High quality accelerator pump? (1 Viewer)

[Pete483]

I set about to diagnose my difficulty in cold starting my 1977 FJ45 and as I suspected, the accelerator pump is no good. I rebuilt the carb quite a while back with a cheap GP Sorensen parts kit and while everything else is fine, the accelerator pump seems like something where quality could vary dramatically. The boot also disintegrated pretty quickly which sounds like is not atypical. This is a non-USA spec truck and my Aisan carb has an H3660 tag on it which from some other threads seems to be Aisan PN 21100-61010. From Mike's rebuild kits it looks like it is identical to other 2f carbs in all the ways that matter for a rebuild kit.

I've done some searching and it doesn't look like anyone sells just the pumps (Mike's has some, but not for 2Fs) , so I am assuming I'll need to buy a full kit, but though I'd check here for recommendations on what has the highest quality pump and boot. I appreciate any advice!

 

[MDH33]

Ethanol will melt the rubber parts. I usually get the keyster kits for the jets and the Napa kit for the leather acc pump plunger and top baffle. I only run non ethanol in my carb'd cruisers.

 

[mattressking]

Rubber or leather accelerator pump? OEM is leather and NLA. Cityracer, Napco, Hygrade provide leather APs. Stick with those - that's it. What makes you think the pump is bad? Did you inspect for a good spray out of the nozzle in the primary? If you have a good spray (and be honest here that you checked, too many folks fake their analysis and make it much harder to determine the fault) then pump is fine. It’s a very simple system that rarely fails unless it clogs or is totally torn/missing.

If no spray, then pop the carb lid off and remove the pump and analyze. A broken boot is not important, but good for keeping dirt out (but let's be real - these truck don't get dirty like they used to).

 

[Pete483]

The GP Sorensen kit came with a leather one, but it was a super cheap kit at the time, so I can't imagine it was the highest quality part.

My diagnosis of the pump was that the truck starts fine as long as the temperature is above 50ish and that pumping the accelerator didn't have a noticeable impact. I took the air cleaner cover off and there is zero spray out of the pump jet and the plunger wasn't moving very smoothly when I pushed it manually. When I took out the pump, the leather wasn't torn, but it was kinda stretched and distorted on one side and won't go back in.

I do still want to confirm that the root cause isn't a clogged port that didn't give the fuel anywhere to go when the pump stroked. It seems like that could explain the damage to the leather.

The boot tore very soon after install but I didn't bother doing anything it because, as you said, I wasn't getting the truck that dirty; however, I'm moving the truck to a place on a dirt road in the spring so I'd like to find one that lasts.

 

[Grayscale]

Pumping the accelerator isn't really how these things start. The carb basically produces three kinds of fuel: straight-up air, the tiny gas droplets mixed with air from the regular fuel circuits, and, a stream of fuel from the pump plunger. The vacuum at cranking isn't sufficient to do much with puddles of fuel in the intake manifold, so avoid pumping the accelerator if you don't have to. The raw fuel from the pump plunger is just to take advantage of the already smooth running carb at idle or above.

Yes, during a hot-start, open the throttle when cranking. But for my worn-out motor, no pump is ever needed if the choke butterfly is in the closed position.

I found that the original Aisan carb is a total f-up when it comes to the design of the pump plunger. If you ever experience a lean-stumble when negotiating traffic, this is one of three common reasons that all might contribute to it. It gets gas all over the interior of the throttle bore. I've seen carbs spray gasoline right to the crack on the throttle plate. It makes no sens trying to scavenge fuel off of cold walls on a carburetor if you don't have to.

 

[Pete483]

Isn't a pump or two of the gas pedal a totally normal start up procedure? Are you saying I should be able to start the truck just fine in sub-freezing weather without an accelerator pump? I'm also not sure what you mean about opening the throttle when cranking on a hot start. Once its warmed up, it generally starts pretty well without the accelerator pump and if its warm enough outside, I can restart it with half or no choke.

