Nissan Altima Non-starting Issue.
With the advent of fuel injectors on Nissan models to replace cranky carburetors, the world’s mechanics may have heaved a collective sigh of relief, but their relief was short-lived. A fuel injector can be just as finicky as any carburetor, and a Nissan model (as any other make) that refuses to start, even if there seems to be sufficient fuel pressure present, can present any mechanic with a thorny problem. Has this happened to you, or worse, does your Nissan only start when you squirt starter fluid into the inlet tract?
This is not an uncommon problem on Nissan products, nor is it uncommon on most other cars, but the problem is made easier to resolve by virtue of the fact that the engine starts with the aid of starter fluid. How so, you may ask? You may well ask, but the problem sounds more complicated that it really is, so in order to explain the possible reasons why a fuel injector does not inject fuel into a cylinder, let us look at what a fuel injector does.
A fuel injector explained.
In simple terms, a fuel injector is nothing but a valve that sprays fuel into the inlet manifold under pressure. Typically, injection pressures exceed 20 bar, which allows the fuel to be vaporized very efficiently when it passes through the injection orifices. However, in contrast to an old-style diesel fuel injector that worked on the principle of an external pressure having to overcome the tension of an internal spring to open the valve mechanism, a modern fuel injector on gasoline engines is managed by electronic impulses that derive from several sensors scattered around the engine to control both the moment, and the duration of injection.
This control mechanism fulfills the same function as the throttle valve on a carburetor, thus by varying the moment and duration of injection, which is measured in milliseconds, a modern fuel injector on Nissan, and all other engines can supply more, or less fuel, depending on operating conditions, throttle position, engine speed, and other factors.
So what can go wrong?
The simple truth is that there are manythings that can, and do go wrong, but let us look at the problem again. Thefacts are that the engine will not start, except when starter fluid is injectedinto the inlet tract, which immediately eliminates several possibilities, whichinclude:
· Defective crankshaft anglesensors.
· Defective camshaft positionsensors.
· Defective ignition system.
· Defective mass airflow meter ifthe engine revs up with the addition of starter fluid.
· Defective engine managementsystem.
· Defective ignition mapping.
· Large vacuum leaks.
However, in the absence of definitive fault data, the best we can do is to tackle the issues separately, but a picture being worth a thousand words, let us look at an image that is representative of all fuel injection systems.
What the arrows mean.
· The black arrow indicates the fuel pressure regulator.
· The yellow arrow indicates the main feed into the fuel rail.
· The six orange arrows indicate fuel injectors.
· The purple arrow indicates the connector that contains the controlling wires for one fuel injector.
· The red arrow indicates the fuel rail, from which all the fuel injectors are supplied with pressurized fuel.
· The green arrow indicates the solenoid valve that isolates the fuelrail when the system is not in use. The mechanism is usually vacuum operated,and its purpose is to prevent the fuel in the fuel rail from draining back intothe tank when the engine is turned off.
· The blue arrow indicates the controlling vacuum hose.
· The thin blue arrow indicates the wiring that connects to the ECU.
Although this image depicts a fuel injection system for a six-cylinder engine, the basic operating principles remain the same for all engines, regardless of the number of cylinders.
Finding the problem.
The fact that the engine starts with the aid of starter fluid tells us a few things, for instance, that the fuel injectors are not injecting fuel, and that the electrical side of the ignition system is in good shape. This means that the problem is fuel related, and assuming that there is fuel in the tank, the obvious place to start the diagnostic sequence is at the beginning, which is;
The fuel pump.
Fuel pumps can fail without warning, and it can happen that the replacement pump does not deliver the required pressure. The only reliable way to establish if this is the case is to attach a dedicated pressure gauge to the pump outlet, and to physically check, and compare the obtained reading with the data in the repair manual, which should be about 45psi.
Another important aspect to check is the power supply to the pump, which requires a full battery charge to work properly. A reduced power supply can cause insufficient delivery pressure, so check that the pump receives a minimum current of 12 volts. It is also a good idea to check the amperage draw against the value stated in the manual, since excessive amps can indicate a wiring issue.
Also do not forget to check the fitment of the fuel lines onto the replacement pump. It is easy to switch them around, which if it happens, will result in no fuel pressure at the fuel rail.
If the pump checks out fine, and a new filter was installed, check that the filter is installed the right way round, since in many cases, filters are fitted with one-way valves. If this checks out OK, do the following:
Check for fuel delivery at the fuel rail.
Make sure all fuel lines are connected correctly, and attach the pressure gauge to the fuel line where it attaches to the fuel rail, which is marked by the yellow arrow on our image. If the fuel pressure at this point is within specification, re-attach the fuel line to the fuel rail, but make sure all connections are secure.
NOTE: Do NOT allow fuel to spray around the engine bay in an uncontrolled manner. Always use a pressure gauge at this point to measure fuel pressure- merely allowing fuel to squirt into a container will tell you nothing, since it is impossible to infer fuel pressure based on the amount of fuel that arrives at this point.
With all fuel lines re-attached and secure, do the following:
Check forpower on each fuel injector.
The connectors that connect the injectors to the ECU on your Nissan will look just like the connector indicated by the purple arrow in the image. So remove one, and attach a 12 volt test light to each point in turn, with the test light connected to earth, or ground. It maybe that the test light does not light up on either pin(there are only two pins per injector) , but repeat the procedure with an assistant cranking the engine.
With a good connection to ground, the test light will light up each time the ECU delivers an electrical pulse to the wire. If the test light stays lit up, there is a wiring problem that is best left to a qualified auto electrician. However, if the test light pulses, repeat the process for each fuel injector in turn to verify that all are still connected to the system. If this test checks out OK, do the following:
Check thep ressure regulator.
All fuel pressure regulators look like the one in the picture, and which is indicated by the black arrow. The purpose of this regulator is to maintain fuel pressure in the rail, and most work with a simple diaphragm that is held in place over an exhaust port by a spring.
Since the fuel pump delivers fuel at a constant rate and pressure, the pressure in the rail fluctuates according to the demand, so when the engine speed suddenly decreases, the pressure in the rail rises sharply because the injectors are now not working as fast as before. This excess pressure is relieved when it overcomes the spring tension in the regulator, which opens briefly to allow the pressure to return to a preset value.
In practice, when this diaphragm ruptures, all, or most of the system pressure is allowed to bypass the injectors, which means that there is insufficient pressure in the injectors, which require very specific pressures to work at all.
The best way to test a pressure regulator is to remove it from the fuel rail, and to blank it off by inserting a solid material, such as a piece of plastic cut from a soft-drink bottle in place of the normal gasket or seal before re-attaching it to the fuel rail. This has the effect of diverting all of the available fuel pressure to the injectors, and if the regulator was defective, the engine will now start, since the pump is delivering the correct operating pressure, and the fuel injectors have been shown to work, as has the ignition system, because the engine started with the aid of starter fluid.
Fuel pressure regulator failures are common, not only on Nissan Altima’s, but on all cars, and eight out of ten failures to start are due to fuel pressure issues. A simple replacement of the regulator will get you back on the road.
However, if the engine still does not start, check the fuel for water contamination, or if the engine is not expected to run on diesel instead of gas. Both conditions will cause the car to start only with starter fluid, but with diesel in the fuel, there will be lots of either black or white smoke coming from the tail pipe when the engine starts with starter fluid.
With water in the fuel, nothing much will happen, apart from the engine shutting off as soon as the starter fluid in the inlet tract is consumed.