1994 Nissan Sentra LE 1.6 starting problem

I had a problem like that and I hooked up a little light bulb to the power supply to the pump so I could see when power was going to the pump when I was sitting in the driver's seat... my problem was intermitt so you may only need to have a friend help and use a test light... my problem ended up being a bad tank that was rusting out and clogging my pump...

-supa

I hooked up an analog meter to the fuel pump connector in the back and placed the meter where I could see it while in the drivers seat. needle didn't move in the slightest when the ignition key was turned.

If it lays still like a dead fuel pump, and it doesn't flow like a dead feul pump, then it's the fuel pump:)

I have the same car, 99 Sentra 1.6. Every time you turn the ignition, you most definitely hear the fuel pump when its working properly. To make sure, close all windows, turn off the radio, fans etc. Now turn the key to the run position. If you hear absolutely nothing, then I guess you'll know, hint hint;)

CD

I've even gone so far as to hook the battery directly up to the pump, and it still makes no sound.

however, the haynes book I have implies that a signal from the computer is needed to keep the pump running. by what means the pump receives this signal, I have no idea. that's what was leading me to believe that the book may be hinting that the computer controls the voltage to the pump, and no voltage didn't entirly imply that the pump was bad.

but then again applying voltage directly to the pump didn't have any effect, which made me wonder if the pump is waiting for a signal from the computer. and that just leads me in circles.

It's the pump, man! Let it go, dude! Put down the Haynes and get cracking. j/k

You should only trust Haynes and Chilton's so much. Only the factory service manual can really tell you things like computer signals and such with precision. I beleive I sent you the link . . . . .

CD

Sorry. Here;

CD

The computer turns on the fuel pump relay. The relay gets battery power from the fuel pump fuse through a brown wire at the relay harness connector. A black with yellow stripe wire goes from the relay to the computer where it is grounded by the computer to energize the relay. When the relay is energized it sends battery voltage to the fuel pump on a black with red wire. The voltage goes through the fuel pump and out to ground on a black wire that is attached to the center rear of the trunk. Make sure the ground is good.

hope this helps.

I'll take a little different path on the problem.

I also own a 1994 Sentra with about 225K miles on it. I use it daily to commute to work.

I've had a similar problem in the past and it was always an ignition problem. Generally speaking it was the ignition wires. I am on my fifth set (Original, off brand replacements (twice) and Bosch Silicone Lifetime (just put on a fresh set after 5 years).

#3 spark plug wire seems to fail most commonly. There is a voltage leak in the rigid part of the plug wire that extends through the valve cover. I noticed on the off brand "lifetime" silicone set that this particular wire is not molded well. On the boot that connects onto the spark plug it was not molded right. Reason I noticed that is because I replaced the original wires in 1999. In 2001 after only 50,000 more miles the plug wires were going bad. On #3 there was a molding defect. When I bought the replacement set it had the identical defect. I think it was a tooling error to happen the same afer 2 years.

Then I replaced them with the Bosch lifetime and they lasted 100,000 miles until a couple months ago, when I replaced them again (for free) under warranty. Can't beat those lifetime warranty.

Anyway over the years and miles when I have had starting problems it was always an ignition problem traced to the ignition wires.

Mark

it does, thanks! here's how the story turned out:

it's a mystery as to how or why, but both the fuel pump was dead and the computer was no longer activating the relay to send power to the pump. the pump replacement while daunting went really well. to get around the computer issue I just grounded the coil side of the relay.

I am pleased to say that the car is now running again.

If I really get bored some day I may construct a simple dead-man timer that runs off the crank sensor to replace the functionality that the computer is no longer serving. It is not a pleasant thought that if fuel line should somehow rupture (through an accident or such), that the pump will continue to pull fuel from the tank even after the engine has stalled, as long as the ignition isn't manually switched off.

Perhaps the pump motor was shorted, which damaged the ECM driver. I would double check that there isn't just a wiring or relay issue that would be cheap to fix.

At least you know of the danger you could potentially invite from leaving the FP circuit in this state. If you are as good with electronics as you sound, you would probably be able to simply replace the defective transistor in the ECM (if that *is* the problem).

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