I replaced my fuel pump and filter in my 96 200sx se last week. About a few days ago i received my fuel pressure tester. In my Haynes manual it says the max psi should be 65 psi and the hold pressure is 50 psi. But when i tested it i only had 45 psi max. Is that too low? I plan on putting new screw clamps on all connections and maybe even changing the fuel lines. I tested the power to the pump with my multimeter and got about 11.89v. What does hold pressure mean? Could this pressure be one of the reasons my car won't start?
Hmm.. Strange. Fuel pressure should be at max.. Have you used the pump without fuel? If you have you may have burned the internals. And results loss of power. Can you try a new one? Borrow one and test again?
Regards
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The FSM manual states that the max fuel pressure is approximately 43 psi. The fuel pressure test using a fuel pressure tester is 34 psi with the vacuum hose connected to the fuel pressure regulator and 43 psi with the vacuum hose disconnected. The 45 psi seems to be fine since fuel pressure testers calibration and accuracy vary.
The Haynes manual is adequate for basic repair, but they do not do a good job with some repairs and tests. That fuel pressure figure they list is wrong.
Thanks for the info. I did another test today and after the initial 45 psi, it jumps down to 10 psi and slowly all the way to 0. The engine is off when i test this. Is this how it is normally?
Thanks for the info. I did another test today and after the initial 45 psi, it jumps down to 10 psi and slowly all the way to 0. The engine is off when i test this. Is this how it is normally?
How much time does it take for the fuel pressure to drop 10 psi after the engine is turned off? If it drops after 5 or 10 minutes it may not negatively affect engine performance that much. I did not see a test specification for how long the fuel pressure should be retained in the system after the engine is turned off. My main experience with fuel pressure testing is on a Honda Accord. I did not have any starting problems with it, and it's fuel pressure dropped like you describe after turning the engine off.
Are you still having problems starting the car? If you can get it started then there is a test to see if the fuel pump can provide enough fuel. With the car running and the fuel pressure tester still on the car, if you compress the fuel return hose located after the fuel pressure regulator and the fuel pressure jumps a lot (such as up to 70 psi) then the fuel pump is strong enough.
How much time does it take for the fuel pressure to drop 10 psi after the engine is turned off? If it drops after 5 or 10 minutes it may not negatively affect engine performance that much.....................
My car doesn't start at all. I am trying to figure out why. I turn the ignition to the "on" position (just after the accessories if thats what you call it). I can hear the fuel pump turn on and thats when i get the jump in fuel pressure. I have a battery pack hooked to the batter just to keep a constant flow of power. As for how much time it takes for the pressure to drop to 10 psi after the pump stops is approximately 5 seconds, but from 10-0 its much slower. I did a fuel pressure test on my dads blazer and after the fuel pump stops, his pressure only drops about 3 psi. I can try using a 12 volt battery to do that test your talking about or is the power supposed to be dc? (and if you happen to have the answer, how can i test to see if a current is ac or dc with a multimeter?). And... if i just kink the hose while its pumping will that work as well?
I think that if you get 45 psi fuel pressure, when the ignition is turned on, you may not have a fuel problem. Your car should at least start with 45 psi. The fuel pressure regulator is the device which tries to maintain the pressure and it seems to be working. The only other element which could cause a fuel problem are the injectors. I believe a car can run (roughly) on only three injectors.
The tests I talked about require that the car be running, but yours is not.
Also cars tend to use DC voltage for everything.
Any check engine light? If not it may be an ignition problem. Have you changed your spark plugs recently? What about your distributor cap and rotor? Also any oil in the distributor may indicate that your distributor is failing or has failed. There is also a chance that your spark plug wires may be leaking spark directly to your engine block. They may pass the test for the presence of a spark, and they may pass the test for the resistance check, but the connection to the spark plugs may be degraded to the point where the spark does not correctly pass through the spark plug but rather directly to the engine block. If your spark plug wires are over 2 years old it may be time to replace them anyway. If none of these ideas help then you may want to check your electrical ground connections for continuity and signs of corrosion.
Last edited by bugmenot : Dec 16th, 2007 at 11:20 PM.
Spark plugs are fairly new and they are getting spark. I have thought about the injectors, but that leads me to my other topic...... http://www.nissanforums.com/ga16de-1...ont-start.html
I thought it might have been a fuel problem, but I guess its not. If you want to take a look at that link I would appreciate it!
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