I have a faulty fuel pressure regulator which makes cold starting difficult especially in winter. I am looking for an engine diagram that would show where the regulator is and how to replace it, to see if I could do it myself.
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Could be the fuel pump relay, or a faulty pump, or pressure regulator. The fuel system is supposed to hold pressure after you turn the engine off. A faulty pump or pressure regulator could allow fuel to drain back into the tank overnight. You would need to crank the engine for several seconds to build pressure back up. The relay could be faulty and not giving the fuel pump power until the oil pressure comes up.
I would be considering testing/replacing engine coolant temperature sensor. A faulty sensor can send signal that engine is already warm when it is still cold, thus, less fuel delivery than needed at time of engine being cold.
This is almost certainly caused by a lack of fuel pressure . The fuel pressure will be fine while the engine is running but when it is switch off the pressure won't hold . In the trade we call this residual pressure . What happens when this fault occurs is that the fuel in the engine fuel rail will vaporize and hence the hard starting .
There are three possibilities : leaking injectors , a faulty pressure regulator valve or a faulty check valve in the fuel pump .
First thing to do is to check the fuel pressure while the engine is running and then switch the engine off , if the pressure drops drastically over a period of 20minutes then you will know you have poor residual fuel pressure . Note if you have not done this before seek help as this can be dangerous as you could set your car on fire .
Next , use fuel hose clamping pliers to pinch the fuel inlet hose ( having restarted engine and then stopped again ) . If the residual pressure drops you have a faulty check valve ( replace fuel pump ) . On the other hand if the residual fuel pressure stays remove the injectors and get them serviced . If the problem is still there replace the fuel regulator .
Note use an approved fuel pressure gauge - the fuel pressure is very high ( 250 - 500 kpa )
If the residual fuel pressure was ok do the same procedure on the fuel return line whilst
I take it you're doing an oil change and made this discovery? Some gas is normal, especially after winter months (high idle/choke) Could be sticky injectors - run a good fuel system cleaner through it, clean MAF and oil change/filter and check after about 2-300 miles. If there's alot of fuel, then you might consider changing injectors
check for a very dirty or clogged air filter, faulty Manifold Absolute Pressure sensor (or Manifold Air Flow sensor), disconnected or faulty Engine Coolant Temp sensor, disconnected or faulty Intake Air Temp sensor, and leaking fuel injectors or a stuck open cold start fuel injector. A pinched or blocked fuel return line from the fuel pressure regulator to the tank is rare but could also be a cause.
you need to have the Engine Coolant Temperature switch checked,since the
computer relies solely
on sensors,the ect tells the computer how cold or hot it is so the computer will
make it a rich or lean mixture to start the engine,if it tells the computer that
it is 75 degrees the computer will lean the mixture like starting a car in the
winter without a choke.
There should be a Schrader valve on the fuel rail (looks like a valve stem on a tire, it is metal).
You need to connect a fuel pressure gauge to that valve and do the following test:
Relieve fuel pressure.
Remove the 12 mm sealing nut from the fuel rail. Attach the fuel pressure adapter nut, 12 mm (90201 - P0A - 003) and the special tool.
Start the engine. Measure the fuel pressure with the engine idling and the vacuum hose of the fuel pressure regulator disconnected from the fuel pressure regulator and pinched. If the engine will not start, turn the ignition switch on, wait for two seconds, turn it off, then back on again and read the fuel pressure. Pressure should be: 260 - 310 kPa (2.7 - 3.2 kgf/sq.cm, 38 - 48 psi)
Reconnect vacuum hose to the fuel pressure regulator. Pressure should be: 210 - 250 kPa (2.1 - 2.8 kgf/sq.cm, 30 - 37 psi) If the fuel pressure is not as specified, first check the fuel pump. If the fuel pump is OK, check the following:
If the fuel pressure is higher than specified, inspect for:
Pinched or clogged fuel return hose or line.
Faulty fuel pressure regulator.
If the fuel pressure is lower than specified, inspect for:
you could have a couple differnet issues. cold start misfires, an intake air leak, poor compression with engine cold,or a fuel pressure issue with a leaking injector or fuel pressure is bleeding back due to a faulty pressure regulator. my recommendation is to buy a fuel pressure gauge and monitor pressure overnight. you could also pull the fuel rail and see if an injector is leaking at the same time. you can spray the intake system with a highly volitile liquid(with engine running) to see if idle speed changes to check for an air leak
It may be due to a failed/faulty fuel pressure regulator. I had this problem: easy start when cold, hard starting when warm/hot, and rotten egg smell from exhaust when warm/hot. My mechanic diagnosed a failed/faulty fuel pressure regulator, replaced it, and now the problems (warm hard start, smell) are gone. I have a '92 GT with L4 engine.