Back in the early 1970’s, I was a Ford Dealership mechanic. One of our customers had bought a new Falcon Utility, but returned the following day saying that it had developed an extremely annoying, intermittent “buzzing” sound somewhere in front of him in the dashboard area. We went for a drive with the owner but heard nothing. This scenario was repeated several times with the same results over the next few weeks.

Eventually an extremely frustrated owner managed to have me drive in the vehicle, and I finally heard the noise! Now we knew the sound we were looking for. We removed the dash and everything else back to the firewall, checked, and re-assembled everything. We never found the cause but the noise was now gone ... or so we thought until the owner returned the following week.

The shop manager and I were put on the case. One of us drove while the other, with feet in the air and head up under the dash, looked for the source of the sound. On day two, I started the car, and the buzzing started immediately. As the seat was too far forward for me, I reached under the seat, grabbed the seat release handle to move the seat, and the buzzing stopped immediately. Hah ... I found it! A small plastic knob mounted on the metal seat release lever, retained by a small grub screw, was loose! I tightened that tiny screw and all was well.

Steve in New Zealand

A few years back, I wrote an article (Do I Need a New Fuel Pump or Timing Set?) on how a camshaft-driven gasoline direct injection (GDI) fuel pump might incorrectly take the blame if an engine's timing is off. The fuel pump is fine, but the computer is adjusting fuel pump pressure up and down at the wrong times. This article is about the opposite scenario, the timing chain is in decent shape, but the GDI fuel pump is finally giving out after heroically generating thousands of PSI of pressure for many hours/miles.

A failing GDI fuel pump might make noise. The pump might stop suddenly or intermittently if the solenoid(s) that are used by the computer to control fuel pressure burn out. Seals inside the pump may start to leak.

Symptoms of a leaking GDI fuel pump might include gasoline showing up in the engine oil. The dipstick could show rising oil levels in the crankcase, and (flammable!) gasoline fumes might be noticeable. Surprisingly, computer trouble codes associated with a too rich air/fuel ratio might start turning on.

When the engine warms up, some of the gasoline now sloshing around in the crankcase vaporizes and gets sucked into the intake via the positive crankcase ventilation (PCV) system. These unexpected gasoline fumes make the mixture too rich, especially at idle when intake vacuum is highest and the most air/fumes pass through the PCV system.

Be sure to follow the instructions in your vehicle's repair manual (found under "Literature" at RockAuto.com) when replacing a GDI fuel pump. It is important to safely dissipate fuel pressure before disconnecting fuel lines. A low pressure electric pump in the fuel tank typically delivers the gasoline to the mechanical high pressure GDI fuel pump. Repair manuals often suggest unplugging the fuse for the low pressure fuel pump while the engine is running. The engine will stall when the available fuel (and fuel pressure) are used up.

As with any fuel pump, it is easier to unplug the fuel line connectors if you have the correct fuel line disconnect tool. The extreme pressure in a GDI system often means the high pressure fuel line fittings are "one time use." A fuel line with distorted fittings has to be replaced.

Fuel Line, Camshaft Follower & GDI Fuel Pump

There is typically a fuel pump camshaft follower that moves with the camshaft and drives the rod/spring jutting out of the GDI fuel pump. The pump's spring is often under a lot of pressure. Repair manuals typically recommend loosening/tightening the pump's mounting bolts evenly to avoid sudden movement and/or twisting that might damage the spring, rod or camshaft follower. While the pump is removed, it is usually a good idea to inspect/replace the camshaft follower if possible.

To minimize the pressure on the spring/rod, repair manuals typically recommend having the camshaft lobe/camshaft follower in its lowest position before installing the new GDI fuel pump. The instructions will typically say to put piston one at top dead center (TDC) or put a thick, rod-shaped tool in the camshaft hole and watch for it to reach its lowest point while the engine is slowly turned over by hand (using breaker bar and socket to rotate crankshaft).

See the fuel pump(s), fuel lines and other fuel system parts for your specific vehicle under "Fuel & Air" in the RockAuto.com catalog. Find camshaft followers under "Engine."

Tom Taylor,
RockAuto.com

To read more of Tom's articles, click this link and choose from story titles on the Newsletter Archives page.