usmc1975

Hi All :
Just got the truck started (break in - only one tank thru). Seems to run until I pull the glowplug igniter then usually dies 5 secs in. Occasionally, the truck will stay running until I give it some throttle then it dies right away. There is fuel spitting from the exhaust. I assume my LSN is to rich and maybe the HSN as well. It is approximately 60 degrees outside. Your suggestions are appreciated. Thanks in advance!

BTW:Using Blue Thunder, which I will change after I finish up this gallon.

LST freaky

slightly lean out the HSN set to factory settings or 3 out on each and go from there

SublimeJason

During Break-in, Its normal to use a Few Glow Plugs,
Because the Engine is being run so Rich, So grab a few spears and Keep going,
I use OS#8 and find its a Good Plug and last for a long time.

25trxxz

Semper FI,
If its spitting fuel its to rich.I'm sure you have figured that one out.I've ran into the same problem.Temp does have alot to do with it,but as we know we have to keep it running.Go to hotter plug,and or a medium hot. Got to try something.

USMC1976

crusher1

Try leaning out the LSN a tad and increase the idle as well. The bottom end is loading up on fuel thus your flame out. You should still see some raw fuel spitting out of your pipe while breaking in your engine that is a guarantee it's still rich Hope this helps.

usmc1975

Hi All:
Thank you so much for your tips and suggestions. The glow plug was fine. I needed to lean out the low end needle approx a 1/4 turn from the factory recommended. This fixed the throttle problem. I also leaned out the HSN 1/4 turn, because the temp was about 150 and I wanted it near 200 for break-in. Over the weekend I will start to tune the engine after running my 5th tank thru it. The pinch-test will be used for the LSN (3 to 4 secs then dies) and for the HSN I will try to peak the temp at 240. Does this idea sound okay? It amazes me how fast the truck became with every tank thru it (4 so far). Again thanks for all your help!!

Nitronutt

My Feedback: (2)

First, tune your HSN for perfect performance - Listen for Max RPM adjust in 1/8 increments and make 50-75 foot WOT passes (After break-in of course). Listen to the engine. Try leaning the HSN 1/8 turn. Run another 75' WOT. Did the RPM's go higher? Go another 1/8. Lower? Go back the other way. When you achieve max RPM, then richen by 1/16 turn. This is the optimal HSN setting. Verify the temperature after you tune it. It should be in the 240-260 range. If it is radically higher (Near 300 or above), then chances are that your engine has an air leak. When you have achieved the optimal HSN setting, proceed to the LSN as stated below.

LSN TUNING 101 (By Frost)

There is NO HARM in running the the S25 up to 270F or so as long as it isn't lean (stuttering/lean-bogging).... They guys on another forum have been performance tuning vs. temperature tuning with interesting results. Their engines are running as long as those who were obesessing over lower temperatures, all the while the performance tuned engines were SCREAMING.
Tune for performance, forget the gimmicks, go with what works.

If you are already getting good top end and you are running at 250F or so and not lean, (if you haven't bought a 20 dollar temp-taker DO IT) here is what to do to get SNAPPY response, this is what pulls wheels and gives you that GREAT take-off:

1. Since off the line "snap" can be given or taken away by being lean OR rich on the LSN the first move is a guess (well it won't be after you get a feel for it, but this will get you going quickly)...

2. Pull the truck up in front of you and let it idle for 8 seconds. Then pull the trigger to WOT... Did it scream and take off? If no:

3. You have to go one way or the other... choose richer or leaner (suprisingly to many beginners, off the line stutters can be caused by too lean conditions just as easily as too rich) and turn the LSN in that direction 1/16th of a turn. Make a short pass at medium to high throttle and return the truck to in front of you.

4. Let it idle 8 seconds and floor the throttle. Did it take off better or worse? If better, turn it a 1/16 in the same direction, if it got worse, turn it 1/8th the OPPOSITE way. Either direction you started in, now you will be going one way based on whether it got better or not... either richer or leaner.

5. Make another short pass at medium to full throttle (AFTER you made the change to the LSN) and return the truck to you. Let it idle 8 seconds and floor it. Is it still getting better? If so, continue to lean or richen using the pass/idle 8 seconds method until you lose preformance and back up a step...

If your temps are in range this is how to quickly get your truck to "explode" off of the line... Always make the pass to clear out the engine and then let it idle 8 seconds. The idling will allow it to either lean out or load up, depending on which way the current settings are off... Get the hang of this and your truck can really take off. If you end up leaning the LSN out excessively make sure to keep an eye on temps, your top end needle may need a bit of enrichment.


For some reason even in the mags when they tell you how to tune they have you pinching the fuel line and timing the result to "set" your LSN. No doubt this is a good way to get in the ballpark, but it is FAR from precise.

bentgear

Nitronutt, what the pinch test would do is let you know if you need to richen or lean the low speed screw without having to guess the first time. Hint, if you pinch it at the carb at idle and it keeps running for several seconds, start adjusting it to the lean side. If you pinch it and it immediately dies, richen it up a bit. Then do your wide open takoff.

Ed M.

MrBillUp

2 bottom threads!! STICKY's!!!!!!!![sm=thumbup.gif] Great advise guys!! Im gonna follow these steps to the letter!!

Nitronutt

My Feedback: (2)

Bentgear, with the pinch test, I can get about the same results in 1/4 turn of the LSN (Making the test not overly accurate)!!! I'm not saying it gets you close, I just saying that it isn't the end of LSN tuning. If you don't want to guess, start at the factory settings and obviously tune more lean!

usmc1975

HI Nitronutt:
Thanks for your suggestion. Just started to tune the beast and hit a curb and broke the a-arms. Will replace them tomorrow. Your help is greatly appreciated. Semper Fi !!!

Nitronutt

My Feedback: (2)

...Do or Die!

Those pesky curbs - always jumping out in front of ya. Try a parking lot...after the store closes, but before they shut off the lights.