Got gas?
Get ready for fuel delivery diagnostics By Craig Truglia Truglia is the owner of Car Clinic, a stateof-the-art repair facility in Mahopac, N.Y. He is ASE certifed with a M.A. from Columbia University. In the automotive world he has been trained by Technicians Service Training and Automotive Technician Training Services. Car Clinic’s facility is fully equipped with factory-level equipment and services American, European and Asian vehicles, including diesels and hybrids.
Tip Number One: Give up on current ramping, or don’t even start if you have heard about it. Back in the day, when 90% of vehicles were made by three American companies, there was not a lot of diversity in what fuel pumps these vehicles had. Not coincidentally, when the amperage of these pumps was ascertained using an amp clamp and a labscope, they produced neat looking waveforms, such as the one seen in Figure 1.
T
he present-day is an interesting time for the automotive technician. Perhaps now more than ever, the vehicles that are on the road resist breakdown, and with the help of a few repairs can routinely last about 200,000 miles. This is a far cry from the day when vehicles had carburetors or early versions of fuel injection. While it appears that fuel-saving technologies such as direct fuel injection and the increased use of turbocharg- Figure 1: This 1987 Pontiac Grand Am creates a nice and neat amperage waveform when running the fuel pump. ers may also break down quicker in the future, many of these vehicles are so new they have not Many technicians think that all fuel yet reached the point where they have pumps can be diagnosed this way. However, breakdown-related issues. if they actually tried the technique on vehiSo, the question service technicians need cles made after the year 2000, they would to ask themselves is whether or not they see that the fuel pump waveforms don’t are prepared to deal with a fuel-related no- lend themselves to such easy interpretation. start or misfre. Take a look at Figures 2 and 3. Does this Because the truth is, it has been about vehicle have a bad fuel pump? 20 years since OBD II technology hit the Many current ramping gurus would say market and aside from General Motors “most defnitely.” The problem is, the vehicles, it is not very common to run into actual answer is no! This fuel pump is fne one of these issues. and this is not even a new vehicle, it is a
34 | March/April 2014
