motor dies intermitently

So my old Ford is acting up on me and being a real PITA.
Motor is a 351M with fresh heads and within the last 6 months has a Mallory HEI style ignition (professionally installed)
It's been sputtering out and dying at random, and becoming more frequent, after sitting a while it will start and run again.
I thought for a while it was a fuel issue. I just removed, cleaned and reinstalled the fuel tank. Tank wasn't dirty, but there was a loose piece of solder floating around I thought was the culprit.

Now I'm starting to wonder, possibly my carb is dirty or plugging up (cleaned when HEI was installed)
or is my coil pack on the HEI bad maybe?

Suggestions on figuring this thing out? I'm HORRIBLE at figuring out electrical, but given some ideas and ways to test can run electrical tools

 

Check the power / ground to the HEI. Gary

 

When motor dies check if you got spark & check if you got fuel. If no spark ,and you say restarts after sits suspect module or pickup coil.

 

If you can get it to do it while idling keep a can of ether handy and spray it in the carb if it picks up check accelerator pump and or fuel pressure if it stalls anyway go for the grounds

 

Power to it appears to be good, had it off today working on other things. There is a negative pole on the coil pack on the side that has nothing attached to it. Should that be a ground?
It always seems to be somewhere convienent that it pulls this,, like miles from home, never in the driveway where there's time to get out and test anything.

Guess I'll throw a plug wrench in the truck and go cruise till it dies

 

If it helps any this is my distributor:


Mallory Ignition 8556701C - Mallory 85 Series HEI Distributors

 

Check and make sure the HEI has a full 12 plus volts, HEI's will get funny on you with low voltage, you should have a dedicated wire to it.

 

I had the same thing happen on my "65 Biscayne. The resistor wire was bad.

 

change the fuel filter... with junk in the old tank the filter can clog (does it start to hesitate or slow down when you are accelerating?

 

Really need more information on the conditions when the problem arises. Are you sitting in traffic? Very hot day? Is your fuel line run near the exhaust any where? I had a similar issue with an SBC running a Mallory HEI and Edelbrock 1406. The problem was narrowed down to the fuel getting too hot in the line which disrupted the flow to the pump and carb. This started happening during the recent/current heat wave we have been enjoying in Houston. The problem did not occur during the morning commute but did develop during the evening ride home in heavier traffic.

 

Happens totally at random. Fuel filter is clean. heavy accelleration makes no difference. When I get the chance and it starts, sometimes slipping into neutral and holding higher rpms will let it stumble and burp enough to come out of it, sometimes not. nothing is close to exhaust. i've driven this down the highway for 3 and 4 hour trips and never had a problem, last night i drove 5 miles to dinner fine, and ended up coasting into my driveway.
looks as though the coil pack does have its own dedicated wire. Don't have a voltimiter/ammeter on the truck. but when it dies it never has any troubles cranking over.

 

Mallory tech said to measure voltage at negative side of coil. battery read 12.4 volts, coil measured 1-2. Thinking this isn't good/....

 

Had a 351M once that would die like that. Turned out to be coil connection that coil had spade connectors in a plastic housing that slid onto the top of the coil over 2 ****ons in the coil. When the spade connectors got hot they would open up and be loose on the ****ons. I just squeezed the spade connectors and never had any more problems with it.
Good luck.

 

Same exact problem I have. Mine is a BBC with MSD dist and 6al box. I changed the carb,fuel filter,fuel pump,dist cap,wires,plugs,cleaned the fuel cell and it still runs like **** sometimes and then quits. restarts after like 2 minutes...Sorry, didn't mean to hi jack your thread.

 

I'd almost agree with the hot cold theory, although after sitting overnight and having plenty of time to cool off still no start. Have a few more ideas to try. Waiting on word back from mallory at the same time

 

check to see if the tank is vented friends car was doing the same thing took the gas cap off and it ran good put the cap back on it started doing it again found out air vent was stoped up

 

I had a coil do this,
and i have had an ignition switch do this to me

 

Fuel tank on this is more or less vented by the filler neck which seals very poorly. I'm thinking my next test should be to run a lead straight from the battery to the coil and see what happens. That would at least narrow down the switch and wiring leading to the coil.

