The D16 is a 1.6 liter 4-cylinder engine used in the sixth generation Honda Civic CX, DX, EX and HX (plus some additional low volume variants.) These were manufactured between 1995 and 2000. This engine employs multi-point fuel injection, an advance over the single port system used previously that Honda referred to as “PGM-CARB.”
Note that the seventh generation Civic, sold from 2001 to 2005, came mostly with the 1.7 liter D17 engine. This has a returnless fuel system, (meaning the fuel pressure is regulated at the pump) so these notes are not applicable to those vehicles.
No special tools are needed beyond a set of metric sockets or wrenches and pliers.
Locating the regulator
When viewing the engine from the front of the vehicle, the regulator is on the right end of the fuel rail. This looks like a length of aluminum extrusion running the length of the engine behind the valve cover. The regulator is easily reached without removing any other engine components.
Whenever you work on the fuel system it is extremely important to follow good safety practices. This includes not smoking and keeping a fire extinguisher close by.
Start by relieving the pressure in the fuel rail. (On this engine rail pressure is between 38 and 47 psi.) There are several ways to do this. The easiest is to remove the fuel pump relay then start the engine. If it runs at all it will quickly die, signifying that the fuel rail is empty.
An alternative is to find the fuel filter – it’s usually mounted on the firewall behind the engine – and loosen the banjo bolt on the top. Be sure to first cover the bolt to catch the gas as it sprays out! You may wish to take this opportunity to replace the fuel filter.
With fuel pressure relieved, disconnect the battery at the negative (black) terminal. This is to prevent any risk of electrical sparks.
Using pliers, disconnect the fuel return line at the regulator. (If a screw-type clamp has been used, a flat-blade screwdriver should do the job.) Also disconnect the vacuum hose running from the air intake. If there is a cover over the rail it should be possible to reach the regulator without removing it.
Use a little gasoline to lubricate a new ‘o’ ring and install this in the rail. Then fit the new regulator and tighten the bolts.
Reconnect the vacuum hose and the fuel return line.
Replace the fuel pump relay and reconnect the battery.
Turn the ignition key to run the pump and pressurize the rail, then start the engine. With the engine running take a look for leaks. Assuming there are none, the job is now complete.