Back From The Dead... Almost

[Austin Merritt]

Hey everyone, I'm new to this forum, and relatively new to the hobby. I have a Duratrax Maximum BX Buggy that I am in the process of resurrecting. Before I get all the "Stop, it's old and not worth it" replies, I'd like to say that I've had this for about 7 years now. Maybe 8. My dad bought it off a guy he worked with and brought it home out of the blue one day when I was younger. We ran the thing so much and had a blast with it, but then the pull starter broke and it sat for a while and we moved to a new state and it got forgotten in a box for the last four years. So that is why I am putting the effort into fixing it instead of buying a newer, nicer car.

The car has a Torq .16 engine on it. The engine IS free, even after sitting for so long. My dad and I put a Tiger Drive on it after the pull start broke, but I don't think it has ever successfully started the car. I took it to a local shop and they did a compression test, which showed around 50 psi. That sounds good to me, and the guy who runs the shop said that is fine. I cleaned the carburetor and put a new O ring on it where it attaches to the... I guess engine block? No leaks, and it is set to the Duratrax recommended settings. Brand new glow plug. Fresh Nitro. However, I cannot get the car to start!

I am using a Makita 18V cordless drill to try to start it with the tiger drive. The fuel appears to be going in the right place when I open the throttle and watch when I prime it. I've tried heating it with a heat gun. I've checked the igniter I have with the new and used glow plugs I have. They are all bright orange.

Any ideas on what else may be wrong with this? Anything I have missed that might be the cause of it not startring? I've been watching videos and reading a lot of things about the no-start issue and they all seem to say the same things.

Any help/advice is appreciated!!

 

[hotrodrob]

Is your carb gap set at about 1mm?...it could be closed all the way,did you clean the needles and passages when the carb was apart?

 

[Paul]

Tough one. Is the enging firing while the drill is turning it over? You say that fuel is being drawn into the carb? In otherwords it primes and SHOULD be ready to start? Exhaust is secured firmly to the engine? Then of course HotTodRob makes a really good point regarding the carb barrel, if its closed all the way the engine will not start.

 

[Rolex]

The first thing you do next is to drop some fuel directly into the carb. Keep the filter off. If it starts and runs but stalls after that small amount of fuel is spent, you either have too small of a gap or the LSN is clogged and needs to be removed and cleaned out.

 

[Paul]

Just a thought...Also want to make sure that the hole in the HSN is lined up correctly to allow fuel to pass through.

 

[Austin Merritt]

I have it set to about 1-1.5 mm, as that was another thing I read to do. Is it possible some of the screws that hold the engine together may be loose, or even passages in the engine are clogged up and keeping it from working properly? When I cleaned the carb I did make sure all the jets and needles were clear. That doesn't mean I dislodged some dirt and it clogged up somewhere else and I need to try again, but they should be good. I can hold it at wide open throttle and look in the carb and see fuel going down into the engine, I wonder if it still primes correctly with the throttle closed? It has never even coughed or attempted to fire yet, so I am thinking it is still a fuel delivery issue. I will try pouring fuel straight into the carb. See if I can get it to burp or anything.

I also wonder if my drill is turning it fast enough. I have it set as fast as it can go, and it has plenty of torque to turn it. I do have a new piston, piston pin, and connecting rid. I could take a crack at opening up the engine to see how the inside looks, even though it isn't seized up. Worst comes to worst I can just rebuild it with the new piston. Obviously that is kind of a last resort, but I would not be scared of tackling that.

 

[Greywolf74]

have you tried setting the needle settings back to factory?

 

[Paul]

Did you remove the HSN at any point?

 

[BamaFan]

Your drill is plenty fast enough even on low to crank the engine. It doesn't take much speed. Honestly sounds to me either your carb is clogged up, your sucking to much air from somewhere, your lsn is way to lean or your glow ignitor isn't getting the glow plug hot enough. I would set the needles back to factory and go from there. Do like Rolex said and dump a small portion of fuel directly in the carb. If it still doesn't even try to fire it's almost got to be in the glow plug or igniter. If it fires then it's in your fuel take, fuel lines, or carb.

