86 mighty max wont start? Carb parts identification and removal tips

Hi, i'm getting fuel to the carb, but i don't believe i'm getting it through it. I'm having a hard time removing the upper half of the carb to get to the bowl. couple questions... what is the switch held on by the two brass plates and screws in the lower right corner of this picture ( stole this picture from a different thread).


http://www.mightyram50.net/vbulletin...id=26050&stc=1

Also, just to double check. I should be able see gas spraying into the valve body when i turn it over, from the brass jet above the butterfly valve on the left correct?

https://lh3.googleusercontent.com/HQ...-no?authuser=0


Also any tips on how to remove the upper half? i see the 4 main head bolts, and the two screws in the valve body. not finding much else and its still solid after removing those. Thanks you

dwittig ~ that is the TPS Trottle Position Switch
you gotta remove more screws including the ones holding the wire loom bracket clips ~ keep removing screws it will come off ~ any screw that is long / long enough to reach into threads of the black phenolic resin plastic carb center section or into the bottom aluminum part must be removed ~ any short screw short enough to not go past the top part means it is not holding the parts together ~ go slow be careful when separating the carb top center and bottom sections otherwise you might break the phenolic plastic center section ~ perhaps use a large flat blade screwdriver and with a turning motion there is a spot that the screwdriver blade can contact on both the center & top sections ~ you will be fine keep asking questions and go slow ~ my photo albums include one about rebuilding the Mikuni carburetor ~ the photo above came from my album ~ good luck & happy holidays
George

You won't see much fuel from the venturis (or more than likely any). There is a small jet on the side of the primary throat that does fuel enrichment on acceleration. You can tell if it's working with the engine off by simply cracking the throttle open. It should have a visible stream of fuel every time you open it from full closed throttle. No fuel = bad enrichment circuit (diaphragm in the housing has failed/blocked jet). If it's weak, the diaphragm is getting tired and is due for replacement (it is part of a rebuild kit - the square block on the side of the carb with a downward facing linkage is the accelerator enrichment pump assy)

If the carb has been off or the fuel lines have been replaced, make sure the fuel line orientation is correct. Swapping the main fuel line and accelerator enrich pump lines will cause a near full fuel restriction problem, swapping the fuel enrich pump and fuel return line will disable the enrichment circuit.

OOC what symptoms are you finding that indicate a no fuel flow problem? Give the top of the carb a good tap with a screwdriver handle if you think the fuel float is jammed. If it's a no fuel delivery through the carb, try sealing the top of the carb with your hands and get someone to crank it for a few seconds (might be enough to purge the carb)

Thanks George. Appreciate your help.

Geezer, thank you for the reply. So you say i should be able to see a fuel stream when i press the pedal down... I'm guessing the primary side would be the side with the choke butterfly? So i need to hold that open.... press the pedal, and i should be able to see fuel?

The carb hasn't been off yet. fuel lines haven't been switched, so i think we're good there.

I'm thinking no fuel, because it won't start, but it will when i dump a little gas into the carb. I've tried tapping on it to hopefully dislodge the float, no change. So i will try to purge the carb like you suggested. If i'm right then i guess i'll be looking at that enrichment diaphragm. Can that be replaced without having to remove the carb? Thanks

You should get a priming shot of fuel from above the venturi when you manually turn the throttle linkage. Try purging the carb before taking it off - it might be enough to pull fuel through the main and secondary (you'll need 2 people to do this as the helper will be in the cab cranking the engine). A tip for a no fuel start problem. Get a clean piece of sponge like a dish/kitchen sponge or a piece of furniture padding, soak it in fuel and wring out the excess (don't use a double sided kitchen sponge with a scourer pad on it) Place it over the throats of the carb and hold it there with your hand and crank the engine. There will be enough fuel vapour to get it to run for 10-15 seconds which might coax some fuel through the carb and get it going under it's own delivery.

*check your fuel filter, the hoses and make sure the fuel pump is actually flowing a decent amount of fuel. Even grab a can of WD40 with the straw, remove the main fuel line into the carb and give it a shot into the main carb fuel inlet and give the top of the carb a good couple of taps with a screwdriver handle in an attempt to free a possibly seized needle and float.

