Carbureted 5.3 lm7 - huge backfire and loss of power
05-14-2020, 05:27 PM
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Carbureted 5.3 lm7 - huge backfire and loss of power Hi guys- I知 hoping you can point me in the right direction.
I have a 1970 Chevelle with a vortec 5300 and an MSD 6014.
i was at cruising speed on the freeway when suddenly the throttle has no effect, I give it extra gas and a massive backfire comes out the exhaust. I cannot give it more gas, it only backfires again. I am able to shut off and restart the engine while coasting, only to have the same thing happen minutes later at a lower speed.
I pull over and change my shorts, check alto see no fluids leaking or parts dragging.
I am unable to get back up to speed.
The same sequence happens again, and when I pull off the road, I get no power when I turn the key. No dome light, no fans, but the line lock indicator light (which is wired to a constant 12V off the starter solenoid) will come on. No ignition.
Could this be explained by the MSD box losing power due to poor wiring connections? The car has plenty of that (previous owner did the LS swap)
what would cause me to lose all electrical power on the side of the road?
I checked battery terminals, replaced the fuse next to the IGN spade- nothing.
I had the car towed and when I got back in it it fired up. Did not try to drive it, I don稚 like the idea of being stranded again.
im very new to the car world, only owned the car since october, had a new cam sensor and tuneup at a speed shop (it was not starting reliably due to non-GM cam sensor they said)
any help would be appreciated, I知 not even sure where to look under the dash to check connections. It痴 very frustrating I知 not even sure what questions to be asking.
thanks
jonathan
I have a 1970 Chevelle with a vortec 5300 and an MSD 6014.
i was at cruising speed on the freeway when suddenly the throttle has no effect, I give it extra gas and a massive backfire comes out the exhaust. I cannot give it more gas, it only backfires again. I am able to shut off and restart the engine while coasting, only to have the same thing happen minutes later at a lower speed.
I pull over and change my shorts, check alto see no fluids leaking or parts dragging.
I am unable to get back up to speed.
The same sequence happens again, and when I pull off the road, I get no power when I turn the key. No dome light, no fans, but the line lock indicator light (which is wired to a constant 12V off the starter solenoid) will come on. No ignition.
Could this be explained by the MSD box losing power due to poor wiring connections? The car has plenty of that (previous owner did the LS swap)
what would cause me to lose all electrical power on the side of the road?
I checked battery terminals, replaced the fuse next to the IGN spade- nothing.
I had the car towed and when I got back in it it fired up. Did not try to drive it, I don稚 like the idea of being stranded again.
im very new to the car world, only owned the car since october, had a new cam sensor and tuneup at a speed shop (it was not starting reliably due to non-GM cam sensor they said)
any help would be appreciated, I知 not even sure where to look under the dash to check connections. It痴 very frustrating I知 not even sure what questions to be asking.
thanks
jonathan
05-14-2020, 07:31 PM
#2
Check for proper ground and a solid 12V source going to the MSD. Since there was other shady wiring you have found I would just rewire the MSD its only 3 wires
Also check for proper grounds at the coil packs, there is a ground for driver and passenger by the coil pack harness/intake
Also check for proper grounds at the coil packs, there is a ground for driver and passenger by the coil pack harness/intake