No power to new fuel pump

I recently installed a new fuel pump into a 1997 jeep grand cherokee
laredo and it is not getting any power to the fuel pump. When the
pump is disconnected the connector reads 11 volts......when the pump
IS connected...........it gets grounded and reads nothing. Switched
around the relays thinking it was that but none of them worked. I
didn't install a new assembly with the fuel pump........but I don't
think thats the problem. Any thoughts?

 

Three things needed: (1) Accurate schematic for (specific to) the
vehicle (FSM or www.allldata subscription), (2) Multimeter, (3) Someone
who knows how to use items (1) and (2) for torubleshooting.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

My neighbor is a mechanic and he did all these things and is
completely stumped too. We use a voltage meter on the connection by
the fuel pump..........and it was getting sufficient power while the
pump was unplugged but when the pump is plugged in..............no
more power.

 

When you run electrical wires beside each other you can see a "ghost"
on a wire that is not connected to anything. Your meter pulls so
little power that it won't bleed off the ghost voltage so it looks
like you are seeing the voltage needed to run the pump. Once you
connect the pump it bleeds off the ghost voltage which is why it looks
like the power goes away when you plug in the pump.

You need to trace the power circuit to the pump to find out where the
problem is. You will need to get a wiring diagram for the vehicle or
have someone who is knowledgeable with electrical troubleshooting.

Steve B.

 

Hi...

Not a mechanic, just an old retired electrical guy - forewarned is
forearmed!

I agree with Steve in part, suspect that the 12 volts you're seeing is
being delivered inadvertently in series with something else, so that
there's virtually no current available.

Quick and dirty test that you and your neighbor can do to verify this,
before you spend the big bucks at the dealer...

Remove the positive connection from the pump, connect it to a light
bulb that wants a fair bit of current like a parking light bulb.
Connect the other side of the bulb to ground. If it doesn't light,
then our guess is correct.

If that's the case - check the fuse, not visually but by replacing
it with another, or by testing it with your meter.

While you're in there, check all the fuses just for the heck of it.
Last summer my neighbor's wife was distressed that her (GM car) power
door locks had quit. The fuse marked "courtesy lights" was the
culprit

If that's not it go back to the relay. Don't swap it again, just
remove and re-insert it half a dozen times - kinda wipe the contacts.

I *think* the asd relay removes power to the fuel pump, check that by
swapping it, and perhaps the wiping trick.

If none of those does the trick, do the old bend the wire trick on the
fuel pump wire as far as you can reach to do it. Trick is to hold your
thumb and two closes fingers together, with the wire in the "hole"
between them. Run your fingers up and down the wire so that your thumb
tries gently to bend the wire as it goes. You're feeling for a point
where the wire bends sharply (if there is one) where the metal wire is
broken and only the insulation holds it together.

Take care.

Ken

 

No offense, but if he was stumped by that, he is not the person to do
the troubleshooting (item (3) of my previous post).

With the pump plugged in, you need to use the meter to find out where
the voltage is lost in the upstream power feed, i.e., there is an
upstream point where you have +12V and below (i.e, as you move towards
the pump) which there is no +12V - that's where the break is. It could
be a relay, or a relay control signal, or a broken wire - but at some
point there is an interruption in the supply of voltage.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Why did you install the new pump? Did the old pump simply stop working,
or did it continue to work, but not so well? Or did it not work at all
but was making some sort of noise?

The reason I ask is to help determine if you had a fuel pump failure or
a problem with whatever provided power to the fuel pump. If the pump was
sort of working or making some sort of sound, then you had power to the
old pump. Under these conditions, if the new pump doesn't work, it is
likely that you have a connector problem or a bad pump.

If the old pump simply "stopped working" and the new pump is acting just
like the old, failed pump; this suggests that the old pump may be OK and
that the problem is elsewhere.

Ken

 

The fuel pump just stopped and I am sure it was bad because we hooked
it up straight to the battery and nothing. I am now thinking that
when it went bad........it caused other problems in the electrical
line (blown fuseable link, relay, whatnot). I did check all the fuses
in the box and everything was ok but I know there are other fuses.
Thanks for all the help on this and if anyone else has any cents to
throw in........please do.

 

Our crystal balls are in the shop for repair. For the third time,
someone competent needs to troubleshoot it with schematics and a meter.
You posted your problem, several of us have given essentially the same
answer, yet you want more.

No offense, but you're like the person who runs out of gas, and three
people stop to help and advise you to put some gas in it, but you keep
asking people to stop and help you figure out why it won't start.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Hey, Fucknuts....................if you don't want to
help..........keep your cock-sucking mouth shut then. I was only
looking for some other peoples opions...........not yours again. And
by the way..........I have a masters degree in Information
Technology. Next time your computer acts up............fix it your
fucking self and stop asking us what to do..................Retard!