You really don't want to take this thing apart unless there are no more options. It is a biatch of a thing to work on and if you do go down that path you will need a rebuild kit on hand as some of the gaskets could/will delaminate and come off in layers. Use a fresh screwdriver with good, sharp points on it as these screws are well known for stripping out (place the screwdriver tip in each screw and give the handle a good tap with a wrench/hammer handle to shock the threads free before attempting to remove any screws you feel are going to be stubborn) Do NOT turn the carb upside down once the top cover is free as there are brass floats and a ball bearing on the fuel bowl end of the carb and you are doomed if you lose them. It's a rookie mistake that 90% of people make - have a parts tray underneath it and ready to collect any components that want to run free. Take photos before and during your first carb strip down as references - and do not adjust any screws with painted threads. These are factory set adjustments and without an understanding of how the slow and fast idle circuit adjustments work will result in crappy performance.

Quote:

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Originally Posted by geezer101

Use a fresh screwdriver with good, sharp points on it as these screws are well known for stripping out (place the screwdriver tip in each screw and give the handle a good tap with a wrench/hammer handle to shock the threads free before attempting to remove any screws you feel are going to be stubborn).

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Speaking of, just get a JIS* screwdriver, which looks like a Philips but isn't.

Hozan or Vessel brands are good and widely available online. I like my ball-grip Vessel with swappable bits, even came with Pozidriv bits that came in handy for assembling Ikea stuff (which comes with screws that also resemble Philips or JIS but aren't either).

Philips screws/drivers are designed to cam-out as a torque limiter for ease of mass-assembly without stripping threads, but this can lead to stripped heads with repeated dis/reassembly or trying to undo even a mildly-seized screw.

JIS screw heads look similar but differ, being designed for a more secure fit between the screw head and driver bit; these often (but not always) have a dimple on the head, so that's a dead giveaway you've got a JIS screw, which is pretty much all of them on these trucks. A Philips driver bit engages these even more loosely than a proper Philips screw head, further contributing to head strip-out.

Nearly anything assembled outside the US will be using JIS or DIN-/ISO-equivalent screws, so having the proper driver/bit will help enormously. Better yet, a JIS driver bit also works better on actual Philips screw heads, and a JIS screw head stripped by a Philips driver/bit may still be recoverable with a JIS driver bit.

*Technically superseded by DIN 5260-PH/ISO 8764-1, but outside the industry ppl still call them JIS anyway as they're nearly-enough identical, and only these newer successor standards are readily available anymore anyway.

tried holding my hand over it to purge, didn't fix the issue.
https://lh3.googleusercontent.com/YA...-no?authuser=0

i assume this is the accelerator enrichment pump? diaphragm looks pretty good. question about that... like you said the linkage is at the bottom, but there doesn't seem to be any outlet (fuel or vacuum line). There is one line that is capped which has always been that way. so how does that work? or is the diaphragm there as a spring mechanism to bump the throttle linkage back quickly?

Ok, so i can see the squirt of fuel from the jet on the primary when the throttle is pushed down and while its turning over i see a obvious mist. still no start. I went back and checked for spark (which was what i thought was my original problem. I was only getting consistent spark on 1&4. New coil and Rotar cap later, and now i'm getting consistent spark. I used a timing light to test. So i got good spark, I have what appears to be sufficient fuel going through the carb. Like i said it will fire when i prime it with fuel into the carb. but it runs like crap when it does (i've primed other carbs the same way and they normally run decently until the fuel is burned out). I've taken a video and put it on youtube of me trying to start it.

https://youtu.be/0q3TTh-lpQY

I did adjust the timing belt as well. my balance shaft was misaligned a little bit. i've double checked that and am pretty confident its correct. Thanks for looking.

