Rvr Checking Fuel Pressure, RVR Checking fuel pressure Options

[aharryph]

Hi,

I tried checking the fuel pressure on a RVR 94 4G63 non-turbo engine. When I started the car it seems the pressure are normal around 40psi (~38 psi based on manual). I tried the procedures in the service manual, removing vacuum lines from Fuel pressure regulator gives around 47 psi. I cant determine if the fuel return hose has pressure in it.

The only thing I noticed is that when I turned off the engine, the pressure gradually drops. Although it does not drop that fast that it is still in ~38 psi after 2 mins. However, after leaving it for about an hour, the pressure drops to almost zero. Is this normal? Also, starting seems not a problem just need to crank it for at least 3 seconds. I still need to observe from cold start though since this is my first time to connect a fuel pressure guage.

[grndsm]

Hi,

I tried checking the fuel pressure on a RVR 94 4G63 non-turbo engine. When I started the car it seems the pressure are normal around 40psi (~38 psi based on manual). I tried the procedures in the service manual, removing vacuum lines from Fuel pressure regulator gives around 47 psi. I cant determine if the fuel return hose has pressure in it.

The only thing I noticed is that when I turned off the engine, the pressure gradually drops. Although it does not drop that fast that it is still in ~38 psi after 2 mins. However, after leaving it for about an hour, the pressure drops to almost zero. Is this normal? Also, starting seems not a problem just need to crank it for at least 3 seconds. I still need to observe from cold start though since this is my first time to connect a fuel pressure guage.

It should stay pressurized for a few hours. If it isn’t, you must have a slow leak in the fuel system (faulty fuel pump, fuel pressure regulator or a fuel injector). But it is such a minor leak that I wouldn’t worry about it.

What made you check for this in the first place? Extra long cranking on start-up? If so, try leaving the vacuum line off and starting it.

[aharryph]

It should stay pressurized for a few hours. If it isn’t, you must have a slow leak in the fuel system (faulty fuel pump, fuel pressure regulator or a fuel injector). But it is such a minor leak that I wouldn’t worry about it.

What made you check for this in the first place? Extra long cranking on start-up? If so, try leaving the vacuum line off and starting it.

My cranking is not that long though and it does not bother me. The reason why I checked the fuel pressure is that my plugs are black (not wet though). I just want to know if im getting high pressure, which causes the dark plugs (running rich). I just changed my O2 sensor but still running rich. O2 sensor always read between .7v - .8v while idling.

[grndsm]

My cranking is not that long though and it does not bother me. The reason why I checked the fuel pressure is that my plugs are black (not wet though). I just want to know if im getting high pressure, which causes the dark plugs (running rich). I just changed my O2 sensor but still running rich. O2 sensor always read between .7v - .8v while idling.

How is your exhaust manifold? Is it cracked, by any chance?

[aharryph]

How is your exhaust manifold? Is it cracked, by any chance?

Exhaust manifold I think is ok. But last month I have my mufflers checked and found leaks. I already have it welded though it does not make any difference.

[grndsm]

Exhaust manifold I think is ok. But last month I have my mufflers checked and found leaks. I already have it welded though it does not make any difference.

Leaky mufflers should not make a difference. But a leak before the O2 sensor can allow fresh air to come in. That gives O2 a lean reading and ECU compinsates by adding more fuel. End result: you run rich. Cracked exhaust manifold often cause this condition.

Now, you might think that exhaust pressure should force exhaust gasses out and now allow fresh air to come in. That isn't always true! A exhaust pulses can create montary "low" pressure spikes (in the exhaust manifold) and sick-in fresh air.

[aharryph]

Any inputs on how to test if this is the cause of running rich?

My O2 sensor behaves like, at start it runs from 0v and slowly rising upto .8v during idle. Cutting the idle switch by opening the throttle body a little, does not make any significant difference. I tried disconnecting the MAF connection and O2 sensor reads lean mixture. Also disconnecting one of the vaccum hose (while MAF is connected) allowing uncounted air to pass directly to throttle body makes the mixture lean as well. By this test, I think the O2 sensor works fine.

Also, if the cause is in the exhaust system, I should be running lean with O2 sensor disconnected, right? But eventhough O2 sensor is disconnected, it still running rich.

Leaky mufflers should not make a difference. But a leak before the O2 sensor can allow fresh air to come in. That gives O2 a lean reading and ECU compinsates by adding more fuel. End result: you run rich. Cracked exhaust manifold often cause this condition.

Now, you might think that exhaust pressure should force exhaust gasses out and now allow fresh air to come in. That isn't always true! A exhaust pulses can create montary "low" pressure spikes (in the exhaust manifold) and sick-in fresh air.

[Benckj]

Disconnecting the O2 sensor will make engine run in open loop mode or very rich. Not sure what O2 sensor you are running and if getting up to temperature for correct operation (600F). Is it a one, two or four wire configuration?

Couple of other comments on your thread. Fuel pressure will not make engine run rich as this is controlled by your injectors. stuck or dirty injectors will make run rich.

