Driver side
If it has a 360 motor the mechanical fuel pump is located below the distributor. there could be an after market electrical fuel pump located near the tank. these answers are based upon my 89 grand wagoneer with a 360. The fuel pump on an 88 Wagoneer is in the fuel tank itself.
twenty gallons
20 gal
It is a mechanical fuel pump located on the engine. It is in the drivers side front below the distributor.
if it has the 360 engine look on below and behind the distributor. you can follow the fuel line from the carb to it.
Electric.
20.3 gallons
Its a manual / mechanical fuel pump. To check it remove it a look inside. It will be obviouse if its bad. More importantly if its running its not bad. There are no injectors on a 87 Grand Wagoneer. Its corroborated.
the fuel capacity for jeep grand wagoneer in the 80s is between 22 gallons and 25 gallons depending on the engine size
check for: Spark Fuel Compresssion
If it is a stock engine; or if when you look at the engine, there is a large, round air cleaner on top of it, then it is carbureted, not fuel injected If it is a Wagoneer then it is fuel injected in 87. If it is a Grand Wagoneer then it is carburated.
Its under the Listerine plate.