Q: I am a regular reader and really enjoy your column. Back in the day, I was a certified auto mechanic. But that was long ago. Perhaps you can help out with an issue I've been encountering.
I have a 2003 Cadillac Seville STS with a fueling issue that has recently occurred three consecutive times.
As one normally would, I go to fill up when the tank is close to empty. But after leaving the station and accelerating slightly, the car shuts down. After a re-cranking, the car will start back up but then spurts and spits and sputters and shuts down again. I have to go through this process six or eight times before it'll finally start properly. The car then runs fine until the next fill-up.
I suspect there's something wrong with the gas-fume recirculation system. Please help!
_ David M.
A: David, see if you can get your hands on a generic onboard diagnostic scan tool and take a look at the short-term fuel trim reading as your Caddy is sputtering.
If you notice a big swing in the reading (positive 20 percent or more), that's confirmation that a lean condition is occurring, likely because of a flakey fuel pump. Sometimes, when an in-tank electric fuel pump is on its last legs, a sudden temperature change brought on by filling up your tank can cause flakey operation or a total loss of operation.
A fuel pressure test during an episode would confirm a pump malfunction.
The EVAP (fuel vapor containment) and ORVR (on-board refilling vapor recovery) systems are unlikely to cause such a fault. If something was going on with one of those systems, you'd likely see rich symptoms, such as black smoke or a negative-percentage fuel trim.
Q: I have a 1989 Ford Mustang with a four-cylinder engine and 107,000 miles on it.
I generally drive it around town, starting it up five to seven times a week. On very rare occasions, it won't start. (It turns over, but just won't start.)
I know the issue's happening right away because I won't hear the electrical fuel pump hum when I turn on the ignition.
I then have to wait a few hours (sometimes overnight) before it will start again.
This happens only every three or four months. Other than these rare occasions, it starts right up and runs great.
My mechanic is sure it is not the fuel pump because the car and fuel pump work perfectly when the car is running. The fuel pump relay and the ECC relay have been replaced. My mechanic doesn't want to just throw parts at it, not being sure of what the problem is. Since it is so sporadic, it's really hard to pin down. Any thoughts on identifying this gremlin?
_ Ron G.
A: I'm thinking it might be the fuel pump.
Try this: Take a length of wire and insert one end _ bared and wrapped around a paperclip _ and insert it into the pink/black wire cavity of the fuel pump connector. Take the other end and connect it to a multimeter.
You'll be ready to go next time the Mustang acts up and will be able to confirm if an acceptable voltage (11 volts or more while cranking) is being sent to the pump. Baring a bad connection at the top of the tank, a good reading at the relay says the pump is not doing as instructed. A tired fuel pump can sometimes be cranky to get going but work acceptably afterward _ for a while.
