The normal mode of operation is to bleed off pressure back into the tank after a period of time. I have a fuel pressure gage and, even when at 0 psi, it starts right up without having to prime / pressurize the system.

Even if it were a bad fuel pump, it would not cause a backfire condition. I just replaced mine and, while it most certainly does induce both poor idle and poor running condition due to erratic ouput, it most certainly will not induce backfire. Even if one or more cylinders were not to receive fuel it would not backfire- run very rough, but not backfire.

That's either a clogged CAT, an ignition misfire due to bad ignition wires, or a number of other things, or, it could be a faulty cam or crankshaft sensor as both affect the timing sequence. Those would definitely cause a rough running condition and backfire.

I would start there first.

 

Ok I dried to test the 02 sensor the way the book tells me to but that did not go so well not knowing how to read the meter so well. So I unplugged the up stream 02 sensor and the problem went away but now eng. lights on. So I have not brook down and spent the money for a new one yet. most like tomorrow. But would this mean that the sensor is bad or this still could mean the power control is bad ? By the way my book says there is a 02 on the left side and so do the auto parts stores but I shore do not see any on left side. Only up stream and down stream on right side.

 

That is totally incorrect. You do not know what you are talking about. A fuel injector cannot pump fuel. A Fuel injected car will NOT START without fuel pressure, unless you pour gas down the valve body.

Second fuel is not supposed to bleed off. Pressure is maintained by the fuel injectors being closed and the pressure regulator check valve, in the gas tank or on the fuel rail.

I never addressed backfire. Backfire can be caused by many different things. In a fuel injected vehicle BACKFIRE can be caused by;
1. Emission control system problems,
2. Faulty spark plug wires or coil
3. Vacuume leak at fuel injectors, intake manifold or vacuume hoses
4. Burnt Valves, or incorrect valve timing.

Please post good info. Look it up. Its in your service manual.

Checking O2 sensor;

there are 1 2 3 and 4 wire O2 sensors. 1 wire O2 signal comes from the one wire and ground is achieved via the metal on the sensor. 2 wire systems use signal and ground to pcm. 3 wire have a heater 2 wires for the heater and 1 wire for the signal. 4 wire 2 wires for heater and 2 wires for signal. The signal should go up and down rapidly. You can use a scope to watch the signal or a scan tool to watch the voltage go from around 0Vdc to .80 Vdc or so. In closed loop the vehicle reads a rich condition and cuts the time the fuel injector is turned on until it reads a lean condition the lengthens the time the fuel injector is turned on. This cycle continues over and over and the average of that cycle gives better fuel mixture rating. The Stoichiometric ratio is the air-fuel ratio necessary for complete combustion is 14.7 to 1. BTW they have a new O2 sensor that works so fast that instead of going up and down constantly it regulates the fuel mixture real time. This new sensor can save about 20% or more on fuel economy. I am still trying to find one to buy.

 

I sure do know what I am talking about and did post good info. Giving you the benefit of doubt here to be the nicer guy here, either you failed to comprehend what was stated or you misunderstood what was written.
Do you run a fuel pressure gage on your vehicle?

This is what I responded to: The vehicle is off and, you had recommended priming the lines by activating the pump in order to pressurize the system PRIOR to starting. My response was that even at zero psi at time of startup, it will still start without issue providing that the pump is fine.

Some fuel systems use a valve at the pump to relieve pressure as a failsafe mechanism to prevent fire due to fuel leaks. Similar to what happened when Ford's were keeping the fuel pump alive while the car was off. It resulted in fuel leaks which in turn resulted in an engine bay fire all while the car was off and sitting in the garage.

My post is accurate and, there's no bad information. I just think that you misunderstood what was said. I recommend getting a gage, installing in-line and monitoring fuel pressure at time of cold startup and learning. Again, a reading of zero psi at time of startup yields no issues as long as the pump output is correct.

Please, for others sakes, slow down and read before telling others that they are posting bad information.

Thanks,

CM,
Engineer,
Aerospace and MIL Electronics P.E.

 

I didn't mean to come off as rude but matter of fact. This site is to help others with problems that have been solved by offering solutions to problems that others have had that match their symptoms. Suggested solutions do not always solve the problem because the symptom may be the same but the problem is different.

