New Carb No Start

Hey again everyone,

So I've got a new Holley Demon 750 CFM carb installed on my 71 Mach 1 (351-4V, 4 speed). The car started hours before when I had the crappy edelbrock carb on there. With the new Demon on there the car will crank endlessly and not catch at all. I've got my distributor vacuum line hooked up to the port on the front, brake booster vacuum line is plugged into the port on my edelbrock intake manifold. 

Things I have already tried:

-Turning mixture screws all the way in then backing out 2 turns

-Put some starting fluid in the carb

-Checked ignition coil leads, choke connections, they all read around 12V

This is actually the first time I've installed a carb by myself so I bet I did some idiots mistake

Thanks in advance

If it didn't fire with the starting fluid I would say you have an ignition problem. You might have bumped the distributor and turned it or dislodged the cap (which could also break the rotor) or spark plug cables. I would get a cheap spark plug tester from Harbor Freight and see if you have any spark.

When you have ump the gas can you see it squirt gas in the carb? You either have a no fuel or ignition issue.

yep it squirts, maybe i flooded it

As the car was running and if you have fuel at the carb, before touch ignition, I'd first remove one plug to see if not flooded.

If not, then its really an ignition issue and you must have disconnected of changed something.

if flooded, (after a plugs clean up session, gap check) try the idle mixture by 1/4 turns increment vs 2 turns right away and no air filter.

if you then still have nothing, its also ignition.

[edit] I see you posted the same minute I did Yes check the plugs first

You may have accidentally separated the ignition plug harness (when doing the throttle cable). (right behind the DS valve cover)

RIght now, I would run a wire from the battery to the + of the coil and try. If it fires, you have a wiring issue. Because with starting fluid and spark IT SHOULD fire.

Mark

I tried jumping the ignition + post to the battery and it still wouldn't start. The plugs I had in the car are copper and they look a bit fouled, I'll get some new ones but I doubt the problem will let me win that easily. I'll check the wiring behind the throttle cable again

To check if you have spark insert a screw driver into the plug boot and hold it near ground to see if you see sparks while cranking the engine (do not touch the ground just leave a small gap).

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I'm not getting spark but the wire going to the + post on the ignition coil is getting 12V

Either your coil is bad or your points aren't opening and closing, or if you have a Pertronix it is bad, or your condenser is bad, or the ground wire is missing inside the distributor that grounds the breaker plate, or the high voltage cable from the coil to the distributor is bad or disconnected, or your rotor inside the distributor is bad, or the distributor cap center contact is bad.

A lot of possibilities, just go through them systematically, so you don't miss something.

Yeah I'm not even sure about the distributor, its a decently new MSD and I opened it up. The cap looks new, the rotor looks new. I'll try a different ignition coil. Is there a way I can use an inline spark tester to see if the distributor is bad?

If you have a timing light hook it up as normal try to start the engine and see if it flashes. If it does, you are getting voltage to the plugs. You can also move the pick-up from wire to wire to check all cylinders in the same way. Chuck

If you put the Edelbrock back on and it starts, your new carb is way maladjusted or faulty. If it won't start with the Edelbrock you know you changed something in the process of installing the Demon carb. Chuck

I might have to indeed put the edelbrock back on and see. I swapped ignition coils to one that works for sure and I noticed there is no ballast resistor. Also I have a red wire and orange wire going to the posts, I put the red on + and orange on -. Also put a known working voltage regulator in there. Damn thing still wont start and I have to wait for my battery to recharge now. This car is from hell

I might have to indeed put the edelbrock back on and see. I swapped ignition coils to one that works for sure and I noticed there is no ballast resistor. Also I have a red wire and orange wire going to the posts, I put the red on + and orange on -. Also put a known working voltage regulator in there. Damn thing still won't start and I have to wait for my battery to recharge now. This car is from hell

Click to expand...

Orange on + coil 

Black on the - coil

Red on ignition key

I've got it wired correctly now. My voltmeter is showing 12.34V on both +/- posts with the key on. So thank god I don't think I have another wiring issue. The coil I have in there is out of my other car and works (exact same model). So from what I understand this would mean it would have to be a problem with the distributor or the coil to distributor wire? Perhaps the magnetic pickup unit is somehow failed? The cap looks new but that contact spot is so tiny I wonder if it isn't even touching. I bent the rotor contact up a little more just in case. I'm unsure how to get any further in the distributor since I don't know how to take the points out.

I wonder if my distributor has been dying slowly; I used to get the car to start but it would backfire like hell after a few minutes

If you’re running an MSD with a box you don’t have points.

Is the rotar inside the distributor turning? If you turn the car over with the cap off and coil disconected is the rotar turning?

I'm not running a MSD box and yes the rotor is turning