Carburetor frustration

[Kevinm207]

I have a 2003 115 v4 Johnson (60* looper) that I haven’t been able to get running this year. First I had trouble with warped plastic carburetor bowls, I got new bowls/floats/float needle/seats and soaked/sprayed/compressed air blew carb passages/orifice and throttle plate passages (including tiny holes in throttle plate near needle valve) Overall I didn’t really find anything definitive for a clog. I put new plugs in and I decided to discontinue the oil injection and switch to premix.

I was able to go out once after that, but the purr sounded lean (I think) and it had hesitation in mid-throttle. After about 20 min it started stalling at low speed, it would still idle and I was able to use key primer to get past low speed and get to higher speed to get home.

Took it all apart again, sprayed/blew out. Put it all back together and same problem. I thought maybe it was like a “limp” mode related to unplugging oil pump so I tried plugging that back up as a test but no luck. I had just plugged the oil line with a bolt and unplugged the two harnesses for the oil system.

I’m wondering about some sort of air leak, the fuel rails with o-rings on the throttle plates seem a little suspicious but I’m not seeing leaking. My new carb bowls definitely are still
compressing gaskets more on the edges near screws then through the middle, but from what I can tell it’s still a good seal. My old bowls poured gas out. Anybody have experience with the needle valve setting on these, my SELOC manual said to match what it was set at which was 3.5 turns out.

I haven’t check compression this year, maybe that’s a good next step.

kind of just lost right now, feeling defeated

 

[Chris1956]

The idle passages are in the throttle bodies, not the carbs. Did you get them clean? New side plate gaskets on the throttle bodies? I pulled the side covers off and sprayed the idle needles to clean 'em up.

They have a mid range orifice. did you blow that out?

The Spaghetti seals on the throttle bodies and carbs can slip out of their grooves easily. Are yours's in their grooves? Are they the correct seals? The original kits I ordered came with the wrong spaghetti seals. They were reals close, but wrong.

 

[Kevinm207]

The idle passages are in the throttle bodies, not the carbs. Did you get them clean? New side plate gaskets on the throttle bodies? I pulled the side covers off and sprayed the idle needles to clean 'em up.

They have a mid range orifice. did you blow that out?

The Spaghetti seals on the throttle bodies and carbs can slip out of their grooves easily. Are yours's in their grooves? Are they the correct seals? The original kits I ordered came with the wrong spaghetti seals. They were reals close, but wrong.

I didn’t end up changing those seals because the old ones stayed in place better then the new ones. I *believe* they’re all in place correctly but I could try again. There’s some small orifice looking things in the plate behind the throttle plate, kinda near the reeds I think. Should I do something with those?

Yes new side gaskets on throttle bodies and blew out those tiny holes in there. I could try to blow out the “inlet” side a little better maybe, the ones near where the needle seats. The ones perpendicular to the needle I could see daylight through so I felt pretty good about, but the other ones don’t go straight through to light (passageway)

my needles didn’t really “seat” they kind of just max out on the spring on the way in. I could potentially change them, they don’t look bad but maybe they’ve narrowed…

Wondering about putting some silicone grease on the fuel rail o-rings going in to throttle plate to help seal, but nervous about grease potentially migrating in to fuel system. I have to pull the rails back out a tiny bit to get the clip that holds them in place installed which is why I’m suspicious of those seals.

also wondering about doubling carb-bowl gaskets in case the carbs themselves have a little warp. I got new bowls but it’s still not has tight in the middle as it is where the screws are. Visually I would guess it’s sufficiently sealed, but it wouldn’t take much. Maybe lap sanding is a better idea then double gasket…

How’s the optical ignition on these work? Maybe I’m chasing a carb problem that’s actually a spark problem?

 

[Kevinm207]

I didn’t end up changing those seals because the old ones stayed in place better then the new ones. I *believe* they’re all in place correctly but I could try again. There’s some small orifice looking things in the plate behind the throttle plate, kinda near the reeds I think. Should I do something with those?

