Offroad-Express

My SJ413 started surging while idling a few weeks ago. It is major surging but and you need to wind the idle up quite high to prevent stalling. Once you break through about 2000rpm it runs faultlessly and you wouldn't know there was a problem til you back at idle. My first thoughts were that it was an air leak but I cant seem to find one. I swapped the carb with a spare one I had and no improvement. I then replaced the intake manifold gasket no improvement. Replaced the fuel filter. I'm getting good sparks on all plugs. I'm running out of things to check. I was thinking that perhaps with a mechanical pump it is not pumping well at low revs but ok at high revs dont know how to test it though. Any advice would be appreciated.

that fuel pump idea sounds like a good one to me

ive had the same prob with my 413 so i just sent it to the garage to get fixed didnt wana stuff around with things as i have no clue of what im doing. comes back tomuro il let you no if its anything other that you have tryed.

Whats the chance both carbs have got shit in the idle jets? Might want to check the filters not full of rust and crap and pull the carb(s) apart and blow all the passages out with compressed air

..... just did my holley tonight and it's idleing again now

Sadam_Husain wrote:
..... just did my holley tonight and it's idleing again now

NICE !

mine runs like a swiss watch since i rebuilt the carb all those months ago ! can believe how nice it runs really

luke25 wrote:My SJ413 started surging while idling a few weeks ago. It is major surging but and you need to wind the idle up quite high to prevent stalling. Once you break through about 2000rpm it runs faultlessly and you wouldn't know there was a problem til you back at idle. My first thoughts were that it was an air leak but I cant seem to find one. I swapped the carb with a spare one I had and no improvement. I then replaced the intake manifold gasket no improvement. Replaced the fuel filter. I'm getting good sparks on all plugs. I'm running out of things to check. I was thinking that perhaps with a mechanical pump it is not pumping well at low revs but ok at high revs dont know how to test it though. Any advice would be appreciated.

Replace your fuel filter, pull the idle jet out and clean it, pull the drain plug out of the float bowl and turn the engine over for 30 seconds or more on the starter to flush any crap out, throw it back together and it bet it will run sweet!!!!

It won't be an air leak if it runs fine above 2K rpm, and if you are getting a good spark, then its obviously not electrics.

DieselBoy wrote:
It won't be an air leak if it runs fine above 2K rpm, and if you are getting a good spark, then its obviously not electrics.

It could well be an air leak - they tend to be much worse at higher vacuum levels like at idle.
I suspect that all he means by "getting a good spark" is that you can see the plugs sparking when removed from the engine. All this means is that he is getting some spark. A weak ignition system will often fire the plugs fine in open air, but fail to in actual engine operating conditions.

HedgeBoar wrote:

DieselBoy wrote:
It won't be an air leak if it runs fine above 2K rpm, and if you are getting a good spark, then its obviously not electrics.

It could well be an air leak - they tend to be much worse at higher vacuum levels like at idle.
I suspect that all he means by "getting a good spark" is that you can see the plugs sparking when removed from the engine. All this means is that he is getting some spark. A weak ignition system will often fire the plugs fine in open air, but fail to in actual engine operating conditions.

Fair comments mate

He doesn't mention looking at the idle jet though, and thats the first place i personally would go looking if my engine suddenly stopped idling.

mine did it last week, re kit carb now runs better that before
but sure you would get away with idle jet clean out,
carb kit same as Mitsubishi cost $70
but made a new truck