NO PRESSURE
| Truck Trend Garage No Pressure
Question: I noticed a letter called "Start Me Up" in Truck Trend Garage in the November/December issue of Truck Trend, which I found interesting because I, too, recently had the same problem with my 1998 Ford F-150. It had been a mystery for about three weeks. Sometimes it would start fine, then after running errands I would come back and it wouldn't start. The first fix was the IAC valve, but this fix only lasted a week. I had it towed back to the dealership to get it fixed. The mechanic couldn't duplicate the malfunction. The fuel-pressure gauge checked out good, injectors fired in harmony, spark and ignition coil were good, and the OBD II diagnostic scanner wasn't picking up any faults. The third week, I got stuck and had the mechanic come to where I was stranded. Before he got in, I told him "don't get mad if it starts" and, wouldn't you know it, the sucker started. When we got it to the dealership, I turned the truck off and decided to start it one more time. This time, it didn't start. I got the mechanic, he got his fuel-pressure gauge and, lo and behold, the fuel pump was intermittently failing and we had to catch it at its no-start mode to solve this problem. I'm not saying this is a fix, but it's a place to start when an engine turns over but won't start. Put a fuel-pressure gauge on to see if it's up to par. It should read approximately 40 psi. The fuel pump was changed and I've had no more problems since.
Answer: Thanks for your input! Yes, a fuel pump is always suspect when investigating an intermittent no-start condition. Patience from both the technician and driver, along with good communication, is crucial in diagnosing these types of failures. I'm not sure why, but for many years, fuel pumps have been a common failure on a lot of American-made cars and trucks. They often don't reach the 100,000-mile mark. On the other hand, a fuel pump cutting out in most Japanese models is a rarity. There's a big difference in the fuel-delivery systems used in your 1998 F-150 and the 2004 model referenced in our previous reader's question. Your 1998 uses a return-fuel system. This means fuel is sent to the injectors from the pump in the tank, where a mechanical fuel-pressure regulator allows pressure above a specified psi to go back to the tank through a return line. That's how the system maintains the correct pressure. The electronic returnless system, used in the 2004 F-Series, does not have a fuel-pressure regulator or a return line. Instead, a fuel-pump-driver module monitors fuel pressure with a sensor at the injectors (fuel rail) and varies voltage applied to the in-tank pump. This in turn controls fuel-pump speed and pressure output. Several different versions of returnless systems are phasing out the fuel-return method of earlier model vehicles.
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage -- visit Alex Steele at www.RealWorldAutomotive.com.
