Engine Won't Start

[John L]

So here's my story and my diagnositics to date. Took the Pinz for a drive two Saturdays ago. Ran her around for about 40 minutes. Got home and shut her down. She sat for a few hours and when I went to pull her in the garage, she wouldn't start. She turned over fine and seemed to have plenty of power; but no ignition. So I checked for spark at the plugs and there was spark, but I'm not sure how strong. I've read a bunch of posts on similar topics and the plugs needed changing anyway. So, I've put in new plugs, charged both batteries, and jumped the 4500 rpm limiter. At the point of the jump and after the point of the jump for the limiter I have 24.6 volts. When I get to the coil I only have 10.8 volts. First question, is this normal or is this a sign of the problem? I have a 1975 710M. I have Petronix ignition with the flame thrower coil (30 ohm). I checked the voltage at the white wire on the top of the coil and that is where I get the 10.8 reading. I have also pulled the orange distributor cap, cleaned the rotor and all contact points and re-seated it and snugged it in place.

When I go to start it at first she sounds like she's going to roll. Then I will get a very rough idle where one maybe two cylinders are working. If you give it any gas at all it dies immediately. If I push down on the accelerator before I try and start it then it will take several tries before it will idle up again. Something I also noticed is that the back carburetor is loose between the bottom and middle sections. Could my problem be as simple as tightening the carb? If so, I am assuming I'd need to uninstall it and it tightens from the bottom?

I am not a mechanic but my Pinz has thankfully been teaching me a lot. Through your help and a thorough review of Jim's website I've conquered all of the issues thus far and am hopeful this issue won't beat me! I live in south Louisiana if the climate makes a difference in your thoughts. It's just crazy she was running perfect. I turned her off and then she won't start up again. Any help you can provide would be much appreciated. I need to get her running but don't want to just dump money on buying parts that won't change my situation. Thanks in advance for your input!

John

[undysworld]

John,

The loose carb will cause issues. I'd attend to that first, and see what's up.

If that doesn't do it, perhaps check fuel lines for cracks (or replace them if they're old just in case).

Do that and see what ya get.

[Jimm391730]

When running, you should expect about 17 volts at the coil positive terminal. This is an average voltage, as the true voltage is probably jumping up to over 24V and then down to maybe 10V as the points open and close (or the Pertronix opens and closes the circuit to ground).

The Pertronix should not "stick" on; it should be open even when powered as long as the magnet ring is not turning. If you get such low voltages continuously I would suspect the Pertronix. It could also be the burden resistor, but the resistor should be more dependable than the electronics in the Pertronix.

Can you go back to points and condenser to see if it will run? Or try a different Pertronix?

[John L]

Jimm:

Thanks for the input. I say I have Petronix ignition merely because I have the flame thrower coil. When I take off the distributor cap, there aren't your traditional points there. There is electronics, but not a metal plate. I'm assuming this is Petronix; but not 100% positive. (remember I'm trying to learn ) I'll check the spare parts that came with the truck when I bought it a few years back. I seem to think I saw some old ignition parts. When I leave my day job I'll see what I have and if I can give an alternative a go. What I see in the bottom of the "distributor" is some wires screwed down to the bottom of the "distributor". I was too afraid to take them loose and clean them. I do note that one of the screws is rusted significantly. Could this be an issue?

Thanks all for the input. I also plan to try and tighten the carb tonight. If I ultimately need to rebuild them I"ll order a kit and give it a go. All input is welcome.

John

[Jimm391730]

The Pertronix is a black molded plastic block, mounted to the metal base that you would see for points (so that it mounts up the same way). The black plastic block should be no more than about 1/16" away from a black plastic ring around the shaft, right below the rotor.

The Pertronix detects the four small magnets within the ring and electronically makes and breaks a connection to ground (just like points would). But there is no wear of the points cam, mechanically, nor wear of the points contacts - this is the benefit of the Pertronix.

You might be able to twist the rotor and get the ring magnets to move enough to change the Pertronix detection; try this while measuring the coil + terminal. If you can get the voltage to swing from around 22-24 volts, then down to maybe ~10V, then the Pertronix may be good. If not, I'd suspect the Pertronix. These voltages are guesses, if you get a definite change then the Pertronix might be good. If you get NO change, then most likely you've found the culprit.

[edzz]

1. fix the carb
2. insure that th mechanical advance in the distributor is functioning smoothly and not binding
3. insure the fuel solenoids are clicking

make sure the carbs are getting fuel

many years ago when a friend went to leave our shop on his harley he couldn't get it started. So out come the wrenches, he had the carburetor off when one of the guys asked him if he had checked his gas. Doh... long story short he had run out of gas as he pulled into the shop.

Not out of gas are you?

[John L]

Update...

First, let me thank you guys for jumping on this thread. Edd I laughed out loud at your question about the gas. It is generally the simple things that are the problem and not the more complicated. I do have fuel and it's recent fuel meaning it isn't old. I also took everyone's comments to heart and did what I could last night to get to the bottom of this issue. I pulled the carb last night and tightened it. Three of the four retaining bolts were loose enough to require a couple of turns with the screw driver. Before I tightened it there was movement front to back and side to side where the bottom piece meets the middle piece. It is now tight. SO, after performing that repair, cleaning it up and remounting it I gave her a whirl. She now cranks fine and idles perfect. But, if you go to give it gas too quickly it will die. If I feather the accelerator and slowly increase the fuel then I can get it revved up at normal operating range. But, if you merely step on the gas it will kill. So Undy and Edd you guys were right. A loose carb is a bad thing.

