Can I convert to external fuel pump?

ChadroG · November 24, 2005

Hey guys, I got a 99 gmc (new body style) 4wd, 5.3, 4L60E, z71. A few days ago I noticed the fuel pump making the tell tell whinning sound. I would'nt worry to bad but the pitch of the sound varries and fades in a few seconds after it starts. It begins by a lower stutering sound then it becomes more constant sound. I know whats coming, but my question is: Can I convert the internal to an external fuel pump. I did this on a 88 but I can't find anything online about doing it with one of these. If I can, any pump recommendations? I got a holley red setting here doing nothing if it will work. Any help would be great. Thanks

redvett · November 24, 2005

Its cheaper, easier & safer to just remove the box and put a new pump in. Cutting the fuel line and wireing it to work correctly wont be easy or safe. Getting the correct fuel pressure is important too.

99Silver6.0 · November 24, 2005

Holley's 12-902 is a good replacment pump to use. Its a 255LPH pump too.

ChadroG · November 27, 2005

Has anybody actually does this though, if so could you share the steps and parts needed to do it correctly.

99Silver6.0 · November 28, 2005

All thats needed is the pump. Ive seen a few guys on Tech use this pump with no problems. Im gonna use the same one. Gotta drop the tank, remove the sender/pump bucket and swap the pumps. Bout it.

redvett · November 28, 2005

Its easier to remove the box.

ChadroG · November 28, 2005

So you are saying the holley 12-902 is a direct replacement ,99 ? Redvette, if you just remove the "box", don't you still have to drop the tank and remove the old pump which could be blocking the flow a bit? At that point why not just put in a replacement pump and let the "box" do it's job? Or, does the old pump not impead flow at all? Thanks to you both for getting back with me on this. Oh yeah 99, have you reflashed your puter in yours? Just wondering if you got milage increase like I did.later

MountaineerTom · November 28, 2005

By "box", he's referring to the bed of the truck (cargo box). Remove the bed, then swap out the internal pump for a replacement internal pump. When you pull the bed off, the pump is mounted right on top of the tank with nothing else in the way of removal.

redvett · November 28, 2005

Just get 2 or 3 good friends to help with the lifting. First remove the box bolts and the screws to the filler neck and of course the tail light wire plugs. Lift it up and back until you expose the tank and the fuel lines at the top. Remove hoses and the retainer ring can be removed with a screwdriver and hammer by tapping the ring counter clockwise. Replace pump and check for leaks and reinstall the box.

ChadroG · November 28, 2005

Oh,ok I'm with ya now. my wife had an infiniti q45 and it had a fuel pump control "box" and I thought maybe it was something like that which you were refering to. thanks

redvett · November 28, 2005

Stick around here a while and you will be talking truck jargon along with the rest of us.

ChadroG · November 29, 2005

Well, I'm from the south and I have always heard it called a bed. But that's cool. Wouldn't it be easier to run the tank dry (if it will make it that far) and drop it? Also on the removal of the pump/sensor assembly, you can you a big pair of channel locks to remove it. Less chance of sparks vs. the screwdriver and hammer. Look at the "how rare is my panel truck" thread in classic and tell me how to get that cab off safely (wood floor) I think I'm gonna need about 10 people for that! Hey 99 silerado, if you check this thread again, are you saying the holley you recommended is a direct replacement? thanks and later guys.

MountaineerTom · November 29, 2005

Me and my brother had to remove the tank on his '99 Blazer. It was somewhat a pain in the a$$. Not much room to get your hands in there, couldn't see very much. If it had been a truck, we would have definately took the bed off.

If you don't have channel locks big enough, use a brass punch (if you have one of those) and hammer to knock the locking ring loose. The brass punch won't spark.

There's pictures of the tank removal and sending unit replacement of his Blazer in the Tech Articles here at GMTC, if you havn't seen them yet.

redvett · November 29, 2005

If you rather lay underneath and get dirt and gas on you you can do it the hard way. Just remember that the fuel lined and wires are going to be above you and you cant see them from underneath.

37packard115c · December 28, 2005

I've replaced the fuel pump on my 2500 3 times now in 196,000 miles. It's getting ready to go again and I don't want to mess with it. I dropped the tank each time by myself, and it is a filthy nasty job. (I've got an 8-ft bed with a cap on it so taking all that off is a heavy pain too) I'd like to get an in-line pump and mount it to the frame before the filter. Holley makes a 255LPH external pump 12-920 that I'd like to use. It’s rated for continuous duty I'll use Kinsler’s 25-micron filter before the fuel pump, followed by a finer-media 10-micron filter on the pump’s pressurized outlet. What I'm not sure about is whether the old pump inlet screen needs to be replaced. Anybody have any ideas?