 

Heh heh! Meanwhile your Jeep sits for another couple of days. Good
luck with it.

OK - I'll put it in terms you can understand: Someone comes to you and
says that their Windows computer keeps crapping out on them. You ask if
they are getting the automatic Windows updates, have a good antivirus
program that is also regularly getting it's updates, are running regular
scans with at least one good anti-spyware program (that is regularly
getting updated), and have a good surge suppressor on it. They say no -
none of that stuff.

So you spend half a day cleaning up their computer mess and advise them
to do all that stuff, or all bets are off with the problems you fixed
for them.

Six months later, you see them and you ask them how their computer is
doing, and they say "Not good at all - can you help me figure out the
problem?" You ask if they did all the things you suggested, and they
say "No - none of it."

Do you think maybe you would respond to them how I did to you, if not
worse. Actually I thought I was pretty gentle, and still am being
gentle in spite of your attitude of entitlement and completely ignoring
what we've already told you and you're still wanting us to help.

Like I said - good luck with your "project".

Post back when we all have our crystal balls out of the shop in good
working order so we can tell you which wire or relay or whatever is bad.

Seriously - other than a good bit of hit or miss luck, the only way you
will track it down is with a meter and schematics (for now the 4th
time). I know that infuriates you when I say it. Not my problem.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Opinions don't fix cars. And as you just found out, neither do
degrees. People who know what they're doing do.

Bill gave you some good advice and you chose to ignore it, and to be
an asshole on top of that! But, if it's other people's opinions you
really want, here's mine.

1) Please post your 'mechanic' friend's place of business so all here
can avoid him.

2) Get somebody who knows what he's doing to look at your car.

If you'd like more, I'd be happy to oblige.

 

Some other thoughts that may help:
My comments about +12V also apply to the ground - trace that back too -
could be a bad or weak ground connection (but that would probably also
show up as a squirrely-reading fuel gage - not sure - don't have the
schematics in front of me).

You said you hot wired the old pump and it didn't run - thus proving it
was bad - you might do the same with the new one - could have gotten a
bad new one. I know you said the +12V is disappearing (which could be
bad +12V or bad ground depending on where you're connecting the
voltmeter to take your readings) when you hook it up, but it might be
worthwhile ruling the new pump out as being the problem so you don't
send yourself off on a wild goose chase looking for a wiring/controls
problem in case the pump itself is the problem.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Oops - sorry bllsht - I hit reply on the wrong post.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

I haven't done anything to the car this week................I do this
thing called work. I took your advice and am planning to implement it
this weekend........I was just looking for some other
opinions..............you can stop telling me about schematics and
meters for the 5th time. I am only looking for someone else who may
know something else. As for running anti-virus software to fix
problems..........yeah.........maybe if you were in second
grade........or a car mechanic..........it goes way deeper than that.
Thing about me is that I am versatile in a lot of things, bill, as
where you will always work on cars.........so why don't you stop being
condecsending to others and maybe they won't backlash at you. And for
bllsht.........why don't you do your homework before you
speak...........I did take his advice.........I didn't ignore
it..........haven't implemented his advice you bonehead! One thing my
degree does get me.........a high paying job and opportunities you
could only dream of. My friends place of business is a little place
called **** Off Body Shop..............ever heard of it? I would
rather do things myself to learn............its called motivation.
Look it up. Oh yeah as for the word condescending..........let me put
it in terms you can understand..............don't be a prick to others
when they are only looking for help.

 

This is way too funny...

Do you and your **** Off body man have a clue how this circuit is
controlled? Are you even checking the right wires?
Do (either of) you know how to do a voltage drop test?
Do you know when and why it would be appropriate to use a meter
and when and why it would be appropriate to use a test light?

Why is it taking days to troubleshoot something that any
competent person would have done in 20 minutes or less?

Troubleshoot the problem, forget the 'silver bullet' fix.

 

Do you know how to read..............haven't touched the car in 5
days..............worked on it for 10 minutes last
saturday...........resuming work this saturday. Just checking for
some helpful hints. If I would have known that this was the forum for
handicapped technicians............I would have gone to the local
community college for some people with higher IQ's.

 

Funny thing is I know what the problem
is............................blog ended Ding Dongs! You may now go
back to drinking paint thinner. Good Luck on your future endeavors!
<---------------(activities) I promise to keep it simple for you next
time.

 

On Mar 9, 8:48 am, wrote:
One thing my

....and a ten year old Jeep....impressive!!