2000 volvo s70 difficult to start, more so as fuel level drops. Cranks fine. Recently changed MAF sensor, B+ cable, plugs, fuel filter - no improvement.

code p0102 refers to MAF/VAF sensor ---low input ===causes --wiring short to ground. MAF/VAF sensor
code po172 refers to system too rich --bank 1=== causes ---intake blocked --EVAP canister purge valve---fuel pressure ---HO2S sensor
code po random misfires ---plugs --wiring ---injectors--low compression
code po305 refers to cylinder 5 misfire detected ===causes --engine mechanical fault--ignition/ fuel system ---injector ---ECT/MAF

I would check that the air filter is not blocked first as it affects the MAF/VAF sensors . Have a fuel pressure system pressure test done

I understand you replaced the relay but not the pump, right ?
Has the fuel filter been replaced recently ? Are you sure there is gas in the tank ?
You should be able to jumper the pump relay and check fuel pressure.

It could be the converter. The MAF sensor was a guess, because that often is a cause of loss of power. Other possibilities are a dirty air filter, or a partially clogged fuel filter, or a fuel pump/pressure regulator problem not allowing proper pressure at the engine's fuel rail. And that's the short list.
The easiest way to check the converter short of disconnecting it and testing operation of car without it hooked up is with a pocket IR thermometer laser temperature reader. The car needs to be at normal operating temperature-say after a 20 minute run time. Measure the temperature of the exhaust pipe entering the catalytic converter and the pipe leaving the converter. If the exit temperature is about 100 degrees hotter than the entry temperature, the converter is probably good. With a plugged or failing converter, the exit temperature will be the same or lower than the entry temperature.
If the converter is good, check your air filter, fuel filter, and have a free scan test done at AutoZone of your engine's computer (OBD2 fault scan test). There might be a trouble code pointing to the problem, like for example, the MAF sensor.
Good luck. Post back if you need further assistance.

Hello,
When the MAF on most vehicles reach a point of preventing the engine from starting, you can usually just unplug it and the engine will start. If that doesn't work-
You may want to try having the O2 sensor, ( Oxygen sensor ), checked. It works with other components of the emission system and can cause similar symptoms as the MAF, including preventing the engine from starting.

Donnie

Fuel pumps are common on these cars. Its a hard fault to duplicate with a gauge because they rarely die at idle! I would still connect a gauge and see pressures though, see what happens to them when it starts to die (if it will at idle). 99/100 times you need to replace the fuel pump, and fuel pump relay. The relay overexcites and burns out your fuel pump. As long as you dont have AWD its not a difficult job, if its AWD then you have to lower the whole back end of the car (springs, diff, AOC....) to lower the tank enough to get to the pump. Make sure that you align the pump correctly or you will have a false fuel level reading.

I would replace the fuel filter, air filter, and plug wires, that should take care of the obvious culprits

I'm having the same problem. At first I thought it was bad fuel so I replaced the fuel filter to no avail. Then I cleaned the Mass Air Flow sensor which also didn't work. Is your check engine light on?

Have the car checked to see if it has a speed sensor it could be giving you a bad reading.

Sounds like a fuel filter problem, replace your fuel filter. Call an auto parts supply store for the location of the filter

If the air pump system is setting a fault, then the check valve is probably bad. If it is not addressed, eventually exhaust gases can run back through the air hose to the air filter housing and destroy the MAF sensor, causing these types of problems.

The fuel pump also fails and is a more likely cause of the stalling, and it wont set a code.