Yes new side gaskets on throttle bodies and blew out those tiny holes in there. I could try to blow out the “inlet” side a little better maybe, the ones near where the needle seats. The ones perpendicular to the needle I could see daylight through so I felt pretty good about, but the other ones don’t go straight through to light (passageway)

my needles didn’t really “seat” they kind of just max out on the spring on the way in. I could potentially change them, they don’t look bad but maybe they’ve narrowed…

Wondering about putting some silicone grease on the fuel rail o-rings going in to throttle plate to help seal, but nervous about grease potentially migrating in to fuel system. I have to pull the rails back out a tiny bit to get the clip that holds them in place installed which is why I’m suspicious of those seals.

also wondering about doubling carb-bowl gaskets in case the carbs themselves have a little warp. I got new bowls but it’s still not has tight in the middle as it is where the screws are. Visually I would guess it’s sufficiently sealed, but it wouldn’t take much. Maybe lap sanding is a better idea then double gasket…

How’s the optical ignition on these work? Maybe I’m chasing a carb problem that’s actually a spark problem?

Tried double bowl gaskets and no change, it will idle but stalls with low/mid throttle. If I push the key in to prime it will save the stall and run another 10 seconds. So still seems like a carb problem…

I did turn needle out a little more to 5 turns but no change. Manual says to set them at where they were (3.5) but if you don’t have that go 5.75.

I went one by one covering throat intake, most made it big down but one carb made it run faster, wondering if I should focus my efforts on that carb? Maybe the needle is worn? Maybe just some more hidden restriction I’ve missed?

 

[racerone]

Yes have a good look at that carburetor.----When you use the primer valve you are putting fuel directly into the engine.------This extra fuel bypasses the carburetors and metering circuits.----This ( to me ) points at issues with one or more carburetors.------But a carburetor merely responds to air that is flowing / being pulled through it.-----There may be issues there.-----So posting your compression numbers may also offer a clue.

 

[Kevinm207]

Yes have a good look at that carburetor.----When you use the primer valve you are putting fuel directly into the engine.------This extra fuel bypasses the carburetors and metering circuits.----This ( to me ) points at issues with one or more carburetors.------But a carburetor merely responds to air that is flowing / being pulled through it.-----There may be issues there.-----So posting your compression numbers may also offer a clue.

Compression was 94 on all four cylinders. They were 120 two years ago so I might have a bad o-ring or something on my tester. I doubt they would consistently lose the same amount …

 

[Kevinm207]

Went through carbs again and sprayed them all out, checked compression with another tester and they’re all in the low 120s. It used to be mostly a mid-throttle and now it’s idle and mid-throttle. It will idle for about 15 seconds and slowly stall out (like a fuel issue). If I start it again (even without primer solenoid) it will usually start right back up and run for the same 15 seconds and stall. I’m now wondering about the fuel pump. After it stalls I checked and all the bowls still have fuel in them (although I can’t tell if it is proper level at that point) I have already unplugged VRO wires and capped the oil intake and am running premix. I’m thinking I will try an electric pump bypassing everything fuel pump related and tee in to the left and right side fuel lines that go to the rails on the throttle bodies. If that works, should I try to troubleshoot the float compartment? It looks like there’s a little fuel pump on the top that has its own pulse line separate from the main pump below, anybody know what that is? I’ve read about some people just switching to a basic fuel pump that bolts on to line up with a pulse port. Could I just put a regular fuel pump that has a pulse line input, fuel in, fuel out? And then cap the upper pulse line?

 

[racerone]

Fuel component package has a FUEL pump looking thing on it.----That unit is used on many small motors as the fuel pump.----On your motor it was converted to be a vapor extraction pump.----Replace gasket #26.---Check cover for warpage.----Some will argue.---I doubt you need to resort to an electric fuel pump.----The crossflow V-4 motors have a pulse port and a 2 nipple pump can be mounted directly over that with 2 screws and a gasket.

 

[Kevinm207]

I was thinking electric fuel pump just for testing/diagnosing. Then IF that fixes things I’d either a. try to figure out the problem with the current fuel pump/mixing system or b. get a new/simpler fuel pump that’ll run off pulse port/line. Maybe a little ahead of myself, planning solutions after my electric pump test totally fixes all of my problem

when you put a two port pump on the pulse port near starter I’m assuming you’re feeding the right side rail off one port and left side off the other? Do you have a solution for the primer solenoid? Would it be a good idea to cap the pulse lines running the VRO pump and the vapor pump or just leave them hooked up?

