It looks like 5/64 is just under 2mm. So I know the 3mm tuning was a snug fit. I would probably say you will have a hard time with it.
I have noticed in my search for new carburetor that the only one I can find that looks like my 3+2 is used and very expensive. I have found several new ones but all the choke actuators etc are different. What should I be concerned with when looking for a new carb. Thanks for any advise.
I had found one on Ebay for $107 but the choke was different and wasn't sure on all the vacuum lines?
I guess first question is why exactly you think you need a new carb. There are several different rebuild kits out there and all the information is on here now to tune it. If you are set on replacing I would stick with a factory replacement no matter the price. There are some threads that cover replacement with a 3+1. I guess the best thing to ask yourself is how much is you frustration worth? Personally I would spend a few hundred more to not even think about it.
Mine has some mounts that are broken for diaphragms and has too many of the choke components missing Also what would be the difference of a DD51T and a DB51T carburetor because I have yet to find a DB51T carburetor that looks any thing like what's on my truck
You say you have not found one that looks like what is on your vehicle. Are you positive that what is on there is what should be on there, or has someone already done some messing? Hard to guess what has transpired over the years to these vehicles. Fred
I'm pretty sure it is the original it's just when I search carburetor for a DB51T all that pulls up have different vacuum configurations but the carbs for Dd51 seem to look very similar to mine. When I see a used carb for for the DB51T it looks correct. I don't see a reason to buy an used carb for twice the money with who knows what kind of problems it has when a new one is half the price. It's not so much the cost as getting a good working carb. Trying to figure out if there is difference in carbs on the different models or do I just stick with the F6A engine group.
Well I don't know for sure but it wouldn't make sense to me for different models with the same engine to have different carbs. I would think that all F6A would have same carb setup, being that it is specific to the engine.
Cole I wanted to say thanks for all the info in this post. I ordered a new Carb out of Hong Kong that was a modern version of mine and with only a few mods to it was a great replacement. The hardest tuning issue I had was getting the Choke Plate adjustment made. It was remaining at almost full choke and after several adjustments I have it close and may have to do some fine tuning as the weather gets colder. After getting it set I followed your tuning tips and it worked fine. The truck starts with just a bump of the key and goes through its warm up procedure great. The only thing left for me to find is the accessory idle up vacuum line. I'm not sure were the vacuum switch is located that operates this feature.
Hey awesome! No problem. Glad it helped you. If everybody can contribute something we all will benefit!
Great write up i have attached some diagrams and such that i found to be helpful, as well as a picture showing the actuators as well as what they do and finally an diagram to show the diff between 2+3 and 3+2
milmor88, what's that black line off the manifold right in front of the carb going to? I'm drawing up diagrams for the 94 Scrum Van to share, once I get it all sorted
milmor88: in the "vacuum lines overview" pic, black line going to a union in the intake manifold directly left of the alternator and north of the carb, oriented north-south. The nipple/union itself is hidden under the black/gray line running east/west to the thermo switch. It's definately a vacuum line.
Still trying to figure out my 4wd van. I suspect that union is either for the 4wd or the airbox hot air flap system. Leaning towards airbox. Can anyone confirm?
^^ 99% sure that union is connected to the airbox hot idle compensator now, which lets extra air into the engine to lean it out when the fuel in the carb is hot and running rich. The 4wd is connected to the fast idle circuit's vac supply, and works now! woohoo! See my "1994 Every/Scrum van w/AC and part time 4wd vacuum diagram" thread in the Microvans subforum to see the master vac diagram I put together for these vans. I'm 99% sure I got it right, BUT it's not quite working right on my van. As soon as I start the engine the fast idle actuator pulls up even though everything is turned off and the engine cold. I disconnect the cables to the two vacuum valves, and it still pulls it up w/ vacuum coming from BOTH valves, so I'm guessing when no power is applied to them they default to passing vacuum. Any ideas how to troubleshoot the fast idle circuit??
