Electrical problem

[mwood]

Disclaimer: electronics are not my strong point, I'm going to try my best to describe what's happening and I do need help!

Car is an RF88 VD with Kent, used for autocross. Took it out to first event since last September two weeks ago. Car starts fine off plug in jumper battery (starter did sound a little "lazy" initially, then spun ok). Electronic tach working. Take car off of jumper battery, tach stops working, car keeps running. Shut it down, car won't restart off the on board battery, even though it was freshly charged...it just doesn't have enough to crank a full revolution. So, it starts fine off the jumper, won't start off the on board, tach only works when the jumper is plugged in.

Brought car home, recharged on board battery. Still won't turn over using on board. Hook jumper cables to on board. No luck. Disconnect on board battery and run jumper cables directly to +/- leads. No luck.

So, the car will start and run normally via the plug in circuit, but won't start/run on the circuit which originates at the on board battery, it would seem.

Thoughts? (before I start pulling the car apart to look for bad grounds or visible wiring issues).

I didn't mention, but the wiring is pretty fresh and I've had zero problems along these lines in the couple of years I've run the car. Also, the master switch was never wired correctly, as the car will continue to run even with the switch in the off position. So, I'm not thinking bad kill switch (?)

Thanks
Mike

[DaveW]

Most point ignitions will run on as little as 8 volts. Most electronics won't work on less than 11. I think you have a bad cell in the onboard battery, resulting in it putting out around 10 volts.

Check the onboard battery under load with a DVM - if it is at 10-10.5V or less while running, you need a new onboard battery. It should read 12+ if it is good.

The starting failure with the onboard also indicates it is junk.

[-pru-]

Also, the master switch was never wired correctly, as the car will continue to run even with the switch in the off position. So, I'm not thinking bad kill switch (?)

Have you tried puting both Master Switch leads on the same lug to test the switch?

[mwood]

Dave, I've tried disconnecting the on board and wiring in a known good, full size 12v source with no luck. Also, the tach just stopping when I pull the plug on the jumper battery makes me wonder if it is wiring/ground related??

Pru, I did try jumping the kill switch as described. The switch has been wired wrong since I got the car, as it won't kill ignition in the off position regardless as to whether running off plug in battery or on board. So, I'm not sure how it would now become the problem?

[-pru-]

Pru, I did try jumping the kill switch as described. The switch has been wired wrong since I got the car, as it won't kill ignition in the off position regardless as to whether running off plug in battery or on board. So, I'm not sure how it would now become the problem?

I am thinking the switch had failed ON but has now failed OFF...

[Dick R.]

Dave, I've tried disconnecting the on board and wiring in a known good, full size 12v source with no luck. Also, the tach just stopping when I pull the plug on the jumper battery makes me wonder if it is wiring/ground related??

Pru, I did try jumping the kill switch as described. The switch has been wired wrong since I got the car, as it won't kill ignition in the off position regardless as to whether running off plug in battery or on board. So, I'm not sure how it would now become the problem?

Mike,

What Dave said.

Question: Does your car have points or a Pertronix, etc. points eliminator? Points don't need much voltage as Dave said. I don't know about the Pertronix.

Regarding the master switch not shutting off the ignition there are too many possibilities for me to help from 3K miles away.

HOWEVER, it the master switch doesn't disconnect the ignition that means some other electrical device may continue to receive power even though the ignition is off. Even a very small load would drain AND damage a battery over the winter.

FYI if the master switch is in the ground circuit like many formula cars then the ONLY connection to the battery terminal should be one big cable which runs directly to the switched terminal of the master switch. Nothing should operate with the switch off UNLESS a jumper battery or a battery charger is connected.

Formula car wiring diagrams have been posted on Apex. Holler if you cannot find one easily.

[mwood]

The car has Pertronix ignition.

I'm going to try isolating the kill switch again tonight after dinner.

No doubt the little on board could be toast, but hooking the leads to a known good battery, with no luck, makes me wonder how the battery can be the problem...if you follow my logic?

[Dick R.]

Dave, I've tried disconnecting the on board and wiring in a known good, full size 12v source with no luck. Also, the tach just stopping when I pull the plug on the jumper battery makes me wonder if it is wiring/ground related??

