THE PORTAL HUB - Pinzgauers, Haflingers, Volvo 303s and more!

Hi All, I have a problem with my 1979 710... When revving the engine there is a misfire. Its a popping type noise, and the engine is obviously running rough, as it shudders on the mounts. To set the scene, I have changed the oil and filter, rebuilt the dizzy, cleaned the carbs, re sealed the exhaust joints and welded a couple of holes, and generally made sure all is in order. It has misfired since I bought it so its not anything I have done. Two things I haven't checked are ignition timing and carb balance/set up. Can anyone shed any light at all on what to check/do? Thanks, Dave

You need to do a complete tune-up before anything else.

Valve adjustment, points, condenser (if no electronic ignition conversion), inspect / replace spark plugs, and timing and carb adjust / sync.

If the problem continues after this has been done please indicate if the ignition system has been altered. It may make a difference if civilian dizzy cap, plug wires, spark plugs, and points replacement module have been installed.

Until this has been done your just asking people for wild guesses.

So another member in Switzerland, you wouldn’t have any Sig P-210 (Pistole 49) magazines that need a new home would you?

73
Ed

You Swiss guys get all the fun toys with a working happy switch, full auto check the Sig forum for magazines.

He's right about your truck, check all the basic stuff first. Nine times out of ten it will be something obvious that you overlooked because we all gravitate to the worst case.

Good luck and let us know what you find.

I'd pull a plug wire from each cyl and check to see if one doesn't effect idle, then replace that spark plug. Troubleshooting continues from there.

If things work somewhat right,I've used the solonoids to kill cyls. Unplug,miss, and I don't get a Defib treatment! Another option ie to use a "point and shoot Pyrometer,cold(er) is dead..
Mark

Thanks for your answers guy, I have done a full tune up, clearances, timing, new flex exhaust manifold, carb set up and balance, and it is heaps better, but still hesitates under initial acceleration, and the engine appears rough and vibrates as if out of sync, then it smoothes out as the revs climb. As a side note, does anyone know if there is a resistance value that you can check across a pertronix ignitor? I fitted one earlier, it worked briefly, then appeared to quit. Have refitted points and it runs like a dream. Just wondered if you can tell if its duff by putting a multimeter across it....? Cheers

As a side note, does anyone know if there is a resistance value that you can check across a pertronix ignitor? I fitted one earlier, it worked briefly, then appeared to quit. Have refitted points and it runs like a dream. Just wondered if you can tell if its duff by putting a multimeter across it....? Cheers

I'd be keen to know that too. I was having the Pertronix kit fitted a couple of months ago and it blew out two ignitor units the same way- ran like a dream for a few minutes then quit. Replaced first ignitor at hideous expense expedited from EI in California to Scotland and then the second one did the same thing. Everything tested OK as per the EI video, so we gave up on it and refitted the points. I'd be grateful for clues since I still have low rev misfire caused I'm sure by worn distributor shaft giving eccentric rotation at low speed. I can't keep throwing new ignitors at it though. (Loud sigh from Expedition Imports)

Tony

Checked my spare with a fluke 77, red to red and black to black 3M ohm, next red to black and red to black OL. Don’t know what that tells us, haven’t dissected one yet.

edzz wrote:Checked my spare with a fluke 77, red to red and black to black 3M ohm, next red to black and red to black OL. Don’t know what that tells us, haven’t dissected one yet.

Thanks Ed, just tested mine, 0L all round, so it looks like a problem with it. Back to the supplier it will go .......

Dave

Did you bother to pull the tops off the carbs and check float levels? That can and will cause stumbling and a feel kinda like a misfire under load off idle if it is too outta whack! Just a thought outside of the whole Petronix issues. Alotta times you have multiple issues and one is just mask'n the other. Good luck!

There are 2 things that kill igniters, #1 bad voltage regulator, they fail after 30+ volts, #2 reverse polarity(I have found 2 trucks with batteries hooked up backwards) and they started but had no dash warning lights lit This kills the regulator and blows all the diodes in the alternator
So check all connections if in doubt.

I am now having this same issue. Opened my distributor cap only to find lots of oily residue inside, yet it still idles. Ill start a new thread

Guys, I am by no means an expert, but I had issues with the dizzy, timing, hesitation etc, because the dizzy collar was stretched. I also found the teeth on the dizzy were worn because of the loose collar. It is easy to check and worth it. I replaced the end of the dizzy and she is now running great.


Sent from my Mobile

but still hesitates under initial acceleration, and the engine appears rough and vibrates as if out of sync, then it smoothes out as the revs climb.

This part of your description sounds like a bad idle solenoid. One at a time, pull the connector from each solenoid, allow it to run for a several seconds as it takes time to clear the fuel from that system. If you get one that gives no change, it is likely the culprit.