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Do you think this is an electrical/ignition or a fuel problem?

T

toddwallace

Member
I am still struggling with my '66 shutting off under acceleration. A little background..

1966 Hipo 289 w/ SN-92 Paxton
Holley 650 DP
Mechanical Fuel Pump
MSD Digital 6 ignition
MSD 31323 wires
MSD 8253 coil
MSD 8579 Distributor

The car starts and idles fine.. It sat idling for our an hour w/out die'ing. You you can wrap on the accelator as much as you want and it is fine. At very low RPM's in first and second it is fine, but puch it and it cuts completely off. It will start right back up from turning the ignition, but does not seem to start itself from pop'ing the clutch. In third under heavy acceleration, it cuts out, but does not shut off. In fourth, it run fine up to speed. Fuel pressure reads around 6 -7 lbs and does not drop.

I thought it might be a grounding problem on the MSD, so I rechecked all that. I replaced the CAP and Rotor because I had one.. I do notice a bit of a fuel smell..

Dallas Mustang thought it was a spring issue in the distributor allowing it to over advance, but the springs all look fine

Any thoughts
 
Could it be that the gas is being pulled away from the needle valve in both fuel bowls during hard accelaration? This happens alot in drag racing conditions. If I read right, you said that it works fine when sitting still and rapping on the accelarator but when you are going thru the gears is when you have the problem.
 
"6t6red" said:
Could it be that the gas is being pulled away from the needle valve in both fuel bowls during hard accelaration? This happens alot in drag racing conditions. If I read right, you said that it works fine when sitting still and rapping on the accelarator but when you are going thru the gears is when you have the problem.
Click to expand...

That is correct... In neutral sitting still, all is good. In Fourth, all is good.. Third seems to cut out, but it does not die. First and Second die every time I get on it.
 
From your description, it sounds like it might be a sudden break in the electrical circuit. When the engine shuts off do all your instruments dive for "zero"? If so, it might be a short in the main electrical supply from the solenoid to the ignition switch. If not, then I suggest you check your engine to chassis ground as an engine rocking on its mounts coupled with a loose wire could effectively interrupt the ground flow of electricity. One way to rule that out is to take a heavy guage wire that has no damage issues and run it from the block to a clean chassis ground and try again. Hope this helps. Good Luck.
 
That's what I'm thinking....maybe a wire under the hood is moving enough to kill the spark...... Move wires around under the dash and hood while it is running and see it it stutters or dies.
 
"JeffTepper" said:
From your description, it sounds like it might be a sudden break in the electrical circuit. When the engine shuts off do all your instruments dive for "zero"? If so, it might be a short in the main electrical supply from the solenoid to the ignition switch. If not, then I suggest you check your engine to chassis ground as an engine rocking on its mounts coupled with a loose wire could effectively interrupt the ground flow of electricity. One way to rule that out is to take a heavy guage wire that has no damage issues and run it from the block to a clean chassis ground and try again. Hope this helps. Good Luck.
Click to expand...

I don't see a dive in the gauges, but the only ones that would die are the fuel pressure & Boost.. Those don't seem to dive down. I was thinking about replacing the ignition and start working my way back..
 
"JeffTepper" said:
One way to rule that out is to take a heavy guage wire that has no damage issues and run it from the block to a clean chassis ground and try again. Hope this helps. Good Luck.
Click to expand...

I do have a black battery cable from the block to the chasis..
 
If the floats are adjusted correctly, I can't see it running out of fuel and stalling out. The front bowl is going to have the fuel mashed into the jets, while the rear might go dry, I can't see a complete stall. Add that when it stalls, you should be able to lift from the throttle and jam it back down and the engine restarts if there was a sloshing of fuel.

I'd say that it might be possible the fuel line to the fuel pump could collapse and run the engine out of fuel but that should take extended cranking to get the engine restarted. I'd expect that to be worse in 4th gear, under a full load bog to accelerate. I'd go with an electrical issue for power or one of the ignition components with bad solder joints. Perhaps you could bypass the + and - wiring to the ignition system with a temp wiring harness and retest. Of course use fusing in the circuits to the temp wiring.
 
"toddwallace" said:
I am still struggling with my '66 shutting off under acceleration. A little background..

1966 Hipo 289 w/ SN-92 Paxton
Holley 650 DP
Mechanical Fuel Pump
MSD Digital 6 ignition
MSD 31323 wires
MSD 8253 coil
MSD 8579 Distributor

The car starts and idles fine.. It sat idling for our an hour w/out die'ing. You you can wrap on the accelator as much as you want and it is fine. At very low RPM's in first and second it is fine, but puch it and it cuts completely off. It will start right back up from turning the ignition, but does not seem to start itself from pop'ing the clutch. In third under heavy acceleration, it cuts out, but does not shut off. In fourth, it run fine up to speed. Fuel pressure reads around 6 -7 lbs and does not drop.

I thought it might be a grounding problem on the MSD, so I rechecked all that. I replaced the CAP and Rotor because I had one.. I do notice a bit of a fuel smell..

Dallas Mustang thought it was a spring issue in the distributor allowing it to over advance, but the springs all look fine

Any thoughts
Click to expand...

Ok..new thought... When my uncle wired the call, I remember him saying that he put a 1965 harness in the car and that he figured it out when he wired the dash... I got a call lastnight from a guy in Kentucky that said he had the same problem I am experiencing when he installed his MSD as the coil was not getting enough voltage. He bypassed the pink wire and got a full 12 volts to the coil and his problem went away... Could this be it?? I have been wanting an American Autowire harness to rewire things as I am putting in a Classic Air A/C and Sound Deadening. Might be a good time to rewire, but really didn't want to spend the $600 unless I had to...

thoughts?
 
If you are using the resistor wire to power the MSD, it could be an issue. MSD needs 12 volts if I rmemeber correctly.

Also, there is no need to rewire the entire dash because of that or the addition of the A/C.
 
Midlife can set you up with a refurbished factory harness and unless you are doing a lot of power options like windows, seats, and locks, the stock one does good.
 
"AzPete" said:
If you are using the resistor wire to power the MSD, it could be an issue. MSD needs 12 volts if I rmemeber correctly.

Also, there is no need to rewire the entire dash because of that or the addition of the A/C.
Click to expand...

The MSD box 12v source is direct from the battery. Mine is wired to the Bat side of the solenoid. The factory wire to the coil is only needed to power on the box and gets full voltage while cranking anyway.
 
"toddwallace" said:
Ok..new thought... When my uncle wired the call, I remember him saying that he put a 1965 harness in the car and that he figured it out when he wired the dash... I got a call lastnight from a guy in Kentucky that said he had the same problem I am experiencing when he installed his MSD as the coil was not getting enough voltage. He bypassed the pink wire and got a full 12 volts to the coil and his problem went away... Could this be it?? I have been wanting an American Autowire harness to rewire things as I am putting in a Classic Air A/C and Sound Deadening. Might be a good time to rewire, but really didn't want to spend the $600 unless I had to...

thoughts?
Click to expand...
I installed a painless (painfull) harness in a guys 66 coupe a couple years ago. I am convinced the car would have had a ton of electrical issues if the harness was installed as instructed. We soldered most every connection where the manufacturer wanted the supplied crimp on connectors used. I'd stick with a factory harness and if you decide to add things of an optional type (power windows and such), just build your own custom harness with relays and such for whatever you add. Do as I posted before and hot wire the positive and negative to your ignition with bypass wires and see if the trouble goes away. If the resistor wire is still in the loop, your problem is likely found.
 
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