Questions and Answers

Mazda B2300 Won't Start Intermittently Q. Vincent, I have a 1994 Mazda B2300 2.3 liter SOHC, 5 speed manual transmission, A/C and P/S. It has about 85,000 miles. The problem I have is that it will randomly not start. There is no rhyme or reason to the pattern. The engine will turn over just fine and I have fire but no gas.

I can tell when it is not going to crank by turning the key and the hum of the fuel pump doesn't happen. Sometimes if I turn the key off and on several times the fuel pump will eventually hum and she will start right up. Other times no matter how long I try, nothing. Then If I let it sit for a while it may start the first time.

I have had it in the shop two times but you know the routine, by the time it gets towed in the thing fires every time and no codes. I even left it in the shop for over a week and it started three times a day the whole time.

Now to what I have done so far, new fuel pump, new fuel pump relay switch, new inertia switch, fuel filter. If its got anything to do with fuel, it's new. I know these problems are difficult to track down but any help would be appreciated.

I just can't figure out what would cause the fuel pump to not work one minute and work fine the next. Also let me add that once it cranks it runs great and never knocks off, the problem is solely at start up. Help if you can.

A. The Fuel Pump relay supplies power to the fuel pump when a power signal from Powertrain Control Module (PCM) is applied. When the ignition switch is turned ON, the Electronic Engine Control power relay is ENERGIZED, providing power to the fuel pump relay.

Fuel pump power is provided through the fuel pump relay contacts and an Inertia Fuel Shutoff switch. If the PCM does not receive an ignition signal within approximately one second, a timer circuit in the PCM will open the ground circuit to the fuel pump relay, causing the fuel pump relay contacts to OPEN. This action stops the power supply to the fuel pump.

So, at this point I would try replacing the PCM Power Relay and see what happens.