75 318 Dart won't start and backfires!!!

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jball21973

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This my first "project" and I've run into a snag. I bought a little '75 Dart with an original 318 4bbl w/ 49000 original miles and have swapped the intake manifold and carb. I put a Weiand intake and Holley 4160-1850s 600cfm carb in. I've tried to restart it and it seems like it gets no spark, then about 2 seconds after you let off the key it backfires! It has drove me nuts for the last couple of days and I don't want to tear anything up internally by not knowing where to begin. ANY help would be greatly appreciated, THANKS to anyone with ideas.
 
sounds like you did something to the timing . start at the basics, check for a good spark, bring it up to TDC on the compression stroke see where the rotor is in relation to #1 on the cap. make sure you have gas. sounds like its 180* out

Ive also had these same symptoms when my ECU took a dump. loaded up with fuel and when it got that one or two sparks from the faulty ignition box, it would pop out the carb
 
I've seen that before. One spark every time the key returns from start to run. Could be the ignition switch but more likely the dual ballast resistor or ecu.
 
All / any of the above

1--Check the spark, not just "if" but "how big" and "how strong" using either a spark gap, or "rig" a plug, and USE THE KEY, not by jumpering the start relay

2--Wiggle test all connectors---the distributor connector, the ballast connectors, the bulkhead connector, and the ECU. "Work" the connectors in/ out to scrub the terminals clean, and to "feel" for tightness. Inspect the terminals with a flashlight for corrosion

3--You can easily tell (if you had the dist out of the engine) if it's "180 out" or 1/2 turn out. Pull the no1 plug, stick your finger in the hole, and bump the engine until you feel compression. You may have to "go round" a couple of times to be sure. AS SOON as you start to feel compression, watch the timing marks, and bring them up NOT to TDC, but BEFORE TDC---right to where you want initial timing.

For a stock dist. in a stock 318 (stock cam) say, 10-12 or so. Rotate the dist. body until the reluctor tip is centered in the pickup coil, and make sure your plug tower with the no1 wire is where the rotor is just "coming to", IE coming around clockwise.
 
I had pretty much this exact problem and it was my ballast resistor. The backfires were so loud when I turned the key off! I think with the low voltage the coil doesen't have enough juice to produce a good enough spark in sucession but, It stores up enough when your not cranking to make one strong spark. Then when you turn your key off the coil discharges and sparks and lights the massive amount of unburned gas in your exhaust and you get a big boom.
 
I changed the ballast resistor today and now it will backfire a couple of times when I crank it and then it just cranks and no fire again, I'm going to try and turn the distributor 180 degrees this evening and see what happens. Could you guys tell me how to leave a thanks on here, today is my first day and you all have been more than helpful and I hope you all know how much I appreciate it. once again, THANKS A TON!!
 
jball21973 said:
I changed the ballast resistor today and now it will backfire a couple of times when I crank it and then it just cranks and no fire again, I'm going to try and turn the distributor 180 degrees this evening and see what happens. Could you guys tell me how to leave a thanks on here, today is my first day and you all have been more than helpful and I hope you all know how much I appreciate it. once again, THANKS A TON!!
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don't overlook the ECU. make sure it is well grounded to the body and that your battery to block to body grounds are solid. the thank button is in the lower right hand corner of everyones post.
* check for spark out of the coil first* before you mess with the distributor
 
Changed the ballast resistor yesterday and turned the distributor 180 degrees last night. Still nothing. I'm at a loss for words, well not really but I would probably get kicked off of here if I used the words I wanted to. I've used an ohmmeter to check the ECU and its wiring the way my Haynes says to and it seems to be good. The only thing I can think of is that I've got the plug wires wrong on the distributor cap. The cap I've got is not marked for the number 1 position, I'm pretty sure I've got them right but am not absolutely positive. There is a notch in the cap so it will only go on the distributor one way, the distributor is original to the car. I have the #1 plug wire going into the second terminal going counter clockwise from the notch in the distributor cap, am I right? Once again, THANKS to all for your time and help, I appreciate it.
 
see post # 2 you are going to have to find TDC on the compression stroke, either with a piston stop or putting your finger over the #1 cylinder spark plug hole and bumping the engine until it blows your finger off (not literally) , pop the cap , whichever terminal the rotor is at on the cap will be # 1. 18436572 clockwise on the cap. after you get that , then check for spark out of the coil. im trying to help but there is a method which I am trying to relay to you.
 

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OK guys, I've changed the ballast resistor, checked the ECU, made sure the distributor was in correctly-using the finger over #1 spark plug whole method, reconnected spark plug wires, coil wire, and still only get a couple of backfires and then nothing. I'm wondering if I've screwed some thing else up with the intake/carb install that I'm missing? How much gas should I be letting in the carb before trying to start, I'm not sure if I'm letting enough in, I'm scared of tearing something up by getting too much gas into the carb. I've been letting a couple of good shots in from the carb fuel inlets before trying to start.
 
do you have spark out of the coil while cranking with the key on? troubleshooting 101

hold the the distributor end of the coil wire 1/4 of an inch away from the body (away from fuel !!), such as the cowl area and have someone crank the engine. you should have a definite hot constant intermittent spark
 
check the air gap on the pickup coil inside the distributor... .oo8 with brass feeler gauge
 
I doubt it's too much fuel. Easy to tell--pull a couple of plugs and see if they are wet or dry

Hell, to fire old engines to test, I"ve just dumped raw gas right down the intake--couple --three tablespoons or more sometimes.

