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Old 07-18-2011, 10:39 AM   #1
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Default HPI Rs4 evo not starting

cant start the engine!
-glow plug is good, tried 2 of them, they both work on other cars
-starter fully charged again tried on another car just before using it on the rs4
-when I put fuel in the carb it starts for a short time(guess till the fuel I put in is all gone)
-when I put my finger on the exhaust pipe the fuel is priming to the engine, so I'm guess no leakage.

I'm going factory settings except my low speed needle is stuck! its stuck mid way in, so theres no way to make it flush, no matter turning CW or CCW it wont go in or out...

Could this be the problem? thing is when I put my finger on the exhaust pipe the fuel primes to the carb and if i do it too long it floods the engine, so I dont think the low speed needle has anything to do with it not starting... or am I wrong?


I'm using a roto start fully charged(again i tried it on antoher hpi and it starts it fine), it turns and turns but wont start! of course if i drop fuel in the carb it starts for few seconds.

please help!
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Old 07-18-2011, 12:14 PM   #2
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When you put your finger over the exhaust and you get to the point where the engine is almost flooded...does it start? This should be about the same as putting fuel down the carburetor air inlet. If fuel is reaching the cylinder enough to flood it, it should reach it enough to start it.

Start there.
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Old 07-18-2011, 12:21 PM   #3
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Looking in the carb with the filter off, how large is the opening with the carb closed? Using the idle screw set the gap to about the thickness of a credit card.

When it dies after start up does it bog down and die, or does it idle up then die? The low speed needle does have a huge effect on starting the car. It controls the fuel flow at 'low speeds.' That stuck needle could definitely be your problem.
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Old 07-18-2011, 12:58 PM   #4
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Looking in the carb with the filter off, how large is the opening with the carb closed? Using the idle screw set the gap to about the thickness of a credit card.

When it dies after start up does it bog down and die, or does it idle up then die? The low speed needle does have a huge effect on starting the car. It controls the fuel flow at 'low speeds.' That stuck needle could definitely be your problem.
the gap is set to the thickness of a credit card

it only starts for few seconds so I'm not sure about the idle, any easy ways to get the needle fixed, do I just take it apart or have to get the parts replaced? how would I fix the low speed idle? I dont see how to take it apart? theres no screws around the needle?
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Old 07-18-2011, 01:00 PM   #5
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When you put your finger over the exhaust and you get to the point where the engine is almost flooded...does it start? This should be about the same as putting fuel down the carburetor air inlet. If fuel is reaching the cylinder enough to flood it, it should reach it enough to start it.

Start there.
no it doesnt start, could it be since the low needle is stuck at the close position its not letting the fuel from the line into the carb? would explain why if i drop fuel in the carb it would start?
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Old 07-18-2011, 01:41 PM   #6
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Yeah, that low end needle might too far in. Not letting fuel into the engine. Try to get it out. If not, snag a new carb for it.

Will it start up with the throttle full open?
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Old 07-18-2011, 08:03 PM   #7
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Yeah, that low end needle might too far in. Not letting fuel into the engine. Try to get it out. If not, snag a new carb for it.

Will it start up with the throttle full open?
no it won't start with throttle full open, how do I get the needle out? is it the same needle I see when the carb is fully open?
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Old 07-19-2011, 11:20 AM   #8
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Quote:
Originally Posted by oceans View Post
no it doesnt start, could it be since the low needle is stuck at the close position its not letting the fuel from the line into the carb? would explain why if i drop fuel in the carb it would start?
If you can flood the engine then the low speed needle is getting fuel into the engine...that was my point...

Quote:
it only starts for few seconds so I'm not sure about the idle,
So which is it? It only starts for a few seconds or it doesn't start at all. Big difference there. Or are you saying it only starts for a few seconds when you put fuel directly in the carb?

I'm GUESSING it's not starting at all but the fact you can get it to flood is the confusing part. It sounds like a fuel delievery issue...but getting it to flood (by covering the exhaust and trying to start it) means you CAN get fuel into the engine through the fuel system.

I'd say your tank has a small leak somewhere or a blockage in the fuel lines/needles. By over-pressurizing it with the exhaust being covered it's enough to get fuel into the engine but when you are only trying to draw fuel in by the vacuum of the engine and the much lower normal backpressure of the exhaust it's not enough to move the fuel.

I'm guessing the car and engine have been sitting for a while. If so, keep in mind that if it sat with fuel in it, fuel gums up over time and can block fuel passages in the carb and lines.