I read your information and stopped when I read ;

It is not normal for any EFI vehicle to bleed off pressure. It does happen over time and some vehicles may bleed off the pressure sooner than others by way of the parts used in the EFI system but it is not normal. Go to any autoparts store and read about the fuel and exhaust systems on any EFI vehicle and they will all explain about the "Fuel pressure relief procedure"

The one thing that threw me for a loop was you statement " I have a fuel pressure gage and, even when at 0 psi, it starts right up without having to prime / pressurize the system." Think about that statement for a second. It is impossible for an EFI engine to start or run without fuel pressure. Internal combustion engines do not work without air, gas and spark. No fuel pressure no gas.

That is all I have to say about that.

Anthony
SR Service Engineer, Mechanic, Electronic Engineer.

 

It is not impossible. A zero psi does not constitute NO PRESSURE at all and was not what I meant. Your not thinking all the way through as all you see is NO pressure and, in your mind, your assuming that there's no pressure AT ALL hence your comments about how it would not run etc.

The thing is, this is PRIOR to start up- there's NO PRESSURE PRIOR to hitting the key. After the key hits, of course the pump instantly pressurizes the system. I also stated this by means of when the pump is operating correctly. You missed that.

The other thing is that you say it's not normal to bleed off but, then you go on to say that some do bleed off etc. So, that contradicts the statement of it not being normal when in fact, it's only that it doesn't seem normal to you.

Ford bleeds off after a period of time just as I stated in my original comment. Chevy bleeds off and so do Dodge. To my knowledge, I have yet to witness a system that maintains positive pressure 100% / time indefinite. To maintain 45-50 psi indefinitely is dangerous. Most systems maintain pressure for a given period of time but, no system is going to maintain static load indefinitely due so safety factors.

That's exactly why I mentioned Ford. Ford was maintaining full operational psi while non-operational and look what happened. That was catastrophic failure due to holding the psi constant over long periods of time. When the vehicle is off for many hours and that pressure is held constant, something is going to give as was clearly evident in the failure videos of those vehicles. Factor in the environment and thermal loading on the fuel system and the pressure goes up even higher.

Even with high burst ratings on the lines and fittings, the system is still susceptible to leaks at the O-ring interface and cross-over lines as well as at fittings. Fords were blowing out the cross-over interface and / or supply line interface fittings.

Again, due to fault, positive pressure was sustained until the fuel lines started to leak and **** gas all over the hot manifold. So, if one keeps a constant pressure on the system at all times without relieving it at some point in time- the probability of a leak becomes greater. And, as anyone knows, engineer or not, fuel leaks are something to be concerned about no matter how big or small.

 

When I run into Idle problems that make you go humm. I always start with a tune up. Replace wires, cap and rotor and sparkplugs or at least remove and check the condition of the parts. Inspect all plugs, sensors and valves, IAC, MAP, MAF, Battery connections, throttlebody and Air filter. A weak coil can also cause problems and is hard to check. n If you want to go a little further check vaccume at idle and at 2000 rpm, This alone can tell you a lot about your engines mechanical condition and a compression tests and leak down test will tell you every thing mechanicaly you need to know.

Ask an Engineer and he can tell you how to make it. Ask a Service engineer and he can tell you how to fix it.

Anthony

 

It is not impossible. A zero psi does not constitute NO PRESSURE at all and was not what I meant.(are we talking about what is is?) (0 psi means no pressure, or does 0 psi mean something else?)
Your not thinking all the way through as all you see is NO pressure and, in your mind, your assuming that there's no pressure AT ALL hence your comments about how it would not run etc.

The thing is, this is PRIOR to start up- there's NO PRESSURE PRIOR to hitting the key. After the key hits, of course the pump instantly pressurizes the system. (instantly, come on your a Professional, it takes some time to pressurize a fuel system. A milisecond, 2 seconds, 30 seconds?) I also stated this by means of when the pump is operating correctly. (we are trying to determine if the pump is operating correctly that was why I had him cycle power 3 or 4 times, or did you miss that?) You missed that.

The other thing is that you say it's not normal to bleed off but, then you go on to say that some do bleed off etc. So, that contradicts the statement of it not being normal when in fact, it's only that it doesn't seem normal to you. ( try being more precise. I did not contradict my statement read it again "everything bleeds off over time. Due to temperature changes. Different materials expand and contract at different rates )

Ford bleeds off after a period of time just as I stated in my original comment. Chevy bleeds off and so do Dodge. To my knowledge, you said ":I have yet to witness a system that maintains positive pressure 100% / time indefinate (as I said they bleed off over time, but it is not a normal thing but will varry depending on environmental factors) To maintain 45-50 psi indefinitely is dangerous. Most systems maintain pressure for a given period of time but, no system is going to maintain static load indefinitely due so safety factors. (I never mentioned this and have no idea what you are talking about.)

