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small block cranks but no spark

Posted By: b5fish73

small block cranks but no spark - 09/24/12 05:59 PM

Guys,
I'm finally trying to get my 408 magnum with LA style front, fired up in my 93 Dakota and Im having a few problems. Im running a 5 pin chrome box with 4 prong ballast resistor. I believe I have everything wired correctly, since I basically made my own engine harness and spliced into the ign 1 & 2 to the fuse box. It cranks but no spark. If I jump battery form the starter relay to the positive on the coil I do have spark. The coil has propper voltage at both key positions (12v and 6v respectively). I'm thinking the new ballast resistor is bad. Probably pick one up tonight, but looking to see if I'm missing something obvious.
Thanks in advance
Dave
Posted By: RapidRobert

Re: small block cranks but no spark - 09/24/12 09:00 PM

Jump across the ballast at the 2 terminals at the brown wire end & see if it will start. If it starts either ballast or improperly wired. I would take off the yellow "ign" wire off of the starter relay to disable the starter (we know it's good & no need for the noise and unneccessarily running the batt down) and have a helper hold the key to "start" & you under the hood & with your VOM or a test light see if (2) terminals on the ECU and the positive terminal on the coil are getting fire in ign2 (crank) Then see if they are getting fire with the ign key in ign1 "run". Nominal ohms on the dual ballast is .5 and 5 ohms and can measure (used) as much as 1.6 and 6 ohms. If it starts/runs when you jump across the ballast you could probably leave it like that as is. I'd put a bit more current into the auxillary start terminal of the ECU than normal but I bet it'd last forever especially with a stock box.
Posted By: b5fish73

Re: small block cranks but no spark - 09/25/12 02:12 PM

Resistor wasnt the culprit. I had a crimp tap connector that didnt go thru the insulation on the ign wire. Thanks for the help.
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