12 Volt Confusion

[Williespeed]

I'm stumped I have never seen this before and I am curious if any of you have. I have no spark on a 1975 440 4 bbl it's in a motorhome I just got, thats not the problem well in a way it is. the red lead to the battery runs to the cross member and is bolted there to the cross member the negative runs over to the starter relay. so my frame is energized and the power wires are my grounds, I get about 5 volts out of the ballast resistor with the coil plugged in. I'm mainly wondering if anybody has seen this done before and if it causes any spark issues. It's the same 5 pin single pick up system in my PW but this one has me stumped and the distributer does a little bit of a hula when the engine is cranking over.

[KRB64]

First, is the red cable actually attached to the + post or the - post? and same question with the black cable?

No experience with a motor home but a positive ground was common with the older flat fender PWs. I remember hearing why this was but can't recall the reason.

[greg rider]

and the distributer does a little bit of a hula when the engine is cranking over.

If the distributer is doing any "hula" then it is shot. The bushing is worn and it is causing erractic signal to the pickup inside. Replace the whole thing and be sure it is indexed and timed correctly and go from there. You will acomplish squat until you fix the distributer.

[712edf]

On 99% of the 12volt systems I'd say the positive (+) terminal cable goes to the starter relay and the negative (-) terminal cable goes to the engine block (or vehicle frame).

Negative ground was more common in the pre-1956 6 volt ignition systems.

Bucky

[712edf]

5 volts out of the ballast is normal with ignition key "ON". While cranking the ballast is bypassed & the coil should be getting 12v at the "+" side.

Is the ECU body making good ground with the fender/firewall or wherever it is bolted? If not you won't get spark even though voltage will be present at ballast & coil.

Distributor "hula" ain't good. Finally coil could be bad.

Bucky

[Williespeed]

Yes the positive cable is attached to the positive terminal of the battery and then to the frame, the negative is attached to the negative terminal and then to the starter relay. when I switch them so the positive goes to the starter relay I get nothing no lights no cranking when I turn it back around it turns over again. The ECU is well grounded the thing is it isn't instead of having ground on terminal 4 I think it is of the ecu I have the voltage from the chassis. not the chassis ground 12v dc it just needs to complete a circuit but if this is done wrong and there is a diode in the ignition somewhere the circuit will be interrupted at that point. It's like trying to go racing in reverse using only the mirror. I'm gonna pull the coil out of my PW and take it over there sunday and see if that cures it my manual says to see the table in this section for the resistance of the windings but there is no table with that info listed there. As long as I am replacing the distributor what is a good aftermarket brand to go with on 440?

[712edf]

That's a new one on me!

I've heard of vehicles running with reversed polarity at the coil, but never the whole starter motor & all being reversed. Does it look like the vehicle came that way?

Bucky

[Williespeed]

yes it does look like it came that way, so I figure I'll disconnect the auxiliary battery and the inverter and try and switch it back to what I know.

[greg rider]

As long as I am replacing the distributor what is a good aftermarket brand to go with on 440?

A stock replacement is plenty. If you are set on an aftermarket for any reason then either of the big name ones are good. I have always had good luck with Mallery and Accell products on Mopars. I have used MSD products on other vehicles but never had the chance with Mopar. Don't forget that it is as much having good solid connections at the coil,ECM,distributer,plug wires,plugs,etc., as having any name brand product. The stock stuff works really good for a long time with little maintenance as long as it is set right.

[JStinson]

Yes the positive cable is attached to the positive terminal of the battery and then to the frame, the negative is attached to the negative terminal and then to the starter relay. when I switch them so the positive goes to the starter relay I get nothing no lights no cranking when I turn it back around it turns over again.

Wild

[KRB64]

... As long as I am replacing the distributor what is a good aftermarket brand to go with on 440?

I just got a NAPA reman for a small block for less than $40.

[74w300uteline]

Generator?

Thats some screwey wiring ya got there. perhaps the mobile home and had a generator that somehow required screwy wiring. good luck

[Williespeed]

440 Distributor ?

Single ignition coil pickup air gap from the pickup to the reluctor for 1974-76 440 motors (75 motorhome) is listed as .008" When I set this distance and spin the distributor (out of the motor) the magnetic field of the pickup is enough to pull the pickup into contact with the reluctor. Everything else meters out good; the module, the coil, the ballast resistor, the starter relay, all meter out according to my manual. I replaced the pick up because it didn't meter out to the 150-900 ohm range specified. It reads 335 ohms now on terminals 4-5 of the module as it should. terminal 5 has continuity with the ground or body of the module and I have grounded the module right to the battery for test purposes and I know it is a good ground. I get 12v to the Ignition coil on cranking + side, negative side gives an ever so faint glow on the light tester that oscilates but does not strobe like it should this is very faint so is the oscilation. Please can someone help me I'm not sure what's normal for this distributor but I'm 92% sure it is my problem.

[Williespeed]

Upon closer inspection the reluctor hits the pickup and then doesn't and increases the gap so a new Dist is in my future. I'm Napa bound