I have a '97 EL Falcon GLi dual-fuel ex taxi. Around 3 years ago when it was a taxi, one of the drivers let it run to empty on petrol, buggering the fuel pump. The owner decided not to fix it, so it's been running on gas only for the last 3 years.
Few months ago I decided to get it running on petrol again because backfires/lack of performance/starting problems are a pain in the arse. When a mate and I took out the old fuel pump, we found the tank was half full of 3 year old petrol
I siphoned out the old fuel and put $10 worth of petrol in, drove around with it for a day to let it swish around in the tank and hopefully pick up any leftover crap in the tank, then siphoned that out. The tank seemed clean enough, so we put a new Fuel Mizer fuel pump in along with a new fuel filter and hooked it all up.
I went and put $30 worth of petrol in and gave it a shot, but it was a no go. Tried many times starting on petrol, driving along on gas then switching to petrol while moving, all sorts of things, but still no go.
You can actually hear the fuel pump make a noise when you turn the ignition to 'ON', whether switched to gas or petrol. Also when running on gas, you can faintly hear the fuel pump doing something. But I'm not too worried about these noises, as I've heard of different brand pumps being louder than others.
I'm thinking the injectors probably need a good clean (haven't been used for 3 years), or maybe the old acidic petrol has done something bad to the tank or something in it. Are there any other possibilities, or what sounds most likely to be the problem?