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Reversed Battery Hookup?

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PlaidMan

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A 1958 TR3A's battery was hooked up neg. ground instead of positive ground by its owner, he was apparently installing a radio. The car will not start up, was wondering if the reversed connections might have affected the coil or the condenser or anything else? Thanks, Charlie
 
Hi Charlie, my first suspicion would be the fuel pump if it had a SU installed.---Fwiw--Keoke
 
Shouldn't be a problem on a stock TR3. Having the coil polarity wrong might make it a little harder to start, but shouldn't keep it from starting at all (unless of course it has an aftermarket electronic ignition).

More likely, IMO, a wire has gotten knocked loose somewhere during the radio installation. Is the coil getting 12v ?
 
Randall, the coil is getting 12 volts. I should have a chance to check out the car today and will look into the loose wire scenario. Thanks
 
12v to the coil should pretty well eliminate anything under the dash. IMO, time to ignore the polarity reversal, and start normal "won't start" troubleshooting procedures. Has it got spark, has it got fuel, sort of thing.
 
PlaidMan said:
A 1958 TR3A's battery was hooked up neg. ground instead of positive ground by its owner, he was apparently installing a radio. The car will not start up, was wondering if the reversed connections might have affected the coil or the condenser or anything else? Thanks, Charlie
Click to expand...

Charlie - if he was installing a radio, wonder why he disconnected *both* battery cables? Had to be both disconnected to be able to make it a "negative ground" car.

Was there something else going on? Do the gauges come on, ignition light on, etc. when the key is turned?

Tom
 
My TR4 arrived from the prior owner with the battery in backwards. Started & ran fine both before and after I corrected the polarity (even the + ground radio still worked... thought for sure it was fried).

So, as noted, best to look elsewhere for the gremlin.
 
Got it running today! The owner had installed a new vacuum advance but it wasn't connected to the pin on the points plate, the Distributor was loose, the wire on the negative side of the coil going to the points inside the distributor cap was loose, so I put new points in, fixed the wire and timed the engine and it started. Now I need to figure why it stumbles on acceleration, Distributor problem or carb mixture problem? Thanks again for your suggestions, Charlie.
 
PlaidMan said:
Now I need to figure why it stumbles on acceleration
Click to expand...
First thing to check is oil level in the dashpots. If you unscrew and lift the big brass nut on top of the domes, the oil should fight you as you push the nut back down.

Lots of other things it could be, but that is where I would start.

Next, I'd check that both carb pistons lift smoothly (but slowly) all the way to the top. Release and watch that they fall quickly and smoothly to the bottom, landing with a distinct click. Any binding whatsoever must be corrected.
 
The book tells you to overfill them a bit, so the excess oil will run down the rod and lubricate it. But it doesn't need to be nearly that high for proper operation. As long as you can feel the resistance when inserting the damper rod, there is enough oil.
 
When lifting the piston should there be resistance from the point you start to lift it or is there a slight space before you feel the effects of the oil?
 
Don't adjust the carbs until the end or until you have determined that they are definitely the problem. The biggest problem we have with our carbs is the person who last tried to adjust them.
Carbs will show wear over time and eventually need some tinkering or rebuilding. The effects are so gradual that they aren't noticable. If there is a problem, it is usually a lack of oil, dirt in the system, or a non-fuel mixture related item.
I feel it is best to make certain that everything else is functioning properly before moving on the the fuel system.
It's a chicken and egg thing, but it is easier to get the get electricals to work with poor mixture than it is the other way around.
 
PlaidMan said:
When lifting the piston should there be resistance from the point you start to lift it or is there a slight space before you feel the effects of the oil?
Click to expand...

There is a slight space before you feel resistance. If you unscrew the dashpot plunger, you will see a little cylinder on the end that floats up and down a bit. When you initially push up on the piston, that cylinder moves up to the top stop, then you will get resistance from the oil. That thingie is actually a valve. It offers more resistance to the piston going up then going down.

Edit: I agree with Doug....95% of all carburetor problems are ignition related.
 
martx-5 said:
There is a slight space before you feel resistance.
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True, but it should be very slight, like maybe .020". If it's much larger than that, there may be a problem with the check valve thingie.
martx-5 said:
Edit: I agree with Doug....95% of all carburetor problems are ignition related.
Click to expand...
No argument from me ... but likewise at least 50% of all ignition problems are actually carburetion. And since the damper is the only thing that specifically comes into play on acceleration, and is easy to check, it seems the logical place to start.

The real point is to follow a logical sequence of tests to find the problem, not just pick something and start "fixing" it without knowing whether it's broken or not.

One of our local club members went as far as buying all new carburetors, before finally discovering his problem was bad valve lash adjustment.
 
TR3driver said:
The real point is to follow a logical sequence of tests to find the problem, not just pick something and start "fixing" it without knowing whether it's broken or not.
Click to expand...

It's called "Strategy Based Diagnostics", and has served me very well over the years.
Jeff
 
Thanks guys, I will use your strategies this Saturday when I have another chance to work on the car. The carbs are 1 year old, new I believe, but now that I think about it , I remember their being a little catch when I would first turn the rotor in the distributor checking the movement of the weights, maybe that could be part of that stumble problem. Thanks again, Charlie
 
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