 

[racerone]

Do you understand what the primer solenoid does ??---Please explain how it works.----The primer solenoid is a wonderful device.----Remained unchanged for nearly 30 years.----It works very well.---The 2 port pump worked on the crossflow V-4 engines.----It is not practical to use a 2 nipple pump on you 60 degree looper engine.

 

[Kevinm207]

Yes, primer solenoid pushes some fuel through a separate little line directly in to the cylinders on the engine side of the throttle plate beyond carbs. My thought WAS that if I discontinued the VRO pump and used a two port pump I would need a new way to get fuel in to the primer solenoid. But I was getting my crossflow/looper terminology mixed up and missed that.

So, are you thinking on my looper motor I should troubleshoot my existing VRO (OMS?) pump instead of trying to simplify to a basic pulse driven fuel pump?

 

[Kevinm207]

Do you understand what the primer solenoid does ??---Please explain how it works.----The primer solenoid is a wonderful device.----Remained unchanged for nearly 30 years.----It works very well.---The 2 port pump worked on the crossflow V-4 engines.----It is not practical to use a 2 nipple pump on you 60 degree looper engine.

I will be looking at that gasket you mentioned either way, just wondering about next steps

 

[racerone]

The electric primer is a valve.----It is not a pump.-----When the engine is cranking and the key is pushed in ,the FUEL PUMP pushes fuel through the primer valve directly into the motor.-----In my opinion the VRO pump is very simple.----Easy to take apart for inspection / repair.

 

[Faztbullet]

Did you install the plastine washer under the inlet needles? If so this will throw off float setting a tad..not used on plastic 60° engines

 

[Kevinm207]

Did you install the plastine washer under the inlet needles? If so this will throw off float setting a tad..not used on plastic 60° engines

I put one in and saw how far off the floats were and decided they must not be correct for this engine — good tip though!!

 

[Kevinm207]

The electric primer is a valve.----It is not a pump.-----When the engine is cranking and the key is pushed in ,the FUEL PUMP pushes fuel through the primer valve directly into the motor.-----In my opinion the VRO pump is very simple.----Easy to take apart for inspection / repair.

Yep, pushes was the wrong term, but yes I understand it’s just a solenoid valve. I read that rebuild kits were expensive on the vro pump so I was thinking I’d just discontinue it and go simpler since I’m premixing anyway. But, I’m getting ahead of myself, first I need to figure out if it’s even a problem/not working correctly.

 

[Kevinm207]

No luck fixing the idle stalling issue with a bypass fuel pump. I guess I’m back to carbs, some sort sort of air leak maybe. Unclear why it’s able to start and run ok after stalling and then die again 15-20 seconds in. It’s a slow death as it starves for fuel, but then will start back up a little sluggish and then revs up to normal for 10 seconds and then start to slow down and eventually die out. I do see a little fuel coming out the bottom carbs after it dies sometimes but I think that’s just because of the way stalls and not a reed thing. Any ideas why it will restart ok but consistently die like this? Seems if it were a carb issue it wouldn’t run ok for 10-15 seconds so consistently. Maybe the starter is generating more vacuum through the carbs then it does when it’s running?

 

[RBoyd1971]

Make sure you didn't put the floats in upside down or something. What kind of shape is the foam in the cowling in? Maybe it sucked some into the reeds.

 

[Kevinm207]

Reeds all looked fine and moved freely. I pulled one of the intake manifolds so I could get a look at the gasket and remove the reed block for inspection. Couldn’t really see anything wrong with the gasket, but maybe the gasket was letting a small air leak in. It looks like the bottom is partially held in place by the throttle plate bolt so it’s possible with removing/reattaching the throttle plate the gasket isn’t sealing. I ordered the new intake manifold gaskets and the throttle plate gaskets. Looks like the replacement gasket is a fiber sheet like a head gasket instead of just a solid piece of rubber it has now, maybe that’s an improved design.
We shall see…

 

[FreeBeeTony]

Did you fix your problem? I have the EXACT same problem w/ a '95 175 60* Johnson. Did the intake gasket fix it?