Idle surge and backfire

[jze1212]

Hi there. I have got a 1988 100hp I-4, serial# OB312239, running with a hose hooked up - take a bit to get started then will run smooth for a couple minutes, then the idle will sort of "stumble" and it will backfire and throw a puff of smoke.. The it will catch itself and run smooth for a few seconds and repeat. When you hit the gas it seems very responsive and when the motor speed is slowing down you seem to get more little backfires and "pops" than normal? Maybe this is normal for this motor? I have replace the plugs, wires seem ok, compresssion is 110-115 (give or take) .. Any suggestions? I havent run it in the water yet, maybe just needs a good running? I just dont want to mess anything up! Thanks in advance...

 

[Laddies]

Re: Idle surge and backfire

It is a little lean, richen up the top carb 1/4 to 1/2 a turn there is no adjustment on the bottom

 

[jze1212]

Re: Idle surge and backfire

I would turn that screw counter clockwise right? Why just the top carb?

 

[jze1212]

Re: Idle surge and backfire

could that be a leaking oil injector perhaps? That would explain the surge and the large puff of smoke?

 

[Laddies]

Re: Idle surge and backfire

Yes counterclock wise to richen the mix, there is no low speed adjustment on the bottom carb because the engine only runs on the top 2 cyls when at idle

 

[jze1212]

Re: Idle surge and backfire

Ahhh, it is one of those huh? I thought it has 4 carbs? Thanks for your help Laddies

 

[jze1212]

Re: Idle surge and backfire

Well, I put it in the water this morning, now that it is in the water, when the backfire occures it stalls - is fine when you have some throttle on it, smoooth, but at idle it will "puuuuurrrr" then a little "pop" and stall out.. What could this be? I tried the scre on the top 2 carbs (there are 4 of them , bottom 2 no screw) .. That did nothing.. I am stumped, anyone?

 

[jze1212]

Re: Idle surge and backfire

:| Still stuck here, going to have to bring to marina shop to have fixed, NOOOOOO - Last call - help......

 

[jze1212]

Re: Idle surge and backfire

I also found that when you tilt the motor back fuel starts leaking out like crazy from the carbs... This must be because the floats are stuck or perhaps there is some gel in the fuel and the carbs are not able to do what they need to do?? It will not start after ut floods out like that, clean the plugs and will start again, run good, then pop and stall out..

 

[Laddies]

Re: Idle surge and backfire

It sure sounds like it's time to clean the carbs and install new inlets

 

[jze1212]

Re: Idle surge and backfire

Soon as the weather breaks here (T-storms, etc) I plan to tear into the carbs and see, there must be a float sticking or somthing which would make them leak like that right?

What are the inlets that you are talking about laddiesservice? Would that be in a rebuild kit? It sems that everything is pointing towrds the carbs, obviously if is spilling gas out there is a problem and I am hoping that when I open them up something will jump right out , meybe gel or something, I dont even know how old the gas is in the tank but it does the same exact thing on external fuel tank also

 

[jze1212]

Re: Idle surge and backfire

I removed the carbs and cleaned them out, there was one carb that had a very small amount of gunk around the small gasket which goes around the large tube that goes thru the center of the carb... (that was the best I could describe it..) it does not seem to POP and stall out anymore, but now it is very hard to start, Seems to be flooding out, It appears that when you hit the choke on the key it dumps a mass of gas in there.. If you tilt the motor up the gas pours out of carbs.. Could this be because I backed the mix screws out too far on the carbs? I counted rotations turning them all the way in and they were each about 2 1/2 turns out...

Idle is very low now... Does anyone out there have some advice for me besides bring it to dealer? That is the next step...:/

 

[jze1212]

Re: Idle surge and backfire now beeping also

Re: Idle surge and backfire now beeping also

I am have appt to get the motor looked at next Weds. Meanwhile, Last night while tinkering with carbs and running it after a while I got a "BEEP BEEP BEEP BEEP" from the control box, very steady "BEEP BEEP BEEP BEEP" water was coming from telltale and motor didnt feel hot to the touch.. I was running premix because I havnt monitored the oil level in the oil injection system so I dont completely trust it.. Things arent looking so good for our hero..

 

[jze1212]

Re: Idle surge and backfire

Weds came and went, now they are telling me at least a week or 2.... I would love to haul it back home and fix it. Or just at least get a straight answer as to when it will get looked at, not just a round about guess, I understand they are busy, but I thought I had and appointment, anyway..

Any more idea's folks? I did more reading and I think that the beeping is the low oil, because the reserve may be getting low and there is a sensor in there?

Will idle fine for a bit (actual time varies) then violently stall out, like the motor sort of "jerks" When it was out of the water that came as a backfire but you cant here it when the motor is submerged... Then you go to restart it and is hard to start and seems to flood out.. When it is running there is a rattling noise that you hear when you rev up, hard to say but is sounds like it is coming from inside, I dont think it made this noise until after I removed lower unit to replace impeller.

 

[jze1212]

Re: Idle surge and backfire

Weds came and went, now they are telling me at least a week or 2.... I would love to haul it back home and fix it. Or just at least get a straight answer as to when it will get looked at, not just a round about guess, I understand they are busy, but I thought I had and appointment, anyway..

Any more idea's folks? I did more reading and I think that the beeping is the low oil, because the reserve may be getting low and there is a sensor in there?

Will idle fine for a bit (actual time varies) then violently stall out, like the motor sort of "jerks" When it was out of the water that came as a backfire but you cant here it when the motor is submerged... Then you go to restart it and is hard to start and seems to flood out.. When it is running there is a rattling noise that you hear when you rev up, hard to say but is sounds like it is coming from inside, I dont think it made this noise until after I removed lower unit to replace impeller.