Chrysler Fuel pump and battery Questions.
 

Maybe someone here knows the answers to a couple questions a friend of
mine has regarding Chrysler Fuel pumps and his battery.

He has what he thinks is a dead fuel pump in his 94 Voyager.

So he got a used pump and tested it with 12 volts to see it spin up. He
then installed it and it still won't spin up in the tank. He 'thinks'
he heard it spin when he put the key to 'run' once but no start. I am
disabled and can't get under there to check it for him.

I made a couple observations. One, the 'new' pump has 4 wires off the
plug and the old one had 3. The ground for the gauge and the motor
ground appear to be common in the old pump and separate in the new one
so he soldered the two wires together.

The 'old' pump will also spin up when hooked to a battery.

The fuel pump relay looks good with nice clean contacts inside and on
the spades and it clicks when the key is turned. Voltage was observed
at the pump plug. Not enough maybe?

His battery is acting wrong I 'think'. It has a good 24 hours on the
charger to bring it up over 14 volts. 30 seconds with the lights on to
take the surface charge off, then off drops it to 13V. When the key
hits run, it dives to 12.1 or so volts. When the starter turns, it
drops to 10.2V.

I am of the opinion the battery doesn't have enough power to fire it up
maybe.

Could he just plain have the wrong pump in there?

Any suggestions or guesses would be appreciated.

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

On Fri, 21 Jan 2005 10:35:45 -0500, Mike Romain >
wrote:

>Maybe someone here knows the answers to a couple questions a friend of
>mine has regarding Chrysler Fuel pumps and his battery.
>
>He has what he thinks is a dead fuel pump in his 94 Voyager.
>
>So he got a used pump and tested it with 12 volts to see it spin up. He
>then installed it and it still won't spin up in the tank. He 'thinks'
>he heard it spin when he put the key to 'run' once but no start. I am
>disabled and can't get under there to check it for him.
>
>I made a couple observations. One, the 'new' pump has 4 wires off the
>plug and the old one had 3. The ground for the gauge and the motor
>ground appear to be common in the old pump and separate in the new one
>so he soldered the two wires together.
>
>The 'old' pump will also spin up when hooked to a battery.
>
>The fuel pump relay looks good with nice clean contacts inside and on
>the spades and it clicks when the key is turned. Voltage was observed
>at the pump plug. Not enough maybe?

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
>His battery is acting wrong I 'think'. It has a good 24 hours on the
>charger to bring it up over 14 volts.

A fully charged battery is 12.9 volts.

> 30 seconds with the lights on to
>take the surface charge off, then off drops it to 13V. When the key
>hits run, it dives to 12.1 or so volts. When the starter turns, it
>drops to 10.2V.

Anything under 10.4 volts is considered *weak*
but 10.4 volts or better is normal when you put a starter load on the
battery. When you take the load off, it will return immediately to 12
point something.

>I am of the opinion the battery doesn't have enough power to fire it up
>maybe.

See above.

>Could he just plain have the wrong pump in there?
>
>Any suggestions or guesses would be appreciated.

Check the fuel pressure regulator.

Lg


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

It should start with 10 volts. He needs to check for fuel pressure on the fuel rails on the intake manifold. Also check for spark while cranking.

Mike Romain wrote:
>
> Maybe someone here knows the answers to a couple questions a friend of
> mine has regarding Chrysler Fuel pumps and his battery.
>
> He has what he thinks is a dead fuel pump in his 94 Voyager.
>
> So he got a used pump and tested it with 12 volts to see it spin up. He
> then installed it and it still won't spin up in the tank. He 'thinks'
> he heard it spin when he put the key to 'run' once but no start. I am
> disabled and can't get under there to check it for him.
>
> I made a couple observations. One, the 'new' pump has 4 wires off the
> plug and the old one had 3. The ground for the gauge and the motor
> ground appear to be common in the old pump and separate in the new one
> so he soldered the two wires together.
>
> The 'old' pump will also spin up when hooked to a battery.
>
> The fuel pump relay looks good with nice clean contacts inside and on
> the spades and it clicks when the key is turned. Voltage was observed
> at the pump plug. Not enough maybe?
>
> His battery is acting wrong I 'think'. It has a good 24 hours on the
> charger to bring it up over 14 volts. 30 seconds with the lights on to
> take the surface charge off, then off drops it to 13V. When the key
> hits run, it dives to 12.1 or so volts. When the starter turns, it
> drops to 10.2V.
>
> I am of the opinion the battery doesn't have enough power to fire it up
> maybe.
>
> Could he just plain have the wrong pump in there?
>
> Any suggestions or guesses would be appreciated.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's

--
Mike Walsh
West Palm Beach, Florida, U.S.A.

