MP5 not firing?

Eoghan S

Hey guys
Seems I've hit a spot of bother... My MP5 has completely stopped firing altogether, making no sound at all when I connect the battery.
I'm not sure its the fuse , as I did connect the two metal components around the fuse, but to no avail.
Could it be the wiring?
It was working 100% before I took it apart to have a look at the internals, then I decided not to and put it back together, to which it doesn't fire!
Any help is appreciated, as I need it up and running by tomorrow!
Thanks all

Rooky1

Did you re check your motor connections?
They can pop off quite easily.

Eoghan S

Rooky1 wrote: »

Did you re check your motor connections?
They can pop off quite easily.

Yeah, I found them quite hard to put on, but I'm sure they're on fully now
Maybe I have them on backwards (as in black and red are on the wrong side?)

Eoghan S

Just checked, and its still not working, no matter how much pressure I add to them!

Southern Dandy

Eoghan S wrote: »

Just checked, and its still not working, no matter how much pressure I add to them!

Do you have a multimeter?.

Eoghan S

Southern Dandy wrote: »

Do you have a multimeter?.

No I don't have a multimeter

Southern Dandy

Eoghan S wrote: »

No I don't have a multimeter

Right, 1st You should be able to tell by sight if your fuse is blown.

2nd:Inspect your connections for blackening, burnt insulation etc.

3rd: Try it with a new battery or try the MP5 battery in a different aeg.

4th: Remove the motor and pull the trigger, if she turns then it is a gearbox issue. If it does not spin then disconnect the motor, get some cable anything really and connect it to a 9v battery then to the motor, ensuring polarity is correct +positive to +positive, -negative to -negative. If it turns then you have eliminated the motor as the issue.

5th: Inspect all wiring for nicks, breaks and cable core exposure etc to rule out a short circuit.

6th: and finally if you have now eliminated the fuse, connections, battery, motor and cable condition then all you have left then is the trigger contacts. Depending on the type of battery you use the contacts maybe fried or at least blackened caused by arcing, this is more prominent in aegs that use high voltage lipos. You can use some emery cloth to clean these and ideally if you have some contact cleaner or maybe isopropanol to clean hem thoroughly after you sand them.

These are electrical fault finding techniques, whilst looking at these you find a mechanical cause of your problem as like I said above if the motor turns when removed then chances are you have a mechanical issue.

Anyways hope this helps.

Eoghan S

Southern Dandy wrote: »

Right, 1st You should be able to tell by sight if your fuse is blown.

2nd:Inspect your connections for blackening, burnt insulation etc.

3rd: Try it with a new battery or try the MP5 battery in a different aeg.

4th: Remove the motor and pull the trigger, if she turns then it is a gearbox issue. If it does not spin then disconnect the motor, get some cable anything really and connect it to a 9v battery then to the motor, ensuring polarity is correct +positive to +positive, -negative to -negative. If it turns then you have eliminated the motor as the issue.

5th: Inspect all wiring for nicks, breaks and cable core exposure etc to rule out a short circuit.

6th: and finally if you have now eliminated the fuse, connections, battery, motor and cable condition then all you have left then is the trigger contacts. Depending on the type of battery you use the contacts maybe fried or at least blackened caused by arcing, this is more prominent in aegs that use high voltage lipos. You can use some emery cloth to clean these and ideally if you have some contact cleaner or maybe isopropanol to clean hem thoroughly after you sand them.

These are electrical fault finding techniques, whilst looking at these you find a mechanical cause of your problem as like I said above if the motor turns when removed then chances are you have a mechanical issue.

Anyways hope this helps.

Thanks for your help mate, will perform those tests now so.
I don't fully understand question 4 however?
I'll get back to you
Thanks

Southern Dandy

Eoghan S wrote: »

Thanks for your help mate, will perform those tests now so.
I don't fully understand question 4 however?
I'll get back to you
Thanks

If you completely remove the motor and get an ordinary 9 volt battery (the square ones you find in a smoke detector). get some cable and connect the battery to the motor, the motor should spin, if it works, then the motor is not your problem.

