Running rich. How to "lean out?"

Engine troubles? Try here.
Twin Pinzies
Posts: 545
Joined: Mon Jan 03, 2005 1:33 pm
Location: San Juan Mountains, CO

Re: Running rich. How to "lean out?"

Post by Twin Pinzies »

Hotzenplotz wrote:
Twin Pinzies wrote:...but they still foul plugs. (WTF?!)
I'm now fussing with my float levels (they were high) to try to solve the continued fouling problem.
Have you converted to civilian ignition ? What make and model of spark plugs do you use ?
I have a civilian setup and use NGK BKR6EKC in the Alps betwees sea level and 2700 meters altitude.
I have civilian ignitions and run the same NGK plugs that you do. I've also tried running Bosch plugs and had the exact same problem. (I use 20w50 oil too)
The thing is, my trucks run PERFECTLY as long as they don't do any steep descents. My fouling spark plug problem is somehow directly caused by long, steep descents.

Through the process of elimination, I plan to finally solve this nagging issue. :x
So far I've swapped in the correct jets, balanced the carbs, and adjusted the float levels... which has helped them run better... but I still need to pull and clean the plugs (on BOTH of my trucks) every three days! If not, my trucks will end up running on two or three cylinders right after a long descent... until I pull and clean the plugs again!!

They (both trucks) have never (ever) acted up after driving uphill or on flat terrain.
pinzinator
Posts: 917
Joined: Thu Jul 29, 2004 3:12 pm
Location: Indio, California

Re: Running rich. How to "lean out?"

Post by pinzinator »

Could it be oil fouling instead? Oil could be getting past the rings and/or valve guides in a high RPM/throttle closed situation. Oil is getting sucked in while the plugs are running cooler temporarily, this fouls the plugs. Pinzgauer engines run much cooler downhill, the heater reveals this fact especially in winter.
User avatar
pcolette
United States of America
Posts: 1614
Joined: Sun Dec 10, 2006 7:38 pm
Location: Southwest Wisconsin

Re: Running rich. How to "lean out?"

Post by pcolette »

I would consider installing the PinzSSI ignition on one of your trucks and see if that solves the plug fouling problem. With hotter and multiple sparks (3), I think you'd get more complete combustion and less unburned fuel to foul the plugs.
Paul C.
_________
'73 Swiss 710M
'89 Puch 230GE
Twin Pinzies
Posts: 545
Joined: Mon Jan 03, 2005 1:33 pm
Location: San Juan Mountains, CO

Re: Running rich. How to "lean out?"

Post by Twin Pinzies »

pinzinator wrote:Could it be oil fouling instead? Oil could be getting past the rings and/or valve guides in a high RPM/throttle closed situation. Oil is getting sucked in while the plugs are running cooler temporarily, this fouls the plugs. Pinzgauer engines run much cooler downhill, the heater reveals this fact especially in winter.
The plug's electrodes become black and sooty not shiny and oily. So isn't that a fuel issue rather than oil? Also, if it were worn rings and or valves, why would both trucks act exactly the same? I wouldn't expect both trucks to have the exact same symptoms in that case. Unless it's a HUGE coincidence that BOTH trucks just happen to have the same worn rings and valves... at exactly the same time as each other.
Whatever my problem is, the symptoms are happening at the same rate... to both of my trucks... at the same time. Weird!

P.S.- Both of my trucks came straight from the Swiss Army, are the same model, same age, same condition, and have had the exact same maintenance done to each of them over the past 11 years (for consistency and continuity).
JimmyC
Posts: 217
Joined: Tue Feb 18, 2014 4:59 pm
Location: Lafayette, LA and Highlands, NC
Contact:

Re: Running rich. How to "lean out?"

Post by JimmyC »

You might try the next hotter plug. When a motor is not producing much power (like when you are going down a hill) the exhaust temperature gets low and the plugs get under the design temperature and soot up. The hotter plug does not make a hotter spark. It just stays at a hotter temperature because the heat path is made longer. You have to get up like 850 degrees for the carbon to burn off, but if you get up like 1500 degrees the plug get eaten up and you might get pre-ignition or knocking. You just have to experiment, like go from a 6 to a 5 and see how that works, then maybe try a 4.

http://www.ngk.com/learning-center/arti ... otter-plug
Jim Chance
710M

All my post fully incorporate the Dunning-Kruger effect
JimmyC
Posts: 217
Joined: Tue Feb 18, 2014 4:59 pm
Location: Lafayette, LA and Highlands, NC
Contact:

Re: Running rich. How to "lean out?"

Post by JimmyC »

I have been studying up on emission problems (stench and eye burn) when engine braking and came across something that may be useful. There are emission problems during engine braking because the intake manifold pressure is so much less than the exhaust manifold pressure. When the intake valve opens the exhaust gas can flow up into the intake manifold than bake into the cylinder when the piston goes down. The result is a combustion charge that is mixed with exhaust gas and burns poorly.

One solution is to shut off the fuel flow when the vacuum is higher than idle. The pinz has anti diesel solenoids so all you need is a pressure switch (I am using the Dunning-Kruger Effect here).

I am thinking about implementing it for mine as I am adding a catalytic converter and do not want to overload it. One thing that I found is that on my truck idle vacuum is like 17" or 18" and engine braking is barely above 19" - pretty close together to do any sort of switching. I will be fiddling with it in the next few weeks.
Jim Chance
710M

All my post fully incorporate the Dunning-Kruger effect
one2many
Australia
Posts: 178
Joined: Sun Dec 22, 2013 5:53 pm
Location: Melbourne Australia

Re: Running rich. How to "lean out?"

