pumps, test them, clean them, and ship them out to john q. citizen to buy. the same applies for starters, and alternators and a lot of other things

 

[feellnfroggy]

Once the pump is pressurized the voltage lowers to slow the pump down. When the pump runs at full speed it will recieve full votlage. Rule of thumb, anything inside a circuit board should be either +5 volts or nothing(on or off) anything such as a power wire will be 12 volts at full draw. A partial draw will weaken or slow down the component/s.

 

[89jeeper]

So... you think he might have issues with his evap canister? Could it be possible its sucking in debris from off roading? Causing things to end up in the fuel tank burning up his fuel pump? Is the evap canister even serviceable?

 

[BRUTUS_T_HOG]

the evap system can have problems and cause too much condensation in the tank. water clogs the pickup sock

 

[S10-CRUSHER]

Hmmmm...this is all so interesting. Thank you guys for all of your advice.

What scares me is it IS an Airtech pump! All 3 of the pumps have been Airtech.

I'm not getting any check engine light codes at all! The light isn't even on.

Fuel pressure is perfect! Right in the specs! Also, I just replaced the Fuel Pressure Regulator about a month ago.

Maybe I should look into the EVAP canister for malfunctions. So, is this canister serviceable?


Well, the truck runs now. I took the tank down, cleaned it completely as there was a lot of suet and sand inside. I replaced the pump and BAM...the truck runs great again! Maybe I'll get a few more months out of this one!

Thank you all again for your assistance.

-TNT