When the pump was working, it used to give a nice mist of gas in the primary. I could certainly see how a dribble instead of a spray would be less than ideal, but I don't see why there would be puddles of fuel in the intake manifold unless you pumped it a ton or just let it sit for a while after pumping it.

Now that it's not working at all, I need to give it a spray of carb cleaner to get it started in the cold. It still runs totally fine in the summer and I don't notice stumbles on acceleration, but I am pretty sure the pump has been out for a while and I do notice lean stumbles in cold weather. My understanding is that fuel atomizes more poorly in cold air, so the engine tends to run leaner in winter. In doing some research to trouble shoot, I've seen that there are people who change jets in the winter. I'm not about to do all that, but it seems consistent with my experience that my truck has run okay in warm weather without a functioning accelerator pump but not great in cold weather, and the lack of the accelerator pump is to blame for that.

 

[Grayscale]

Yes, pull the choke, turn the key, regardless of how cold it is. This is my experience on every carb I've run. It should keep the plugs from fouling if you minimize the gas at startup, and avoid diluting the oil with gas. Under the carb is a depression where gas can puddle in the intake manifold, not really when it is running, but when you are starting the engine.

When folks report vapor lock, a "hot-start," just open the throttle (depress the gas pedal) a bit while you turn the key. It is thought that the the carb is too rich when hot, and the throttle can let in some more air.

 

[flx]

When I did my carb the accelerator pump included in the Keyster kit was really not of great quality, felt very cheap in hand.
So I bought the plunger from Mike's carb and the quality is really great (and it's a leather cup).

Can't find the plunger for a 2F carb sold alone but they have a complete kit that includes the plunger: Aisan Toyota Carburetor Kit | Land Cruiser 1975-80 K4422 - https://www.carburetor-parts.com/aisan-carburetor-rebuild-kit-k4422
So maybe if you send them an email they can sell the accelerator pump alone?

 

[Pete483]

When I did my carb the accelerator pump included in the Keyster kit was really not of great quality, felt very cheap in hand.
So I bought the plunger from Mike's carb and the quality is really great (and it's a leather cup).

Can't find the plunger for a 2F carb sold alone but they have a complete kit that includes the plunger: Aisan Toyota Carburetor Kit | Land Cruiser 1975-80 K4422 - https://www.carburetor-parts.com/aisan-carburetor-rebuild-kit-k4422
So maybe if you send them an email they can sell the accelerator pump alone?

Thanks. I went ahead and just ordered the full Mike's kit. I had the same experience with the GP Sorensen pump, it was leather but just looked cheap.

 

[Pete483]

I don't know, it would seem like if your carb is running rich enough to start that easily in cold weather, its probably running way too rich in warm weather. Having poked around mud for a while, it seems like it is not at all uncommon to give a couple pumps before starting. I rebuilt the carb following the Pinhead video and set it up following the FSM proceedure. How are you setting up your carbs that they start so easily?

I still don't see how a couple pumps from the accelerator pump is going to pool in the half second between pumping the gas and turning the key . . .

I've never had vapor lock issues, but isn't that a completely unrelated issue? The only time I touch the gas pedal while starting is if its flooded, but the upside of the non-functional accelerator pump is that it is nearly impossible to flood.

 

[Grayscale]

How do your spark plugs look? Proper ignition and no vac leaks, and it will not require pumping the gas pedal.

I probably get more "vapor lock" than others because the atmospheric pressure is much lower here. Everything boils at lower temps.

I only get FSM numbers when I set the idle rpm in the higher range of normal setting. The pic below tells you that I'm already too worn out for further service according to FSM, lol. Right now, cold start, below freezing, and no problem. Plus, the choke itself already "pumps" gas when the fast-idle cam is set.

 

[Grayscale]

Was your carburetor ever put out-of-service? Either on the vehicle or not? Is it alloy or cast iron on the bottom section?

