Wire hot to touch

[JAllenWAG]

I've been trying to chase down a couple fuel/ignition problems and have tried almost everything. I realized I wasn't getting any voltage to my elec. choke so I fixed that and in the process noticed I have a wire that is heating up when the key is on (but not running). It's a red wire that is spliced into the positive lead to the coil. Electrical work is not something I know a lot about. Should this wire be getting hot when the engine is not running? Could it mean a bad ground somewhere? Any help would be appreciated.

[JAllenWAG]

btt

[Joe Guilbeau]

Originally posted by JAllenWAG:
I've been trying to chase down a couple fuel/ignition problems and have tried almost everything. I realized I wasn't getting any voltage to my elec. choke so I fixed that and in the process noticed I have a wire that is heating up when the key is on (but not running). It's a red wire that is spliced into the positive lead to the coil. Electrical work is not something I know a lot about. Should this wire be getting hot when the engine is not running? Could it mean a bad ground somewhere? Any help would be appreciated.The Coil needs to have voltage sent to it's primary side in order to provide the Distributor enough voltage to fire the spark plugs.

When you turn your key on, the Red wire is providing the Coil with power, it should be about 12Vdc. There should be another wire that is on the same terminal, this wire provides power to the Coil when the vehicle is running, as some of the coils were not designed for continuous application of 12Vdc, something lower, in the range of 7-9Vdc should be available when the vehicle is running.

The operation of the Ignition Coil is controled by grounding the Negative side of the coil to ground, and that is controled by the relative position of the distributor position.

In the older "Points Style" vehicles, the distrubutor opened and closed the points, thus routing voltage to the coil, when the contacts were closed, current would flow from the positive side of the coil thru it's primary windings and to return to ground potential via the closed points. When the points were opened, the coil primary windings would charge, then discharge thru the closed points, and charge again in a pretty much endless cycle while the engine ran.

You are experiencing the electronic equivelance of the points being closed, so current flows from the Ignition Switch thru the primary side of the coil, out thru the Negative side of the coil (thru the Green Wire).

This is normal, if you "Bump the engine" over by turning the key to start, and let the starter bump the distributor to a new position, it should open up the Negative side of the Ignition Coil so that current will no longer flow.

By the way, this is a good way to test the system for Spark, you can simply pull a spark plug (depending on where the rotor is positioned) and removing the Green Wire from the Negative Ignition Coil terminal, touch and remove the Green Wire to watch the Spark Plug fire.

The engine must be in the state you describe in order for the spark plug to fire (assuming that you have a relatively stock set up).

What you describe is normal operation for a relatively stock engine, by the way, what year is the Jeep and model, this sometimes helps out with troubleshooting.

[JAllenWAG]

It's an '89 grand wagoneer with tfi coil. It's been surging at idle and lacks power and I'm pretty sure it's ignition related. I've tried timing at different points and right now I wanna check for weak spark but don't really know how to go about checking that.

[mtn goat]

Wow Joe! that was quite an explaination...just to simplify, The wire you are talking about is the resistance wire, so yah, it is supposed to get hot.

[ November 26, 2003, 10:38 AM: Message edited by: mtn goat ]

[JAllenWAG]

How can I check for spark or for lack of spark? I've unplugged each wire one by one and didn't notice a difference in idle with any of the wires removed.

[Gawdzilla.]

Originally posted by mtn goat:
Wow Joe! that was quite an explaination...just to simplify, The wire you are talking about is the resistance wire, so yah, it is supposed to get hot.Hey, I like Joe's explanations!!! smile.gif

[JAllenWAG]

What I meant was how can I check for WEAK spark? What should my voltage be at +/- terminals with key on or engine running?

[mtn goat]

AT the coil terminal, you should have 12-13 Volts while cranking the engine over. after its running (or with the key in the on position) You should have about 7-9 like Joe mentioned.

[Gawdzilla.]

Originally posted by JAllenWAG:
What I meant was how can I check for WEAK spark? What should my voltage be at +/- terminals with key on or engine running?Ok, you're going to need an assistant for this. Get a digital camera and a measuring tape. Go outside and remove a plug wire. With the wire w/the terminal 1/4" from your hand, and the measuring tape extendended over your head, have your assistant start the engine then take a picture. Do this with your rig, and a known good test vehicle. Compare how high your hair goes on each photo...

OK Sorry for that. I really don't know. JOE???

