Strange dying problem

[Piston]

I was out with the truck today and noticed a wierd problem starting up. When I land the truck of a 3ft jump and it hits a bumper or on its top, the engine will die. It immediatly restarts with no trouble and takes right off as if nothing ever happened. I assume its the jolt affecting the piston/rod movement for a split second causing it to stop?
It dies the exact same time it hits the ground... I wonder if the engine is getting a little low on compression and its just not a strong idle, I dunno. It does seem to happen more when I'm not on the gas as it lands.

Glow plug is new and lighting up as it should, this was my first thought since I was having a hard starting issue too. I replaced the glow plug and cured the starting problem but the dying problem is still there.

 

[RatzoRC]

Take off your air filter and see if you can push the carb closed. Your Idle stop adjustment might be off. Or, you may have cracked something.
Check all around for a possible loose carb screw (that holds the carb on the engine), or crack in the block, gas tank, back plate, fuel line, ETC.
If a jolt is killing it, you might be sucking in air when it hits, or maybe the mill needs a rebuild.
How many tanks are through the engine?

 

[Piston]

I've run about 6 tanks through it so far.. it was used when I got it.

I'll check the carb linkage and idle settings, thanks.

 

[olds97_lss]

You also might want to check for a broken or cracked motor mount. I had that on one of mine. On rough landings, the gear mesh would get so tight it would stall. And it was moving enough to drive the crankshaft tip into the trans case, which was probably also making it stall.

 

[hb1111]

i had a problem simular to that evertime my car would flip or crash it would die but on the straights it was fine...then i found out my clutch shoes were mushroomed (aluminum)and one of the pins that hold the shoes were loose so everytime the car would come to a low idle it would die due to the friction on the bell you might wanna check your clutch

 

[Piston]

Well its still there and I'm thinking more about the compression problem.

The wierd thing is, I've got the idle screw all the way in and it still is a bit low on the idle. I leaned out the LSN which helped.. it was too rich. Then dialed in the HSN to get top end performance back, its running really well right now as long as you don't slam on the brakes or bounce of the front bumper on a jump.

I kept thinking it was a tuning issue so I took it back to basics 2 times then adjusted out from there with the same results. I wonder if I don't have a backing plate leak causing the low idle issue. Either way, it doesn't feel like it has great compression, its harder to tell now that I've installed the rotostart but before that I could pull the cord and not lift the truck off the ground.

Today I disassembled the whole truck to install the new dual disk brake mod, and new side plates with stainless steel bolt kits. I can't believe how this thing stops now LOL good gawd man, it sounds like a hound dog if you apply full brake (all 4 lock up and skid), only problem is whenever I do this it dies... every single time.

 

[canadian-mgt]

have you pressure tested the engine for air leaks? maybe you have a crack in the engine crankcase that's opening up when you hit something or have a sudden jolt.any signs on the heatsink of the engine having hit the ground? scratches,bent fins,ect.maybe you could try moving the engine around by hand or lightly tapping on it or the tank with a screwdriver handle to see if you can jolt it into stalling.just some ideas :shrug:

 

[ZANDOR]

So you say that the idle is screwed in all the way..thats not right have you taken off the air filter? and looked down the carb to see were the slide is.

 

[Piston]

I'll have to take another look at it tomorrow, I can't remember for sure but it does move in a ways if you back the idle screw out.

one thing I forgot, a week ago I was running pretty hard and the air filter fell off. then later the glow plug shot craps... I didnt realize the filter fell off until it wouldn't run right (this was all in the same session).

The idle screw has always been all the way in since I got it (used).

 

[Rolex]

A whole 'nuther story. You got dirt in it. Tear it down NOW !!. Clean the internals of the engine, piston and sleeve, and remove the carb and the needles and clean everything thoroughly and blow it out with an air hose. Do it before you try to run it again.

 

[Piston]

I should probably go ahead and get a new piston/sleeve since its compression feels low and would have scratched the cyilnder walls with the dirt/debris. I totally forgot about the air filter incedent until tonight... thats about when all this started too.

hindsight is 20/20 eh...