 

[flx]

The engine may start without pumping but it's part of the official cold start procedure to pump the gas:

 

[Pete483]

I have no clue on the history of the carburetor, but this thing is a former Nicaraguan farm truck so it is safe to say whatever the worst thing that could have happened to it has probably happened. The bottom section is cast iron. No vacuum leaks and there are hardly any vacuum lines on this thing anyways. I replaced the intake/exhaust manifold gasket. Last time I checked vacuum pressure it was in the normal range and I did a compression test and everything was within spec. I've done timing, but haven't adjusted the valves.

When I bought it, it was super rough overall and only started by pouring gas down the top and didn't have a choke cable. I rebuilt the carb, got a choke cable and got it to the point where it could actually start and drive. It then sat for a while as I got the brakes sorted out, but I didn't bother dialing in the carburetor until then. Got it running well enough although I have it set to idle a little high as the throttle linkages are pretty sloppy. At some point it has developed the accelerator pump issue. In general, this truck has sat a fair amount since I've had and I really don't drive it too much. It has the Central American farm truck anti-corrosion package (no heater), so normally I don't take it out in the winter at all and I'm sure that has contributed to issues. I try to remember to put some Seafoam in the gas if its going to sit for a while, but I don't awalys do that. I bought some of the ethanol stuff that Mike's sells to give that a try. I need to move it around a bit this winter which is why I decided to try and tackle this now.

In any case, I was able to mush the leather back together enough that it fit in and it seems like there is a blockage in the nozzle somewhere. I'll probably just strip it and dip it again at some point since I bought the whole rebuild kit, but is there another way to clean the nozzle? I'd rather wait until spring to rebuild it since it won't get driven much over the winter. Maybe just filling up the area where the outlet check ball is with carb cleaner or taking out the outlet ball and spring and try to blow air back up the nozzle? My recollection from the rebuild is that the nozzle is permanently in there.

I knew about the pumping for cold start, but I didn't realize the the factory specifies holding the gas pedal half way on a warm start. Good to know.

 

[Grayscale]

My original carb was an Aisan that was cast iron. After rebuild it ran with lean symptoms. Replaced with new Aisan. This time, they built it with an alloy base. I'm concerned that my original carb was too internally rusted to ever run correct, as it sat without gas for how many years. I understand that carb dip can remove varnish, but, what about the rust? Now I get better mpg, my jets are smaller, and I don't have as much of lean stumble. I don't know what is going on, but, I'd like to throw my original carb in the trash if it can't actually be cleaned out.

I'm a spark-plug-reader-type. They tell you way more information than the internet, especially if you don't have EFI.

 

[Pete483]

I don't recall it looking too bad, but haven't had it apart in a while. The outside isn't paricularly rusty. Everything seems to repond as it should when I do the lean drop procedure. I'll try to the get the accelerator pump working and take it from there.

I just pulled a plug and it's a little carbon fouled, which I think is a symptom of my current starting difficulties rather than the cause. In the summer when I drive more and don't have trouble starting, the plugs look fine.

 

[Grayscale]

You know that the power valve enriches the fuel circuit when vacuum is low, like at startup?

 

[Pete483]

All I know about the power valve is that it is turned "off" when the plunger in the top of the carb is pulled up by vacuum and "on" when the vacuum drops and the plunger falls, so it should be off at idle and on at higher power. I've seen from diagrams that its vacuum source is down in the bottom section. I would have thought that with the choke on, vacuum would be higher during startup so the power valve would be off.

 

[Grayscale]

I have a couple of USA intake spacers/insulators, and I don't think that I'm getting vacuum to my non-USA Aisan's power valve. Your thread just made me realize it. I wonder who else wasn't informed that the vac is different on the non-US Aisan 2F carbs, ughhhh. I must have been out of my mind because I didn't question it. Too often with shopping for mech, it is like, here it is and we are done. No, these threads go for pages in the forum, and they won't give you enough pixels to see what you are buying. I guess I need to drill a hole in my spacer/insulator to get full performance out of this thing?

 

[flx]

Mhhh isn't a passage going in the main body to get the vacuum of main body?
I don't think it's meant to go through the insulator.