Whenever my boat sits for more than about 4 days, the engine is impossible to start without putting some gas in the carb. (Weber 4bbl) I changed the fuel filter and the check valve at the tank (which was indeed bad, so I thought I found the problem) and had the carb rebuilt. The choke is closing. Only a couple of drops come from the nipples inside the carb when pumping the throttle. In order to get it started for the first time of the day, I have to fill an empty soda can about 1/5 of the way up with gas, then dump it in the carb. I know, not the safest way to do it, but otherwise the damn thing just won't start. For the rest of the day, it fires right up with just the slightest touch of the key.
Hard Starting Issues....
Tommygun
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Whenever my boat sits for more than about 4 days, the engine is impossible to start without putting some gas in the carb. (Weber 4bbl) I changed the fuel filter and the check valve at the tank (which was indeed bad, so I thought I found the problem) and had the carb rebuilt. The choke is closing. Only a couple of drops come from the nipples inside the carb when pumping the throttle. In order to get it started for the first time of the day, I have to fill an empty soda can about 1/5 of the way up with gas, then dump it in the carb. I know, not the safest way to do it, but otherwise the damn thing just won't start. For the rest of the day, it fires right up with just the slightest touch of the key.
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I have heard that on the weber's, and rochesters, the fuel will drain back into the tank after sitting for days, so what you need to do is crank it for 4-5 seconds to get the fuel back up to the carb, then give it 1-2 pumps with the throttle, then crank again, and it should fire right up, Works for me, and I dont even have a choke....
But then again, it never gets below 80* in South Florida, so who needs one
But then again, it never gets below 80* in South Florida, so who needs one
Sounds like the float is leaking and/or the accelerator pump is shot.
The accelerator pump draws fuel from the bowl. If the bowl has no or little fuel there will be no pump shot. There should be a sizeable stream of fuel coming from the accelerator pump when throttle is applied - apparently you don't.
Tell the rebuilder and have him fix it right.
The accelerator pump draws fuel from the bowl. If the bowl has no or little fuel there will be no pump shot. There should be a sizeable stream of fuel coming from the accelerator pump when throttle is applied - apparently you don't.
Tell the rebuilder and have him fix it right.
I took it back to the rebuilder today, and told them the problem. They claim it has to be a "needle seat", and that somehow it's impossible the accelerator pump could be the problem. I guess that's code for "we don't really feel like fixing it." Are accelerator pumps costly or something? What does a "needle seat" do? I'm still learning about carbs, so please pardon my ignorancecfm-tech.com said:
The needle and seat is the 'door' for the fuel to come in the bowl.
The float works this. If the bowl is full the float rises to the top and shuts off the needle and seat. When the fuel lowers the float drops and opens the needle and seat.
Parts for these carb's are very cheap.
Again, the accelerator pump uses fuel from the bowl. When the throttle is applied the acc. pump squirts a large stream of gas into the throttle bores.
A cold engine needs a lot of raw fuel to get started. If there is not much fuel in the bowl or the accelerator pump doesn't inject much fuel you will have a hard time starting it.
The float works this. If the bowl is full the float rises to the top and shuts off the needle and seat. When the fuel lowers the float drops and opens the needle and seat.
Parts for these carb's are very cheap.
Again, the accelerator pump uses fuel from the bowl. When the throttle is applied the acc. pump squirts a large stream of gas into the throttle bores.
A cold engine needs a lot of raw fuel to get started. If there is not much fuel in the bowl or the accelerator pump doesn't inject much fuel you will have a hard time starting it.
The Webers needle and seats are on top - so I don't see how it's possible that they are letting fuel leak out. Maybe sticking closed and not letting enough in? Dunno - but that should cause other drivability issues too.
Okay, not that familiar with the Webers, but something to try.
If I remember correctly, the accelerator pump uses a piston and spring.
If you apply the throttle slowly the spring tension let's this circuit soften, or bypass, how much fuel is sent into the throttle bores. This was done because the rate of fuel the engine needs this circuit is determined by how fast the throttles are opened.
IE: quicker engine acceleration creates a larger time delay of booster response to the changing airflow. Slower acceleration shortens this gap.
So, try this - when first starting give the accelerator a few very quick pumps and see if this helps.
Okay, not that familiar with the Webers, but something to try.
If I remember correctly, the accelerator pump uses a piston and spring.
If you apply the throttle slowly the spring tension let's this circuit soften, or bypass, how much fuel is sent into the throttle bores. This was done because the rate of fuel the engine needs this circuit is determined by how fast the throttles are opened.
IE: quicker engine acceleration creates a larger time delay of booster response to the changing airflow. Slower acceleration shortens this gap.
So, try this - when first starting give the accelerator a few very quick pumps and see if this helps.