I don't think you answered the question? Did you have? the distributor out? of the engine?

I'd bet spark/ timing.

Get/ rig a long clip lead, multimeter, test lamp

Turn key to "run" and see what you have for voltage at the coil+ terminal when cranking the engine USING THE KEY. You should have "same as battery" or close to it

To be sure, temporarily run a clip lead from a battery source---like the battery stud on the start relay---to the coil + terminal. Don't leave this longer than to check for spark. Now crank the engine and check for spark at the coil.

If you get a good rythmic spark, you most probably have a timing problem.

Was the engine running OK before you tore it down?
 
Car ran like a top prior to intake/carb upgrade. Yes a buddy pulled the distributor to check out the shaft, Why he did it? I don't know. He pulled it and put it right back in, I could have killed him at the time, and now it sounds as if it would have been a good idea!(to kill him that is)
I just checked the coil on the body as instructed by 73AbodEE and there is a hot spark but it only occurs every 2-3 seconds. Just checked to ensure the air gap is correct, and yes it is at .008 with brass feeler gauge.
 
Hi guys, I'm still trying to get this Dart going. I've made sure the distributor is in correctly by doing the finger over the #1 spark plug hole method, the ECU is less than six months old as of purchase date, new coil, plugs, plug wires, coil to dist. wire, and dual ballast resistor. Now it will start one out of ten times trying to start it and runs like S**T for approx. 5 seconds and dies. I've come to the point where it is driving me nuts trying to think of things to do or things I've missed with the 4bbl upgrade. The dual ballast resistor is the only thing I'm wondering about as far as installation goes, one plug has 4 wires while the other has 3,I think I've got them right but just to make sure--I've got the four wire plugged into the end with the notch cut out of the end of the resistor and the three wire plug plugged into the end with the notch in the middle of the resistor-is this correct and if so what next? I've Checked the resistance on both the primary and secondary sides of the resistor and they are both in the ranges given in my Hayne's repair manual so I assumed the resistor was good. Could the distributor be so far out of whack I need to turn it a lot more to get it in time? Once again any help or thoughts would be greatly appreciated.
 
SOunds like timing to me. After you found TDC did you lock the distributor down there? I would move it one way or the other just a little bit. SOunds like its close if it does start sometimes.
 
I cannot take credit for this diagram, someone else posted it previously. Notice it's drawn with the cutout at the bottom. That plug is jumpered across. That is the end of the plug comiing from the ignition switch up to the right, and "all that" is used as a junction, as it's the switched ignition source

So in the diagram, the upper right goes to the coil+, and also is tied to the brown bypass circuit coming from the ignition switch in "start."

You may have timing still retarded. Try setting the timing on the starter.

You may not be getting hot enough voltage during crank. Hook up a temporary clip lead from the coil + to a battery source. Do not leave this hooked up for more than a minute, long enough to test, and watch "coil heat" with your hand.

Pull the coil wire, and use a grounded clip lead with a probe / screwdriver held at the top of the coil tower. Crank the engine USING THE KEY. Alternatively, if you attach the clip lead to the coil as above, you can jumper the starter relay and crank the engine. You should get a nice hot blue spark at least 3/8 and typically 1/2" long
 

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It sounds to me like your friend didn't do you any favors. It sounds like you have spent some change throwing parts at your car when you say it was running good before you started. Cost you some money and headaches.
If it was running good before you started, the only things that changed were carb and intake and you pulled the distributor. You can't mess up too bad installing a carb and intake(at least to the point that it won't even start) so my money is on the distibutor and your timing.
I agree with 75dartsport. If it starts sometimes or tries to start, you are probably close with the timing. Move it a little bit at a time in one direction or another, if it gets worse, you must be going the wrong way, start going the other way. Take a marker or pencil and mark the base of the distro and the block so you know where you started and you can always get back to there. Dennis
 
67Dart273 said:
I doubt it's too much fuel. Easy to tell--pull a couple of plugs and see if they are wet or dry

Hell, to fire old engines to test, I"ve just dumped raw gas right down the intake--couple --three tablespoons or more sometimes.

I don't think you answered the question? Did you have? the distributor out? of the engine?

I'd bet spark/ timing.

Get/ rig a long clip lead, multimeter, test lamp

Turn key to "run" and see what you have for voltage at the coil+ terminal when cranking the engine USING THE KEY. You should have "same as battery" or close to it

To be sure, temporarily run a clip lead from a battery source---like the battery stud on the start relay---to the coil + terminal. Don't leave this longer than to check for spark. Now crank the engine and check for spark at the coil.

If you get a good rythmic spark, you most probably have a timing problem.

Was the engine running OK before you tore it down?
Click to expand...
I am kind of in the same situation as this post but I did NOT pull my distributor out of the car. Would it still be a timing issue? Haven’t had a chance to check for spark yet but will do that as soon as I get an extra set of hands.
 
^^You should start a new thread on this^^ Either that or ask a moderator to move you post to a new thread
 
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