Post by one2many »

This might be way off but just a thought...do you buy your fuel from mostly the same petrol station or chain? I agree that sooty plugs would generally indicate a fuel issue over an oil one, prolonged idling could also cause sooty plugs. And it is odd that both your trucks have this same issue...indeed it would be a huge coincidence for both of them to have simultaneous valve or piston ring issues, however checking your valve clearances should be included in any pinz's routine service schedule and couldn't hurt any to check.

Where I'm from (down under) it is not unheard of for dodgy fuel vendors to dilute their petrol with all sorts of nasty things in an effort to make an extra dollar, occasionally this causes havoc with peoples cars and about once a year a current affairs TV program will have a random sting operation where fuel is tested and many service stations get caught out.

After reading about your strange ongoing plug fouling problems in two trucks simultaneously I thought that dodgy fuel or additive could be an explanation, that is if you get your fuel from the same chain of service stations.

I just thought I would put it out there as a possibility, I hope it helps.
1985 pinzgauer 712K factory 2.7lt civilian (RHD, 4 door K)
1979 Volvo tgb 1314a (under construction to om606 diesel/722.6 trans. Dual cab/tray)
Pinzcat
France
Posts: 21
Joined: Sat Jan 24, 2015 4:53 am
Location: France, Evian

Re: Running rich. How to "lean out?"

Post by Pinzcat »

Long, steep descents are not so frequent: a good solution could be to implement a manual switch, in order to cut the solenoids when descending?
ExpeditionImports
United States of America
Posts: 436
Joined: Wed Apr 14, 2004 2:53 pm
Location: Vallejo, CA
Contact:

Re: Running rich. How to "lean out?"

Post by ExpeditionImports »

At 9000-13000 feet, 125 main jets are still too large. Given your use, and the fact you have 2 trucks running at significant altitude, I would either pay to borrow someones "sniffer" and actually see what your exhaust numbers are. Or trial and error.

I don't have much experience tuning for above 7000-8000. However, when we are tuning for this elevation, (Sierras) we are most often running 125 main jets. I would bet in order to get proper burn you are going to need to get down into the 115 range.

A hotter heat range on the plug may be helpful. NGK has a decent article on their plugs here: http://www.ngksparkplugs.com/tech_suppo ... p?mode=nml

Cheers,

Scott
Expedition Imports Corporation
Vallejo, California
www.expedition-imports.com
"You didn't buy a Chevy..." "Hows that Amazon tech support working out...."
Twin Pinzies
Posts: 545
Joined: Mon Jan 03, 2005 1:33 pm
Location: San Juan Mountains, CO

Re: Running rich. How to "lean out?"

Post by Twin Pinzies »

Thanks everyone. It seems that the 125 jets helped my trucks run better/smoother, but didn't solve my fouling-after-descents problem. Scott, I think you're right.

I realize that my case is really rare... running at super high elevations with long/steep descents (4,600 feet in only 8 miles).
I've already changed the jets, tweaked the float levels, use the thickest oil available, and tried hotter burning plugs.
Next I'll try the solenoid cutoff idea and maybe get the piston rings and valves checked after that.

JimmyC's clue about the exhaust getting sucked into the engine just might be it too. After all, my carb internals DO get a little sooty, and that would make total sense!

Luckily my touring season just ended so now I have all winter to figure this out while the trucks take a long break.

Thanks again dudes.
User avatar
JungleJudah
United States of America
Posts: 17
Joined: Sun Oct 06, 2019 11:27 pm
Location: Jemez Springs, New Mexico
Contact:

Re: Running rich. How to "lean out?"

Post by JungleJudah »

Thanks for the information on this post. I just moved from 600' elevation to 8000' (northern NM, should be mostly operating between 6000'-8300') and truck is not driving well. I am planning to change out my jets as described in this post.

Can you please confirm what I need to order (from SAV)?

Main Jet 125 Carburetor Zenith NDIX 36. Part No: 7001084041-25
https://swissarmyvehicles.com/pinzgauer ... th-ndix-36
How many do I need to order?

Idle Jet 55 Carburetor Zenith NDIX 36. 7001084051-55
https://swissarmyvehicles.com/pinzgauer ... th-ndix-36
How many do I need to order?

Do I need any ""Idle Air Jet 110 Carburetor Zenith NDIX 36" or 130?
Do I need any "Air Correction Jet 170 Zenith NDIX 36" or 230?

And how do I install? simply open the engine cover and find these parts and replace? And then do I need to make adjustments?

Thanks!
pinzinator
Posts: 917
Joined: Thu Jul 29, 2004 3:12 pm
Location: Indio, California

Re: Running rich. How to "lean out?"

Post by pinzinator »

I recently set the floats in my Zenith carbs, the needle valves in each took 2-1mm shims. Shims come in .5mm and 1mm thickness. When you add shims, the fuel level will drop 4 X the thickness of the shim. 1mm shim = 4mm fuel drop.
I found it easier to measure the fuel level in the bowl while I was verifying the shims. Use a small ruler and mark off 18.5mm. I was able to get it exact and the engine runs great now.
I had installed 2 new float assemblies that I bought from Scott, which is actually 4 floats total. There is a float for each barrel.
You can remove the top by removing 5 screws and the accelerator pump rod at the upper arm. Angle the top right and the arm will come out and go back in. Leave the fuel line connected.

float adj.jpg
float adj.jpg (112.62 KiB) Viewed 2099 times
Post Reply