73 Charger cranking but not starting

[73 STP]

Hi folks, I have read many, many threads here about similar issues. Here is what I am dealing with...

1973 Charger (nicely built 340 with 4bbl Quick Fuel carb) that started and ran awesome over the last summer and fall. During the winter I decided it was best to fire it up and run it a little every month. That went well until about a month ago. The car would not start and was backfiring thru the carb and the exhaust. Replaced the ballast res and then the ECU (the Volt reg was already new) and then the cap and rotor. The car fired up and ran well after the cap install. I thought that was the end, but went out again about a week ago and it cranks, tries to fire but wont. No backfiring this time. Since it seems intermittent, I decided to start tracing from the ignition switch (original to car). Here's what I found...the DBL (ign 1), the BK (acces) have 12.3v and the BR (ign 2) has only 6.75v in the RUN position. The Y (start) and the BR (ign2) have 9.6v in the START position. With everything connected, the coil "+" reads 1.5 v in both the RUN and START positions. I am getting spark from the coil but it is not a crisp blue, kind of orange-ish.

Any thoughts appreciated...

 

[Don Frelier]

Points or electronic ignition?

 

[steve340]

Charge the battery so you know it if correct.
Try some fresh fuel direct in to the carb. Gas can go off and it will run on it but you get hard starting.

 

[Ranger16]

Points or electronic ignition?

He said "Replaced the ballast res and then the ECU", so my guess would be electronic ignition.

 

[Don Frelier]

A couple things to check:
1. bulkhead connector
2. Magnetic pickup resistance and reluctor gap
3. ECU has a good ground? scrape a little paint off underneath the screw heads.
Spark should be blue and crisp, not yellow/orange
What is the ECU you are using?

 

[Gold Rush]

In start mode the ignition switch should be supplying full battery voltage via the brown wire ( IGN 2) to the coil positive terminal. If your battery is fully charged as it appeasers since you have 12.3 accessory volts and IGN 1 in the run mode sure points to defective old switch start contacts.

You can prove that by using a jumper wire to apply battery + 12 volts direct to the coil. Soon as the engine fires and you release the ignition switch, pull that jumper off (might need a helper).

 

[73 STP]

here are few extra tidbits....new 93 octane gas (dropped tank to fix leaking sender seal), good ground at ECU (new Chrome from NAPA, cant recall the name), no longer have any bulkhead connectors (all electronics in the interior with new wiring)

 

[73 STP]

A couple things to check:
1. bulkhead connector
2. Magnetic pickup resistance and reluctor gap
3. ECU has a good ground? scrape a little paint off underneath the screw heads.
Spark should be blue and crisp, not yellow/orange
What is the ECU you are using?

will check the gap and pickup res tonight...I know the gap should be .008, what is a good range on the pickup resistance?

 

[73 STP]

In start mode the ignition switch should be supplying full battery voltage via the brown wire ( IGN 2) to the coil positive terminal. If your battery is fully charged as it appeasers since you have 12.3 accessory volts and IGN 1 in the run mode sure points to defective old switch start contacts.

You can prove that by using a jumper wire to apply battery + 12 volts direct to the coil. Soon as the engine fires and you release the ignition switch, pull that jumper off (might need a helper).

I will try the jumper wire tonight...my first thought was the "old" switch since it has been intermittent...

 

[73 STP]

...pickup gap is .008 and the pickup res was at 269 ohms...measured from the pigtail, I just don't know how to interpret that (good/bad). I will have to get some clips to make a jumper wire tonight. I will report back with the results. Thanks for the suggestions.

 

[Gold Rush]

...pickup gap is .008 and the pickup res was at 269 ohms...measured from the pigtail, I just don't know how to interpret that (good/bad). I will have to get some clips to make a jumper wire tonight. I will report back with the results. Thanks for the suggestions.

If you find the ignition switch is bad, I somehow managed to buy two replacement switches for my '74 Charger so have the extra I'd gladly sell you. $30 and the ride from 76903 to your house.. Let me know. [email protected]

 

[Don Frelier]

...pickup gap is .008 and the pickup res was at 269 ohms...measured from the pigtail, I just don't know how to interpret that (good/bad). I will have to get some clips to make a jumper wire tonight. I will report back with the results. Thanks for the suggestions.

I believe 269 Ohms is within range. I sounds like you do have some low voltage issues.

