Fuel delivery problem; maybe?

-
Calipag

Calipag

Well-Known Member
Joined
Apr 11, 2018
Messages
453
Reaction score
288
Location
Corona California
The 70 Dart slant 6 with the holley 1920 carb is have an odd problem. It will start right up and die. I can keep it running if I keep the starter engaged but as soon as I release the key the engine shuts down. I ordered the carb rebuild kit and did the rebuild tonight but it is still doing the same thing. The fuel filter has a air bubble that does not go away even while I keep the starter engaged. I did pull the fuel line and the pump is pumping; I did not test the pressure. This is what I believe may be wrong:
1) I rebuilt the carb incorrectly
2) The fuel pump is bad just not pumping the correct pressure

Thank you as always for any help or ideas
 
Calipag said:
Is there a way to test the resistor?

Thank you for the quick response.
Click to expand...

Take your volt meter and measure voltage at the IGN side with the key ON. You should have "around" 12V. Then measure the coil side. No voltage = bad ballast. You should have "some voltage" since it is a resistor, it will not be 12V, it will be maybe 8-9? Maybe Del will chime in, but no voltage means the resistor is bad. The reason it will run with the starter engaged is because the system is wired to bypass the resistor while cranking and give a full 12V so then the ignition sees voltage and then does not when you release the key.
 
Last edited:
Just jumper the resistor, and see if it keeps running, when the key is released. If it keeps running the resistor is bad. Do not let it run very long with the resistor bypassed, as it will overheat the points and coil.
 
Charrlie_S said:
Just jumper the resistor, and see if it keeps running, when the key is released. If it keeps running the resistor is bad. Do not let it run very long with the resistor bypassed, as it will overheat the points and coil.
Click to expand...

I have a 4 prong resistor. I bought a new one and I'm going to try it after work today. I'm doing research to figure out which ignition system I have. We just bought the car and I am still learning about the dodge. I'll post some pictures of what I have.

ign.JPG


ign1.JPG


ign2.JPG


ign3.JPG
 
Them little blue things squeezed all over your wires, t-taps- get rid of them. The scurge of all electrical systems. There is no way to seal them and they create a break point.
 
Tooljunkie said:
Them little blue things squeezed all over your wires, t-taps- get rid of them. The scurge of all electrical systems. There is no way to seal them and they create a break point.
Click to expand...

I agree. I have to get it running and get it where I can go thru the wiring. That is one of the first things I wanted to do to the car until it stopped running. I don't understand the ignition system enough to go in and start cutting and putting everything together. I want to do the right way, one time. Is that an electronic ignition?
 
Sadly, I came home with the new resistor and it still doing the same thing. starts up and dies right away unless the starter is engaged. I know the wiring is a mess but it ran fine up until a week ago and then this problem started started.

fuel pump?
 
Last edited:
The white box you pictured is the voltage regulator. MOST Mopars these days have had the original electronic ignition box replaced and it is "in reality" usually known as a "4pin" ECU, which can use either a 2 or 4 pin resistor

The old OEM box WAS a 5 pin box and REQUIRED a 4 pin resistor

Your car never originally came with a Mopar electronic ignition........it would have been breaker points originally. I believe if you go to MyMopar and download the 72 shop manual, that it shows the electronic system in there as an option. Also at MyMopar are some basic diagrams for the system

MyMopar - Mopar Forums & Information - MyMopar Tools/Reference

Older 5 pin box/ 4 pin resistor

Ignition_System_5pin.jpg

Newer 4 pin box/ 2 pin resistor. FOUR PIN BOXES may have 5 physical pins. Only way to tell is to take a multimeter and see if there is ANY resistance reading = 5 pin box, VS completely open (infinity)= newer 4 pin

Ignition_System_4pin.jpg


NOTE in the diagrams, the coil resistor bypass circuit "IGN2" is not shown. It comes out of the firewall connector, and connects to the resistor connection feeding the coil POS terminal This is THE ONLY WIRE that is HOT in the "start" position of the ignition switch.
 
Last edited:
Here's a post I made about the simplest way I know to get across testing the ECU/ ignition parts

You need a coil, the ECU and the distributor

Lay it out on the bench. Follow the diagram. Find the two distributor pickup terminals on the ECU. Hook them to the distributor

Hook the ECU case to battery NEG

Coil does NOT need grounded

Distributor does NOT need grounded.

