Paul Brand: Put down that hammer, check the fuel pump

Q I have a '99 Chevy Suburban 1500 which has been having a fuel problem. The car will crank but not start. Hitting the tank with a rubber mallet from below while cranking the car will start it. It will then run perfectly and then it will happen again whenever it wants. This problem happens when the tank is full or empty. Is this an ethanol or fuel pump problem?

A Who's your co-driver? Or do you have a very long arm? On a more serious note, how loud is the fuel pump when the engine does run? Can you hear it over engine or road noise? If so, the fuel pump is probably worn.

You can have a shop check the fuel pump for pressure, volume of fuel flow and electrical amperage draw -- how much current it takes to operate the pump. The rule of thumb is roughly one ampere of current for every 10 pounds of fuel pressure. The GM Vortec CSFI (central sequential fuel injection) system requires 60 to 66 psi of fuel pressure, so you'd expect to see roughly 6 to 8 amps of current flow to run the pump. Significantly higher current flow indicates a tired pump.

Can you hear the fuel pump run for two seconds when the key is first turned to the on position, before you crank the engine? If so, but the pump does not run when you engage the starter, perhaps voltage available at the pump drops too low to run the pump -- at least until you "bump start" it with the mallet.

If you don't hear the pump run when the key is first turned on, put your fingers on the fuel pump relay located in the underhood relay center at the rear of the left front fender. When the key is switched on, do you feel the relay click? If so, the pump should run. If not, try a light tap on the relay, or simply try a replacement relay.

If the engine simply takes an extended period of cranking before it starts, the pulsator in the fuel pump might be allowing fuel to drain back into the tank after shutdown. If the engine cranks for a long time but won't start until the oil pressure comes up or the idiot light goes out, the problem might be the oil-pressure switch on the engine, just to round out the list of possibilities.

Bottom line? If the fuel pump won't actually start running until you "thump" the fuel tank, make sure its connections and grounds are solid, but the pump itself is probably the culprit.

Q I own a '95 Chevy Cavalier Z24 with a 2.3-liter DOHC engine and a five-speed manual transmission with 150,000 miles on it.

I just installed a new clutch kit, which consists of a pressure plate, clutch disc and hydraulic release bearing. I have also replaced the shift cables, the shift assembly, the clutch master cylinder and the hydraulic line from the master cylinder to the release bearing.

After replacing all this stuff and bleeding the clutch, I cannot get the car to shift into gear. When the engine is off you can shift into all the gears beautifully, but as soon as you start the engine you cannot shift into any gears.

A Focus on bleeding the clutch. Unless one of the hydraulic components you've replaced is defective and sucks air, or there's an air leak somewhere in the clutch hydraulics, you've probably not bled all the air from the system.

GM issued a service bulletin, 01-07-31-002A, with an updated bleeding procedure for the clutch system on this vehicle. It involves repeatedly applying and releasing 15 to 20 inches of vacuum on the reservoir, using a hand vacuum pump and adapter, until no more bubbles appear and the fluid level no longer drops. The idea is to pull any air from the hydraulic release bearing, up the tube and into the reservoir -- more effectively bleeding the system.

When you installed the new clutch disc, it should have slid easily onto the splines of the transmission input shaft. If the disc is binding on the splines, even a clutch that's properly releasing will drag significantly, causing shifting problems.