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I have Fiat Punto 2 1.2 with LPG (sequence, stag 4).

There is problem with the injection on the 1st and 4th cylinders. Sometimes it works and sometimes it doesn't. 2nd and 3rd work without problems. It does not matter whether it is running on gas or lpg.

Any clues what may be wrong? Where is the fault?

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It's not a fuel injection problem

I don't see this issue as a fuel injection problem, I see it as an ignition problem.

You have two coils in your car. One for 1 and 4 and one for 2 and 3. It's setup is similar to a motorcycle with a 4 cylinder engine.

If you have one of the coils go out you lose spark on two cylinders.

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I am not familiar with you exact model so it may be different. All of the cars I am familiar with don't run LPG through the same injectors that are used for gasoline. The LPG has an entirely separate fuel delivery system. What makes you say the injectors aren't working?

I suspect, again based on the models I am familiar with that you have a spark problem not a fuel problem. If the spark plugs for 1 and 4 share a common coil that's the first thing I would check.

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We have checked a coil and sparks, they are working fine. What we have checked signal on injectors controller and found out that sometimes there is no signal on 1st and 4th. So it is not injectors itself that are broken but their controller. There is + signal all time but - is never there. Sometimes after a moment on full gas it works fine. Electric schema of this controller would be helpful to search for a problem. We try to avoid replacing a full element. – Gustek Apr 21 '13 at 13:55
@Gustek But the propane doesn't go through those injectors does it? The propane system uses a separate fuel control in the vehicles I am familiar with. – Move More Comments Link To Top Apr 21 '13 at 17:02
Injectors are separate but controller is common. We are going to detach LPG this week to check if it is going to be fine just on fuel. – Gustek Apr 28 '13 at 13:02

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