Pru, I did try jumping the kill switch as described. The switch has been wired wrong since I got the car, as it won't kill ignition in the off position regardless as to whether running off plug in battery or on board. So, I'm not sure how it would now become the problem?

Mike,

Trying to use a process of elimination before you introduce additional changes.

When you tried the "known good 12 volt source" was that a full size battery? Did you connect it with the terminals removed from the on board battery? If so did you also connect all the terminals at the master switch together on one terminal bolt?

Where does the jumper battery connect to the car? Does it "share" any cables that the on board battery uses? For example, my jumper plug connects the ground terminal with a very short cable to to the transmission. The positive terminal connects to the starter at the same location that the positive terminal from the battery connects. As a result, the current to the starter from a jumper battery doesn't use the normal on board battery to starter cable/connectors.

The reason for this question is to try to isolate the possible bad connection or cable.

[Dick R.]

Mike,

Link to the wiring diagram thread.

See post #24 for the easiest to understand version of the diagrams.

http://apexspeed.com/forums/showthre...ram#post422288

[mwood]

Thanks, Dick. I just took the master disconnect entirely out of play, putting all three cables on a single bolt/post. I've pulled the on board battery out of the car and charging the jumper battery. When it is up to charge, I will hook it directly to the leads and see what I get.

[Dick R.]

Thanks, Dick. I just took the master disconnect entirely out of play, putting all three cables on a single bolt/post. I've pulled the on board battery out of the car and charging the jumper battery. When it is up to charge, I will hook it directly to the leads and see what I get.

3 cables? What size are they? What do they connect to?

Mine has one big cable directly from the negative terminal of the battery and one big cable which goes directly to an adjacent stud on the frame. At the frame stud I connect the small ground lead for the rev limiter simply because it was a convenient location.

FYI, I'm "done" for tonight but will check this thread in the AM.

Goodnight from Raleigh . . .

Dick

[mwood]

Thanks, Dick. Have a good night.

Just an update: after doing the stuff described above (taking master kill out of circuit), the starter just won't turn over with any speed, like it isn't getting enough voltage.

So, it doesn't appear to be either the battery or the kill switch.

[akilcoyne]

Batteries, like most automotive systems need to be tested with a load present. It used to be taught that isolating a circuit to check "continuity" or resistance(ohms) was an acceptable way of checking a circuit. A more fool proof way to check a circuit, conveniently also easier, is to perform a voltage drop test with DVOM(digital volt/ohm meter). A voltage drop test is done by measuring from two points on a live circuit as it's being operated. Example: positive stud on the battery with one lead from your meter and the positive stud on the starter. Set the meter to the 12V DC voltage scale. Attempt to start the car with the meter in place. You should expect to see 0.0V on a perfectly working circuit. .3-.6V would be acceptable voltage drop on a starting circuit since there is a very high load on that circuit. Most other circuits you never want to see more than a .2V drop. The reason this test is so accurate is that two major electrical rules apply. Voltage takes the path of least resistance and voltage flows from positive to ground. If you have a voltage drop in the circuit, voltage will flow through the meter and register a voltage value. In a properly working circuit you should expect a voltage value of "0" as the voltage should flow freely through its circuit and not through the meter. This test will work on the + or - side of the circuit.

Not knowing how your system is wired, I'd start with doing the test as I described above. Positive lead at the battery and negative lead at the starter. If you find a voltages drop you can start pinpointing smaller sections of the circuit. If it goes from battery to master switch and then master switch to the starter, you could measure from battery + to master switch. Etc etc. Remember, this test only works if you measure the voltage drop as the circuit is being operated(attempting to start the car while taking your reading).

After knowing that you have good source voltage(known good battery), I'd suspect that you have a ground issue. Does your jump plug ground directly to the starter? Anything recently painted that would prevent a ground path?

Pm me if you don't follow what I'm saying or need further tips

[mwood]

Thanks, very much, for taking time to detail. Yes, I do follow what you're saying. I don't have a voltage/ohm meter, but will pick one up (should have one, anyhow). I've always swapped or paid for electronic work...kind of like bodywork, it has been more efficient to farm out than screw up myself

I've been thinking bad ground. I didn't wire the car, but believe the jump plug does ground directly to the starter.

