So, a fuel pressure regulator, does exactly what it sounds like, it supplies fuel pressure.
It is capable of, putting out pressures, from 25 to 60 psi, depending on the type vehicle you have.
But, it does not do, it all by itself. It is actually, the (ECM) that controls it, based on inputs from, sensors and vacuum levels in the engine.
The fuel pressure regulator and all related parts, work together, to maintain a mixture ratio of 14.5 to 1. As a result, the pressure is constantly changing, based on the needs of the engine.
The computer uses, sensors to determine everything from:
- Air density
- Air temperature
- Temperature of the engine
- Load on the engine
- Position of the throttle
The computer takes this information and decides on a strategy; to get the best performance out of the engine. So, one of these strategies is; to determine, how long to keep the fuel injectors on. Consequently, to maintain this fuel ratio; the fuel pressure must be maintained, within one pound. When the engine is suddenly under heavy acceleration; the vacuum drops off. Only, momentarily and then recovers, within a very short period of time.
This sudden drop in vacuum during acceleration, also affects the pressure. As a result, the injectors are suddenly opened longer. The fuel pump takes a second to catch up with the pressure. So, the regulator reacts to the drop in vacuum; by closing the fuel return line momentarily. Finally, this gives a momentary boost in pressure.
Signs of a Bad Fuel Pressure Regulator:
Blackened spark plugs
Take out a spark plug to see if the end is sooty, which could mean a bad regulator.
Runs poorly and engine stalls
If your engine isn’t running smoothly or idles poorly, it could be a sign of a bad regulator. The same goes for your vehicle occasionally stalling.
When black smoke comes out of your car’s tailpipe; it is a sign that there is a problem with the regulator.
Fuel smell on dipstick
If you smell gas on the oil dipstick, it is a sign of the fuel pressure regulator failing.
Fuel dripping from the tailpipe
If you notice gas dripping from the tailpipe of your car; it is a sign of either overfilling the fuel tank or a bad fuel pressure regulator.
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