 

[Paul]

Did you set the carb slide to the 1mm gap while the venturi was installed? If so remove the venturi from the carb inlet, set your gap and replace the venturi. When you are setting the gap, have your radio system on and go full brake. Make absolutely sure there is no change, none, zip, zilch, in the gap. Actuate the throttle back and forth making sure that the slide ALWAYS returns to and stays at the gap you've set. Something else you may want to look into is that all of the associated settings in your transmitter good (endpoints and such).

 

[Paul]

You asked about the other screws on the engine for the head and back-plate. Yes those could be an issue and would cause major headaches if not tightened properly. Make sure they are TIGHT and each tightened equally one after the other down to just barely snug. Then start to put some effort into the final turns but do a bit on one and then move to the next in a crossing pattern down to the final turn. If you're gonna take the back-plate off and re-seat it, might as well grab some high temp RTV and seal it (be sure to let the RTV cure over night). An improperly tightened glow plug can also cause major headaches. At this moment in time I have an inexpensive Traxxas glow plug and the washer it came with is bowled on one side to fit the hot end of the plug. To seat the plug properly I had to tighten it beyond what I felt comfortable with which wasn't the case with the flat washer of a different brand, engine wouldn't run at all initially..I will say this though, the Traxxas plug has preformed really well for me...REALLY old fuel?

 

[Austin Merritt]

I did have the HSN out. It was all clean when I put it together, and it is back to factory specs. All of the needles are set to factory. The gap is set so that it doesn't move at all when I brake it. The fuel was brand new when I bought it a couple weeks ago. I think he said it was 30% fuel, but it was all he carried in the store and he seemed to think that is fine. What do the percentages mean with regards to fuel? I've read that 20% seems most common in racing these cars. I haven't had a chance to try pouring fuel straight in it yet, I will update you all once I do that.

Edit: I have also suspected the ignitor since it is a simple C cell battery type, but I have a whole pack of batteries to keep it fresh and fully powered! I'll see what I can do with the fuel straight in the carb before I start looking into that though.

 

[Paul]

Are you feeling bombarded with questions and different solutions? Do you feel like you've tried everything and nothing is working? Stop, reset, and start over. LOL Bottom line is that if the crank-case is seeing fuel, the engine is turning over, and the glow plug is getting hot, there will be combustion if not but for a small number of causes. The crank-case is getting flooded, in which case the piston will almost always get stuck and the flywheel will be extremely hard to turn. Empty the engine of fuel by removing the plug and turning over the engine a bit (preferably holding the car so fuel doesn't spray you in your face). You are getting to much air in the mix and bad compression. Backplate isn't tightened properly, head isn't tightened properly, glow plug isn't tightened properly, carburetor isn't set up and or tightened properly, exhaust not seated properly. If the air leaks/bad compression issues are small the engine will typically still run but you will have trouble getting the engine to hold a tune or stay running for long. One more thing that just sprung to mind, when you turn over the engine with your drill, are you sure it's engaging the crank and actually turning over the engine? Try this, do not prime fuel to the point of it hitting the HSN nipple, turn the engine over with finger over exhaust, does the fuel move into the carb?

Even without finger over exhaust the fuel should still move, albeit more slowly.

Edit: I have also suspected the ignitor since it is a simple C cell battery type, but I have a whole pack of batteries to keep it fresh and fully powered! I'll see what I can do with the fuel straight in the carb before I start looking into that though.

If in doubt take the plug and check it with ignitor off engine, if it glows then it should be good. Does your ignitor have the locking mechanism where it attaches to the plug? I don't know if ignitors have always had this but I could see really old ones not having it and so maybe the ignitor isn't maintaining contact with the plug while you're trying to start the engine.

The percentages are related to the amounts of nitro-methane and lubricant (caster oil, synthetic blends) in the fuel. People will tell you that you should use hot plugs with lower nitro percentage fuels and cold plugs with higher nitro percentages. Doesn't matter which percentage fuel you're using though (or plug for that matter), the engine will still fire up if everything else is in order. I don't really know anything about turbo plugs, think I read if you don't have a turbo head you can't use turbo plugs or something to that effect, don't quote me on that though.