 

[hb1111]

you probably be better off rebuilding it anyways at least you know how much fuel has been though it for future refrences

 

[olds97_lss]

You may save yourself some $ in the long run if you just replace the engine. If your filter was off that long, you may have some crap in your main bearings as well. After you buy a new con-rod, piston/sleeve and bearings, your probably pretty close to if not over the price of a new engine.

The only time I replace a piston/sleeve is when I know how the engine was maintained and ran in the first place. If you bought it used, I'd have to say it would be a good idea to start fresh.

 

[Piston]

I agree with ya on that one, there are just too many variables that are not known when its used.

I did some playing around with it today... took the carb apart, cleaned and inspected every thing then took the backing plate off and inspected / sealed that area. Nothing out of the ordinary though.. everything looked ok.

I reset the needles back to a break-in setting then started dialing it in from there. My idle didnt not change, seemed low even though the screw is all the way in. It also still dies when returning to idle quickly... I also noticed a strange midrange "bobble" as it runs through the rpms, eventually it would die during this area too. I'm thinking what the hell is going on with this setup, I've got to be missing something there! Thats when I thought about what was actually happening. It was running "ok" but didnt sound clear. I mean it was close but it just didnt have a clean sound to the exhaust so I decided to take a quick run around the lot with the glow starter on it and TADA!!!!! Idle increased, no more dying problem and no more midrange bobble. It's 100% kicken' arse as long as the glow starter is left on. The second you take it off, the idle drops down and it doesn't sound clean/crisp when you are on the gas.

I think the LHS gave me the wrong glow plugs or something. This problem started after the air filter incident, remember I had replaced the glow plug at that point because it would not start or run at all.... so I bought 2 new plugs and I've been fighting it ever since.

Now I realize a rich mixture will do this too but I've had these needles all over the place and nothing changes the basic poor idle and midrange problem it had... I'm headed to the LHS right now to see if what they sold me was incorrect.

Sorry for the long post but I figure it might help someone searching the forums with this exact problem.

 

[olds97_lss]

I don't think you ever posted the engine make that your dealing with. I'd suggest running an OS #8 on anything that's a 21-28 engine. Especially if your running 20% fuel. I noticed that with the #8 plug, I get much better performance out of my 21 engines than running a colder or hotter plug.

Do you know what kind of plug they gave you?

 

[Piston]

I sure don't. I tried to look on the plug but I see no markings and I can't find the package . I relied on the LHS's knowledge... anyway

It's a stock engine in a Savage 21.

 

[olds97_lss]

If it was an OS #8, you would see a 8 on a flat spot of the nut portion of the plug. In fact, I think OS put's their number on all their plugs, so that probably rules out it being an OS plug.

Like I said, try an OS #8, they work like a charm for me in my 21's. (omega 21 and OS 21 RG)

Someone else may have a better clue for that specific engine though.

 

[Piston]

well imagine this... I just called the LHS and talked to the manager there. I mentioned how it ran outstanding with the glow starter on and that both glow plugs acted the same way and all the sudden I hear a big sigh and a pause... "Did ******* sell you those plugs?" Yep I said. "Well bring them back in and we'll give you the right ones, we're so sorry this happend" then a big pause... " AGAIN " lol. appearently ***** was handing out the wrong parts to alot of ppl lately and I happen to be one of them.

at least I know my truck intimatly now that I've been through ever part of it LOL.

 

[olds97_lss]

That's cool. Not many places would do such a thing.

I hope it works out for you.

 

[Piston]

*Update*
Just got back from the LHS with a new set of glow plugs... I Have no idea what that kid sold me but I came home with the McCoy MC-8 (its what they wanted to swap for) and this truck is now a live wire!!!

It runs perfect. I had to retune again. Idle was too high, mixture was too rich all the way around so I spent half a tank of fuel tuning and its all good now. It's perfect! all I have to do is tap the button on the rotostart and its ready for action.

Amazing eh? all this trouble because of a improper heat range glow plug.

Thanks for all the suggestions guys, I do appreciate the help.