Chrysler Fuel pump and battery Questions.

On Fri, 21 Jan 2005, ottertailfamily wrote:

> I would guess a normal alternator would take at most 3 hp to turn

No need to guess. We can do the math.

Let's assume the vehicle in question has a 90-ampere alternator, and was
under full load demand.

90 amperes x 14.2 volts = 1278w ~ 1.28kw

1kw ~ 1.33hp

Therefore, 1.28kw ~ 1.7hp

But alternator conversion efficiency is not 100%. Assume 75%.

1.7 x 1.75 = 2.975hp

So, your 3hp guess is probably pretty close.

"Daniel J. Stern" wrote:
>
> On Fri, 21 Jan 2005, ottertailfamily wrote:
>
> > I would guess a normal alternator would take at most 3 hp to turn
>
> No need to guess. We can do the math.
>
> Let's assume the vehicle in question has a 90-ampere alternator, and was
> under full load demand.
>
> 90 amperes x 14.2 volts = 1278w ~ 1.28kw
>
> 1kw ~ 1.33hp
>
> Therefore, 1.28kw ~ 1.7hp
>
> But alternator conversion efficiency is not 100%. Assume 75%.
>
> 1.7 x 1.75 = 2.975hp
>
> So, your 3hp guess is probably pretty close.

I have had rpm drop like that before. From a hand throttle 2000 rpm
down to 800 rpm or so. Only when I have serious draw like stalling my
Warn HS9000i winch on full load which is a 450+ amp draw or trying to
boost a bad battery.

It must be trying to stall the alternator from the sounds of it. I was
watching the belt expecting it to start slipping. It did start
wobbling.

Just noticed this post was cross posted to Chrysler Dan. What use is
that if they haven't seen the reason for the draw and the original
question and some answers?

Yes it has the 10 volts evident at the pump when the starter is turning,
this is the result of a boost after a 24 hour charge and no start but
the starter still turning.

I will copy the original post below:

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, Mike Romain wrote:

> Just noticed this post was cross posted to Chrysler Dan. What use is
> that if they haven't seen the reason for the draw and the original
> question and some answers?

They have, 'cause I crossposted my response to your original question,
with most of your original text quoted, to ramc.

DS

"Daniel J. Stern" wrote:
>
> On Fri, 21 Jan 2005, Mike Romain wrote:
>
> > Just noticed this post was cross posted to Chrysler Dan. What use is
> > that if they haven't seen the reason for the draw and the original
> > question and some answers?
>
> They have, 'cause I crossposted my response to your original question,
> with most of your original text quoted, to ramc.
>
> DS

I certainly missed your original response as did 'both' newsgroups it
would appear.

Did your server forget to post it?

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