Eoghan S

Southern Dandy wrote: »

Right, 1st You should be able to tell by sight if your fuse is blown.

2nd:Inspect your connections for blackening, burnt insulation etc.

3rd: Try it with a new battery or try the MP5 battery in a different aeg.

4th: Remove the motor and pull the trigger, if she turns then it is a gearbox issue. If it does not spin then disconnect the motor, get some cable anything really and connect it to a 9v battery then to the motor, ensuring polarity is correct +positive to +positive, -negative to -negative. If it turns then you have eliminated the motor as the issue.

5th: Inspect all wiring for nicks, breaks and cable core exposure etc to rule out a short circuit.

6th: and finally if you have now eliminated the fuse, connections, battery, motor and cable condition then all you have left then is the trigger contacts. Depending on the type of battery you use the contacts maybe fried or at least blackened caused by arcing, this is more prominent in aegs that use high voltage lipos. You can use some emery cloth to clean these and ideally if you have some contact cleaner or maybe isopropanol to clean hem thoroughly after you sand them.

These are electrical fault finding techniques, whilst looking at these you find a mechanical cause of your problem as like I said above if the motor turns when removed then chances are you have a mechanical issue.

Anyways hope this helps.

Here we go!

1: Fuse doesn't seem to be blown, so its not the fuse.

2: No blackening that I can see

3: New battery has the same problem, so its not the battery

4: Motors still didn't turn, even with the 9v battery test. However, I used the motor for my other , fully working AEG, and nothing happened, so its not the motor

5: I did notice some tape around a part in the wiring, which has the copper wires inside exposed. Potential problem?

6: I use a 8.4v NiMH battery, so I doubt any surge occurred. However, it wasn't firing in semi auto before it stopped working, potential problem #2?


So it seems likely that either
- The trigger contacts are failing
Or
- The exposed wires short circuited
Or both!

Thanks for your help, if you could guide me further that'd be much appreciated

Southern Dandy

Did you take the motor completely out of the gear box and test it with a 9v battery?. Provided it is connected correctly it should spin away.

Provided the exposed core did not short to the housing it should be fine, again you might see dis-colouration or a burnt look. And your fuse would have taken care of that by right.

Seems you have ruled out nearly all electrical faults and the only way to get to the contacts is to fully strip the gearbox. This is now looking more mechanical really. Could be anything from your selector plate, anti reverse latch, tappet plate, gears all of which are easy enough to spot.

airsofter232

I doubt the wires are the cause of the problem as if they had short circuited you would have almost certainly suffered blown fuse. As long as the wiring was not exposed and didnt come into contact with any metal while the battery was connected it should be fine. just make sure that the wire is covered in insulation tape and there should be no problems with the wiring.

brenak47

When u say u started to open it up and then decided not to how far did u go ie. did u open the gearbox. Also check your height adjuster screw that its not up to high as it will not turn over if it is. I did run into this problem myself before and it was the trigger contacts as u had mentioned yourself.

Eoghan S

Southern Dandy wrote: »

Did you take the motor completely out of the gear box and test it with a 9v battery?. Provided it is connected correctly it should spin away.

Provided the exposed core did not short to the housing it should be fine, again you might see dis-colouration or a burnt look. And your fuse would have taken care of that by right.

Seems you have ruled out nearly all electrical faults and the only way to get to the contacts is to fully strip the gearbox. This is now looking more mechanical really. Could be anything from your selector plate, anti reverse latch, tappet plate, gears all of which are easy enough to spot.

I may have connected the battery the wrong way alright :P

The exposed wiring looks fine really, no discolored patches or anything odd about it

Damn, I was hoping to stay out of the gearbox! Oh well I'll try I guess

Eoghan S

brenak47 wrote: »

When u say u started to open it up and then decided not to how far did u go ie. did u open the gearbox. Also check your height adjuster screw that its not up to high as it will not turn over if it is. I did run into this problem myself before and it was the trigger contacts as u had mentioned yourself.