I believe there is a dark green wire with black tracer at the pump
relay. That's the main power wire for the pump. It should be hot when
cranking. Is it? You may have an initial prime for a few seconds, with
the key in the on position, engine not cranking. After that, the
computor will kill it, unless there is an rpm signal, you can't get a
rpm signal without cranking the engine. If it is hot at the relay,
check it at the pump plug, if that's ok, check the ground. If it will
spin with B+ and a ground outside the vehicle, it should do the same
thing on the vehicle. hmm

Lawrence Glickman wrote:
>
> A fully charged battery is 12.9 volts.

Nominal battery voltage is 12.6 volts, i.e. neither charging nor discharging.

> Anything under 10.4 volts is considered *weak*
> but 10.4 volts or better is normal when you put a starter load on the
> battery. When you take the load off, it will return immediately to 12
> point something.

10 volts might be weak, but I have seen many engines start with 8 volts.

--
Mike Walsh
West Palm Beach, Florida, U.S.A.

He checked at the pump on those wires and had the same 10+ volts.

Do you think this is enough to spin it up?

I am thinking a lack of amps as well with a weak battery cell. The
charger does boil one cell harder than the rest and that one was low on
water. I tried boosting and it sucked my new alternator and new battery
hard enough to drop me from 2000 rpm on a hand throttle down to 800
rpm. Serious draw.

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

oilyspill wrote:
>
> I believe there is a dark green wire with black tracer at the pump
> relay. That's the main power wire for the pump. It should be hot when
> cranking. Is it? You may have an initial prime for a few seconds, with
> the key in the on position, engine not cranking. After that, the
> computor will kill it, unless there is an rpm signal, you can't get a
> rpm signal without cranking the engine. If it is hot at the relay,
> check it at the pump plug, if that's ok, check the ground. If it will
> spin with B+ and a ground outside the vehicle, it should do the same
> thing on the vehicle. hmm

I am wondering about the 10 volts and the available amps.

I tried a boost even and it sucked my new alternator and battery hard.
Dropped me from 2000 rpm on a hand throttle down to 800 or so.

Mike

Mike Walsh wrote:
>
> It should start with 10 volts. He needs to check for fuel pressure on the fuel rails on the intake manifold. Also check for spark while cranking.
>
> Mike Romain wrote:
> >
> > Maybe someone here knows the answers to a couple questions a friend of
> > mine has regarding Chrysler Fuel pumps and his battery.
> >
> > He has what he thinks is a dead fuel pump in his 94 Voyager.
> >
> > So he got a used pump and tested it with 12 volts to see it spin up. He
> > then installed it and it still won't spin up in the tank. He 'thinks'
> > he heard it spin when he put the key to 'run' once but no start. I am
> > disabled and can't get under there to check it for him.
> >
> > I made a couple observations. One, the 'new' pump has 4 wires off the
> > plug and the old one had 3. The ground for the gauge and the motor
> > ground appear to be common in the old pump and separate in the new one
> > so he soldered the two wires together.
> >
> > The 'old' pump will also spin up when hooked to a battery.
> >
> > The fuel pump relay looks good with nice clean contacts inside and on
> > the spades and it clicks when the key is turned. Voltage was observed
> > at the pump plug. Not enough maybe?
> >
> > His battery is acting wrong I 'think'. It has a good 24 hours on the
> > charger to bring it up over 14 volts. 30 seconds with the lights on to
> > take the surface charge off, then off drops it to 13V. When the key
> > hits run, it dives to 12.1 or so volts. When the starter turns, it
> > drops to 10.2V.
> >
> > I am of the opinion the battery doesn't have enough power to fire it up
> > maybe.
> >
> > Could he just plain have the wrong pump in there?
> >
> > Any suggestions or guesses would be appreciated.
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
>
> --
> Mike Walsh
> West Palm Beach, Florida, U.S.A.

