DME pin 1, Coil question.

[dubrooks]

I've read here on the forums that DME pin 1 should be an open circuit (more than 1k ohms) when probed to ground. My DME pin 1 has like 4v on it when I do this (and no resistance).. what's up with that?

Also, when checking for voltage at the coil, it isn't quite battery voltage... while in operation, voltage on the negative side of the coil is like 10v. This is switched to ground by the DME correct? should this be battery voltage?

Engine runs rich and misfires like crazy, hardly stays running and any bit of throttle will choke her out. Been going through the steps, just trying to figure out these couple quirks before moving on. If I connect a spark tester to one lead at a time while the engine is running the spark seems strong and blue... but intermittent. Can anyone shed light on these couple of things? I have cleaned all battery terminals and wiring from the battery to the little junction box and check to make sure the fusible link is working properly.

[spdracrm3]

the wire from the coil Neg to DME pin 1 should "not" be open when ohm testing with it disconnected at both ends (you cannot ohm test a live circuit, has to have no voltage and disconnected preferably) ,as it is the control wire it need to be nearly 0 ohms. i have never seen a spec for ohms to ground (basically a test to see if its shorted to ground causing a no start issue? again only test with no voltage present) but i would think 1k sounds good (infinte if disconnected) .

when key is on and engine not running you should see close to the same voltage at DME pin 1 as you see at the coil Pos terminal (voltage flows thru the coil up to the DME which grounds it to allow current flow ,this current is what creates the spark). as for the voltage at the coil positive should be close to whatever battery voltage is maybe a couple tenths less due to switches/connections in the circuit . if your worried about it causing and issue jumper direct from coil + to the battery or the main cable lug at starter to see if problem goes away ,then you know a voltage drop causing low voltage is problem. the coil negative side will read about 8-10v (voltmeter is averaging ) as voltage is switched on and off by the DME when engine is running

[dubrooks]

in a write-up from jlevie he says:

1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.

DME pin 1 to ground is NOT an open circuit in my case. Nor do I have continuity from coil neg to DME pin 1. I DO, however, have 2-4v flowing from pin 1 to ground with the ignition switch on.

Furthermore, I see battery voltage while the car is not running, but while running if I hook a meter up to the positive coil, there is less than battery voltage, and spark is intermittent. Providing direct battery voltage to the coil did not solve my problem. Coil itself is 5200ohm (200 too high) and .8ohm (within spec).. is this enough resistance within the coil to cause this problem?

[spdracrm3]

in a write-up from jlevie he says:

1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.is the DME disconnected also ? i think you'll find jlevie is assuming so as otherwise you have to remove the cover to backprobe at the DME connector.

DME pin 1 to ground is NOT an open circuit in my case. Nor do I have continuity from coil neg to DME pin 1. I DO, however, have 2-4v flowing from pin 1 to ground with the ignition switch on. again is this with DME disconnected? and without continuity (between pin 1 and coil neg) im surprised it runs then! if you have voltage present with both ends of the circuit disconnected then yes there is a problem with a short to voltage somewhere in the wiring. if your testing the ciruit with the DME connected then you will see very unusual readings as there is a transisitor switching the ground control and depending on its state you will see different resistances and possibly voltage on the circuit when live

Furthermore, I see battery voltage while the car is not running(where?), but while running if I hook a meter up to the positive coil, there is less than battery voltage, and spark is intermittent. Providing direct battery voltage to the coil did not solve my problem. Coil itself is 5200ohm (200 too high) and .8ohm (within spec).. is this enough resistance within the coil to cause this problem? coil spec is close enough and sounds like its not a voltage supply to coil issue then ,maybe a problem in the secondary ignition components

[dubrooks]

Yes, the DME is disconnected during both mentioned. I did not disconnect the coil on either side in determining there was voltage on dme pin 1. It was non-continuous with coil negative disconnected to dme pin 1.

battery voltage at coil while car is not running. While running (sort of) the voltage at the coil is say .5v below battery, sometimes more.

by secondary ignition components you mean dist, plugs, wires? tried other wires, dist, rotor (in spec), and coil . Injectors work in non-intermittent sets of 3. I've looked for escaping spark to no avail.

Ideally I would like to bypass all potential problem areas leading straight to the coil.

I know the negative is switched through DME pin 1. Could I just provide a flip switch for positive coil to battery, then DME pin 1 to negative coil? Is this the path electricity normally takes anyway (from ignition switch?)

[spdracrm3]

Yes, the DME is disconnected during both mentioned. I did not disconnect the coil on either side in determining there was voltage on dme pin 1. It was non-continuous with coil negative disconnected to dme pin 1.what is the resistance reading on that wire from coil neg to DME pin one then?

battery voltage at coil while car is not running. While running (sort of) the voltage at the coil is say .5v below battery, sometimes more. good enough

by secondary ignition components you mean dist, plugs, wires? tried other wires, dist, rotor (in spec), and coil . Injectors work in non-intermittent sets of 3. I've looked for escaping spark to no avail.yes all components after coil are secondary ,and can break down under load causing no spark issues

Ideally I would like to bypass all potential problem areas leading straight to the coil.

I know the negative is switched through DME pin 1. Could I just provide a flip switch for positive coil to battery, then DME pin 1 to negative coil? Is this the path electricity normally takes anyway (from ignition switch?) jumper wires are worth trying if you think they are the issue (see above re resistance of said wire,which should be close to 0ohms ),and a good test strategy and the switch will be the kill as it wont shut off with key (use a fused wire to prevent melted wire if accidentally shorted)