Q: I am having an odd problem with my 2001 Saab 9-3. After the car is fueled, it is hard to start. I have to crank the engine, then stop, crank again, stop cranking, etc. This problem occurred after I had a valve job done on the vehicle. Never happened before. The car will run normally until fill-up time. I thought I could duplicate the problem by removing the gas cap and re-installing it again. No dice. I actually have to add gas. This happens when I refuel at any tank level. Gas cap seal is like new. No tears. What do you think? Air in system, fuel pressure regulator, filter screen? I need your help before I burn out the starter.

A: The two most likely possibilities are a loss of fuel pressure upon shutdown or a problem with the evaporative emissions system. Since you must actually add fuel to create the hard-start symptom, fuel pressure bleed-down is less likely but easy enough to check. Rather than repeatedly engaging the starter, just turn the ignition key from "Off" to "Run" for two seconds, and repeat this a half-dozen times before cranking the engine. If this significantly helps, fuel pressure is bleeding down. This can be confirmed by attaching a fuel pressure gauge to the test port on the fuel rail. The fuel pressure should be 43 psi with the engine running and should hold at least 33 psi for 20 minutes after shutdown.

Check for any fuel leaks near the fuel rail and injectors — all these components were removed during the valve job. Also, pull the vacuum hose off the fuel pressure regulator to see if there's any raw fuel in the vacuum line, which would indicate a leaky diaphragm in the regulator, allowing raw fuel into the intake system.

But I'm more suspicious of the so-called evap system, specifically the spring-loaded float valve that should close as the tank nears full. If this valve doesn't close, as the tank nears full, liquid fuel could be forced into the charcoal canister and flood the engine when the purge valve opens at start-up.

Q: I have a 1994 Mercury Topaz with a 2.3-liter engine and approximately 106,000 miles. During the last three months the engine has stopped as I was driving down the freeway. The first time, after the car coasted to a stop the engine started immediately. The second time, the engine started but ran rough as I limped the car along for about 10 miles, then began to run smooth after I got back into town. My mechanic could not tell me what is wrong because it wasn't having the problem when I took the vehicle to him. I have had "helpful Nellies" tell me the problem is the ignition module, the fuel pump and the injectors. Do you have any correct ideas what is wrong? Hopefully it will be something simple like a fuel filter.

A: The freeway stalling could be related to any of those possibilities, but my first thought was the catalytic converter. If there is a restriction in the flow of exhaust gases due to a failure inside the converter or a crimped exhaust pipe, the symptoms would match your experience closely. Next time it stalls, pull over to a safe location, open the hood and see if the exhaust manifold is glowing. Your mechanic can do an exhaust back pressure test for any restriction in the exhaust.

Motoring note

I just had to include this response to the stuck license plate bolts on a pair of Toyotas. From Pete Gorman, "We had the same problem last year with license plate bolts on our Toyota RAV4. But as soon as we switched from American wrenches to metric wrenches, the bolts came right out. Maybe not the solution for everyone, but it was the solution for us."

You've got to love it — the KISS principle at its best!

Paul Brand is the author of "How to Repair Your Car" and "How to Repair Your Truck and SUV," published by Motorbooks.