Chrysler Fuel pump and battery Questions.

aarcuda69062 wrote:
>
> In article >,
> Steve B. > wrote:
>
> > I would start by putting a VOM on the wires going in and out of that
> > relay to make sure you have power going to the pump then check at the
> > pump to see if you get power there. You should have power for a
> > couple seconds when you turn the key on so that the pump can
> > pressurize the system. Sometimes a failing pump will pull more
> > current than the wiring can handle and burn up the wires and
> > connections.
>
> At the pump, instead of using a VOM, I'd suggest something that
> actually loads the circuit, he could have a wire broken down to
> one strand which will satisfy his VOM but not flow enough current
> to run the pump. Suggest using a seal beam headlamp, it would
> better approximate the load of the pump and makes the testing a
> one man job being that the lamp is easier to see in the short
> time span during prime than trying to discern a meter.

That sounds like a good suggestion. We do get power on a VOM back there
but it is all buttoned up right now. My friend has a lot of digging to
do before he has room to get back under there so we will try that one
first off. We are also suspecting something shorted or 'one stranded'.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

I'm just shooting the breeze, you might isolate the pump from the rest
of the system, just to see if it will run. Come off the battery posts
with B+ and a ground, use an inline fuse, that way you don't have to
use the key and activate the other circuits.

Or you could use a jumper on the relay connector, with the key turned
on, but you would still be using the circuit that runs to the pump.

Even if you got the pump to make a noise, you still need to check for
volume.

Until recently, I haven't been to this site for several months, it sure
has changed.

On Mon, 24 Jan 2005, oilyspill wrote:

> I'm just shooting the breeze, you might isolate the pump from the rest
> of the system, just to see if it will run. Come off the battery posts
> with B+ and a ground

Read back in the thread. Already been done. Both "new" and original pumps
work fine when powered this way.

Mike Romain wrote:
> aarcuda69062 wrote:
> >
> > In article >,
> > Steve B. > wrote:
> >
> > > I would start by putting a VOM on the wires going in and out of
that
> > > relay to make sure you have power going to the pump then check at
the
> > > pump to see if you get power there. You should have power for a
> > > couple seconds when you turn the key on so that the pump can
> > > pressurize the system. Sometimes a failing pump will pull more
> > > current than the wiring can handle and burn up the wires and
> > > connections.
> >
> > At the pump, instead of using a VOM, I'd suggest something that
> > actually loads the circuit, he could have a wire broken down to
> > one strand which will satisfy his VOM but not flow enough current
> > to run the pump. Suggest using a seal beam headlamp, it would
> > better approximate the load of the pump and makes the testing a
> > one man job being that the lamp is easier to see in the short
> > time span during prime than trying to discern a meter.
>
> That sounds like a good suggestion. We do get power on a VOM back
there
> but it is all buttoned up right now. My friend has a lot of digging
to
> do before he has room to get back under there so we will try that one
> first off. We are also suspecting something shorted or 'one
stranded'.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's


Wire in an ammeter either at the fuel pump relay or fuse and measure
current draw of the fuel pump.. if you really want to get sexy you can
use a CT and view current draw & pump RPM with an o'scope, but usually
just an ammeter is enough for basic checking.

Jim

I did read the thread, the pump won't spin in the tank, again I
suggest, bypass the old circuit, see if the pump will not only spin but
have volume and pressure. If the pump can't draw enough amps because of
a bad circuit, the bypass wire should take care of that as well. My
info shows that main circuit to the pump is a 20 amp circuit. It is
interesting.

I am tending to agree with that.

If the sucker runs with custom wiring then I likely will set up a fused
relay with a double trigger for him. One momentary on switch for
starting with a loop back off pin 87 so it stays powered as long as the
key is on once started with the switch.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

oilyspill wrote:
>
> I did read the thread, the pump won't spin in the tank, again I
> suggest, bypass the old circuit, see if the pump will not only spin but
> have volume and pressure. If the pump can't draw enough amps because of
> a bad circuit, the bypass wire should take care of that as well. My
> info shows that main circuit to the pump is a 20 amp circuit. It is
> interesting.

Another thought, If your first voltage test was at the battery posts
with the engine cranking, and showed around 10 volts, then the second
test at the pump with engine cranking, showed the same voltage, if the
circuit was faulty between the relay and pump, why wasn't there a
voltage drop at the pump? Maybe the pump just wasn't putting a load on
the circuit.

Running a dry pump off battery voltage is one thing, but I would sure
want to see what the pump would do under load, pumping gas.