[Joe Guilbeau]

Originally posted by JAllenWAG:
I've unplugged each wire one by one and didn't notice a difference in idle with any of the wires removed.Not good, the beast must be running so bad that unplugging wires does not make much of a difference?

Ouch!

[Joe Guilbeau]

Lets get back to the basics, what have you done recently to the vehicle?

Something must be related to your problem, or did it just suddenly appear.

If it just suddenly appeared, take a look at the Rotor and the Distributor cap, perhaps spraying it with Electrical Contact spray will reveal a crack or something in the Distributor Cap, my idle smoothed right out after I replaced a Cap and Rotor recently, there was a hairline crak in the distributor, did not look like it would affect anything, guess again!

A really boring way would be to have someone use a High Amp probe to measure the 40,000 Volts or so sent to the spark plugs.

You would need to slowly turn the engine by hand with a wrench, the distributor will do it's thang and you can measure the spark energy at each plug when it's turn comes around. Technically correct, but it will consume lots of time and set up to properly measure. Why go to all of that trouble.

Unplug all the spark plug wires on the Jeep, start with the engine at TOD Dead Center...take all the spark plugs out and using the timing marks on the Harmonic Balancer, ensure you are at TDC 0-Degrees. Stick a screwdriver down the No. 1 Spark Plug hole, if it goes deep you are 180 Degrees out, crank the engine over by hand until you are again at TDC 0-Degrees and the No. 1 Piston is at the top of it's travel.

Now, the rotor will be...or should be pointing at the No. 1 Cylinder..., get your BRAND NEW NGK PLUGS that you just purchased for $40 bucks, and insuring that the gap is correct, install them.

Now, following the firing order in all of the Jeep Manuals, go ahead and route the spark plug wires to the associated cylinders.

Or just follow the direction by JC Jones on the subject matter...

Reference Items:
Firing Order AMC 360cid : 1-8-4-3-6-5-7-2

Distributor Rotation : Clockwise
Drivers Side cylinder numbering ...front to back... : 1 3 5 7

Passenger Side cylinders numbering ...front to back... : 2 4 6 8

I hope the following diagram stays intact:

Pass________Driver:

__8____________7

__6____________5

__4____________3

__2____________1

-> Rotation of distributor

5____O_O____7
6__O_____O__2
3__O_____O__1
4____O_O____8


<- Rotation of distributor

Note: on the above diagram, #1 may not be in the same position as on your vehicle - I don't remember exactly which direction #1 is so the above diagram is for example purposes only.

1) Disconnect the battery.

2) Remove all 8 spark plugs to make the engine easier to turn over by hand.

3) Put your thumb over the #1 spark plug hole and rotate the engine in the direction of normal running rotation with a socket wrench on the center crank pulley. There are other methods of rotating the engine manually, but I will not mention them here since they are not very safe.
...you can check the rotation direction by watching the engine from the front while someone "bumps" the key to cause the engine to rotate slightly with the starter before you disconnect the battery...

4) You will feel air pressure on your thumb when you have rotated the engine to the compression stroke on cylindar #1. Continue rotating the engine until the #1 piston is at the very top ...Top Dead Center or TDC... on the compression stroke. Once you know you are compressing on calendar #1, you can use a long screwdriver as a feeler for the piston to know when it is at the very top, but be careful not to get the screwdriver jammed between the piston and the spark plug hole. Also, be very careful of the
threads in the spark plug hole to not damage them.

5) Now, re-install the spark plugs, and reconnect the spark plug wires making sure that they all reach the distributor with plenty of slack. Make sure you do not turn the engine at all or you will have to repeat step #4.

6) Disconnect all the spark plug wires from the
distributor cap and remove the cap. Note the
direction that the distributor rotor is pointing,
and determine which plug wire hole on the cap
the rotor points to. This is where the plug wire
for calendar #1 goes. Once you determine this
you can put the distributor cap back on. If your
distributor cap has a 1 molded into it, that should be the hole that you identified ...if not you need to check more thoroughly to see what the problem is, because that indicates that you might have a mechanical timing problem.... If your distributor cap does not have this molded marking on it then you should mark your distributor cap for future reference.

7) Now, you can re-install the plug wires on the
distributor cap by following the firing order
above in a clockwise rotation from the #1 position you have identified.

8) Reconnect the battery, make sure you removed
the socket wrench from the crank pulley and have
retrieved any tools you had under the hood.

9) You should be able to start the truck and it
should run fine now. Use a timing light to adjust your timing to within specs for your altitude.

