How many volts to the fuel pump?

[85 Jimmy]

Well, I have ANOTHER issue with my TPI swap. Last weekend my truck was running fine. Today, I go to crank it up and my fuel pump is not cycling on with the key in run or cranking.
I pull out my multimeter and it doesn't work, swap the batteries and still doesn't work. So I grab my test light, get my wife to feel the relay to tell me if it is clicking and it is, so I use the test light to see if I'm even getting power to the pump. IIRC the purple wire is for the dash, so I checked the white wire. It barely lit up the test light. So I guess I need to fix one of my multimeters to see how many volts are going to the pump.
Is it supposed to be a full 12v or is it cut down somewhere along the way?

 

[ryoken]

yeah, you'll definitely have an issue.. either low pressure, or more likely wont run at all... fuel pumps LOVE good voltage...

check your ground and also doublecheck/eliminate the relay by putting 12 volts directly to the red jumper wire hanging out of it...

 

[85 Jimmy]

Just fixed my multimeter and checked my stuff. Battery shows 12.04v, the fuel pump relay shows 11.96v going into it, and it was 7.45v out, but I had a spare relay, so I swapped them out and now have 11.68v out, then the pump shows 11.64v at the connector before the pump...

I guess I need a new pump. This will be my 3rd pump since I swapped in TPI...

 

[ryoken]

try the walbro 255's, mine kicks arse...

make sure that tank grd is good... and make sure you bench test the pump when you pull it to verify it has an issue....

I recently had the wire in Mutt fail as it goes thru the plastic piece into the tank... I thought my pump was bad.. pulled it, threw 12v at it and it worked fine.. woulda been pissed if I had just thrown a new pump in it and it didn't work...

 

[85 Jimmy]

I'll bench test the old pump. The bad thing is I have 3/4 of a 31 gallon tank...

 

[ryoken]

been there... it's doable.. just take your time setting it up.... floor jack and the proper lumber and you can do it.. I find not only is it important to have good balanced x-bracing between the jack and tank, but also blocking for the tank to sit on when you drop the jack down.. extra pair of hands is a big help too...

 

[dyeager535]

Crack the fuel filter, it will siphon. It's slow, but you don't have to sit there. If you wanted to not loose all of it, you could put a hose over the end of the hose to a bucket.

 

[K85 Octane]

Walbro= yuk
Delco unit for a TPI= win

And only cause my 255 was whiny from the start, gave me problems, and finally struggled to pushed ~20psi.

You can also put a cheap pump on the line and pull all the gas out through the dead intank pump. Or do like I (and so many others) have done. Rear access panel

 

[ryoken]

my Walbro kills it daily...

 

[eagle mark]

Just had a new post in garage with another dead Walbro pump...

Is it supposed to be a full 12v or is it cut down somewhere along the way?

Yeah, 12 volt or very close to whatever batt is. Then the ground back there by tank is always an issue. When I build a harness or redo a pump I run the ground back up to engine block.

To get all the Walbro has to offer it usually needs bigger wire then what comes on stock GMs.

 

[ryoken]

delete

 

[85 Jimmy]

I'm going to test the current pump before I drop the tank. If it is confirmed dead I'll just put an ac delco in it.
Hopefully I can mess with it this weekend or next week after work, since it's my spring break and I can actually do stuff after work.

 

[85 Jimmy]

Well, I dropped the tank and tested the pump, it was bad. I replaced it with an AC Delco ep241, so I guess I'll see how long this one lasts.

Is there anything in particular that will kill a fuel pump? Just so I can know if there's something I can do to prevent this again?

 

[ryoken]

running them low on fuel a lot is bad for them, as they get their cooling from being submersed...