Diagnostics & Repair

Our technicians are factory authorized and can answer any questions you may have about diesel diagnostics. Make an appointment at our drive-in facility in Eugene, Oregon or contact us to have your problem diagnosed. You can also find diagnostic information and tips below.

Pump and Test Room

Diesel vehicles and components today often require specialized diagnostic computer tools to get to the root of a problem. We can test injection pumps including Bosch, Stanadyne, Delphi, Zexel, CAT, Denso, Cummins, Siemens and more. Our staff is also factory authorized to test Bosch, Denso, Delphi and Siemens common rail injectors.

Light Duty Diesel and Diesel Pickups

Industrial, Construction, Farm, Marine and Other Applications

Diagnostic Tips

Below are common diagnostic issues with diesel vehicles. While we do not advocate replacing parts before a complete diagnosis with a professional, these tips below may help you find a solution.

Pyrometer Probe Installation

  • We recommend that the pyrometer probe (stinger) is installed into the exhaust manifold ahead of the turbocharger. This allows for a more accurate temperature reading.
  • The old “rule of thumb” that the reading is 150 degrees less if installed after the turbo is no longer accurate.
  • The difference in temperature readings varies with boost pressure increases. For example, at 15 PSI boost pressure, the difference will be about 150 degrees. Many engines today run 30 PSI (300 degrees difference) to 40 PSI (400 degrees difference) of boost pressure, particularly after performance modifications. In other words, if the probe on your pickup is installed after the turbo and you are getting 900 degrees at 30 PSI boost, the true temperature of the exhaust gases are (900+300) 1200 degrees.
  • We have heard concern of the probe possibly break off and going through the turbo, but we have not seen a broken Isspro pyrometer probe in over 15 years.

Low Power

  • Always change the fuel filter before conducting further diagnostics if it is dirty or if it has been more than 7,500 miles since the last change.

Fuel Filter Changes

  • We recommend changing the fuel filter(s) every 7,500 – 10,000 miles.
    Note: Dodge is the only manufacturer that recommends a different interval for severe service. This is because more fuel is used during severe service, thus the filter has to filter more fuel.
  • DO NOT fill the fuel filter through the fuel outlet!
  • A secondary fuel filter is normally rated at 8-10 microns (25 microns = .001 of inch).
  • You can’t see the contamination that a filter will remove from the fuel.
  • If there is a way to prime the fuel system without filling the filter (electric fuel supply pump or hand primer) do that. If not, then fill the filter through the inlet holes (usually the smaller outside holes). That way, the fuel will be filtered before it gets to the injection system.
  • The newer fuel systems need even closer tolerances. HEUI (i.e. Ford PowerStroke) requires 4-7 microns and high-pressure common rail (i.e. Duramax and 2003 Dodge) requires 2-4 micron filtration.
  • We carry the O.E. filters for Dodge, Ford, and Chevrolet diesels as well as add-on units from Racor.
  • Do not cut open the fuel filter to check how dirty it is. Instead, vigorously shake it out into a clean container. Look for extreme amounts of contamination (fuel that looks like mud) or water. This will help determine fuel filter change intervals.

Contact Us

At OFI, our factory trained experts have the proper scan tools and repair equipment. The best way to solve a problem is to perform a complete diagnosis. Contact our diesel specialists today.