spark and no spark

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67barracuda

67barracuda

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Ok, still fighting problems with the barracuda and not sure what to do next.
I have spark while cranking form coil but not through to the plugs. If I remove the plugs so motor cranks faster and less draw from battery, it can get spark through to the plugs. It look like a weak spark to me. I have 12volts to coil but drops to 6 at the blaster when cranking motor over.
Had battery tested they say its good. I have the battery in the trunk grounded to frame and engine has ground strap to frame.
What should I do next.
 
67barracuda said:
I have 12volts to coil but drops to 6 at the blaster when cranking motor over.
.
Click to expand...

I have NO idea what this means

What exactly do you have for an ignition system?

Hook meter from coil + to the engine ground. Crank engine and read meter while engine is cranking. Post results.

You should have no less than 10.5 at the battery and at the coil+ when cranking
 
11.57V drops to 8V at the coil when cranking with plugs out. Guessing it would drop even lower with them in.
Only me so can't check it at the battery when cranking.
 
67barracuda said:
11.57V drops to 8V at the coil when cranking with plugs out. Guessing it would drop even lower with them in.
Only me so can't check it at the battery when cranking.
Click to expand...

Why not? You don't have alligator clips? You need to get some.

How exactly are you cranking the engine?

If you are checking coil voltage by jumpering the starter relay, this does NOT activate the coil bypass circuit. You MUST check cranking coil voltage by USING THE KEY to crank the engine.

This is because when doing so, the "run" circuit goes cold, and the coil bypass circuit supplies power direct from the key. That circuit may not be working.
 
I have alligator clip on coil and ground with voltmeter setting up right where I can see it through the windshield while turning the key.
Battery is in the trunk, so might be able to get someone to help me tomorrow.
 
OK great............ so let's get clear on this. You have the voltmeter clipped to the coil + and to engine, and using the key you are only getting 8V or so cranking? That is low. That probably shows a problem in the key switch bypass circuit.

What I would do is clip to something in the engine bay that gets you "battery" that is starter relay stud, or the starter stud. Crank and read, see what you get. If you have 10+ there but only 8 at the coil, then the problem is in that area, ignition switch, switch connector, or bulkhead connector, or a problem where wires come together at ballast resistor connections

You have a shop manual? Wiring diagram?
 
I have the FBO ecu ignition system, so I running a jumper across the ballast resistor. I will check it tonight.
 
This is what I got.

12.25volts at battery, 10.57 while cranking.
12.20volts at coil, 8.37 while cranking.
12.02volts at starter relay, 8.37 while cranking.

Checked impedance of battery ground wire to frame, .000
Checked impedance of engine to k frame, .002
checked k frame to frame, .000
 
If RPM is improving the spark then you probably have a wide reluctor gap. Set that a little closer using a thin plastic or paper gauge of around 0.006
If you are drawing voltage down that low at crank it may be time for a new starter or engine ground.
 
I'll check the gap, but I was able to run a 16g wire from the battery ground wire in trunk to engine checking ground, 00.6 impedance. I thought anything less than 1.2 was good.
 
You cannot measure what you are calling impedance (DC resistance) on circuits that large. Your ohmeter is not accurate. You need to test "while cranking" and test for voltage drop at different points. The 8 something at the coil shows a serious problem

Don't worry about ignition for now, you need to fix the cranking voltage problem. You need to figure out "where you are losing" the voltage.

How stock is the wiring? Battery up front?

The 10.57 at battery cranking is OK.

Check at the battery clamp on the positive cable, as well as the "top" of the battery post. Should be nearly zero voltage different. This is cranking.

Next move your meter down (clip if necessary) and hook meter to starter "big stud." If all that is between is battery cable, and voltage drops, then the problem is "in the cable."

Measure the drop directly across the ground again, while cranking

Clip one meter probe to engine block. Stab other direct into top of battery NEG post. Crank engine. You can jump the starter relay. You should have no more than a couple or three tenths of one volt, the less the better.

You can check positive drop same way. Clip one meter probe to starter "big" stud. Stab other probe into top of battery, and crank, and read. Again, the less the better, you should have no more that .2--.3V drop.
 
I removed the brown starter wire from the starter relay, and check voltage at the relay when key is turned. I have 12.02 volts.
 
67barracuda said:
I removed the brown starter wire from the starter relay, and check voltage at the relay when key is turned. I have 12.02 volts.
Click to expand...

Not sure what this proves?

Is this the wire off the "square" terminal which fires the solenoid?

I see you mentioned battery in the trunk. Are you running a trunk mount solenoid, or one hot wire from battery to starter?

you need to see what this voltage drop is. You need an extension cable so you can reach your voltmeter from the battery in back to "up front." This can be any scrap wire of any kind, say, 20GA on up larger.

Where and what have you for grounds? Details? How large?
 
Not sure what it proves, other than I have 12volt from the ignition switch.

yes, wire is off square terminal on relay. I though I was eliminating the starter while give everything else the same voltage when key is turned to start.

Battery in trunk with one hot wire up to starter. Battery is grounded to frame.
Engine has a 4G ground braided wire to the k member and the stock ground from fire wall to engine head.

