hey yall, got a problem. I have as sbc (350 w/305 crank) built buy a reputable shop. ran in the shop. droped it into an impala (had an sbc in it before). now it turns over, but wont fire off. has fuel, firing order is correct, getting spark, but just wont run. I put a volt meter on the coil, with key in the run position I get around 12v, in the start position (engine turning over) it drops to around 9v (seems wrong to me). has new msd blaster coil, and msd electronic ignition. everything seems to be wired right. but I just cant figure it. any thoughs?
Have you had the distibutor out since it ran in the shop? Could be distributor turned 180 degrees off maybe........
What year Impala? 74 or older or 75 or newer? Newer is set up for electronic ignition from the factory but 74 and older either run a ballast resistor or have a resistor wire to drop the voltage to the coil. Those need The resistor bypass wire hooked up to the starter if you aren't going to eliminate the resistor. Still see BigPoppaPump's post in post 2. Do you have spark to the plug? Meaning if you stick a screwdriver in the terminal at the end of the wire and hold it close to the engine and have someone crank the engine over is there a spark. No spark, backtrack to the coil, distributor and primary ignition. Spark, Check timing and fuel supply. The voltage drop when cranking may be because the starter is drawing enough amps to pull the voltage to the coil down to 9 volts. That could hinder starting a bit but it should still try to fire. First you need to get spark to the plugs. Then you need to make sure that it is actually in time. That is pull number one plug and bring it up on top compression and get the timing marks lined up, then make sure that the rotor is pointing at number one on the cap. Once that is done you need to make sure you have a fuel supply but the plugs may already be wet from cranking and not being fired up.
distributor hasnt been out. fuel may be old, but is clear and smells ok. I havn't gone plug by plug to check spark, but i checked #1 and lookin good. plus it ran fine on the same plugs when they broke in the cam at the machine shop. my primary concern at this point is the voltage drop at the coil when the starter is engauged.
Then you have spark? You don't need a resistor wire , ballast resistor or even a condenser . Just 12 v to the unit, 12v ign. switched wire to unit The points just trigger the MSD (white wire) You HAVE read the instructions, right? If not, you can get them on line.
thanks mr48, its a 68. so it has the balast resisted wire. but we're running an aftermarket starter that bypasses it, and only uses the other wire. nothing (timing wise) has been screwed with since the cam break in. it did pop and studder a bit. on the last try. but still no start.
markyak, yeah we read the instructions supplied with the ignition system. they're about as clear as old oil.
Resistor wire doesn't come from the starter, it somes from the firewall. The wire that your not using on the starter bypasses the resistor wire for starting. Still may be a low voltage problem.
If you read the instructions you'll see they say to not use a ballast resistor with an MSD system. Get rid of the resistor and it should fire. I've found the instructions to be very good with MSD systems. From the instruction sheet: "Ballast Resistor: If your vehicle has a ballast resistor in line with the coil wiring, it is recommended to bypass it."
Did you check compression? I know it sounds funny being that it is a brand new engine. I was petrified of wiping the cam on my brand new motor. It would not start. I had a friend that I respect very highly come over and I just acted as a helper. (actually the second friend to come by and try) I only go 40 lbs on a couple of cylinders. Wiped cam, right? My buddy said squirt some oil in each spark plug hole. I did and it started right up, smoked like a drunk sailor but it ran. We broke the cam in and it has started like a champ ever since. I know where you are coming from. I couldn't figure it out either. Spark, fuel and timing. It should run right? but it wouldn't until it got enough compression for it to to fire. The fact that, you like me, have spark tells me it is not an ignition problem. It could be timing or compression. I once spent a whole weekend trying to start a Pontiac I memorized the GM firing order that weekend I checked it so often. Pontiac's are CCW rotation. We sometimes get convinced that we have a certain problem only to find out later we were barking up the wrong tree and all that time chasing our tails was wasted. I suggest a compression test first and assuming nothing, start from the beginning again.
Very simple to check. just run a jumper from the battery and see if it starts.If that cures it , go and hook the wiring up correctly , locating the original wire at the firewall bulkhead connector , and replace with a non resistor regular wire that will stay at 12 volts . You shouldnt need the wire from the starter that should already be in the stock location (piggy backed to the other pos. lead to the coil .
Its 180 out no doubt. Common problem. hey did anyone report that fucking fremaneler, or am I the only one who bothers to report spammers.
When cranking, the coil should see a full 12 volts. When running, around 9 volts. Check your wiring again, your voltmeter readings lead me to believe something is wired backwards.
YO, Lookie hear. He never had the distributor out! He's got an MSD ignition box! I read that right here!
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