I need to know what size fuel tanks i have for a 1987 Chevrolet r10 pickup

13 gallons

change coil coils go bad they short out when they heat up

I don't have a diagram but I can tell you the pink wire going into the tank should be the sending unit for the gauge.

Is there power getting to the fel pumps? perhaps a restricted filter?

yes, it could be a relay... you could also have a leak. Is the pump in the tank or outside the tank? if inside,. you may want to recheck your work..

try to smack the gas tank with a rubber mallet with someone cranking the key .if it starts then the pump is no good .otherwise the relay should be on the pass side of the firewall.poss under a long black cover.the fuse will be in the fuse box under the hood on drivers side. var fctb_tool=null; function FCTB_Init_0b704873de9943d2aa9b1abbb4656a28(t) { fctb_tool=t; start(fctb_tool); } FCTB_Init_0b704873de9943d2aa9b1abbb4656a28(document['FCTB_Init_72d341bf61da4120a5167e6de35ebcf0']); delete document['FCTB_Init_72d341bf61da4120a5167e6de35ebcf0']

The fuel pump is in the fuel tank,it needs to come down to replace the pump.Probably a 4.3l v6.

For 1987 Chevrolet Truck R10 1/2 ton Sub 2WD 5.7L TBI 8cyl the Fuel Filter is located under vehicle, passenger side, below seating area, near fuel tank, mounted on frame rail in fuel line.

Hope this help.

check the float on the carb is stuck shut not letting fuel in

Assuming you don't have some kind of Space Shuttle technology to work with, the best thing to start with is an empty gas tank. When you install the sending unit the little float will be hanging down and the gauge should read empty. You can do some minor adjustments to the float while you are monkeying around with it so that, for example, "Empty" is not empty. This way even if the gauge is reading empty you will know that you have a few gallons left in there as a back up reserve so even if you are reading in the reserve range that you know you will still have a couple gallons left in the tank when you hit the big "E".