I've been working on this Savage 4.6 for 3 weeks and I can't get it running, help!

[FreezeCtrl]

So I've decided to get my Savage 4.6 running again and it's been nothing but problems

At first, the engine wouldn't crank with the roto start, so I toke it apart and found the starting spring was broken, switched it out no problem there, cranks great now
While taking the engine apart I decide to seal it using RTV silicone copper, again no problem, pretty straight forward

Got it back together, and it is impossible to start, I got it once in like thirty minutes but it was running super poorly, open throttle barely moves it forward then it dies right away. Found that my fuel tank was leaky so replaced the o rings, it now no longer leaks.

Things I have tried up to this point
New fuel
new glow plug
new glow driver
new different glow plug
new fuel lines
having the carb needles at stock
changing the carb needle slightly
cleaned and re oiled the air filter
changing out the exhaust manifold gasket (was worn and torn), I couldn't find a stock one and had to buy a venom racing one ( could that be the problem?)

After trying to start it today I think I blew the spring again, it barely cranks now so that's another 10$ gone

What else can I try at this point?
The only other thing that I've thought of is the o ring for the high speed needle looks pretty worn as I was taking it apart to add green slime. Could that make it that hard to start

The car is a Savage 4.6 with a stock F4.6 engine, sidewinder 20% fuel, OS 8 medium plug (also tried a OS 7)

 

[xtremsavage]

How do the internals look? Rusty, corroded, worn out? How the compression on the motor? It'll be a little harder to check the compression with a rotostart cuz you can't slowly turn it over like you can with a pull start. Look into that & maybe make and post a video of what it's doin might help. If the internals and compression are good, set your needles to factory then lean out the LSN about 1/2 a turn and the HSN about 1 full turn. Also, if you have a stand for your truck use that to get it started so the wheels can free spin til you get it runnin a few mib and warmed up.

 

[FreezeCtrl]

How do the internals look? Rusty, corroded, worn out? How the compression on the motor? It'll be a little harder to check the compression with a rotostart cuz you can't slowly turn it over like you can with a pull start. Look into that & maybe make and post a video of what it's doin might help. If the internals and compression are good, set your needles to factory then lean out the LSN about 1/2 a turn and the HSN about 1 full turn. Also, if you have a stand for your truck use that to get it started so the wheels can free spin til you get it runnin a few mib and warmed up.

Here are some pics of the internal while I was changing out the pressure spring and starting pin, I think it looks fine?
The engine has good compression, hard to turn while the glow plug was in

I can't get it started anymore because the pressure spring is now broken again and needs to be changed out, it doesn't crank at all
When it started, it would only run for like 10 seconds, so I couldn't get footage

 

[xtremsavage]

Doesn't look too bad, could use a good cleanin though. What does the top of the piston look like? How are the outside temps & humidity when your tryin to crank it? Try the needle settings next time and maybe just slightly open the carb a little more to keep it runnin.

 

[FreezeCtrl]

yeah I cleaned it all before putting it back together
Its a little chilly outside right now, under 20 Celsius 30% humidity. I even tried to preheat the engine and it was still the same

It also seems like the engine is starved for gas? When it did run I opened the throttle for like a good 1-2 seconds before it would lurch forward
It also got pretty hot pretty quickly for how little it ran

yeah I'll try those needle settings if I run it again after fixing the spring, I did lean it out quite a bit on both needles while trying to start it when stock needle settings didn't work

 

[xtremsavage]

Ok. Keep us posted.

 

[olds97_lss]

I can't recall, but does the tank have a stone filter in it? If it sat a long time with any fuel in it, that could be gummed up if it has one. Forcing fuel into the outlet might help break up the sludge on it if it has one.

 

[FreezeCtrl]

So I toke out the engine today to replace the starting spring, and to my surprise the starting spring was not broken! It was the hex thing grabbing on to the starting shaft that has slipped, causing the shaft not to be able to turn.

There was a lot of oil on the starting shaft and the whole back plate, mostly likely from the exhaust

Can the exhaust manifold seal between the manifold and the exhaust port not sealing well cause fuel delivery problems? How does one check the seal on that? I changed out the old one because it had a giant crack on it but I no one had the HPI one, so I bought a generic one.

I also cleaned out the carb today and it looked pretty clean, one of the o rings has now broken so I'll have to get another one

@olds97_lss It does havea stone filter, I think it's fine because I was able to blow fuel throw the line by blowing on the back pressure line

 

[olds97_lss]

The exhaust gasket being ripped/torn will cause tank pressure issues. Usually not enough to keep it from running, but makes it hard to prime and hard to tune once it's running.

 

[FreezeCtrl]

Welp, after 3 weeks of troubleshooting and fixing, I finally got my savage 4.6 to run today!
For one tank lmao
Everything now works, fuel flows properly, carb is working, glow plugs and igniter all god
Just the nitro start is messed again and won't physically turn the engine

One of the screws on the hex thing on my nitro start is cracked, and won't tighten the hex onto the starting shaft
Turns out one screw trying to grab the starting shaft is not enough. It slipped immediately as soon as there was oil on it
I got it to start once
So it's awesome that it starts, just now I have to somehow fix the set screw on the hex
Might have to buy a whole new nitro start backplate or rotostart, cause I don't think they sell that hex thing seperately..

Plus HPI being barely alive on life support doesn't help lol

Thanks everyone for the help! I can't believe I got it to run after all that, definitively needed every tip that was given here

 

[guinnessdublin]

Good to hear you have got it running again, that’s half the fun & battle with nitro I love over electric if something doesn’t work keep going until it does!
Should be able to get a non hpi back plate to fit! ??

 

[Thanos]

Good morning guys and happy holidays to all. I need to thank you for all the ideas... I started my savage 4.6 after two - three years and what helped is "If the internals and compression are good, set your needles to factory then lean out the LSN about 1/2 a turn and the HSN about 1 full turn" by @xtremsavage. It wouldn't start at the beginning. Now it is awesome as it used to be !! fyi, I am using 10 years old fuel !!!
Thanks again wishing a happy and friendly 2025

 

[guinnessdublin]

Wow 10 yr old fuel Happy Holidays indeed my friend! 🍺👍🏻