Guest47904

Engine running. Set meter to AC. If you can select it, use the 1 to 10 volt scale. A good reading is less than .03 Volts AC. Go from the output lug of the alternator to the negative battery terminal.

AdsoYo

Ok speedy, I'm not sure how this can be. I drove about 6 miles for groceries then tested the alternator lug to the negative battery cable for AC voltage and got this:



When it comes to electricity, I'm a total novice. Is the multimeter set correctly? I thought V~ was AC volts. If you say I should be getting under .03 volts, then something must be very wrong. I also tested DC and got 12.6 but didn't take a picture.

Guest47904

Easy mistake. Your meter is set for Ohms 20K. The meter could well be fried now.

If the AC voltage was near that high. Your PCM and probably a few other things would def be fried.

AdsoYo

Oh, ha. You can't see it in the picture but there's a hash mark on the flat side of the dial pointed at 200 V~. The rounded side isn't the side that points at the selected value, it's the flat side. Sorry for the confusion. So I probably shouldn't drive this thing until I get a new alternator then if there's that much AC voltage?

Guest47904

I don't believe that meter if it's set correctly. Try another meter. If they agree, I agree.

AdsoYo

I took it to a shop that a friend owns and asked them to measure the AC volts. Their meter showed zero and they also hooked up this big green diagnostic device that gave my electrical system the OK. I did about 10 miles of driving around town and had it idling in their parking lot for 10 minutes before they looked at it. It died twice in their parking lot and didn't throw any codes.

I got it back home and hooked up my fuel pressure gauge. With key on, it showed 40 psi. With engine idling it showed 35 psi. As it idled, I watched the gauge slowly fall to 10 psi at which point it would try to die and idle rough, then shoot quickly back up to 35 psi and be OK. It did this about 5 times in the 5 minutes I had it idling in my driveway before I gave it some throttle at 10 psi to see what would happen and it died.

So I guess this changes things. Should I be looking at the fuel pump at this point?

bw_hunter

Yes, it sure seems to need a pump....

siguy

the one thing I don't understand if why would it throw all the codes you listed if its just a fuel pump?

AdsoYo

Good question. Maybe the pump is one of the things being affected by something else? And the shop said my electrical system is fine even though my scanmaster is only showing 12.6 volts and lower...

Injuneer

The ScanMaster reads the volts off the PCM. That seems to typically read 0.5 to 1V lower than the dash volt meter. If you are concerned about voltage to the fuel pump, measure the voltage at the fuel pump connector in the rear of the car.

http://shbox.com/1/fuel_pump_wiring.jpg

AdsoYo

The pump connecter gets its 12 volts with key on. I'd be interested to see the volts with engine running and while it's running poorly. Does anyone know a method to do this before I go rigging something up myself?

I drove 60 miles on the highway today with no problems. As soon as I came to a prolonged stop, it died while idling, no codes. Started it a few minutes later and drove 60 miles back with no problems again. Once I was in town doing 35 mph at about 2000 rpm, it would do this thing where the car acted as if I ran out of gas for a second then the power would come back for a second or two, then cut out, then come back. Like the gas would be cut off, then come back, then cut off. It did this for a few minutes because I never had to stop. Once I pushed the clutch in to make a turn, it died.

I would hate to think this is fuel pump because it's only a year and a half old. On top of that, siguy had a good point about the weird codes if it's just the pump.

Guest47904

You don't have to really do any rigging. Since the problem occurs while it's idling, you can remove the left rear wheel and put the meter on the connector to the fuel pump and monitor voltage there.

However, I don't feel that based on what you said about the pressure dropping that it is due to voltage dropping.

I think your pump is defective. The voltage test should bare that out.

As the engine is dying and spinning slower and slower, the alternator is putting out less and less. Until it gets to the "brown" condition and the PCM sets all kind of weird codes. If the codes were the result of a legitimate problem they would return right?

FWIW
I don't know if it was entirely the result of the pump itself or improper installation but I have read terrible things about Walbro pumps here for years.

AdsoYo

I guess it didn't even cross my mind that spinning that slow for a short amount of time is all it takes to set the codes. Thanks for all the help. I've been keeping my dyno tuner in the loop with this and he initially said the PCM may be going bad but after yesterday, he agrees it's the fuel pump. Grrr! I know exactly where the receipt is and hopefully there's a warranty on it.

AdsoYo

I'm really digging my heels in about replacing that pump. I completely forgot that the pump has a relay behind the dead pedal. I pulled the relay and saw this:



That black prong is #87. #'s 30, 85 and 86 are the good ones. Is this cause for concern? Maybe overdraw on the circuit? Like I said, electricity and anything having to do with it are beyond me for the most part.

Guest47904

It's entirely possible it's restricting currently flow. The voltage test would have proved it. However, I think the low voltage level would be because the pump is pulling too much current, not because the electrical system is dropping voltage to the pump.

In other words, your Walbro pump is crap. Replace it with an OEM pump available at Napa.