Dirty MAF or AFM will make a rich mixture as will a blocked induction due to dirty air filter. Presume you have done the basics first before you started diving into all the internals.

I'll attach a link on O2 operation so you may check your volatge values to the correct readings. I believe from memory you are running very high values at idle.

http://auto.howstuffworks.com/framed.htm?p...G/o2sensor.html

Jim

[aharryph]

Thanks Jim. Ill check your link. The stock O2 sensor is 2-wire but I converted to 4-wire by putting the 12V to the heater wires.

By the way, I just replaced my air filter with a new OEM filter. Im not so sure if the MAF works right but when I pulled the connector the engine almost stalls, so I think its working well right?

I did also pulled up the injectors and cleaned it. I think its not blocked or stucked.

Disconnecting the O2 sensor will make engine run in open loop mode or very rich. Not sure what O2 sensor you are running and if getting up to temperature for correct operation (600F). Is it a one, two or four wire configuration?

Couple of other comments on your thread. Fuel pressure will not make engine run rich as this is controlled by your injectors. stuck or dirty injectors will make run rich.

Dirty MAF or AFM will make a rich mixture as will a blocked induction due to dirty air filter. Presume you have done the basics first before you started diving into all the internals.

I'll attach a link on O2 operation so you may check your volatge values to the correct readings. I believe from memory you are running very high values at idle.

http://auto.howstuffworks.com/framed.htm?p...G/o2sensor.html

Jim

[Benckj]

Not sure how you would get on adding a 12v supply to an aftermarket O2 heater. I think it goes through a warm-up stage and then turns it off like a thermostat. You may be getting too hot and receiving false signals which coresponds with your values. Should run lean though and not rich if I'm interperting this right.

I don't think that unplugging your MAF is a reliable test. There is more to than just that, such as your ISCV and temp sensor. Someteimes these just need a good clean with contact cleaner and replace. Have you tried doing this and possibly testing like the manual suggests.

You really can't 'clean' the injectors by removing and giving them a polish. They are calibrated to spray correctly internally. If it isn't correct they will not spray but squirt raw fule and not combust. Best thing to try is to run some injector cleaner through the tank to see if makes any differance

Jim

[aharryph]

Yes Jim. At first, I observed that 3 of the cylinders are running rich while the other is running good. After several diagnosis, I found out that it is the injector that makes the cylinder run different from other by swapping the injectors with other cylinders. What I did, I run a fuel injector in the tank to clean it but it still behaves the same. So I decided to clean them myself.
I cleaned my injectors by pulling it, putting a fuel hose on it with Fuel injector cleaner and pressurized air and supplying voltage to make it spray. It seems that all of them sprays evenly. Although at first it does not spray evenly but later it did after a few tries. After that, I think the injectors run evenly causing all the cylinders to run rich.

With regards to O2 sensor, I really would like to have the O2 heater to turn off when the sensor is already heated. However, the stock ECU I got does not have the pin where it is connected. Im looking if I can put it in ECT circuit but havent tried it yet.

I already checked and cleaned my ISC motor and throttle body. Im not sure of the temperature sensor (Engine Coolant Temperature sensor right?). Since I do not have a good thermometer on hand, I cannot do the test as what the manual says. However, I saw in the manual that when ECT is damaged, the ECU will assume that the coolant is hot (failover behavior). What I did is that I pulled the ECT connector to appear malfunctioning in the ECU, so the ECU uses the failover behavior. But it does not make any difference in the O2 reading.

[Benckj]

To the best of my knowledge you cannot clean & check injectors at home unless you have an ultrasonic blaster. They also need to get calibrated to deliver the correct amount of fuel and spray pattern. I'll attach a useful link for you to read.

http://www.bba-reman.com/content.aspx?cont...air_mass_meters

http://tunemycar.com/index.html

On the O2 sensor if you only have a single or two wire configuration you probably do not need the heater as the sensor is placed near the exhaust manifold and gets up to the correct temp on its own. By suppling auxilary heat not controlled by ECU the system may not work correctly excepton start-up. Leave the heater off and test the sensor for correct operation to ensure it is working properly.

The temperature sensor I was referring to monitors the incoming air temp and adjusts the fuel
ratio accordinaly. Not sure about the RVR but usually its located just upstream from the throttle body as part of the AFM in the induction pipe. I know if you mess with them to much they get damaged as the thermistor is quite fragile. If you wanted to test could probably measure the reistance at various temps.

Jim

[aharryph]

Thanks Jim. I will try your advices.

One thing I noticed is that the purge control nipple in the throttle body does not produce any vaccum. Idle also does not change when the vaccum hose is pulled. Im not so sure if this is normal.

Also, my BISS screw head is already damaged that I cannot adjust it anymore. I noticed that when I cover the top of the screw with my fingers, the idle changes slightly.

Hopefully the vaccum leak is the culprit. Releasing counted air out from the intake manifold thus making the mixture rich.

Will a vaccum leak puts the ECU into open loop operation?