1977 Dodge Truck 318, no spark: Need Troubleshooting

Posted By: GuruRanger

1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 08:11 PM

I have a 1977 Dodge W-200 truck with a 318 automatic. I don't use it very often. Yesterday, I went to use it to pull stumps and haul mulch and it's not getting spark. I've swapped out the following:

1. Ballast Resistor
2. Coil
3. Electronic Control Module
4. Voltage Regulator
5. Starter Relay

The truck has a fresh battery and cranks over ok, but it's still not getting spark at the spark plug wires or from the coil to the distributor cap. The only thing I haven't replaced is the pickup in the distributor. Should I start there or am I missing something somewhere else?

Posted By: SomeCarGuy

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 08:14 PM

The pickup, poor ground for ECU, broke wire someplace. Key switch?

Posted By: GuruRanger

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 08:24 PM

I've been jumping it at the starter relay. Would the key switch still be an issue if I were jumping at the starter relay? The key switch is in the "on" position.

Posted By: 72gtx4speed

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 08:26 PM

make sure the key is on.

clem

Posted By: Supercuda

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 08:28 PM

You can throw parts at it until you give up or run out of money.

Or you can do some troubleshooting.

A coil needs only two things to spark, voltage and ground. Once both are hooked up the coil charges up, remove either and it will produce a spark. The factory setup removes the ground to spark the coil

You are either missing the voltage at the coil, or the ground is either always missing or always present.

You can use a spark plug int he coil wire to see if it has spark, you can use a test light to see if there is voltage to the coil +, light should be on if the key is in run or start. You can use a test light on the coil -, it should flash as the engine is cranked over. Any of those conditions fail the test that is where you problems area is.

Posted By: jwmotors

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 08:44 PM

The rotor contact could be corroded or the center post in the cap
could be the trouble

Posted By: GuruRanger

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 09:10 PM

OK, more info. My headlights are not coming on and the key switch is not cranking the engine. I have to arc the posts at the starter relay to crank it over. I also swapped the starter relay for a new spare that I had laying around.

Posted By: amxautox

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 09:15 PM

turn on the headlights or the heater fan

wiggle the fusable link between the + post on the battery and the bulkhead connector, and check it for volts thru it with a volt meter.

then go to the bulkhead connector and wiggle the heavy RED wire while watching to see if the lights come on. If not then wiggle the heavy BLACK wire.

If not, then go under the dash and wiggle those 2 wires again.

One might be corroded and not making contact. Then fix that which is bad, maybe by doing the MAD bulkhead connection fix.

Also check the amp gauge to be sure it isn't burned out, including the circuit board around it.

Posted By: amxautox

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 09:25 PM

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Posted By: RTSrunner

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 09:35 PM

I agree with this.The fact it will not crank with the key switch it is more likely in the wiring harness and not the ignition parts.Have you tried a jumper wire to the coil positive and then jumping your starter relay to see if it starts?So there is no power to the starter relay from the key switch?Nuetral switch possibly,but still does not explain no run.Check the pickup coil air gap and contacts for rust.-RT

Quote:

turn on the headlights or the heater fan

wiggle the fusable link between the + post on the battery and the bulkhead connector, and check it for volts thru it with a volt meter.

then go to the bulkhead connector and wiggle the heavy RED wire while watching to see if the lights come on. If not then wiggle the heavy BLACK wire.

If not, then go under the dash and wiggle those 2 wires again.

One might be corroded and not making contact. Then fix that which is bad, maybe by doing the MAD bulkhead connection fix.

Also check the amp gauge to be sure it isn't burned out, including the circuit board around it.

Posted By: GuruRanger

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 09:57 PM

OK, wiggled the wires at the bulkhead with no headlights coming on. I then moved the wires at the back of the AMP gauge, now the key switch cranks the engine in neutral and the headlights come on, but still no spark. I'll check the pickup gap for rust.

Posted By: GuruRanger

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 10:01 PM

Quote:

...Have you tried a jumper wire to the coil positive and then jumping your starter relay to see if it starts?...-RT

OK, showing my ignorance here, one end of the jumper wire gets hooked to the coil positive, where do you hook the other end of the wire?

Posted By: SattyNoCar

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/21/13 10:16 PM

One other location for a 'bad connection' is back on the column. Check where the ignition switch plugs into the harness (you're looking for the wide, narrow plug that has the heavy gauge black and red wire in it). I had a '76 PU that had cooked the connection here over time and left me stranded. Would crank all day, but had no fire.

Posted By: GuruRanger

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/22/13 02:59 AM

Thanks Satilite73, I checked it and it was OK.

Posted By: RTSrunner

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/22/13 03:10 AM

Quote:

Quote:

...Have you tried a jumper wire to the coil positive and then jumping your starter relay to see if it starts?...-RT

OK, showing my ignorance here, one end of the jumper wire gets hooked to the coil positive, where do you hook the other end of the wire?

To the battery positive terminal or other known 12v source.Hot wiring the coil.

Posted By: RapidRobert

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/22/13 03:27 AM

I'm assuming OE 5 pin ECU/4 terminal ballast. Tighten the 2 3/8" nuts on the ammeter & pull the yellow "ign" wire off of the starter relay to disable the starter (You know the starter works & no need to engage it & run the batt down for these tests plus the noise is a distraction). Have a helper hold the key to "start" & at that point (ign2 crank), 2 pins on the ECU need fire as does the coil positive primary terminal. With the ign key in run (ign1 run), 1 terminal on the ECU needs to be hot as does the same coil primary positive terminal but in "run" power goes to the end of the ballast that has the blue loop on it & on that end on the side that has the brown wire on the other end power flows from the blue wire loop to the brown wire on the end & flows out the other wire that's connected to the brown wire there on that end to the coil positive primary terminal. Need a VOM or a test light. If no fire work back to the bulkhead & seperate the halves & see if the terminals are clean & the firewall half has fire & if not seperate the pull apart electrical connector dangling under the steering column & check continuities. Holler back when you can.

Posted By: 82ramIndy493

Re: 1977 Dodge Truck 318, no spark: Need Troubleshooting - 04/23/13 03:28 AM

I would also check rotor to see if it turns while cranking. Have seen many of the earlier plastic on aluminum timing gears in these strip teeth and its possible the cam is not turning so the distributor wont turn and you wont get a spark. Not saying this is the problem only a possibility. Worth checking if all else fails. A compression test will tell for sure. Should be extremely weak or non existent.