Quit screwing around and fix your intake manifold vacuum leak. Start by setting your idle speed to 550 RPM And then check all the possible leak points. You won’t be able to tell the speed change if you are “idling” at 1500 RPM.
Carb leaking fuel (2 Viewers)
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
- Thread starter
- #22
I ordered a new intake, I think @mattressking is right and its not sealing on head properly. Was too fixated on other possibilities. There was wmnarpage on this intake in both direction. Got a new carb coming off of City Racer as well.
On another note, How can one check if idle solenoid is malfunctioning? Does the whole connection need to be replaced or just the second part that clips on? For the chinese carb I had simply used the one that came with my stock aisin, but not sure if that is a bad idea and I need to rewire to a two wire connection than the clip in connecting I now have.
Thanks for your guys input. Slowly but surely....
Dan
On another note, How can one check if idle solenoid is malfunctioning? Does the whole connection need to be replaced or just the second part that clips on? For the chinese carb I had simply used the one that came with my stock aisin, but not sure if that is a bad idea and I need to rewire to a two wire connection than the clip in connecting I now have.
Thanks for your guys input. Slowly but surely....
Dan
- Thread starter
- #23
Replaced the intake itself. Bought a city racer carb and am currently using that. New gasket etc spark plug gap is good, all spark tubes work.
Dealing with vacuum and running issues still. I Am wondering if it’s still somehow intake related even though everything was straight or machined. Intake had 1/32nd of variation in it crossways and a 64th on the top where the carb mounts (more on that later) I can get it to idle at 490, it’s just super rough and vacuum is at 12 mercury. I can get it to 15 mercury at 800 rpm and it actually looks steady when I advance the timing. But it doesn’t last and eventually starts to rough idle again. It’s impossible to tune still though.
Sprayed soapy water on intake surfaces everywhere and nothing was getting sucked in, but brake cleaner was causing revving. But I guess it’s possible the brake cleaner spray direction made its way to the carb by deflecting the hood.
I sprayed on the EGR block off plate and got a huge drop in RPM a few times in a row, but minutes later it stopped having an effect but vacuum stayed the same?
Can vacuum/ intake leaks come and go?
Can a too tight if valve be chasing this?
Is going underneath the vehicle and using brake cleaner on the underside mating surfaces needed or does spraying above give same results? Don’t know how to do soapy water method on underside of intake, and brake cleaner method is inconsistent seemingly.
Is a 12-15 mercury reading at idle a guarantee of an intake leak?
Dealing with vacuum and running issues still. I Am wondering if it’s still somehow intake related even though everything was straight or machined. Intake had 1/32nd of variation in it crossways and a 64th on the top where the carb mounts (more on that later) I can get it to idle at 490, it’s just super rough and vacuum is at 12 mercury. I can get it to 15 mercury at 800 rpm and it actually looks steady when I advance the timing. But it doesn’t last and eventually starts to rough idle again. It’s impossible to tune still though.
Sprayed soapy water on intake surfaces everywhere and nothing was getting sucked in, but brake cleaner was causing revving. But I guess it’s possible the brake cleaner spray direction made its way to the carb by deflecting the hood.
I sprayed on the EGR block off plate and got a huge drop in RPM a few times in a row, but minutes later it stopped having an effect but vacuum stayed the same?
Can vacuum/ intake leaks come and go?
Can a too tight if valve be chasing this?
Is going underneath the vehicle and using brake cleaner on the underside mating surfaces needed or does spraying above give same results? Don’t know how to do soapy water method on underside of intake, and brake cleaner method is inconsistent seemingly.
Is a 12-15 mercury reading at idle a guarantee of an intake leak?
@Beehanger Did you properly tune the carb after you installed it and are you seeing steady fuel in the float bowl?
Yes vac leaks can come and go, but they mostly go. Metal expands as it heats up, so that type of vac leak would mostly be seen on a cold start. Once all the metal bits warm up and expand they seal better.
Was the intake torqued to spec? was the exhaust manifold outlet and EGR block off torques to spec? Is the EGR inlet to the manifold properly plugged? Is the carb isolator plate bonded gasket in good condition? Have you verified vacuum line routing for the systems you're keeping? Why did you rewire the fuel cut solenoid? Is the carb bolted down properly? did you check all the screws on the carb were tight when you opened the box? There's a lot of things you haven't mentioned that could be the source of a problem.
Yes vac leaks can come and go, but they mostly go. Metal expands as it heats up, so that type of vac leak would mostly be seen on a cold start. Once all the metal bits warm up and expand they seal better.
Was the intake torqued to spec? was the exhaust manifold outlet and EGR block off torques to spec? Is the EGR inlet to the manifold properly plugged? Is the carb isolator plate bonded gasket in good condition? Have you verified vacuum line routing for the systems you're keeping? Why did you rewire the fuel cut solenoid? Is the carb bolted down properly? did you check all the screws on the carb were tight when you opened the box? There's a lot of things you haven't mentioned that could be the source of a problem.
I'm gonna say no. If I advance my timing the vacuum goes up, retarding makes it go down.
- Thread starter
- #26
I didn’t have a vacuum leak as far as I know at the carb/insulator plate surface, but when I pulled it the gasket seems to be soaked in gas. Is this normal or indicative of a vacuum leak?!
Hokie LX
SILVER Star
I can't tell from your pic but are your studs in good shape with useable threads? The ones that go through the insulator plate that you bolt the carb to. Is the carb getting torqued down to spec or are the nuts spinning on bad threads causing an air/vacuum leak due to the loose carb?
A carb leaking gas out of the throttle plate shaft bushings is often a sign of an engine with an intake manifold leak. Because of the air leak, the engine can’t get enough fuel to idle, so to compensate, the idle speed is increased so that the engine can barely run off of the main nozzle. This leads to fuel dribbling on out of the nozzle and onto the throttle plate, where it seeps out and on to the insulator below. Take the air cleaner off and look to see if you can see fuel dripping out of the primary main nozzle when “idling”.
If you have a new intake manifold and gasket and you still cannot get a idle vacuum above 18 inches, then you may have problems with something that connects to the intake, like the brake booster or you may have a couple of intake valves that are not seating or out of adjustment.
If you have a new intake manifold and gasket and you still cannot get a idle vacuum above 18 inches, then you may have problems with something that connects to the intake, like the brake booster or you may have a couple of intake valves that are not seating or out of adjustment.
Last edited:
- Thread starter
- #29
Advice on whether I should buy a Land Cruiser
What do you mean has caused you some excitement? I don't wanna talk about it.
forum.ih8mud.com