I do know there are some different size plugs that if not used with the right number of head shims the filament end of the plug can make contact with the piston head preventing combustion.

 

[Paul]

Right now I'm running 30/11 Byrons. That's 30% nitro and 11% lube...Higher number is always the nitro content unless it's maybe some home-brew stuff or some other nitro fuel I've never heard of. Does the fuel jug have a label on it? lol

Should have said.....If you are priming by blowing into the fuel pressure line try letting the engine prime its self by only turning over the engine to see if the fuel moves through the line.

 

[Austin Merritt]

Haha, Being bombarded with questions is why I came here! I ran into a wall on my own and wanted as many third and fourth opinions as possible!

When I hold my finger over the exhaust, it does move fuel to the carb as it should.

As I stated in the first post, it has 50 psi when checked at my local shop for compression. It has a nice pop when turning it over, so I don't think the compression or an air leak is my problem, but I won't rule anything out at this point! Does that sound like a reasonable number for compression? I don't know what these small engines should make, I have specs I can look up for my cars and ATV's, but this is a little different!

I did drain a lot of crap out of the engine. It looked like some old fuel may have still been hiding in it when it sat (old fuel was pink, new fuel is blue. Stuff I drained was slightly pink) but it is all cleared out now. Also, I have always been able to turn it by hand with a nut driver on the bit for the drill. If it were flooded I would expect I would not be able to turn it by hand. I noticed it looked like an extra washer was under the glow plug when I took it out last time. I wonder if it is a very old washer that is stuck to the head...? I'll see if I can clean that up and get a good look at it. Maybe the glow plug is too far from the piston? Doesn't seem very likely, but possible.

 

[hotrodrob]

Get yourself a good quality igniter,those c battery ones are junk, could be part of the problem,a bad engine flood can screw up a glow plug,...do you have the proper glow plug

 

[Paul]

I noticed it looked like an extra washer was under the glow plug when I took it out last time. I wonder if it is a very old washer that is stuck to the head...? I'll see if I can clean that up and get a good look at it. Maybe the glow plug is too far from the piston? Doesn't seem very likely, but possible.

I think that having two washers for the glow plug would be bad. Definitely only use one washer for the glow plug and possibly 2 head shims when using 30% nitro, I'm using one head shim with 30% and its fine.

As I stated in the first post, it has 50 psi when checked at my local shop for compression.

How was the compression checked? Is that 50psi in the space between the piston deck and head when at TDC? Or just how much pressure the crank case can hold before leaking air? Not being facetious just curious how they arrived at 50psi and exactly how they measured that. I have no clue what a typical rc nitro engine's compression ratio is or how much force should be measured as the piston cycles from BDC to TDC. Anyone?

 

[ninnon]

Try these
1) Put fuel directly inside the engine, replace the glow plug, see what happens
2) Try some newer different fuel.
3) Double check the head screws
4) Check whether it is sufficiently primed
5) Check for air leaks in the tank
6) Check idle gap is open
7) Try blipping the throttle whilst starting

 

[Austin Merritt]

I have no idea if it is the "proper glow plug", it is just what the guy at the shop sold me off the shelf... I did not know there was a huge difference in the plug.
I don't really want to buy more fuel yet because I just bought this when I started trying to resurrect this car a couple weeks ago...
Are there any good quality igniters that are not super expensive? Like closer to $10? Money is hard to come by for college kids like me!

The compression was checked by screwing a gauge into the glow plug hole and turning the engine with a drill and seeing what the gauge read.

 

[Greywolf74]

A decent quality ignitor probably starts at about $20 but as long as the one you have now is making the plug glow a nice bright orange color its probably fine to use until you can afford a better quality one. As much as I hated the stock one that came with my LST2 it worked fine until I could get one that I felt was good quality.
THIS is probably along the lines of what youd want but you can also do what I did and I ordered a 4500mAh NiMH sub c to replace the 1800mAh stock battery in my Dynamite ignitor and I replaced the D battery in my OFNA ignitor with a 10,000mAh D battery. If I ever had to replace one though Id most likely go with one that has a lipo in it like the one in the link.