Hello dittwig ~
Using a remote starter switch & having the ignition switch in the ON or OFF position (ignition switch ON the spark plugs should fire & truck can start when cranked) <---- CAUTION
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COMPRESSION TESTING (round #1 no oil & round #2 oiled cylinders
* Remove all spark plugs
* Use free compression tester from O'Reillys
* Use remote starter switch & with IGN switch in OFF position crank 4 compression strokes
* Decent 130psi or more means rings ok & valves timed ok and holding pressure (oiled cylinders 150psi or more)
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Check for Spark
* With IGN switch ON crank with #1 spark plug on #1 wire
* Do same on #2 #3 and #4 means all four ignition system wires & plugs check OK for spark
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Carburetor is either too lean or too rich ~
☆ Remove carb top section inspect float for any fluid leaking inside of it
☆ With carb top section held upsidedown apply vacuum to the fuel inlet nipple with a hand vacuum pump to test needle seat for leakage
☆ Check the float level adjustment
☆ Failure of these checks could indicate a flooding or fuel starve carburetor condition
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Gotta test the mechanical fuel pump ~ crank engine look for fuel coming from pump outlet hose
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If valve & ignition timing, fuel, spark & compression are OK then the engine should start and run
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Check all 3 types of spark timing ~ your 1986 truck distributor should be equipped with all 3 types
* Initial
* Vacuum advance
* Centrifigal advance
* Use the hand vacuum pump to check for movement of the vacuum actuator arm inside the distributor
* Use your timing light & mark the crank pully timing notch with white nail polish or paint
* The timing notch is on the crank pulley lip closest to the engine timing cover ~ it's a tiny notch
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Check valve & spark timing while the spark plugs are removed to find TDC of #1 cylinder piston
1) Use your thumb to cover the #1 spark plug hole ~ the compression stroke will blow your thumb off
2) Use a wooden chopstick placed into the #1 spark plug hole & the fan belts to find exact TDC
3) Then check to see if the distributor rotor is pointing to #1 spark plug terminal on the cap
4) Ignition switch ON twist the distributor until spark occures on #1 spark plug ~ sets initial timing to 0 degrees
5) Do same step 4 with the crank pulley notch aligned with the timing cover timing marks ~ 10 degrees approx
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Once you get her running & timed make sure to clean inspect the PVC valve AND replace both (2) air filters & check fastener tightness & check for vacuum leaks

P.S. How fresh or how old & rotten is the gas or water contaminated fuel in the gas tank ??
Good Luck

I don't know. The cough back through the carb would normally indicate a timing issue like it's over advanced...? whether it's cam timing or ignition will only be exposed by an inspection. Go back to basics - check plug gaps and physical condition like carbon or contamination from oil etc, timing mark alignments on the cam and crank TDC #1 etc. I would loosen off the distributor retaining nut and slowly swing the distributor from full retarded timing to full advance while getting someone to crank it. It is very close to a start/run situation. There also could be something like a jammed advance, failed vac advance servo or broken/missing counterweight springs in the distributor that is causing a problem.

Hi I'm having problems with my 86 ram 50 2.0 5spd. I replaced plugs, wires, points in distributor, coil and resistor when I first got it almost a year ago. Recently I had the carb rebuilt to fix my cold start issues fired right up when cold. Ran poor when warm and bucked around was a little harsh with no real wot went to drive it home from shop it died multiple times and couldn't handle running past 3rd gear. The next day it started it just fine cold ran poor warm adjusted til it ran decent warm shut it off won't start since it's always ran real rich from day one before hand. So I took all fuel lines off they were not crossed blew all Gass out of intake and carb won't start off spray coil is shooting spark plugs were changed still not starting any ideas also not sure if we put the 3 solenoid back in same spot they are all same plug in just different color wires

First check the valve adjustment on the MCA jet valves. Clean the EGR if it has one and make sure it’s closing. Replace the fuel filter if you haven’t do so. It can also be the float is to low.

Rebuilt carb ??? WHO ??? Too many problems after carb rebuild ???

It's for sure getting way too much fuel but also my coil spark is orange and won't hit even with just spray so I'm going to replace my resistor and possibly the coil for the third time. Where are the mca jet adjusters I didn't rebuild it my boss did I took one look at it and knew it was above me

My boss has been a mechanic twice as long as me so I know rebuild had a better chance with him it just ran too rich also it's not possible for us to move the mixture adjustment screw at all. The one behind the little plug