Packard Forum Index » Post-War (1946-54)

Tim,

As long as both gauges don't stop working together, it's not the cluster voltage regulator.

The symptoms your car exhibits are very common. What happens is that the float moves a contact that rides along a plate with varying resistance, similar to a dimmer switch. High resistance = lower gauge reading, low resistance = higher gauge reading. Back in the day they used a coil-type rheostat to vary the resistance, but most senders now use a plate with a resistive coating applied.

Basically, these things get dirty and when the contact is at that point you'll get very high resistance, i.e. an "Empty" gauge reading. Just like the headlight switch has a rheostat in it to control the instrument panel brightness, when these things get dirty, they don't make good contact, but you can easily clean them with electrical contact cleaner.

I don't know which one you have, I haven't actually ever seen an original Packard fuel sender, but if you have a resistive coating rather than a wire rheostat, you have to be careful as contact cleaner will pull that coating right off if you aren't gentle. While I've always found it humorous to say to people "you told me you didn't want the gauge to read empty when there's still 1/2 tank left, but you didn't say it couldn't read FULL all the time," it's probably best to either replace the sender or carefully clean it. Most mechanics today would rather replace the sender than troubleshoot and repair the existing one, so as to avoid the possibility that this same thing won't happen again once the tank has been reinstalled, but if you're careful, it can be done.

I haven't actually ever seen an original Packard fuel sender

The 51-6 Packard senders used the wire rheostat. As DrewLA mentioned, the wire or the wiper contact can get dirty. Like the resistive coating, the wire is also supported on a length of phenolic riveted to the sender body. It's shaped in an arc to match the wiper swing but the phenolic has a nasty habit of distorting. If that happened, it could also be causing an intermittent loss of contact or high resistance at a certain area.

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thanks so much for the great info. You guys explained it so well as do the other posts.
I did the ohm test and yes I just need to order a new sending unit.

update:
It sure takes me a long time to complete my projects. One thing always leads to another. And , as I am sure you all will agree, having an old car there is always something new to figure out.
I did get the fuel tank repaired and painted and installed a new sending unit.
Before I put the tank back I decided to clean the metal under the trunk bed as well as inside the trunk. So I have been brushing, sanding and scraping away. I took the original coated cardboard type matt out of the trunk and started to clean. I found one hole, rust, about the size of a 50 cent piece. then I started underneath. too bad about the hole , but at least I am going to stop the problem. while I was under the car I notice that the PAX side shock absorber WAS NOT even bolted on the top. I guess it must have come off. WOW. and I also found that there is like a mud or splash guard missing on one side. & one more thing , I think the car had minor body repair in the rear. does not look too bad.....so who knows when I will get this car back on the road. after all this prep I will clean and or replace the fuel line and check the fuel pump.
ADVICE: once I prime the trunk bed do you guys think it would be a good idea to coat the trunk bed with "truck bedliner paint: You know that thick heavy rough coating they protect bedliners with now a days>>>>? any advice.

cont: I figure later down the road when it is time to repaint I can paint over the trunk with the original color.
I also wonder if the original floor matt doesn't trap moisture......? I think these floor coverings might trap in moisture.

Quote:

IIRC, this observation came up before. If it is a metal plate at the rear of the fender well you are wondering about, think the conclusion was a splash or mud guard is on the drivers side to protect the gas fill pipe but there is none on the passenger side.

Tim49, the bedliner can be good, it's down to personal choice and originally most Packards had a coating of black bituminous 'sound deadener' that resembles the bedliner anyway. Many trunk spaces had flock applied to the coating to dress it up a little. Do you want to keep the car totally original? Many owners simply carpet the trunk but in some cases that's not original.

Biggest issue is that you do need to remove / neutralize any rust that exists before applying the liner as rust can still progress slowly under the coating. And certainly it's wise to avoid carpet and floor coverings that don't breathe or trap water behind them (typically rubber-backed ones), if you have any water ingress at all to the trunk.

again, thanks for the advice. and hh56 thanks for your comment on the mud/splash guard on drivers side to protect the fuel filler pipe. great info.
I want to keep the car as close to original as possible. on that note a lot I am doing on this car is learning . my expertise well evolve as I move along. just what I have expiernece since I have owned this car I think I will coat the trunk with the bed liner product. only use a carpet for going on drives then remove when I store the car.
I will work very hard to get all the rust and neutralize as best I can. I've been reading up on such products..
thanks for all the help

The latest on this project:
The fuel tank has been cleaned , repaired and painted &reinstalled in the car. I cleaned the road side of the trunk floor where the tank is located. primed and painted.
(I found 1 rear shock that was not fastened at the top. repaired). cleaned fuel line. ok for now , but will replace.
here is my question:
yesterday I took the fuel pump off. I am so curious about it. I took the after mkt. fuel filter off(it was only on a short time, 1.5 yrs) I cut it open and there was a white paste. almost like wet chalk. strange to me.???????
I do not have a heat shield. from what I have learned from this site . I will order a heat shied.
any how , I took the pump off and removed what I call the bowl. it is the bowl shaped metal piece directly on the bottom. in the bottom of the bowl was about 1/2 -1/4 of a teaspoon of a gray paste. it like it is the metal from the pump itself. the inside of the bowl is pitted.
advice??????
I suspect it is the new fuel.
the piece that takes the bolt to hold the bowl on is craking and deteorating.
I have been told I can rebuild the pump.
I think I should just order a new pump.
what do you guys think? and if I order a new pump who is the best to order from.????

I believe a new pump will be compatible with todays fuels. can I use ethanol free fuel too? here in Hawaii you can still by fuel w/out ethanol. it is 89 octane.
also my pump does not have an air dome in the outlet position like it shows in my shop book. It eliminates pulsation....... should I have this.???
sorry for such a long list, but when I start on something I get all these ?. thanks . you guys are great.