1994 Nissan Sentra LE 1.6 starting problem
Robert C. Henney
but not sure it's the cause of the problems.
was running fine up until I attemped to start it up (just a few hours
after last using it) and it wouldn't start. turns over fine and battery
voltage looks good, but doesn't even sputter. pulled out a plug and am
indeed seeing what appears to be a strong spark. plugs are dry, which I
believe indicates that it isn't flooded. color of the plugs is good
too. they're not too old, but not newly installed either, so I trust
them.
I am seeing 12v at the fuel pump relay (the big green block between the
battery and the distributor), and have checked that the fuse is intact.
pulled up the back seat to access the fuel pump, but am NOT hearing it
turn on when I turn the ignition to ON.
also I am not seeing any voltage at the pump itself when the ignition
is ON, which would at first seem to indicate that the problem is the
wiring between the pump and the fuel pump relay. however I've read that
the Sentra's computer may pulse or regulate in some way the voltage to
the pump when needed and so I'm no longer sure about what reading if
any I should be expecting at that location. does anyone know if the
wiring goes straight through from the relay to the pump or does it go
elsewhere first?
I can jump and go buy a new pump, but I really want to make sure the old
pump is bad. is it suggestible to just hook 12v directly to the pump
and see if it turns on? is there a way to check that the computer is
indeed trying to tell the pump to go on?
sorry about so many questions right away. let me know if there's any
more details you want.
--
robh
supafly
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
Robert C. Henney
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.
--
robh
Codifus
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
Robert C. Henney
> 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;)
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.
--
robh
Codifus
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
Codifus
> 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
>
http://www.nissanforums.com/b14-95-99-chassis/60760-b14-full-service-manual.html
CD
Kevin
"Robert C. Henney" <ro...@osmium.mv.net> wrote in message
news:e69p4a$r8s$1...@pyrite.mv.net...
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.
--
Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green
Mark Fields
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
"Robert C. Henney" <ro...@osmium.mv.net> wrote in message
news:e6763e$2ao$1...@pyrite.mv.net...
Robert C. Henney
> 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.
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.
--
robh
Comboverfish
Robert C. Henney wrote:
> 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.
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.
> 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.
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).
Toyota MDT in MO