Help! Stock Carb Tuning. 80 D50

[bchavez93]

Hello everyone,
Hoping to get some help tuning my stock carb on my Automatic 1980 D50 2.6L w/AC. I recently put in a new motor and sent the carb to be rebuilt. When I first got the truck, it was not in running condition due to someone blowing up the engine. Rod shot out the block. I figured it would be a good idea to have it rebuilt since I didn't know the condition of it or how long it was sitting. Right now the truck idles when cold, albeit rough, but drives fine. I am able to drive it if I keep my foot slightly on the gas with rpms at or above 900. when warm it doesn't like to idle and will stay idling very rough for about 10 seconds before dying out. Will start right up, with help from a little bit of throttle, afterwards. I was wondering how I go about even starting to tune the carb and how to identify the SAS screw and Mixture screw mentioned in the service manual. Is there a certain number of turns for each screw that I should start at? I really want to get it running and since I'm in California, I would like to keep the stock carb. I'll attach a picture of the screws I can see.

[xboxrox]

bchavez93 HELLO
I tried rebuilding a Mikuni carb never understood the settings much
Try a new ignition coil

[FMS88]

Look at this 1980 factory manual that's in the Manuals and Other Tech section: http://www.mightyram50.net/d-50/Fact...UEL_SYSTEM.pdf

Hopefully it has all the answers to your questions.

[bchavez93]

Yea, thank you. I've gone through the manual. But I cant seem to get it set right. I'm very mechanically inclined, but carbs are before my time. I've read these are a pain to tune, and I would like to get it working myself instead of paying someone to. I don't want to move screws willy nilly and end up with a non-running truck.

[FMS88]

Okay. I've never worked on a 1980 Mikuni, only later models which are much more intricate and difficult to diagnose or rebuild. Yours is much less complex, but you're still wise to proceed with caution.
In your photo the idle mixture screw is on the left, while the right screw adjusts the idle speed. The rebuilder may have set these as part of the rebuild. So if you can contact them, see how the set them and what recommendations they have for making adjustments. They may also be able to offer advice on how to correct the poor idle issue.
Other possibilities are that there's a significant vacuum leak, one or both of the EGR valves are stuck open, or the choke isn't opening. Check that the hoses are routed correctly and that they have no cracks or tears. Look for carbon build up that is keeping open the primary EGR valve (attached to the intake manifold) or the sub-EGR valve next to the carb base. Lastly make sure the choke is fully open when hot.
I'm lost when it comes to the two valve EGR system and the water choke, but there are other members who can help you with those if they appear to have issues.

[xboxrox]

What I would do is turn the idle adjusting screw while using a digital $20.00 tachometer and set the idle speed to sticker specs when the engine is fully hot THEN if not fixed I WOULD. install a NEW Ignition Coil...

My signature says it all DODGE

Please share how you fixed the issue & good luck

[bchavez93]

Thanks for all you suggestions. I replaced all vacuum hose and i believe i have them routed correctly, but I'll double check. The intake and EGR valve were cleaned when they were off the engine, and everything seemed in working order, at the time. I'll have to check the Sub egr, not sure which that one is. I do believe the Choke is open after warm up

Yea, im currently using an Actron multimeter that can measure RPMs. Got the Rpms down to 700s but misfire and die. Any particular ignition coil you'd recommend?

[FMS88]

If you haven't already, look at the emissions section of the service manual: http://www.mightyram50.net/d-50/Fact...ROL_SYSTEM.pdf .
It discusses the primary and sub-EGR valves as well as other emission components. Being that some are integral to the carb, it's very possible that what seems like a carb problem could in fact be an emission system fault.

[xboxrox]

Any original style canister coil nothing special ~ for ignition high tension wires twist & flex them while using your DMM to check for continuity & remove all dielectric grease from their end connections including spark plug tip (dielectric grease can cause misfires) the distributor cap & rotor should be good as new condition ~ distributor point gap and/or Icm gap must be correct ~ what else !?!

FUEL a weak fuel pump clogged fuel filter bad gasoline (contaminated with water sludge etc) recommend using NON ETHANOL gas purchased at a boat marina its the best gas I can find here in Hawaii (suggest you buy 5 gal at a marina and remove all the exiisting fuel in your truck's fuel system) ~ my truck ran better after replacing the plastic purge valve & plastic check valve near the gas tank ~ my truck also has a 2nd fuel filter inside the gas tank attached onto the tank's drain plug I replaced these 3 parts with new factory parts ~ I am not sure what your 1980 truck is equipped with..?

Keep trying you will get the solution ..!