I've tried pumping it like mad both before, during, and after cranking. I easily pump it 50 times trying to start it, yet the only thing that will fire it off is pouring about 1/3 cup of raw gas into the carb. I had an assistant pump while I looked into the carb, and just a drop or two comes from that horn thing with the 2 nipples at the front of the carb body. Is there a way the fuel pump could be bad, yet still provide enough fuel to run the engine? How would you test one? I don't have any starting problems for the rest of the day after it's been warmed up.
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One of my old pontiacs did the same thing. It turned out to be a fuel pump. I might be wrong on this but I believe if the diaphram in the fuel pump has a small leak, you will not get enough fuel pressure while cranking to lift the needle off the seat which fills the float bowl. It may produce enough pressure to keep engine running due to the increased rpms while it is running. All this pertains only if you have a mechanical pump on the engine block.
Either way, your carb is fairly easy to work on. You have to remove the top of the carb. Disconnect linkage to choke butterfly and remove the two mounting bolts on top front of carb. Remove rod from accelerater pump(arm attached to linkage that moves up and down when throttle is pumped, top right front of carb) and several slotted screws. Once the air horn(top of carb) is removed you can remove accel pump diaphram(rod with a spring around it). Slide it out and slide a new one in. They cost about 4 bucks, and you can get them anywhere. Put it back together and your done.
Either way, your carb is fairly easy to work on. You have to remove the top of the carb. Disconnect linkage to choke butterfly and remove the two mounting bolts on top front of carb. Remove rod from accelerater pump(arm attached to linkage that moves up and down when throttle is pumped, top right front of carb) and several slotted screws. Once the air horn(top of carb) is removed you can remove accel pump diaphram(rod with a spring around it). Slide it out and slide a new one in. They cost about 4 bucks, and you can get them anywhere. Put it back together and your done.
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I would try pouring fuel down the bowl vents rather than down the throat of carb. Maually fill the bowl, then immediately pump the throttle. If gas squirts out in two steady streams for each pump then accelerator pump is good. Let it sit overnight with a full float bowl. If you pump it in the morning and nothing comes out, it could be leaky float, etc. Most accelerator pumps ive seen go bad caused a hesistation from off idle. Chances are if when its running and doesnt hesistate or stumble when you come off idle i doubt accelerator pump is bad. Hope this helps
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NMH - good Idea, I have been thinking about this thread and I agree, if the accelerator pump was bad it would stumble or "lean pop" when trying to accelerate. The pump can't pump when the bowl is dry either (after sitting)
A friend told me a while back that there was a fuel filter for the Quadrajets that had a little flapper valve in them so fuel couldn't drain back out of the carb. I know the Webers filters in the carb is a little screen @ each needle so I guess that wouldn't work on those.
What gets me is that all modern boats have an Anti-siphon check ball thingy and you can't blow back through 'em so in theory the fuel can't go back to the tank!
The Weber has two vents - does that make a difference with evaporation? As posted earlier, EVERY Weber I have seen is a hard starter and I really don't know why.
A friend told me a while back that there was a fuel filter for the Quadrajets that had a little flapper valve in them so fuel couldn't drain back out of the carb. I know the Webers filters in the carb is a little screen @ each needle so I guess that wouldn't work on those.
What gets me is that all modern boats have an Anti-siphon check ball thingy and you can't blow back through 'em so in theory the fuel can't go back to the tank!
The Weber has two vents - does that make a difference with evaporation? As posted earlier, EVERY Weber I have seen is a hard starter and I really don't know why.
Well I got my carb back from the rebuilder. Now it finally works. They replaced the needle and seat, and another float. Well we went in the back of the shop to run the carb on their test engine, and low and behold, nothing would squirt from the accelerator pump nozzles, no matter what. They took it apart, blew compressed air through the nozzles, put it back together....success! Not only did it start the test engine, but mine cranks right up too! Haven't ran it in the water yet, but hopefully my stumble on hard acceleration will be gone too. Thanks for all the good inputs here everyone. One more question; how does gunk get in the accelerator pump nozzle and block it when we religiously replace spin on filters on boats? Is there something I can do to keep it clear other than taking the carb apart and using compressed air? Thanks!
"One more question; how does gunk get in the accelerator pump nozzle and block it when we religiously replace spin on filters on boats? "
There is "varnish" in the gasoline. Every time the accelerator squirts, a thin film of gasoline is left in the tube and evaporates. Over many pumps, the varnish builds up. I would guess that eventually it will plug the tube.
A car gets many more changes of throttle setting. Just guessing that maybe each new squirt on a car ether keeps it wet or helps to wash out the old. Boats usually maintain a fixed setting for several minutes and would not squirt from the acc nozzles.
There is "varnish" in the gasoline. Every time the accelerator squirts, a thin film of gasoline is left in the tube and evaporates. Over many pumps, the varnish builds up. I would guess that eventually it will plug the tube.
A car gets many more changes of throttle setting. Just guessing that maybe each new squirt on a car ether keeps it wet or helps to wash out the old. Boats usually maintain a fixed setting for several minutes and would not squirt from the acc nozzles.
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