VW Golf 4 1,4 16V 55KW / 75HP - It fires hard after a few hours on gasoline

Golf fires hard on gasoline for a few hours. You have to spin several times until it catches up, when it starts and comes a few seconds, there is no problem with the next firing. It has a gas installation STAG sequence installed (about a year) and when it stops and I want to start on the gas itself there is no problem fires the first time, the problem is only on gasoline.

After connecting the car to the computer there are no errors. He replaced the throttle (used), intake manifold gaskets, spark plugs, I cleaned all connections in the intake system and nothing helped, I also checked the fuel lines from the fuel tank to the engine, if there is any leakage and everything is ok. After turning the key you can hear the pump clearly Fuel runs for a few seconds. After starting the car runs without problems on gas and gas, no jerking.
What else can I do because I have no ideas ???

Check the injectors and fuel pressure regulator.

The fuel pump in this car is supposed to start for a few seconds and raise the pressure on the strip after opening the driver's door - check it. If it does not work then you have a damaged microstock in the lock ... quite a common fault in G4 and derivatives

the pump starts when the door is opened and the ignition switch is overestimated, and when today I tried to turn the ignition several times so that the pump strikes the fuel in the system, the car fires. So I'll replace this pressure regulator and see if it helps, all indications are that when the car stops, the fuel retracts and the pump fails to finish the fuel at once. In this case, I do not know how to check the injectors so I will leave them alone.

Symptoms indicate a fuel pump - gives too low pressure

it's just strange that once it fires up it can be extinguished and fired once without a problem, there is no trouble jerking while driving.
I ordered a pressure regulator and we will see how it will not help the pump will also need to be replaced, I will let you know next week how the effects

You run on LPG, i.e. in the tank, as a rule, you do not have too much gasoline, which makes the pump often unwell - I would start by changing / replacing the pump

in my opinion, the car drives normally, i.e. it is always in the tank 1/3 tank - no reserve, but it can be a pump, this week I will replace the pressure regulator and the next one is the pump, let me know how the effects

Check the fuel pressure on the rail, pump or regulator still suspicious.

Check what the cold temperature sensor shows. Unplug for gas test and put it out on gasoline, see how it fires.

I tried to extinguish on gasoline, but the same effect, I even drove on gasoline for some time, and it still does not work well. I already have a regulator, if I write it I will write what effect

after replacing the regulator there was an improvement, it is not 100% of what it should be but I have to stop there, the car belongs to my friend and said that it is already good, for me it is not quite a successful repair, but we will see how it will deteriorate and it will be replace the fuel pump then let me know if it helps, sometimes thanks for the hints they helped