Have you tried pulling the wire from the fast idle relay that is under the dash(based on parts Diagram I'm fairly certain you can reach it by hand) to see if the actuator stops pulling up? If it does, you have a faulty relay. I had a 1995 Every where that relay, the place where it is supposed to be screwed on, and the wiring was removed and the actuator did nothing due to not getting power. It moving when no accessories are on would indicate the relay is not functioning correctly.
Well, I'm assuming those vacuum valves are normally open, because even with power disconnected from the two valves I'm getting vacuum from both of them, so pulling the relay would not change anything that that did not accomplish... The system DID work before I fixed other parts of the vac system, but I've got it plumbed according to this diagram and I'm not sure what's going on:
Hey just replacing a carb now and the small line from the manifold direct downstream of carb goes to a tee which then goes into the airbox right beside where it connects to the boot that goes to carb, and the other part of tee goes to the forward airbox vac. Line nipple on bottom of airbox. Back bottom nipple on airbox connects to the warm air actuator thing which i have removed and therefore capped. The line off the intake came off on mine today couldnt figire out why it couldnt idle and dipped in rpm randomly on way to work. It also had a hell of a time starting...backfired so loud it was like a 12 ga.
can anyone tell me where this #6 screw is? i cant find it.... the pictures Cole has posted here isnt exactly how my carb looks... manual hasnt shown up yet.
If you don't want to get crazy over that A/F ratio screw, just drill a ½in hole beside the seat belt anchor...
^^^^^ nice common sense tip! might just have to do that! cant even get that plastic protector off of the top of it as it is currently.
Here's another diagram for the vacuum line (came from megazip.net site) with a 3+2 configuration. Does anyone knows what is the purpose of #7 part. It kind of cut vacuum to the choke actuator and also the EGR valve...
No clue what that thing is there. The Japanese did things back then that somewhat useful but some things were more of a "why not?' kind of thing so unless you can find someone with the knowledge of what it is.....its just that little thing on our trucks with a couple vac lines going to it that you don't dare disconnect or it will run worse than it already does.
Back on this carb topic. I have never been able to set my choke rpm's with the #5 screw. My carb is tuned perfectly, vac lines are new silicone etc, truck runs perfect and all other carb functions work perfectly. Only problem is that as the choke backs off as the coolant circits warm the rpms don't settle down because they never start high. In fact it starts at the regular ide rpm's all the time. Only problem with this setup is that when it gets below 50degrees F it doesn't start. I can look at the choke and it is working and opening up perfectly as it should as the pusher pin retracts. I had my #5 screw turned all the way, nuthin. backed it out 2 turns …..nuthin. does backing the screw out raise the choke rpm's? Anyone have any input on this one?
#7 is a thermostatic vacuum valve. They came in various flavors, with the various ports opening and closing at different water temps. Typically they were color coded, with the color being cast in the plastic body or seal of the screw in base to the port assembly. I used to have a chart which explained what ones did what. But unfortunately, I got rid of it a few moves back. NiponDenso made them for most Japanese manufacturers, and if needed you should be able to find a new one using the number of ports, and color. NAPA might even have them, and be able to match them up if you go in on a week day afternoon when they aren’t busy.
Where can you find these threads for a 3+1 conversion? I'm new to this site (and owning one of these little trucks), and maybe I'm not searching the site right, but I can't find anything. Before I read this (and out of frustration with my old carb) I bought a new one, but it is a 3+1. It had a 2+3 originally (1993 year model). The new carb runs a lot better at higher rpms (over 2000 rpms), but dies if less than that. Sometimes at some lower speeds it will run for a bit, then (seemingly for no reason) quickly tries to die. Pumping the accelerator is the only way to keep it from dying. I've worked on a lot of car engines. Cut my teeth on GM and Ford V8's, have worked on tons of boats and Sea Doos - motorcycles too, and thought I was a pretty good mechanic, but these things are a seemingly needlessly over complicated pain! Especially the crazy vacuum maze! Anyway, help with adapting a new 3+1 carb to what was a 2+3 would be greatly appreciated!