I then took Jim's suggestion and checked voltage at the positive terminal of the coil. With the engine off but the key engaged I had a consistent 10.4 or 10.5 volts at the terminal. I used the starter button to advance the rotor as it would not turn by hand. Regardless of the location of the rotor I had the same 10.4ish voltage. I then remounted the cap and (it was removed to make sure I wasn't testing the voltage with the rotor in the same spot) and started the engine. With it in idle I had 18.3 volts at the positive terminal of the coil.

Does the voltage being constant with the engine off, regardless of the position of the rotor, mean the Petronix ignition is faulty? Would this explain the failure of the spark advance when I dump fuel into the carb by stepping on the accelerator? Or do I have a vacuum leak somewhere? Or is there some other explanation you guys may be aware of? I now have her running... just not good enough to driver her Any thoughts would be appreciated. Thanks,

John

[Jimm391730]

Sounds like the Pertronix is working as it should; I've actually never checked the coil voltage when an engine was not running. 18V running is a good number.

My carburated truck starts exactly the same, when I'm too lazy to pull the choke. Once it warms up for a minute or two then I can get on the gas without worrying about feathering the gas. Before it warms up it will die if I stab the pedal (unless I continually work it to get lots of fuel in with the accelerator pump). I've always assumed that this was just how Pinzi's start.

[John L]

Jimm you may have a point. Before this happened I would always let the engine warm up before driving it as she would buck and fuss a bit. But if it warmed up it ran fine. Maybe I'll warm it up a bit and see how it goes around the neighborhood. It just seems to be a bit more extreme than before. I'll keep you posted and thanks for the input.

John

[Jimm391730]

I used the starter button to advance the rotor as it would not turn by hand.

You should be able to advance the rotor (turn it clockwise a bit) against the advance springs. It should turn roughly 20 degrees and then spring back. If not, the weights/springs are probably rusted and stuck. Try a good dose of WD40 through openings in the base plate and work the rotor. If it is still stuck, you have to remove the rotor, Pertronix magnet ring, the Pertronix itself, and the base plate in the dizzy to get to the advance weights and springs under the base plate. Under the rotor is a felt in the center of the shaft; this should be oiled to lube the rotor portion of the shaft that advances over the driven portion of the shaft. Once the weights and shaft are free then re-check the timing.

[Texas710]

I'm seconding the advance weights. Either stuck, or not timed correctly to take into account the advance. Will give the same symptoms, Idle's fine, but bogs down when you put gas to it. Kind of like running to lean, or incorrect jetting.

[Jim LaGuardia]

Did you re-sync the carbs? Are the pump rods in the top hole(furthest in) on the carbs? Screw the voltage check, what is the current coil resistance and does spark jump 1/2" or more? Re check spark after warming engine up. A failing coil will loose spark with heat. Leaving the key on without running the engine will kill the pertonix flamethrower coil.

[John L]

Thanks guys. Got in way late last night and no time to work on the Pinz. I'll get on these suggestions this evening and report back. Thank you all for providing input. It's much appreciated.

[John L]

Jimm and Tex... BINGO! Jim L I still need to sync the carbs; but I got on her last night to see what would come of it. I let it warm up for a while and then took it for a spin. While it drove, it bucked and sputtered as you put gas to it. If I really hit the accelerator it wanted to kill. So, I pulled her back to the house and went to work on the Petronix. I pulled the cap and the rotor button. The rubber sleeve that sits around the shaft of the rotor looked pitted at first glance. (Upon further inspection it was filthy.) So, I unscrewed the electrical component mounted on the plate that the rotor spins by and wiped it down to make sure it was clean. I pulled the sleeve and found two things... 1) the shaft of the rotor was rusted; and 2) the rubber sleeve had four magnets that I could see on the inside of the sleeve but I could only see two of them on the outside of the sleeve. Discussing item 2 first, upon further inspection I realized that all four magnets were supposed to be clean and clear of the sleeve so that when they rotated on the shaft by the electrical component they could advance the spark. They had gotten totally fouled with gunk over the years. They were covered with a film that actually made it look like there was a rubber coating on top of the magnets. But this film was just crap that had spun up around the rotor and the sleeve over the years. The bottom of this sleeve seemed to have a rubber piece that held the magnets in place. Mine separated (i.e. broke). But, I was able to clean up the sleeve and the magnets stayed put. (When I pushed the sleeve back on it seated properly and the magnets stayed put.)

I then tackled the shaft. I sprayed it all down with a good dose of WD 40 and used some fine sand paper to clean up the shaft. It was nice and smooth and shiny when I was done. I also checked the pad and made sure it was oiled. Last, after putting the Petronix back together I twisted the button back and forth and loosened up the rotor so it had a little play each way by hand. I then buttoned up the cap and gave it a shot. I am going to tell you that I have more power and my Pinz is running better than when I bought it!!!! She doesn't appear to be cold natured any more. As soon as I fire it up she's ready to roll. Instant power when you press on the accelerator.

I can't tell you how valuable this blog is and everyone's input. You read your manuals and you don't get most of the information you need. The technical data is there but not the diagnostic trouble shooting we need to keep these babies rolling. The knowledge and experience shared here is much appreciated. If anyone else is having the symptoms I described, try cleaning up the Petronix!

Levers down!!!