That's exactly why I mentioned Ford. Ford was maintaining full operational psi while non-operational and look what happened. That was catastrophic failure due to holding the psi constant over long periods of time. ( I have never heard of this and think you may be talking about the cruise control module that was catching fire) When the vehicle is off for many hours and that pressure is held constant, something is going to give as was clearly evident in the failure videos of those vehicles. ( what a crock of ****, these systems are engineered and designed for continuous duty, which means you can start you vehilce from the dealer and never turn off except for refueling and service and it should last for the time rated on age and exposure, degradation) Factor in the environment and thermal loading on the fuel system and the pressure goes up even higher.

Even with high burst ratings on the lines and fittings, the system is still susceptible to leaks at the O-ring interface and cross-over lines as well as at fittings. Fords were blowing out the cross-over interface and / or supply line interface fittings.

Again, due to fault, positive pressure was sustained until the fuel lines started to leak and **** gas all over the hot manifold. So, if one keeps a constant pressure on the system at all times without relieving it at some point in time- the probability of a leak becomes greater. And, as anyone knows, engineer or not, fuel leaks are something to be concerned about no matter how big or small. (Blow your smoke somewhere else......)

 

So, you tell me what is normal then. According to you, it is not normal to bleed off as witnessed in the above quote but, here we have a contradicting statement: So, which one is it, not normal for any EFI system to bleed off or, "everything" bleeds off? Do you see that? That's a contradictory statement if I ever saw one being implied.

So, if everything bleeds off, then everything (being all EFI systems) must NOT be normal. True?

If that's the case, normal would be to hold pressure at a constant. Yes? No? Maybe? What is the norm? Since the opposite of losing pressure is to maintain and hold pressure, it is the same as constant / static pressure when the vehicle is off. If this is true, then why do Fords, Chevy and Dodge Truck vehicles lose pressure over long periods of time? Are they all in need of repair? The answer is no, they are not in need of repair as the normal mode is to bleed off pressure as a safety precaution.

As for Ford, this was not relating to the cruise control switch that was igniting brake fluid but rather another issue.

We are talking psi and, zero psi means just that- no pressure. Are you still confused? Next:

Now as far as the pump latency in delivering fuel- it was a figure of speech and, of course it's not instantly but, it's not a matter of seconds either. Your really splitting hairs here to support your weak argument.

Where does this come into play? This is called the coefficient of expansion rate and is applied to dissimilar mating materials such as two substrates that come into contact with one another. It also creates a shear force. The plenum gasket is a great example of this and why they fail and leak at the gasket interface.

But, in this case, the lines are steel, they are all made out of the same material and, are round, are thin walled, are not solid, thermally are not affected to the point of changing internal diameter to drop 50 psi and, even if they were made out of rubber, (I use rubber) the material does not expand to the point of dropping 50 psi. So, that rules that theory out. Next.

I know you have no idea what I am talking about as it's quite obvious. I know you didn't mention that directly but, in a way you did without even realizing it. It is a good thing your not a lawyer as you'd be losing all your cases due to verbals.

When you mentioned the fact that bleeding off is not normal, you are implying that normal mode is NOT not to bleed / lose pressure. Since the opposite of losing pressure is to maintain and hold pressure, it is the same as constant / static pressure.

Another weak argument. You know I saw that as seen here: So, yes, I saw that. That's why we have them do this but, why you asked that question I will never know as I had commented on that very same thing twice. Next.

Sure, that's the INTENT but, let's look at some real world examples. At one time, I worked for Boeing Space as well as Raytheon and numerous other defense contractors as an engineering contractor / consultant. Not as an auto mechanic fixing cars. So, when you work in the field on the design end and, in the manufacture of the products, you know and experience things that many find shocking to say the least.

Let's look at all the failures from faulty wheel bearings, to failing steering knuckles, failing front end axles that just fall out as one is driving. Supposed to be designed and all factored in right? And, what's the safety factor at? It's supposed to be high yes? You do know what safety factor is correct?

Then, with all these factored in, one may ask, why do we have failures? I will answer that because you don't know. It's because an error was made in either design or, it was made at time of manufacture. It wasn't detected until out in the field under real world use.