 

[73 STP]

found some time over the weekend (found out mom has cancer, life-long friend died in car accident...both last Thursday) so this helps keep my from dwelling on the bad crap! Bought a new ign switch, coil , and volt reg...they all test the same as the my old stuff. Right now, draining the fuel. The only thing that has occurred on the car is that I dropped the tank to fix a leaking sending unit gasket. I put new 93 octane fuel in it but maybe the gas is stale?? I got to thinking that many people probably don't buy too much of that in my little town, LOL. Any other thoughts out there, this is driving me crazy!!! (BTW, also tried a buddies carb as well)

 

[Gold Rush]

Lets go back to the beginning for a moment. Did you ever substitute a known good battery into the Charger? It's a possibility. Also did you actually install the ignition switch (at least electrically). You don't have to physically swap them out to test the operation.

Since the engine started and ran well a week before you started this thread, gas is not the issue. Unless you are not getting any to the engine now.

You are right.. This is a bit crazy! We all hope it is a diversion from all the other things. Keep us in the loop please.

 

[73 STP]

hmmm, the battery "tests" good, but no, have not swapped it. My timeline may be a bit off, I don't think it has started since dropping the tank...and yes, I just hooked the switch "inline" and got all the same readings. (but did not try starting with it hooked up. I haven't returned it yet, may try that after the funeral) Thanks for the suggestions. I will repost Thursday with results.

 

[Gold Rush]

hmmm, the battery "tests" good, but no, have not swapped it. My timeline may be a bit off, I don't think it has started since dropping the tank...and yes, I just hooked the switch "inline" and got all the same readings. (but did not try starting with it hooked up. I haven't returned it yet, may try that after the funeral) Thanks for the suggestions. I will repost Thursday with results.

Did you ever hook a jumper between the positive battery and + coil posts then turn over the starter? The 6.75 volts in run is what I'd expect but 9.6 in start mode seems very low to me.

You might give the carburetor a squirt of gas while cranking also. See if the engine tries to fire. Looking at the carbs squirter nozzles while pumping the throttle linkage should tell you if there is gas in the fuel bowls though.

 

[Dennis H]

They don’t like being run for short spurts. Possible it is just loaded up? Tromp on it, if it starts go blow the crap out of it. Drive at least 45 minutes.

 

[73 STP]

ok, with all the crap has been going on, becoming a grampa has brighten my spirits greatly!! Now back to the car...the battery and starter removed and test good, the fuel has been replaced. I have tried the jumper and I connected the new switch, as suggested, with no luck. After replacing all the elec stuff, again! (except the starter relay) I have these results...in RUN, 12.4v blue wire, 12.4 black wire and 7.3v brown wire at the connector and follow them to the ballast res and to the + coil with same volts. In START, same tests, same results EXCEPT the brown (and +coil) has 10-11v and the yellow wire has 12.4v at the connector. I have spark at coil and at all plugs (and spark is jumping at electrodes) I ran a compression check and all cyl are nearly the same @ 125psi. Now, this seems low to me since my racecar (chevy 350) was hitting 140 to 145 psi. The plugs are getting wet very fast (tested power valves and even a different carb) after drying them, I have better "hits" but no start.

 

[Gold Rush]

Well, it sounds to me like the voltages are pretty close now and you do have sparks. The wet plugs is interesting. Even though you put on a different carburetor the plugs get wet fast? Something isn't making sense here... Spark - Fuel - Timing... All that should be needed. The compression you mentioned should not be an issue. Engines with way less than that start and run just fine.

Just for grins pinch off a rubber gas line somewhere to stop gas flow then see what happens originally. You might have to manually feed a little gas into the carb but keep the gas delivery shut down for the time being. Yes, I'm pulling at straws here but you have to admit this is strange deal.

 

[73 STP]

YES, very strange. It ran perfectly over the summer and fall. I have spark all down the line, not a thick/blue but it does snap. A funny thing I found last night is that as I cranked and added fuel (some by bottle, some with accel pump) that I thought I had flooded it. So, I took the plugs out once again and this time noticed that there were differences between them. Four were very wet, two were very black sooty, and 2 were dry as a bone!! (they were all removed, cleaned and dried before performing that latest test) I haven't mentioned this before but the fuel at the log is reading 6 to 7 psi (which is similar to our old racecar)

This is killing me! LOL I know I have to be missing something to test...can anyone supply me a systematic list (or order) of how I should be doing the testing? With the continuities and voltages I have been getting, I cant imagine that I have a broken wire, chaffed insulation, or some other calamity in the system...