Hook coil + to the power lead terminal on the ECU. Get a clip lead hooked there and let dangle. This is your battery "hot" when you are ready

Hook something from coil "case" to a probe for testing spark.

Hook up your power clip lead. Twist the distributor shaft while holding the test probe near the coil tower. The thing should make sparks

If not, unhook distributor. Take first one, then the other pickup clip leads, and "tap tap" ground them at the battery connection. Coil should make 1 spark each time you do so.

If not, try another coil. If that does not fix it replace the ECU

IF you hook it all up and it WORKS, then there is something AFU in the car harness. SUSPECT a bad ECU connector OR a bad DISTRIBUTOR connector
=============================================
This is all you need to test the basics of the ignition. You can easily test the ballast separate. A battery, the ECU, distributor and a coil, and of course some test leads

2ai0wsj-jpg.jpg


Below, the basic diagram for a 4 pin ECU

166lmj7-jpg.jpg


Below, the wire for testing spark. I use my 12V test light. No, LOL the spark won't blow up the bulb

166lmj7-jpg.jpg


Below, the ground connection. ALL you need is one wire from batt NEG to the ECU case

xawjl-jpg.jpg


Below, the two distributor connections. In the car these are polarity sensitive, but for testing does not matter

b3opvm-jpg.jpg


Below, the coil NEG connection

6jfywp-jpg.jpg


Below, battery PLUS connection, one wire to this terminal of ECU and jumpered over to + side of coil


11lqu5l-jpg.jpg


Below, all hooked up and ready to test (except for battery ground). Should produce sparks at least 3/8" and typically 1/2" long

1zzoya0-jpg.jpg


Below, distributor "one wire" test. I have removed the other distributor wire for simplicity. Take the bare connector end or this clip lead (the yellow) and with everything hooked up, ground it repeatedly. Each grounding should result in a spark (In this photo you need to hook up the ECU ground wire, I left it off for the photo)

vgitld-jpg.jpg
 
Thank you all for all the info.
I know what I'll be doing this weekend. I will follow up with what I figure out or find. With any luck and patience, I hope to have it straightened out.

Sorry for what probably seems like dumb questions. I feel like a fish out of water with this car.
 
Tooljunkie said:
Them little blue things squeezed all over your wires, t-taps- get rid of them. The scurge of all electrical systems. There is no way to seal them and they create a break point.
Click to expand...

Buying an old car is like a box of chocolates....you never know what you got til you bite into it. Yeah, those taps and the spliced wires covered in electrical tape coming out of the ECU are suspects until checked out and preferably eliminated. Places like Mancini Racing and probably NAPA sell new ECU connectors with leads that would help you out a lot. If you go by the connection diagrams posted here, it wouldn't be hard to rewire with solid connections. If it was me, they'd be soldered with shrink tubing for insulation.

You must have a clear fuel filter and the air bubble you see is pretty normal. It seems to me the filter never seems to get 100% filled with fuel. I used a plastic clear filter when I fired up my 225 just to verify I was getting gas and later replaced it with a stock looking metal-bodied one. Air bubble or not, mine runs great and so will yours once you get this problem fixed.
 
I have a new twist to the saga.

So tonight I started to get rid of the stupid blue clips and testing continuity and voltage. All the while I was testing the staring situation. After getting rid all of the clips, it finally starts up and runs as it should. I leave it run for about 10 minutes and go thru the wiring harness shaking and jiggling it to make sure I did't have a short somewhere and the car didn't shut off. I shut the car down and went to start it again AND NOTHING! No click and the starter is not engaging. I checked power at the starter and i have power there; so i'm guessing the starter gave up on me.

Could the starter have been my culprit the whole time?
 
Calipag said:
I checked power at the starter and i have power there; so i'm guessing the starter gave up on me.

Could the starter have been my culprit the whole time?
Click to expand...
No, if it was the starter, it would not start at all.

Where do you have power? At the large wire, or the small wire on he starter? The large wire should have battery voltage all the time. The small wire should have more then 10 volts, when the key is in the start position.
 
It could be the ignition something in the switch. Making it do that had that happen with one of my trucks put a switch in it did fine
 
You must log in or register to reply here.
-

Back
Top