Bad voltage limiter? (New owner!)

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FrozenCaveman

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Hi everyone,

I just became the proud new owner of my mom's 1971 Plymouth Scamp. She bought the car new originally in the SF Bay Area and it's been running around Marin for the last 37 years! I still remember getting picked up from school in that thing. So on Sunday, when I picked it up, I felt a little bad driving it up to Sacramento - it's finally got a new home. But it drove great, was cruising 65-70+ the whole way on that slant-6 in 100 degree heat by the time I hit Fairfield.

Anyway, the problem I'm about to deal with is this - the fuel gauge doesn't work at all and the temp gauge just barely gets to the bottom end of the normal range when it should be fully warmed up. From what I've read, the voltage limiter is typically the culprit when both of these gauges aren't working, or it can be a bad ground. I'm hoping it's not the sending unit, but what I'm wondering is this: if the temp gauge still moves a little bit, does that rule out the voltage limiter as the problem?

My 80-year old mom was pretty good about getting the car serviced, but the mechanic last told her that the sending unit is bad and it would cost $1000 to repair. That's mostly the reason that I got the car. Thankfully she thought of me instead of just letting the mechanic have it. After reading other posts, I'm hoping it's something a little more accessible than the sending unit. And given the temp gauge isn't working too well, I'm really hoping it's as simple as a new voltage limiter or maybe tightening the connections in the dash.

The car's paint is still the original metallic brown (not sure what the paint code is yet), with the tan (almost gold?) interior. No vinyl top. 211k on the speedo after one engine and tranny rebuild about 20k miles and 5 years ago. Unfortunately, it's got some significant rust at the corners of the rear window, which caused the trunk and rear quarters to rust out in front the rear wheels. And the heater core has been disconnected, so I assume it was starting to leak. Other than that, though, the car is in good shape and drives like a champ. I'll probably drive it to work now and again as the weather cools. And I'll definitely keep it under cover once it starts raining.

Anyway, thanks for any input you have. This is my first post on my first day.

-John
 
First off, welcome aboard. Wouldn't worry about the temp gauge. Bottom of the normal range is where a good Mopar wants to run. At least that's where most of mine wanted to be. To find out if you need a new sending unit get under the car, disconnect the wire going to the sending unit and short it to ground. If the gauge doesn't read full when you do this you have a bad gauge or the ground strap on the fuel line is open. If the gauge does read full you have a bad sending unit. If a shop told me it would cost $1000 to change it I would find another shop. You don't even need to drop the tank to change the sending unit. You want to do this with the tank nearly empty though. Ran mine out of gas, put in 2 gallons and drove it home and tore into it. Run the car up on a lift and the rear end will sag far enough to allow you to remove the tank ring and the sending unit and put in a new one. I changed mine in less than an hour working off jackstands and the ground. If you do this yourself, don't forget to lubricate the the rubber ring that goes between the tank and the sending unit or it will leak when you are done. Hope this helps.
 
The voltage limiter is not nessesarily easier or more accessable than the fuel sender. First test, find your temp sender and short that wire directly to ground and see if the fuel gauge does a full swing. Then do the same thing at fule sender. Dont leave them shorted for longer than a couple minutes.
If we eventually determine the limiter is the problem...
Oriellys auto parts did carry the stock type limiters at around 18 dollars.
If the fuel sender is bad its a 60 dollar repair not 1000 LOL
 
Welcome to FABO. The guys are absolutely correct. The fuel tank sender is a 1/2 hour repair and not much money. The temp gauge may be fine but your thermostat could be stuck open causing the engine to run cold. Your'e on the right track by asking questions. Answers here are free. Good luck! toolmanmike
 
Wow,thanks for the quick responses! Thanks for the tip about the potentially bad thermostat - I hadn't considered that.

Yeah, I thought the repair quote was insane, but my mom is 80 - hard to know if I got all the details. :) She sent me on my way with the wrong gas cap key. Heh.

So when grounding out the sending unit and temp sender, I'm guessing I need to have the key on, or no? Hopefully I'll get a chance to quickly check these two tonight after work. And I was afraid I'd have to drop the tank, so good to know I can replace the sending unit more easily.

Regards,

John
 
Yes, the key will need to be on to test the senders. Like someone above said, don't leave them grounded for long. Just long enough to see if the gauges are moving.

BTW welcome aboard!!
 
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