What the heck have you got for an alternator that will drop your engine 1200
rpm? Man that must suck a LOT of power from the engine, or your engine
doesn't produce much torque at 1200 rpm. I would guess a normal alternator
would take at most 3 hp to turn, especially at such a low rpm.
tad

"Mike Romain" > wrote in message
...
> He checked at the pump on those wires and had the same 10+ volts.
>
> Do you think this is enough to spin it up?
>
> I am thinking a lack of amps as well with a weak battery cell. The
> charger does boil one cell harder than the rest and that one was low on
> water. I tried boosting and it sucked my new alternator and new battery
> hard enough to drop me from 2000 rpm on a hand throttle down to 800
> rpm. Serious draw.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
>
> oilyspill wrote:
>>
>> I believe there is a dark green wire with black tracer at the pump
>> relay. That's the main power wire for the pump. It should be hot when
>> cranking. Is it? You may have an initial prime for a few seconds, with
>> the key in the on position, engine not cranking. After that, the
>> computor will kill it, unless there is an rpm signal, you can't get a
>> rpm signal without cranking the engine. If it is hot at the relay,
>> check it at the pump plug, if that's ok, check the ground. If it will
>> spin with B+ and a ground outside the vehicle, it should do the same
>> thing on the vehicle. hmm

That surprised the crap out of me too. My Jeep engine has 100% of it's
torque at around 1750 rpm and is a real strong runner climbing sand pit
walls down to 400 rpm. It won't stall.

The alternator is just a new remanufactured GM 'one wire' (3 wires
actually) 70 amp unit I think with an Optima battery. My Warn HS9000i
winch on full load doesn't drop my rpm like that unless I stall it and
and that stall is a rated 450 amp draw.

The only time I have seen that in the past was trying to boost a battery
and start a vehicle with a dead cell if I remember right....

Even with no draw, when I hooked up the booster cables the rpm took
about a 100 hit.

I do have heavy gauge booster cables with good clamps

Mike

ottertailfamily wrote:
>
> What the heck have you got for an alternator that will drop your engine 1200
> rpm? Man that must suck a LOT of power from the engine, or your engine
> doesn't produce much torque at 1200 rpm. I would guess a normal alternator
> would take at most 3 hp to turn, especially at such a low rpm.
> tad
>
> "Mike Romain" > wrote in message
> ...
> > He checked at the pump on those wires and had the same 10+ volts.
> >
> > Do you think this is enough to spin it up?
> >
> > I am thinking a lack of amps as well with a weak battery cell. The
> > charger does boil one cell harder than the rest and that one was low on
> > water. I tried boosting and it sucked my new alternator and new battery
> > hard enough to drop me from 2000 rpm on a hand throttle down to 800
> > rpm. Serious draw.
> >
> > Mike
> > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> > 88 Cherokee 235 BFG AT's
> >
> > oilyspill wrote:
> >>
> >> I believe there is a dark green wire with black tracer at the pump
> >> relay. That's the main power wire for the pump. It should be hot when
> >> cranking. Is it? You may have an initial prime for a few seconds, with
> >> the key in the on position, engine not cranking. After that, the
> >> computor will kill it, unless there is an rpm signal, you can't get a
> >> rpm signal without cranking the engine. If it is hot at the relay,
> >> check it at the pump plug, if that's ok, check the ground. If it will
> >> spin with B+ and a ground outside the vehicle, it should do the same
> >> thing on the vehicle. hmm

On Fri, 21 Jan 2005 20:10:07 GMT, Mike Walsh >
wrote:

>
>
>Lawrence Glickman wrote:
>>
>> A fully charged battery is 12.9 volts.
>
>Nominal battery voltage is 12.6 volts, i.e. neither charging nor discharging.

Where do you get this *stuff* from?

My fully charged battery -measured out at 12.9 VDC
Now, a week later, and with no charging or load given to it, it reads
12.82 VDC.

Stay away from those books and pay more attention to what your eyes
are telling you.

Lg


>> Anything under 10.4 volts is considered *weak*
>> but 10.4 volts or better is normal when you put a starter load on the
>> battery. When you take the load off, it will return immediately to 12
>> point something.
>
>10 volts might be weak, but I have seen many engines start with 8 volts.