Everything I have check while cranking motor, voltage has dropped
coil
ballast
starter relay-large top bolt
Battery drops to 10.5
distributor pickup gap is .006
white wire in pic from ground is grounding the FBO ecu
checked battery cables from post to wires and from post to frame for negative; no change.
 

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Should I check the coil + now while turning key to start, with the square solenoid terminal disconnected. Doesn't this keep voltage normal to everything, while eliminating the starter?
What to do next?
 
I would not worry about trying to start or coil voltage until you verify that the engine / starter is getting good voltage.

At this point I would clip your meter to the engine and starter big stud, crank the engine and post results. That right there will tell you if you have a basic problem from front to back


You may not and probably don't have a good ground from engine to frame. REMEMBER the K frame is BOLTED to the welded body shell. And, it can (will be) rusty. A 4ga ground strap is marginal with trunk battery.

You have to remember that "12 volt sized cable" only applies with normal factory cars.......short cables in the engine bay. Voltage drop gets worse with length of cable, therefore needs to be larger.

So.......follow in your mind the possible voltage drop only associated with the starter.

1....Hot side..........battery post to battery clamp........length of main cable........cable to eyelet end...........to starter

2....Ground side....battery post to battery clamp........in the cable.......connection to body........all way to front through body........to K frame bolts.......through K frame.......to ground strap.......through ground strap.......to engine block.
 
I would feel much better grounded to a frame rail rather than the K member. I've seen plenty of corrosion between K members and the frame rails.....
 
Just put 12V to coil from another battery....? it will draw about 5A so even a decent battery charger would provide voltage. Kettering will get you home....
 
Very interesting results.
With the meter clamped to the large bolt on the starter, the same one that holds the + cable from battery, with the grounded going to the motor. 12.2 volt initially and 8.37 volts when cranking.
So from there I went from the motor being the ground to a place on the frame I cleaned off as ground. The meter now is 8.57volts initially and 5.7volts when cranking. This is with the meter still being clamped to large + starter bolt.
 
Sounds like you are drawing more current with the new ground location(good) but with the voltage drop you have dead or sulfated cell(s) in the battery (bad). If the battery is good then the starter has issues or your engine is binding.
 
67barracuda said:
Very interesting results.
With the meter clamped to the large bolt on the starter, the same one that holds the + cable from battery, with the grounded going to the motor. 12.2 volt initially and 8.37 volts when cranking.
So from there I went from the motor being the ground to a place on the frame I cleaned off as ground. The meter now is 8.57volts initially and 5.7volts when cranking. This is with the meter still being clamped to large + starter bolt.
Click to expand...

Please be EXTREMELY specific when posting where you connected and what you did.

The reading at the starter stud is obviously low. So now we need to figure out

"Is it"

in the ground circuit?

in the hot circuit?

Or a bit of both.

YOU KNOW the cranking voltage to the engine / starter is LOW. WAY too low. That voltage should not be below 10.5, 10.0 at worst

So now do this

Determine ground circuit or hot circuit

Easy........

Clamp one meter lead to starter large stud

use your extension cable and run back and have a partner "stab" the remaining meter probe right into the POS battery post

Crank the engine and read. You want "lower the better" and more than .2--.3V (3/10 of one volt) is too much.

If that is OK, check the ground.

Same thing.......

Clip one meter lead to the engine. Run your extension back and stab into the battery NEG post. crank and read. Same as above. More than .2--.3V is too much, the lower the better.

How to narrow it down?

Let's say the hot side showed OK, but the ground showed a lot of drop. Leave one probe clipped to the engine block as before. Move the remaining probe

to NEG cable battery clamp. Crank, read, post back.

Move probe to stab into the trunk sheet metal near battery cable connection. Crank, read, post back.

Now, move up front.

Leave one probe clipped to engine. "Is it" the ground cable / K member?

Stab remaining probe into body sheet metal, the firewall. Crank and read

Move remaining probe "stab" into K member near where ground cable is bolted, crank and read, post back here.

I wish some us could get together. I could teach some of you more about voltage drop and troubleshooting in 1/2 hour than I can typing pages on here.
 
Some really great information above. My concern is the uni-body is not designed for starter current. Steel has about ten times the resistance of copper, for same cross section. The engine and battery ground straps add about double resistance compared the stock location, then add the great length, and poor conductivity of steel uni-body. The lower the voltage the starter sees, the higher the current it pulls to meet the load demand.
Running a large conductor copper battery to engine ground cable may be necessary.

And as others suggest the battery is sick. Any battery reaching about 11V without load is in the danger zone for loss of capacity, due to deep discharge.
 
KitCarlson said:
Some really great information above. My concern is the uni-body is not designed for starter current. Steel has about ten times the resistance of copper, for same cross section. .
Click to expand...

That may be true, but this has been done by many, myself included. "In a previous life" the old 70 RR had a warrmed up 440, rear battery, and back then we didn't have mini-starters, so the starter drew way more current back then. This was a factory 10.X:1 440 Cranked over just fine.

There are some that advocate a separate ground cable, but the body can be and has been successfully used.

But you and I both know, "guessing" is not the way to fix this. Logical testing will show up the problem.
 
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