[Dick R.]

Thanks, very much, for taking time to detail. Yes, I do follow what you're saying. I don't have a voltage/ohm meter, but will pick one up (should have one, anyhow). I've always swapped or paid for electronic work...kind of like bodywork, it has been more efficient to farm out than screw up myself

I've been thinking bad ground. I didn't wire the car, but believe the jump plug does ground directly to the starter.

Mike,

When you say the jump plug probably grounds directly to the starter do you mean that both jump plug wires connect to the starter? That is the positive wire connects to the big stud on the starter and the negative goes under the head of a starter mounting bolt?

The way starters are normally grounded is by their bolted connection to the engine block. The block in a formula car is then bolted to the frame. In my car the jumper negative side connects directly to a bolt on the transaxle. The jumper positive goes to the same terminal as the battery positive cable. The battery negative goes to the master switch which when on connects it to a big stud welded on the frame.

Before doing anything else with troubleshooting verify that the jump battery will still start the car via the jump plug. If it does, then you "only" need to isolate the bad component between the on board battery location and the starter. An easy way would be to substitute a jumper cable for first the negative cable and then the positive cable.

Dick

[Steve Demeter]

My bet is a bad connection between the onboard battery and starter. And the Petronix could be acting up. They have a way of doing that intermittently.

This all assumes that the onboard is not bad.

Also, when connecting the big battery to the onboard terminals, make sure that everything is good and clean.

I had a problem once where it seemed like the onboard was bad. Found out the hard way, thanks to Scott at SBS that lead terminals will develop an oxidization on them which is a pretty effective insulator. A little work with a wire brush and magically the onboard has worked for two years since.

[DeepThought]

Hi Mike,

I run 1264 another RF88. Main wiring on it is as follows.

Jump plug,

• +ve goes to main stud on starter,
• -ve goes to a ring connector under a nut on the gearbox side plate.

On-board battery,
+ve

1. same main stud on starter as jump plug
2. one side of starter switch (other side to starter solenoid)
3. one side of ignition switch.(other side to tach, pertronix and rain light switch

-ve to one side of battery master switch.


Battery master switch (interupts -ve),

• one side to on board battery
• other side to frame AND engine block.

Those are the main players to get the starter rotating. As for the eratic tach, my tach picks up it's ground on a ring connector bolted under one of the front swaybar mounting points.

My car is in the trailer ready for the weekend's racing but if needed I can take as many pictures as you want or you can pm your phone number and I can call. If you have skype I could even show you!


I have received so much help with my first few months of racing it would be a pleasure to help in any way.


Regards ... Dave

[mwood]

Thanks for all the helpful comments and suggestions. I'm leaving tomorrow for an overdue vacation, so won't be playing with the car until I get back.

I believe it is just a matter of testing the leads from the on board, based on what I've tried so far. Now, I just need the time to get a multimeter and test.

[Jonathan Hirst]

I agree with your feeling about the bad ground. I would start by cleaning / inspecting the ground connections between the chassis and the onboard battery.

As stated, the jumper plug (which works?) uses its own direct connections for the ground and you established the starter and the tach work fine when connected to an external battery.

A poor ground connection between the OB and chassis would account for the tach not working and the starter struggling. I would also check the tach connection to the chassis as well, a 30 second check to rule it out.

If the engine still starts from the jumper then I would not worry about the Pertronix.

Once the issue of starting using the onboard wiring is resolved using a known good battery, I would heed the advice about checking the OB battery if there appeared to an unintended draw on it over the off season.

Jonathan

[mwood]

Just to close the loop on this...ended up being a bad battery I discovered a month or so ago. Embarrassing, as I thought I had completely eliminated that as a possibility, but there you have it. I guess the battery was only getting some kind of surface charge, which fooled my voltmeter, but had an internal failure. (?)

Thanks for the help.

[Pi_guy]

I carry a toaster type load tester. First thing I do is check battery. Cuts down on much BS.

