View Full Version : SBC misses when warm
Rayhill
10-13-2002, 06:03 AM
My SBC all of a sudden has picked up a huge miss after the engine warms up. It feels like a total electrical shut-down.
I double checked all my wiring to the MSD 6AL box, Msd Dist., and MSD Blaster Coil.
No Vaccum leaks.
Could it be the alternator?
MSD instructions to the coil read not to have anything other than the + & - connected. My alternator is a 3 wire set up. The 3rd wire being connected to the old coil. For the past 2 seasons I have not had that wire (resistor wire) hooked to anything. No problems. Have I been a dumb-ass and fried my alternator over a long period?
2 boats down now !!! UGH
MikeF
10-13-2002, 08:07 AM
R, I would change the wiring to the way it is on Chris' liquidaddiction.net site (link to pump info...wiring dia).
As far as the missing goes, Check for any carbon tracking or moisture in the dist cap. Also it is very important to keep all the plug wires separated (no wire to wire or to ground contact).
Check it again and report your findings. :)
Havasu Hangin'
10-13-2002, 11:13 AM
That wire from the alternator is probably the excite wire. It needs to be hooked up to a switched B+ source, which may be why it is on the positive side of the coil. It polarizes the field in the alternator for charging.
The resistor insures 12 volts to the coil- no more (for points).
Is your coil getting 12 volts? Is it hot or warm to the touch? How soon does it shut down? A minute? 10 minutes?
Could it be a fuel issue?
BrendellaJet
10-13-2002, 08:03 PM
I agree with MikeF. I just installed a three wire alternator, after my two wire died. If you are looking at the alternator(mine was a delco #7127) from the back, the left terminal needs to connaect to the output wire, the other is wired to the accessory wiresoming from the front of the boat. Good luck
Rayhill
10-14-2002, 02:12 AM
I checked the wires at night while the engine was running. No lightshow.
Replaced the cap and rotor. No change. Things looked a little rusty though. Thought that was strange for a MSD Billet Marine Dist. $$$$$$.
The miss will not start right away if I cruise awhile. In other words I tried staying out of it and it didnt start missing until about 30-40 minutes. If I go out and get into it. It starts missing in about 3 minutes of WOT.
The coil is not hot.
Will try that wiring diagram soon.
MikeF
10-14-2002, 07:12 AM
After your WOT run and the missing starts, What is your voltage @ the battery (shut down and check w/ voltmeter)? That alt does not need to spin @ 9000rpm eek! . Maybe an overcharging problem?
Do you have a friend w/ another MSD6 box that you can borrow?
The coil normally gets hotter @ idle than when running @ speed.
Bahner tunnel
10-14-2002, 10:46 AM
I just put a 6al on my boat last weekend and I thought I remember reading in the instructions that there is up to 470 volts going from your box to the coil. eek! This would fry your alternator as well as eventually fry your MSD box. Double check your instructions and even put a volt meter on the coil + and - at idle and see if are getting the higher voltage as mentioned above. Good Luck.
bajaruner
10-14-2002, 09:44 PM
This is a long shot but, I had a similar problem once. It turned out to be the electric holley fuel pump (I know piece of junk!) It was locking up and arching within itself, causing a miss, but only after the boat would run for some time. This momentary lock-up of the pump was not enough to blow a fuse, but enough to cause a bad miss in the engine beacause I had the ignition and pump feed off the same terminal. Changed to a manuel pump, problem solved. Not sure what fuel pump your running but it's just a thought.
Other things to check:
Fuel filter
Fuel pressure
Maverick
10-15-2002, 03:42 PM
Rayhill:
My SBC all of a sudden has picked up a huge miss after the engine warms up. It feels like a total electrical shut-down.
I double checked all my wiring to the MSD 6AL box, Msd Dist., and MSD Blaster Coil.
No Vaccum leaks.
Could it be the alternator?
MSD instructions to the coil read not to have anything other than the + & - connected. My alternator is a 3 wire set up. The 3rd wire being connected to the old coil. For the past 2 seasons I have not had that wire (resistor wire) hooked to anything. No problems. Have I been a dumb-ass and fried my alternator over a long period?
2 boats down now !!! UGHMaybe a head gasket??? eek!
Stupid Fast
10-15-2002, 05:45 PM
Maverick:
Maybe a head gasket??? eek! Man that hurts my eyes just thinking about it.
lghtnin33
10-16-2002, 08:15 PM
sounds like a normal chevrolet, thought they all did that!
Rayhill
10-17-2002, 02:03 AM
"Maybe a Head Gasket"
I think I am going to hurl !!
Wouldnt doubt it, though?
Just bought this engine off E-Bay from Zigouras Racing a year ago. Very poorly put together!
Rayhill
11-14-2002, 05:32 PM
BAD ALTERNATOR
Got it fixed just in time to enjoy WINTER! eek!
Bahner tunnel
11-19-2002, 09:25 PM
Do I get 1/2 credit for mentioning your alternator in my reply? :D Glad to hear your back on the water .
Rayhill
11-20-2002, 03:13 AM
5 stars your way BaynerT. I am gonna do a rewire this winter!
Thanks
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