solex backfires, need some help

[madera]

volvo aq130, 2 single solex 44pai carbs, engine timed, new plugs, wires, carbs sync'd, adjusted mix screws also. however when you hit gas, engine stumbles with carbs back fireing, would rebuilding solve this? what is causing this? can you help, all advise apprc'd---thanks

 

[marlinempress]

Re: solex backfires, need some help

have you checked your fuel filter or water separator, if they're blocking flow it'll cause it to have a lean condition which makes it backfire through the carb. You could also have some clogged jets and stuff. Rebuilding never hurts unless you don't do it right....

 

[DHPMARINE]

Re: solex backfires, need some help

I'm guessing your engine is an overhead cam type.If so,check the belt timing to be sure the belt hasn't jumped a tooth.<br /><br />We don't do alot of older Volvos,but this is a common problem on the few we do.IF this is the problem,at least do a new belt and rebuild/replace the tensioner.<br /><br />DHP

 

[Don S]

Re: solex backfires, need some help

Like DHP stated, the timing belt has a lot to do with the Volvo OHC engines. Look at the belt, the gaps should be the same width as the cogs on the belt. If the gaps are wider, the belt is worn out. <br />Spark plugs are another item that they are very picky about. Make sure they are the proper heat range, or it will backfire. Did you set the points by dwell or feeler gauge? Also make sure the accelerator pumps are working.<br />Improperly adjusted carbs will also cause your problem.

 

[Peter J Fraser]

Re: solex backfires, need some help

This should be the B20 OHV engine I think.<br />Check your Ign timing is correct and lift the air intake silencer off the carbs.<br />Operate the throttle and watch for the accelerator pumps jets are actually delivering fuel to the carb. Check also that the external linkage is all connected and working properly<br />Also check the screws around the carb body to throttle body are nipped up tight as if they are loose the mixture will lean out due to the air leaking in there.<br />The carbs are pretty simple in construction and dont take very much maintenance.<br />Good luck<br />Peter

 

[jimmythekid]

Re: solex backfires, need some help

lean fuel mixture, most likely, check for vacuum leaks, and proper fuel flow/pressure

 

[madera]

Re: solex backfires, need some help

engine is aq130d, no timing belt, gears, i rebuilt the carbs today but to late to test, if the engine still stumbles or back fires what next, b20 engine timed to 8btdc, any suggestions? if it is still acting up?

 

[trog100]

Re: solex backfires, need some help

u have twin carbs i assume.. two seperate ones as opposed to a twin choke thing.. did u find any thing obviously wrong with em when u took em apart..<br /><br />if it still behaves the same as before u rebuilt the carbs it still comes down to fuel starvation.. just not the carbs being the cause of it..<br /><br />lets hope it goes anyway.. let us know if it does..<br /><br />trog100

 

[rabidfish]

Re: solex backfires, need some help

almost has to be accelerator pump issue, or carb synch. The check-valves in the acc pump system may be the cause (or missing if they were rebuilt by the same guy changing the timing belt)

 

[Peter J Fraser]

Re: solex backfires, need some help

Ok on B20. Check the throttle shaft sync very carefully as they must both open at exactly the same time.<br />Your engine idle must also be the equal on both carbs. You can check that very easily without a "Sync Gauge" by using a length (3ft or so) of 1/4" plastic hose like a stethoscope. Release one clamp on the throttle shaft joining rod to allow the carbs to separate.<br />With the engine idling place one one end of the tube in your ear and the other end into the top of a carburettor. Switching from carb to carb you can hear the difference in the idle airflow very easily and make the necessary idle screw adjustments to balance the carbs.<br />Recheck the idle mixtures after each adjustment change.<br />When you're satisfied that they are balanced then reset the clamp on the throttle shaft link and then make sure that both throttle valves open together.<br />The carby's are now synchronised. <br />Very simple when you say it fast.<br />Make sure you check those accelerator pumps too.<br />Good luck.<br />Peter