Does anybody know what, the normal amperage range is for a 2000? I have a good even signature but my amperage is low siting at 3 to 4.

 

Signature ? Amperage of ?

Alternator amp output: 70-100+ amps
Battery volt output: 12 v
Alternator volt output: ~14.4v

 

Ok let me clear this up, I did some testing on my car this weekend (with a friend's help). We saw some discoloration on my 1st and 3rd spark plugs, all the rest were white. So he did a test with a scope on my fuel pump amperage. My fuel pump amperage for a 2000 max on the positive side was sitting between 3 to 4 on (6-cylinders). We did a test on a 93 altima (4-cylinder, that’s all we had) and it was sitting at 5 to 6 amps. We think the 2000 should be higher. We are going to clean the fuel injectors and throttle body but we wanted to know if any one had a wave form or knew the amperage numbers.

 

Are you talking about a brownish color on the LONG white insulator part of the plug, ie top not firing end?

 

I would recommend running a fuel pressure test first at the fuel rail if you suspect a fuel delivery issue. Not sure why anyone would want to test the amperage of a fuel pump unless they wanted to see what its current draw was.

Your car is notorious for bad ignition coils, browse threads in this forum for more info. I would strongly advise that you replace all 6 ignition coils if not done previously as they tend to go bad and cause misfires. If two of yours are bad that would probably explain the discoloration (i'm assuming it's probably black?) on your #1 and #3 plugs. In any case that would indicate excessive fuel in the mixture, not the sign of a faulty fuel pump.

 

We thought about the coils but I replaced all 6 at 60K. We checked for codes and there weren't any so the coils are still good and the O2 sensor's are good. He was looking at the wave form to see where my car was holding. I called the dealer and they said the fuel pump shouldn't go out but has anyone had to replace there's? We think cleaning the fuel injectors should clear up things but just in case we may have to look at the pump since everything else is good........

 

I don't think you are going to have much luck on the signature analysis for the fuel pump.

Judging from experience, most of the local Nissan techs are hard put to read the service manual. Forget an oscilloscope or FFT analyzer. Therefore the manufacturer is not going to provide a "nominal" signature that you might use for diagnosis. (I humbly beg the pardon of any actually competent Nissan service people who may be reading this. May you be extravagantly fecund. If you exist.)

What would you hope to find, anyway? Infer the pump motor speed? It's not like the fuel injectors are synched to the fuel pump in any way. The fuel pump pressurizes the fuel line; there is a pressure regulator and maybe an accumulator somewhere and a (nominally) constant-pressure manifold feeding each set of 3 injectors. The injectors are actuated electrically by the ECM. The fuel pump is just "on" or "off" according to a relay that is also contolled by the ECM. From your postings it sounds like you are trying to diagnose a fuel delivery problem by looking for irregularities in the fuel pump's current draw but I'm not sure the information is there to be had. It's not a diesel.

 

Thanks for the info. So right now from all the post, we should clean the injectors and if the 1st and 3rd spark plugs are still dirty then we should check the coils. Other than that does anyone know to spot a bad fuel pump? Or how to change it?

 

Bad fuel pump most common test would be a pressure drop/peak pressure test using a 0-100 PSI fuel pressure gauge connected to the fuel rail -- you want to look at readings before turning key on, after turning key on, while cranking engine, and while revving engine. The readings should never be lower than 20 PSI at any time and should not drop at any time while turning key on, cranking or revving engine. Needs to be done after car's sitting over night.

How are the plugs reading? Black wet look? Burnt insulator or electrode? In other words, lean or rich?

If you're handy with a scope, and it seems like you definitely are, you could read the injector open/close signal from the ECU, or use a CONSULT tool to monitor injector 1 and 3 pulse width sync (how long the injector is open in ms and how it is timing with the coil fire signal to fire the plug.)

Fuel delivery problem indicates either too much or not enough fuel, right?
If cyl 1 and 3 are fouling due to insufficient fuel then they may be clogged, not staying open, or out of sync. If they are fouling due to too much fuel then the injectors may be leaking, staying open, or receiving bad pulse data from the ECU.

HTH

 

A $20 Haynes manual and $35 fuel pressure gauge from Autozone will tell you how to EASILY verify a weak fuel pump/clogged fuel filter screen, bad FPR, or leaky injectors.

 

Normal amp draw for FI cars are 3-8 amps. It does not mean that it is good or bad.

 

Certainly mixture problems can be reflected in the plugs, and that may well be the source of your problems. The suggestions about leaky injectors etc are on the mark. But I wonder whether we are asking the right questions here.

Were you led to suspect the fuel delivery system for a reason? Reviewing the posts in this thread I am not sure just where the focus on the fuel system and injectors came from... if it is no more than plugs that look a little brown, that may be jumping to a conclusion. For example, is there excessive oil consumption? Perhaps the rings or valve guides of the #1 and #3 cylinders are at fault. Have you done a compression check?

There is another thing to consider here. The ECM in these cars expects to control the a/f mixture to very close to stoichiometric. If the exhaust chemistry (O2 concentration) does not respond to the ECM's control actions, then you get an SES light and one or more error codes. Absence of codes means more than just "the O2 sensors are good." It means the whole plant is working right, at least to the satisfaction of the ECM, and it is pretty finicky. The fact that there is no code argues against any serious problem with the fuel system - even if everything is not perfect, you have not saturated the control action. You could still conceivably get some variation among the cylinders in each bank that could not be detected because of mixing in the exhaust manifold, but there could not be much mixture imbalance before the engine would start missing, and the ECM ought to be able to detect that.

Just how severe was the discoloration that you saw? A little bit of variation between cylinders is normal and isn't a cause for concern. Don't fix what ain't broke. But more power to you if you just want to mess around with it.