With it not starting at full throttle the low speed needle itself is eleminated as a culprit since at full throttle it is out of the equasion...but it's seat isn't. The low speed needle seat...where the low speed needle goes into when the throttle is closed or at low speed...is also reffered to as the Mid-range adjustment or Mid-range needle. (But isn't really a needle at all.) It is through this hole that all your fuel enters the carb throat to mix with the incoming air. The amount of fuel that passes through this opening is controlled by the high speed needle. The low speed needle just further restricts flow at low speeds.

Start by taking apart your carb and soaking it in NEW fuel overnight. If you can't get your low speed needle to budge out of the carb barrel, soak it as a unit and see if it can be moved the next day. The needle could just be gummed up with bad fuel. If you can take it out, resoak the barrel and slow speed needle to fully clean them.

If it still doesn't move, it could be the previous owner over-tightened the low speed needle and siezed it in the barrel. In this case, the low speed needle may be damaged beyond salvation and need replacing. I would also replace the low speed seat (mid-range "needle") if possible and maybe the barrel if the low speed needle cannot be removed at all.

Take the easiest stuff first and eleminate that as possibilities. Hook up a different tank, replace lines, try and clean the carb. Those are all free (seeing as how you have "other" nitro cars you have been trying those glow plugs on) and this eleminates them as possibilities right off the bat. Then go into replacing parts.
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Old 07-19-2011, 11:48 AM   #9
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If you can flood the engine then the low speed needle is getting fuel into the engine...that was my point...



So which is it? It only starts for a few seconds or it doesn't start at all. Big difference there. Or are you saying it only starts for a few seconds when you put fuel directly in the carb?

I'm GUESSING it's not starting at all but the fact you can get it to flood is the confusing part. It sounds like a fuel delievery issue...but getting it to flood (by covering the exhaust and trying to start it) means you CAN get fuel into the engine through the fuel system.

I'd say your tank has a small leak somewhere or a blockage in the fuel lines/needles. By over-pressurizing it with the exhaust being covered it's enough to get fuel into the engine but when you are only trying to draw fuel in by the vacuum of the engine and the much lower normal backpressure of the exhaust it's not enough to move the fuel.

I'm guessing the car and engine have been sitting for a while. If so, keep in mind that if it sat with fuel in it, fuel gums up over time and can block fuel passages in the carb and lines.

With it not starting at full throttle the low speed needle itself is eleminated as a culprit since at full throttle it is out of the equasion...but it's seat isn't. The low speed needle seat...where the low speed needle goes into when the throttle is closed or at low speed...is also reffered to as the Mid-range adjustment or Mid-range needle. (But isn't really a needle at all.) It is through this hole that all your fuel enters the carb throat to mix with the incoming air. The amount of fuel that passes through this opening is controlled by the high speed needle. The low speed needle just further restricts flow at low speeds.

Start by taking apart your carb and soaking it in NEW fuel overnight. If you can't get your low speed needle to budge out of the carb barrel, soak it as a unit and see if it can be moved the next day. The needle could just be gummed up with bad fuel. If you can take it out, resoak the barrel and slow speed needle to fully clean them.

If it still doesn't move, it could be the previous owner over-tightened the low speed needle and siezed it in the barrel. In this case, the low speed needle may be damaged beyond salvation and need replacing. I would also replace the low speed seat (mid-range "needle") if possible and maybe the barrel if the low speed needle cannot be removed at all.

Take the easiest stuff first and eleminate that as possibilities. Hook up a different tank, replace lines, try and clean the carb. Those are all free (seeing as how you have "other" nitro cars you have been trying those glow plugs on) and this eleminates them as possibilities right off the bat. Then go into replacing parts.
It only start when I put fuel directly into the carb. I have tried with a different tank/lines and it wont start, the fuel does goto the carb when I cover the pipe... so I think the low speed needle is the problem, which I have no clue how to take it apart from the engine since theres no screws anywhere near it.
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Old 07-19-2011, 07:42 PM   #10
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Double check the fuel tank cap o-ring. I've had a similar issue with my Savage. Make sure the cap is sealed and even push it down a little to make sure it is sealing...
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Old 07-20-2011, 10:30 AM   #11
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Quote:
Originally Posted by oceans View Post
It only start when I put fuel directly into the carb. I have tried with a different tank/lines and it wont start, the fuel does goto the carb when I cover the pipe... so I think the low speed needle is the problem, which I have no clue how to take it apart from the engine since theres no screws anywhere near it.
Yea the needle is way too far in. That's for certain. If you can't move it I'd call HPI customer service and see if they can help you out.
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