That pretty well sums it up. Once everything is hooked up correctly, then she should run much better. If not, then you probably have jumped a timing tooth on the timing chain and the real fun is about to begin...

For those of you who wish to change the position of the distributor relative to the engine, as long as the rotor points to the place where the No. 1 spark plug wire goes to on the distributor cap, and the sequence is correct, it dosen't nuch matter which way to rotor points, most folks simply point the rotor to the No. 1 Cylinder and leave it at that.

Thanks to Mr. JC Jones...I did not have to type all of that into the message board!

[Joe Guilbeau]

Originally posted by Joe Guilbeau:

Reference Items:
Firing Order AMC 360cid : 1-8-4-3-6-5-7-2

Distributor Rotation : Clockwise
Drivers Side cylinder numbering ...front to back... : 1 3 5 7

Passenger Side cylinders numbering ...front to back... : 2 4 6 8

I hope the following diagram stays intact:

Pass________Driver:

__8____________7

__6____________5

__4____________3

__2____________1

-> Rotation of distributor

8____O_O____7
6__O_____O__5
4__O_____O__3
2____O_O____1


<- Rotation of distributor

Note: on the above diagram, #1 may not be in the same position as on your vehicle - I don't remember exactly which direction #1 is so the above diagram is for example purposes only.
Well, it's fixed now!

[JAllenWAG]

I recently changed timing chain...put in edlebrock double roller. Old chain was bad. I can't remember exactly when the problem started b/c I did so much at one time. It seems like it started after I did tfi upgrade with new plugs and wires. First I had tfi wired backwards...fixed that. Then had one plug that was fouled...fixed that. Have tried timing and idle mixture and all that. Could it be a problem with my vacuum advance? It runs ok but surges badly at idle. Choke also works great..1 pump and cranks up when cold and I drive away. However very hard to start when it's been sitting for about 20 minutes to an hour. I've read through here and tried most everything. I'm gonna try pulling all the vac hoses again too. Last time I found a plastic connector that had cracked...Any more suggestions would be helpful. I'll be at home for thanksgiving so I'll have my garage.

[JAllenWAG]

By the way Joe..great explanations.

[Joe Guilbeau]

Not sure if you have the Ford Thick Film Integrated unit or another aftermarket system.

Sounds like something is not quite right...the Resistor Wire to the Positive Side of the Ignition Coil terminal (are there two or only one wires going to this terminal?) should not go thru the Resistor Wire when the Key is turned to the "Start" position and the engine has not yet started. If you have two wires connected to the Positive Terminal of the Ignition Coil, then you have it set up for 12Vdc to be sent to the Ignition Coil when the vehicle is started, and when the Ignition Key is released, the Ignition Switch provides 12Vdc to the resistor wire, and it gets reduced down to something around 7-9Vdc.

Some newer Ignition Coils can handle the full 12Vdc and current and therefore do not need a resistor wire (Mallory's come to mind here, they have both types of Ignition Coils for sale).

Pulling a spark plug wire should really make a noticeable difference, if everything is connected OK and the vehicle is running OK.

Just take your time with a good flashlight, you may just spot the offense.

[Rogue]

Stick a screwdriver down the No. 1 Spark Plug hole, if it goes deep you are 180 Degrees outif you are 180 out your piston will still be at TDC, it will just be on the exhaust stroke

A really boring way would be to have someone use a High Amp probe to measure the 40,000 Volts or so sent to the spark plugs.
You would need to slowly turn the engine by hand with a wrench, the distributor will do it's thang and you can measure the spark energy at each plug when it's turn comes around. Technically correct, but it will consume lots of time and set up to properly measure. Why go to all of that troubleim not exactly sure what you are talking about, it seems what you are trying to describe is an oscilloscope which number one is used while the engine is running and number two can tell you a LOT about what is happening inside the engine without tearing a dang thing apart



jallenwag - easiest way I know for a home mechanic to check for weak spark is to simply pull the wires off the cap while the engine is running - it is not good for the coil as it will full field possibly damaging it but hey we are talking shade tree here right? i don't have a $2000 o-scope at home do you? the spark should easily jump a 1/4" from the cap to wire you just pulled off and SHOULD be a bright blue color - if it is yellow or doesn't jump the gap at all than you do in fact have weak spark, good luck

PS - resistor wire or not, it shouldn't be HOT - pretty warm yes but not HOT

[ November 27, 2003, 09:41 AM: Message edited by: RogueStar ]