Engine Misfire - #2 not firing?

Engine troubles? Try here.
User avatar
Jimm391730
United States of America
Posts: 1456
Joined: Wed Apr 14, 2004 10:58 pm
Location: Idyllwild, CA

Re: Engine Misfire - #2 not firing?

Post by Jimm391730 »

I am now back to the original problem - the loss of power under load remains?
Poor spark can also give loss of power under load, even though the idle is still smooth and consistent. The reason is that the additional compression of fuel and air when the throttle is opened above idle "quenches" the weak spark. To check this, first measure the voltage of the + coil terminal (NOT the terminal that goes to the distributor) to chassis ground -- expect to get ~17V here during idle. If you have less, then the most likely culprit is the 4500 RPM box. This happened to me and I only had about 8V at the coil. I had smooth idle but no power, and even significant missing under load. If you get low voltage readings then unplug the RPM box plug (it has six terminals, two rows of three) and jumper the harness plug center terminal of one row with the center terminal of the other row. This disables all of the RPM box features and just gives full voltage to the coil and ballast resistor (the ballast resistor is why we get around 17V at the coil, and this is correct and expected).

You may not have any mechanical issues at all if the above is true for you. Let us know what you find. This should not dissuade you from doing valve adjustments and other "normal maintenance" work, they still need to be done if you expect a good running truck.
Jim M.
712W and 710M
User avatar
David Dunn
United States of America
Posts: 2274
Joined: Wed Apr 14, 2004 7:08 pm
Location: Arcadia, CA

Re: Engine Misfire - #2 not firing?

Post by David Dunn »

We adjusted timing and she run (idles) good at about 23deg
WAY TOO MUCH. try 8 to 12 btdc.
iirc correctly, the mechanical advance has 29 degrees of it own, you're probably over advancing the engine... it has been 12 years since I had a "spark" ignition Pinz :D
.
The Trojan Horse... the 1st Pinz used to covertly carry troops into battle .




ATL Pinzgauer XM 718K TUM(HD) 6x6 FFR (aka The Green Grail)
User avatar
edzz
United States of America
Posts: 1309
Joined: Tue Aug 11, 2009 12:13 am
Location: Coeur d'Alene, ID

Re: Engine Misfire - #2 not firing?

Post by edzz »

Factory ignition, engine cold 1-3 mm behind the point of the bolt, engine warm 0-2 mm before the point of the bolt.

If equipped with Petronix 7-10 bdc from Scotts video. At the very end.
Not Bad going from memory David. :)

http://www.youtube.com/watch?feature=pl ... ivi6tux690
Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.
User avatar
David Dunn
United States of America
Posts: 2274
Joined: Wed Apr 14, 2004 7:08 pm
Location: Arcadia, CA

Re: Engine Misfire - #2 not firing?

Post by David Dunn »

Crap Ed , that video was uploaded April Fool's Day, 2010 (wonder if there is a message in that? :P ) I had done both my 710 and 712 in 2001 and 2002, and experimented with advances up to 17°. The data from then may still be in the database on the Yahoo group. With a electronic timing light I had documented my distributor's advance at different RPM and the mechanical advance was "spot on" as the Brits would say. :D ... I then entered the era of the blue smoker Pinzes at the end of 2002, and never looked back. :mrgreen:... who would have guessed that I would end up with a Pinz that hadn't been built by then?. :wink: :D
.
The Trojan Horse... the 1st Pinz used to covertly carry troops into battle .




ATL Pinzgauer XM 718K TUM(HD) 6x6 FFR (aka The Green Grail)
User avatar
Maxf
Norway
Posts: 14
Joined: Wed Sep 22, 2010 4:32 pm
Location: Reno, Nevada

Re: Engine Misfire - #2 not firing?

Post by Maxf »

Friends,

Belated Kudos to "Stekay" above. It was sticking dist weights. Unfortunately I didn't even remember they were under there and [stupidly] thought that the Pertronics hall sensor upgrade had removed the, But low and behold when we extracted the pertronics point plate there they were. All red and rusty. The spring was weak and the action was mostly spin out and stick. Maybe that was why she was 24deg BTDC - compensating for stuck-ness. Now she's running at 10deg with a slight hesitation on revving.

Anyway the night before the veterans day parade we got a spare Dist base unit with much better advance mechanism [w/o rust], R&Red it and she started fine right away.

Many thanks to Kurt for his spares and mechanical help.
Thanks,
MaxF

1973 712m Reno NV USA
"The difference between theory and practice is much greater in practice than it is in theory"
User avatar
Maxf
Norway
Posts: 14
Joined: Wed Sep 22, 2010 4:32 pm
Location: Reno, Nevada

Re: Engine Misfire - #2 not firing?

Post by Maxf »

Friends,
A quick follow-up.... I am at 90% of normal, but she stalls when I throttle up at a stop light.
Do I need to advance my distributor, or do I need to retard it? to get the best power/acceleration for a standing stop?
Thanks,
MaxF

1973 712m Reno NV USA
"The difference between theory and practice is much greater in practice than it is in theory"
Post Reply