I literally only took off and separated the receivers, and the outer barrel, I didn't open up the gearbox at all, so I'm clueless as to why it suddenly stopped working!
I'm not sure what the height adjuster screw is? I've never had any gearbox faults until now, so I'm not too sure about these parts

brenak47

Height adjuster screw is the centre screw in the grip it adjusts the motor up and down.When u took off the base plate how many screws did u take off to remove the plate.

josh68

hi there is connectors at the back of the gearbox were the stock or back plate is take off the stock and check if they are connected properly

Eoghan S

brenak47 wrote: »

Height adjuster screw is the centre screw in the grip it adjusts the motor up and down.When u took off the base plate how many screws did u take off to remove the plate.

Apologies, I do know what that is, and I haven't touched it yet!
Sorry for the late reply, was too busy to focus on the MP5 this week, so I thought I'd answer when I wasn't in a rush anywhere

Eoghan S

josh68 wrote: »

hi there is connectors at the back of the gearbox were the stock or back plate is take off the stock and check if they are connected properly

Hey mate
Sorry for the late reply, I gave a legit excuse above
The rear connections were connected properly alright

Eoghan S

Just to inform everyone, I decided to bite the bullet and open up the gearbox. Took a large chunk out of my day, and I managed to get the motor spinning every time! Naturally, I was delighted at this, but now for the dreaded part...
I connected the wiring to the motor, and inserted the grip, etc. Crossing my fingers, I squeezed the trigger, only to hear a horrific grinding noise , and when I took out my motor once again, there were scratches embedded in the grooves of the motor pinion (I think it's called :P )
Anyone have ideas on what to do next?
Btw, I didn't notice anything unusual in the gearbox, but the presence of a nut (not the food lol) has puzzled me? Then again, I may have been hallucinating...
Any help is appreciated greatly!
Cheers

Southern Dandy

Eoghan S wrote: »

Just to inform everyone, I decided to bite the bullet and open up the gearbox. Took a large chunk out of my day, and I managed to get the motor spinning every time! Naturally, I was delighted at this, but now for the dreaded part...
I connected the wiring to the motor, and inserted the grip, etc. Crossing my fingers, I squeezed the trigger, only to hear a horrific grinding noise , and when I took out my motor once again, there were scratches embedded in the grooves of the motor pinion (I think it's called :P )
Anyone have ideas on what to do next?
Btw, I didn't notice anything unusual in the gearbox, but the presence of a nut (not the food lol) has puzzled me? Then again, I may have been hallucinating...
Any help is appreciated greatly!
Cheers

What size roughly?.

YbFocus

Eoghan you've put it together wrong some way or another.

The grinding is the motor gear spinning off the bevel gear if the motor teeth are being destroyed.
This means that:

1. The height is wrong on the motor, especially if the gear is only marked near the top.Setting the motor will see the gearbox run, after a new bevel gear and motor of course.

2. The gearbox is locked, something was put together wrong This means that when the power is applied it just chewed up the first two gears in contact with each other.

To fix either of these will involve breaking it down again, replacing the gear or gears torn up, fixing the problem that caused it and finally either a new motor gear if it's replaceable or a new motor.

That's to the best of my knowledge anyhow mate. Next time turn it over by hand first to see if it all functions fluidly without the torque being applied from the motor where it can't be stopped when something goes wrong.

airsofter232

Have you change the shimming around?
If that is done wrong it could over tighten the gear causing a lot of friction when rotating and damage the teeth of the gear and or motor.

Also is there any chance you mixed up the wires on the motor? this would cause it to spin backwards and probably leave marks and strip the teeth because the anti-reversal latch doesnt allow the gears to move backwards causing a lock-up

hope this helps

Eoghan S

Southern Dandy wrote: »

What size roughly?.

I assume you mean the size of the nut?
It's 6mm mate

Eoghan S

YbFocus wrote: »

Eoghan you've put it together wrong some way or another.

The grinding is the motor gear spinning off the bevel gear if the motor teeth are being destroyed.
This means that:

1. The height is wrong on the motor, especially if the gear is only marked near the top.Setting the motor will see the gearbox run, after a new bevel gear and motor of course.

2. The gearbox is locked, something was put together wrong This means that when the power is applied it just chewed up the first two gears in contact with each other.