[Bob Wheless]

Forgive ignorance, but what is a toaster type load sensor? Sounds like i need to get one.... thanks,,, bob

[Pi_guy]

looks like this
I have had the same one since 1984

OTC 100 Amp Battery Load Tester



http://www.walmart.com/ip/OTC-OTC-10...ingMethod=p13n

[BURKY]

looks like this
I have had the same one since 1984

OTC 100 Amp Battery Load Tester



http://www.walmart.com/ip/OTC-OTC-10...ingMethod=p13n

That's one fancy cheese grater!

[Pi_guy]

I do not keep the switch on until the wires glow like a bread toaster, it is a short test puts 100 amp load on it.
My observation is that if the voltage drops to 6v or less the battery is bad, and should be replaced.
Also find it is good to test starter cables this way.
Have looked at the digital ones <snap on> but the swing of the analog meter is often more useful in finding bad connectors/connections. The variable carbon pile testers are not bad but dropping a 300 amp load on small amp hour batteries is a good way to make a battery bad.

[kea]

I do not keep the switch on until the wires glow like a bread toaster, it is a short test puts 100 amp load on it.
My observation is that if the voltage drops to 6v or less the battery is bad, and should be replaced.
Also find it is good to test starter cables this way.
Have looked at the digital ones <snap on> but the swing of the analog meter is often more useful in finding bad connectors/connections. The variable carbon pile testers are not bad but dropping a 300 amp load on small amp hour batteries is a good way to make a battery bad.

Bought mine in the 70's at a local Auto Parts store.

[DaveW]

looks like this
I have had the same one since 1984

OTC 100 Amp Battery Load Tester

I just got a similar Schumacher BT-100 unit from Amazon for $29. Tested my 3-year-old DEKA ETX-18L racecar battery and the same, but 6-year old, spare. I did not have a problem with either one, but was curious about their health. The spare actually tested slightly better (which I thought it might from its charging behavior), but both tested good for voltage at 100A load.

[Modo]

if u charge a battery and watch the amps, if the amps don't drop below let's say 3 amps in 15 minutes, start worrying, 45 minutes or so, it's toast I would think, wasting electricity, at least for our small batteries ....(charging from running vehicle, 10 amp charger and maybe 6 amp, amps drop quickly for those) ........ I like the load tester but make sure u top up the battery afterwards, LOL ...... always keep the battery topped up as soon as posssible, otherwise it destroys itself .....

Scenario is this: race car is 1 -2 hours from your house and u drop it off late sunday night with the battery not fully charged ...... don't get back to car for 2 -3 months ..... not good

[Purple Frog]

About 15 years ago I had a problem at Road Atlanta. John Fergus heard about it, and sent Randy Hartmann over with one of these load testers.
Since then I have always owned one. Use it on cars, tractors, golf carts, race cars, airplanes...
Don't leave home without it.
There is a reason over the years that we tend to migrate from small open trailers to big enclosed trailers. All the "necessary" stuff.

[DaveW]

...
but make sure u top up the battery afterwards, LOL ...... always keep the battery topped up as soon as posssible, otherwise it destroys itself

Words of wisdom, IMO. I am compulsive about charging any lead-acid battery ASAP. Keeping them at low charge for an extended period hastens their demise.

I have had car batteries last over 15 years with proper maintenance.

[Pi_guy]

if u charge a battery and watch the amps, if the amps don't drop below let's say 3 amps in 15 minutes, start worrying, 45 minutes or so, it's toast I would think, wasting electricity, at least for our small batteries ....(charging from running vehicle, 10 amp charger and maybe 6 amp, amps drop quickly for those) ........ I like the load tester but make sure u top up the battery afterwards, LOL ...... always keep the battery topped up as soon as posssible, otherwise it destroys itself

If I understand you: Your guessing by spend time charging it. The load tester quantifies the issue in a short time. In the 30 plus years of using it have not found a battery to become good after failing a load test.
Plus it can be used to test connections and switches and starter power leads.
Most of the current batteries are sealed and if you have one that is not I believe one of the tests you should perform is specific gravity of the solution.
The other tool I use for the new lithium batteries is a individual cell voltage checker available where RC cars and airplanes are sold.

[Albatross]

Good stuff! Thanks Apexspeed.