Question about 1994 Nissan Altima

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Fuel pressure regulator isn't opening

Just changed the head and not to sure if the timeing chain is right. The car did run ok on starting fluid for a while then shut off. There is fuel going to the fuel pressure regulator but the regulator isn't opening up. Got a new regulator and still the same problem. Not sure why the vac line isn't working. Please help
Thank you

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  • Nissan Master
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Garxmx3: 1st, the fuel pressure regulator operates off of engine vacuum. The engine must be running to create vacuum and without it, the fuel pressure regulator essentually is restricting the return to fuel to the fuel tank, but the fuel injectors have all the fuel they could possibly need. The fuel pressure during initial start if ther is no vacuum, is 45-50 PSI which will create a rich condition consequently there would be no need for starting fluid or any other out side fuel source to influence the starting of the motor.
NOW>>>>> Lets see if we can sort the problem out>
If the engine ran alright on starting fluid, this would suggest that the mechanical aspect, meaning, the chain is probably on there correctly because if it's off, it won't run well at all or it will bend valves! Just to make sure, you could run a compression test. At cranking speed with the throttle wide open you should have at least 130 PSI or more. What you are looking for is no more than a 10% difference between the highest and lowest readings. If you have more than that, you will have problems which will be contingent based on the findings. If you have big differences, tell me what they are and I can take an educated guess at what happened or what the problem is. IF the valve timing is correct, we will move on to other things you need to check OK?
"False AIR" is a common problem with no starts and hard starts when a cylinder head has been pulled and put back on.
All air which enters the motor MUST pass through the air mass sensor. It is metered air so the ECM has a means of, with the input of a few other things, controlling the pulse width of the injectors.
The large hose which the air mass sensor is attached to and goes to the throttle body, after they get old, are prone to splitting and/or tearing. Look carefully at it to make sure that there are no splits or places where unmetered air can get in between the air mass sensor and the throttle body. This includes any and all hoses which attach to tthe manifold and/or the intake in any way shape or form.
Check the pcv hose and valve. Some of those hoses get so soft that they almost turn to gum. If you pulled the injectors, make sure that you had put the tip seals back.
If it ran, in theory, the distributor should have been in correctly. Check and make sure that the wire going to the distributor did not get damaged from anything chaffing or pinching them.
Look closely at the coil and it's connection to make sure nothing has come loose.
Some of these EFI harnesses had an independant ground wire coming out of the harness which had to be bolted to the intake manifod. Check yours and make sure yours is secure if you have one coming out of your harness.
You want to know if the injectors are operating? One way, get a screw driver with a long shaft, or something similar which you can place the tip on to the body of the injector. You want to have you ear against the other end of the shaft. If the injector is operationg, you will hear a sharp ticking when the engine is being cranked or if the engine is running. Sometimes it is easier to pull the plugs and spin the engine with the plugs out, to listen to the injectors, because there is less noise when you don't have the resistance of the cylinders working against you. At the same time, the ignition is what pulses the injectors. Pull the coil wire out from the distributor and hold it close to a ground while cranking the engine. You should have a sharp visible spark. If you don't have a spark, you won't have injector pulse.
Coming off your positive battery cable at the positive terminal, is a connector where smaller wire hook into it. Make sure thse have good solid clean connections. They corrode there and can kill the circuits which relate to the ECM.
OH! pull the spark plugs and look at them to see what color they are. See if they look like they have been run rich or lean.
Rich is very dark black almost a fluffy black soot, if the engine was fireing. If you try to spin it over befor you do anything and you pull the plug out and they are wet and smell of gas. that is a story by it self.
I have given you a lot of avenues to explore. Check these out and if they lead to blind alleys, get back to me and I'll continue to see what I can do for you.

Posted on Apr 20, 2009

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