To fix either of these will involve breaking it down again, replacing the gear or gears torn up, fixing the problem that caused it and finally either a new motor gear if it's replaceable or a new motor.

That's to the best of my knowledge anyhow mate. Next time turn it over by hand first to see if it all functions fluidly without the torque being applied from the motor where it can't be stopped when something goes wrong.

Damn, exactly what every noob is afraid of!
The marks on the teeth of the motor aren't near the top I'm afraid, more in the middle of the teeth?
I did roll the gears and they connected perfectly while the gearbox shell wasn't on.
I have a strange feeling it could be a missing shim from the first gear (the bevel gear?), as it seemed to be quite loose, and when I attempted to move all the gears together when the gearbox shell was on properly, and it seemed to be quite weird, I just assumed that i wasn't turning it properly!
I am nearly sure that I simply need to re-add that shim to the first gear
I'll open her up later, just to be sure
Thanks for your help, and sorry if I'm explaining it vaguely, I'm very new to this lark!

Eoghan S

airsofter232 wrote: »

Have you change the shimming around?
If that is done wrong it could over tighten the gear causing a lot of friction when rotating and damage the teeth of the gear and or motor.

Also is there any chance you mixed up the wires on the motor? this would cause it to spin backwards and probably leave marks and strip the teeth because the anti-reversal latch doesnt allow the gears to move backwards causing a lock-up

hope this helps

I may have moved a shim around alright, I'll check that in a bit, the first gear seemed slightly loose?

I don't think that I mixed up the wires, as one side of the motor at the top is colored red, red is positive right?
Any other suggestions mate?
Cheers

airsofter232

Yeah red is positive. Id suggest making sure that the shimming was in order. however if the shimming was too loose there shouldnt have been a grinding noise. not sure what else could have caused it. il get back to you if i think of anything

Eoghan S

airsofter232 wrote: »

Yeah red is positive. Id suggest making sure that the shimming was in order. however if the shimming was too loose there shouldnt have been a grinding noise. not sure what else could have caused it. il get back to you if i think of anything

Damn, that rules out that probability so, please get back to me, I do need help!

airsofter232

Right, well first off i would check if there was any foreign object in the gearbox as that could have gotten caught between the gears

second check that the anti-reversal latch is in good condition and fits into place nicely

third the grinding noise could have actually been from you over tightening the screws on the gearbox. if the gun had tight shimming on any of the gears and you over tightened the screws it would mean that the gears could not spin freely. i suggest maybe cleaning out and regreasing the gearbox, re-do the shimming, check that the anti-reversal latch is fine and finally make sure that the screws arent too tight.

hope you manage to sort the gun out

Southern Dandy

The motor pinion generally keeps the bevel to one side unless it was ridiculously over shimmed I doubt it is the problem. And like you said the aeg was firing fine until lately, and to my knowledge you did not re-shim it yourself no?. The bevel does not require too many shims in my opinion.

If your pinion is worn half way then it stands to reason it was either too high or too low, this can be adjusted via a grub screw normally beneath where the motr sits. But honestly, if you can not figure this I would take it to a store with a good tech and leave them have a nosey.

Eoghan S

airsofter232 wrote: »

Right, well first off i would check if there was any foreign object in the gearbox as that could have gotten caught between the gears

second check that the anti-reversal latch is in good condition and fits into place nicely

third the grinding noise could have actually been from you over tightening the screws on the gearbox. if the gun had tight shimming on any of the gears and you over tightened the screws it would mean that the gears could not spin freely. i suggest maybe cleaning out and regreasing the gearbox, re-do the shimming, check that the anti-reversal latch is fine and finally make sure that the screws arent too tight.

hope you manage to sort the gun out

Have it opened once again

1: No clogging of gears, or missing teeth in any of the gears as far as I can see, they seem to run smoothly enough without the cylinder, etc installed.
2: Anti reversal latch seems to be fine, and works fine well enough also, stops the gears spinning if I twist them backwards.
3: The screws definitely weren't too tight, if anything they seemed a bit too loose!

Thanks again for your help