Speaking of that, here's a good one for you to chew on. At time of designing fuel injection systems on Chevy vehicles long ago, they had tested them and stated that they met spec at x-miles before MTBF. All looked good and they were on their way.
Well, they failed almost immediately out in the field under real world use. Why? They didn't test them right. What they did was to put a brand new set in an engine and ran the engine non-stop for months and months ok, but, what they failed to replicate was the fact of stopping and starting the motor! Sludge buildup! Trapped particulates from the fuel pumps and unclean fuel etc. Someone erred OK.

I have done failure analysis involving space satellite components, to missile components to auto components in both vibe and shock as well as thermal loading, thermal shock, salt tests, fungus tests, corrosive tests, humidity, UV tests etc. This includes hoses and, let me tell you, that some human chose the materials, some human made the part and some human checked the parts and, at one of those stages, someone erred.

Let's look at the Ford tire fiasco that killed lots of people. Those tires were SUPPOSED to be rated for x-amount of miles and, at x - amount of speeds. Look at what happened- they fell apart while new. Obviously FAILED to meet OEM continuous duty may I point out.

I now know that there's no way your out working as a designer or, in the field making products because, if you were, you would have never made that comment about how things are designed for continuous duty. I do however, believe that your an auto mechanic working on cars primarily.

Every product ages as a function of it's use environment and, every product is susceptible to failure thus never meeting it's life expectancy. This is due to variables in the desgn, raw materials, in the manufacture of ALL components and sub assy levels to, how well it was tested to final assy, quality control and a whole lot more.

Another example is the Ford switch issue. It was "supposed" to last at least the OEMs MTBF spec but, reality was, it FAILED to meet those specs just like the tires on Fords FAILED to meet their ratings. So, you say it was designed to last ok, but, the reality here is that it too, FAILED to meet it's MTBF ratings.

I have seen fuel pumps in Boeing planes explode in mid flight. Walk to talk about MTBF? Are you familiar with that term MTBF? Do you know what this means? Reliability engineering: are you familiar with it ? I am but, I don't think that you are. The argument of continuous duty ratings is now is riddled with holes. It holds no water due to real world examples of real failures on real parts that were supposed to last a hell of a lot longer than they did. This can be applied to anything made from home appliances to hi tech defense weapons.

Heck, in some cases, good luck getting it to meet the warranty period never mind the product life expectancy.

 

My father was the best "needler" as we called it. When playing golf and you were down you "needled" or agitated your so called oponent to get him upset and make mistakes. I was just having fun with you cmckenna.

I really don't care to argue. I have been repairing cars and trucks for over 20 years. I currently fix cnc machines, cars and trucks that no one else can figure out whats wrong with them, or they have spent thousands to try and fix and they give up. I know what I can do.

I have read everything on EFI operation theory, OBDII systems and emmision controls just to name a few things. I would call myself an expert and cannot off the top of my head give every detail on every manufactures system but can find the answer to any problem.

I have a god given tallent to fix anything. Once I understand how something works I can determine why it is, or not working, unlike Engineers with whom I argue with all the time because on paper it looks good but in reality it doesn't work for some reason or another.

The biggest problem I run into when helping others is that they do not check things correctly or replace parts with NEW bad parts it happens all the time.

If you really want to know how EFI systems work and how to trouble shoot there are several great articles on the internet that will explain everything and make you an expert. Check out this article http://www.aa1car.com/library/2003/us60324.htm

"Fuel Pressure Checks
Depending on the application, the fuel system may require anywhere from 30 to 80 psi of fuel pressure to start and run. Pressure specifications will vary according to the type of fuel injection system on the engine as well as the performance, fuel economy and emission requirements of that particular model year vehicle. There are no rules of thumb. Every application is different, so always look up the pressure specs when troubleshooting fuel-related performance problems.
When there is too much fuel pressure, the engine runs rich. This causes an increase in fuel consumption and carbon monoxide (CO) emissions. An engine that�s running really rich also may experience a rough idle, surging and possibly even carbon-fouled spark plugs.
When there is not enough fuel pressure, the engine may not start. Or if it does, it may idle roughly and run poorly. Low fuel pressure creates a lean fuel condition that can cause lean misfire, hesitation, rough idle, hesitation and misfire on acceleration."

Thanks for the fun no harm intended.
Anthony