Reduce Gas Direct Injection Fuel Pump Replacement Comebacks By Checking The Timing Set

When a newer gasoline direct injection (GDI) engine shows a “low fuel pressure” code, the standard repair procedure is to replace the fuel pump. Yet, a failing fuel pump isn’t always the cause of low fuel pressure.

If the timing set in a GDI engine fails, the engine may put out a diagnostic trouble code for high or low fuel pressure. So that means there may be issues with the timing chain or the chain tensioner. Your shop will reduce comebacks if your techs take the time to check the engine timing set while replacing the fuel pump.

Symptoms Of A Failing Timing Chain Or Chain Tensioner

Broken timing chain
Image Credit: NutJob
  • Non-smooth rpm increase from idle
  • Knocking or rattling sound coming from the engine while idling
  • Metal shavings in the oil pan
  • Trouble starting the engine

Timing Chain And Chain Tensioner Diagnosis Tips

  • Use a stethoscope to listen for noise coming from the engine. Listen for a knocking or rattling noise.
  • If the engine runs a little rough, it may have timing set issues.
  • Ask about oil consumption and oil change interval history, and check for signs of an overheated engine. Those issues can lead to timing chain failure.

Recommended Replacement Fuel Pumps

Of course, a fuel pressure code may simply mean that you need to replace the fuel pump. When replacing a fuel pump, keep GMB pumps in mind. Our pumps are designed to meet or exceed OEM specifications. GMB fuel pumps:

  • Provide OEM grade electric motors that meet OE specs for operating voltage, current draw and resistance.
  • Use 99.9% pure copper in the windings of the motor. This helps the pump run cool, and increases longevity.
  • Meet or exceed OE specs for pressure and flow rate.
  • Use an external aluminum housing to shed heat and improve longevity.
  • Come with a 150 micron pre-filter (strainer). The pre-filter uses a long lasting synthetic filter media.

GMB manufactures more than 1600 fuel pumps. You can search for a pump on this page.

Why It’s A Good Idea To Check The Engine Timing While Replacing The Fuel Pump On A GDI Engine

When your shop gets a car with a “low fuel pressure” trouble code, be sure to have your techs also check the engine timing. Whether or not the fuel pump is failing, you want to make sure that the car’s engine timing is good.

A failed chain tensioner or stretched timing chain could cause an increase or decrease in fuel pressure a moment too early or late. This leads to symptoms associated with low fuel pressure. A GDI engine with timing issues may put out a “low fuel pressure” diagnostic code. This occurs when the timing issues haven’t become severe enough for the ECU to recognize them as such. Until then, the issues may be misinterpreted as low fuel pressure. If your shop is working on a high mileage GDI engine that still has its original timing chain and tensioners, it may need a new timing set.

The next time a GDI engine shows a low fuel pressure trouble code, be sure to check the engine timing set in addition to the standard diagnoses for low fuel pressure. It’s possible that the problem is with the timing chain or chain tensioner. If the timing set is found to be faulty, replace it along with the fuel pump. That will help reduce the number of fuel pump replacement comebacks.


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