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| Minimum Voltage Required For HEI To Fire When Cranking https://slantsix.org/forum/viewtopic.php?t=36171 |
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| Author: | LWS1967 [ Tue Jul 07, 2009 5:13 pm ] |
| Post subject: | Minimum Voltage Required For HEI To Fire When Cranking |
Well now that I've got the two barrel conversion up an running fine, I then did the HEI conversion on my van, (already did it on my sons 79 Cordoba with excellent results) but my van is giving me fits in regards to starting when hot. Got the MSD Blaster on the side of the engine like stock, module mounted on a heat sink on the outside of the doghouse (it's in the interior behind the drivers seat) and thick wires connecting everything. First thing in the morning it starts, though not as fast as I think it should. Runs at all rpms perfectly, got close to 13+/- volts at the coil when running. When I crank the starter the voltage drops to around 10.8 +/- at the battery, and has the same reading on down the line as I check. I know about the battery, crank, solenoid checks for draw etc, but my question is: At what point (voltage) will the HEI not fire? 10.8 is seems way too low I know, but luckily I'm running dual iginitions so I can switch between the two if any problems...and the Chrysler ECU setup fires right up with same voltage readings...... |
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| Author: | SlantSixDan [ Tue Jul 07, 2009 5:17 pm ] |
| Post subject: | |
In general, HEI draws more current than Mopar EI, so any voltage drop effects are going to be aggravated by that need. I don't know what voltage is the threshold for the module to work—I bet it varies by module design, i.e., different makers' modules may have different thresholds—but it sounds as if you're dropping below it. I wonder about the health of your starter, which might be drawing too much current, and the health of your battery. Others have had good results installing a power relay for the HEI module… |
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| Author: | LWS1967 [ Wed Jul 08, 2009 4:10 am ] |
| Post subject: | |
Thanks Dan, yeah, I have a feeling when I go to check those things I may find my problem. But along with that, these A vans with the doghouse "ovens" also create more problems with severe heat retention. All the electrical components as well as wiring see extreme heat both during and after running, with temps actually rising and having no place to go but "soak" after being parked (conditions unlike the cars).....not to mention 40+ years having to deal with it. Will be checking those things and may end up replacing some wiring too....it never ends! |
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| Author: | slantzilla [ Wed Jul 08, 2009 1:58 pm ] |
| Post subject: | |
IIRC, the threshold for HEI is 7 volts. |
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| Author: | cavisco [ Wed Jul 08, 2009 5:08 pm ] |
| Post subject: | |
You may want to try moving the HEI module as close as possible to the distributor, or use twisted pair wire. The stray inductance in the wiring from the pickup coil may be causing some problems. Keep us posted on how things turn out. Scott. |
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| Author: | LWS1967 [ Thu Jul 09, 2009 4:23 am ] |
| Post subject: | |
Well I checked the related wiring and cables and found at least one issue. The low quality "Made In India" starter relay main post was loose in its mounting (starter/battery cable connection) Checked/cleaned all the connections, mounted another India made relay and it fires up, but my voltage to the coil/module still drops to about 10.9-11 volts when cranking. It does'nt fire right away though...seems delayed, where-as the Chrysler ECU fires immediately. I think Dan's suspicion of the starter is correct. All my cables and wires are either newer and/or sound...it is one of the million times rebuilt with China or ? components, and is a few years old. If I disconnect the starter and turn the key the voltage to the coil/module is about 13, so.......I hope that's all it is! |
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