 

Mallory tech line says its a bad coil. So I'm sending it back for warranty replacement.

 

Hopefully the coil is the problem. But if you get it back and you still have the problem consider changing out the HEI ignition module inside the distributor. I had a similar problem a few years ago. Initially the car died when it got hot and almost alway happened at a busy intersection so I had to push it to the curb. After a few weeks it had starting problems when cold or hot. My guess was the module got heat stressed and then was on its way out. If you replace it be sure to put heat sink compound under the module. Normally that is included with the module. It's not the same as diaelectric grease.

 

I believe they are replacing the whole unit. I will be getting a spare module for the glove box also. Did a lot of reading about HEI and looks like having a spare module around would be a good idea.

 

OK, still havent figured this out. Checked and replaced coil, tested module and it showed to be good. Truck ran for a day and died. I've tried jumping the coil pack straight to the battery, and ive replaced the key switch/ignition switch.

When it wont start it does have gas in the carb, and I did check to make sure its sparking when cranking the starter.

Whos'e the smart guy who can tell me the next step.

 

Any denver area folks, if youve got an idea or a trick ill gladly accept help, fridge is full of pop and barley pop.
if i cant figure it out its going back to nebraska to a friends shop and id rather not go to that extreme

 

in my highschool shop cl***, my instructor showed me a way to test the ignition module in my O/T mitsubishi eclipse for a failure during a "hot condition." because, my car was behaving the same way you are describing.

the instructor took a hairdryer and heated up the unit while the engine was running. sure as ****, the engine died once the unit was heated up. and it started back up just fine when he cooled it down with some ice.

i replaced the unit, and never had a problem with it, again

 

In the garage it ran for 3 minutes, not even enough to get the fan to kick on. Some days it will fire up 10 mins after dying, sometimes 2 days after dying.

 

Is the ground wire/strap attached to one of the coil body screws, and do you have a good ground between the dist. housing and the block?

Don't ***ume anything at this point, hook up ground jumpers and hot lead jumpers until you find an answer. It sounds 99% percent like your problem is in the wiring somewhere.

Also, make sure there is no sign of contact between the reluctor poles and the magnetic pickup. If that is an HEI clone it should have the 8 pole pickup ring around the reluctor, right? If anything is loose or the top bushing is bad you will not get a signal to the module.

 

Where would I hook ground jumpers to the dist to check that?

Not sure what a reluctor ring is, i'll look it up and check.

one more thing i've questioned, when its dead and im cranking it i can smell the fuel. think that maybe my carb is flooding it out enough to kill it? lst time after it died and i got it running id didnt want to idle, only run with some higher rpms. ive got a stock 2barrel carb im thinking of putting on to check...

 

If you look down in the distributor housing, there is a wheel with 8 points on the dist shaft. This is the reluctor. The magnetic pickup will either be a single magnet perched next to the wheel, or a ring with 8 points facing inward (stock HEI type).

Are you pumping the throttle as you try to start it? Keep your foot OFF the gas pedal. If it's cold out, push the pedal down ONCE and release it, then crank the engine. If you have to keep pumping the throttle to get it to start, there is another problem with the engine.

 

Based on all the things you've checked, and the fact that it has spark and fuel while cranking and not starting, my next check would be carburetion. I didn't see what you are running for a carb, but it sounds to me like you could have a piece of garbage in the needle/seat, or a sunk/sticking float. At idle/cranking, it may be pumping fuel straight straight through, and flooding the engine out. If you hold the throttle opened, at some point it will get enough air flow to allow it to run poorly, but will die when you let off the throttle because it went rich again, and flooded out. The carb leaking through, could be trash in the needle/seat, sticking float, sunk float, blown power valve, or bad gasket, depending on what carb you're running. Good luck with your continued testing.

 

edelbrock 1406 carb (600cfm electronic choke) its starting to be my next good guess, and ive got a spare carb to swap out and try.