dodge ram d50 mightymax trucks


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Thread: New to site, problems with mighty max

  1. #1

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    1988 Mitsubishi Mighty Max
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    New to site, problems with mighty max

    hey everyone. im new to the site and this site seems very knowledgable. i just bought a 88 mighty max with a 2.0l carb'd engine. im having acceleration problems. when i drove it home it would hesitate anytime i pushed the gas unless i very easily pushed the throttle. so i checked the timing and it was off so i set the timing back to manufactures specs. i also replaced the wires, plugs dist cap and rotor button. now since i have done all that when i go to take off it accelerates fine in 1st gear but once i hit second it starts to stumble like its starving for fuel. so i have to ease into the throttle again. i have figured out that i can feather the gas between 1/2 and 3/4 throttle and i can feel it picking up slowly then it just takes off like its suppose to. i hope this is not too confusing but i want to figure out whats wrong with it so i can drive it. i dont know anything about these trucks since iv been a chevy man my whole life so hopefully some of you guys can help me.

    one more thing that may help, the previous owner unhooked the manual fuel pump and hooked up a universal electric fuel pump.

    1. could this have anything to do with the problem im having above?
    2. how hard is it to replace the manual fuel pump and would it be worth it?

    thanks in advance for any help!!!

  2. #2

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    That electric pump could be overpowering the carb causing it to leak internally making you run too rich causing the accel problem. Also that rich condition could dump fuel onto the catalytic converter and melt it causing that same problem also. Best way to check that is take out the O2 sensor and run a back pressure gauge but I know on these trucks, good luck getting the O2 sensor out without damaging it or the manifold. You could also take off the bolts at the front of the converter and drive it with the open header and see if it helps. Manual fuel pumps are usually pretty easy to change. Just 2 bolts and some hoses. I'd put that back on and you may need to rebuild the carb if it blew out any gaskets. I know some of the other guys are more knowledgable on carbs than me. I've heard them talk about swaps since these trucks had puny carbs to begin with but I think that was the 2.6L I'll stick to EFI or diesel
    1981 Chevy C10 305 longbed - work truck / daily driver.
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  3. #3

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    Welcome to the site. The problems you mention could be any of a couple of things. The first thing I would do is make sure that the choke is opening properly and that the accelerator pump is working. If you just got this truck you may want to replace the fuel filter (Buy 2 and keep one in the glove box). If it sounds like the engine is starved for fuel, a clogged fuel filter can cause that. It is located between the box and the cab on the drivers side normally. If the previous owner put an electric fuel pump in, he may have put a filter in somewhere else or added an extra one. Is the electric pump mounted back at the gas tank and plumbed properly? Electric pumps are made to push fuel, not suck it through 6 feet of fuel line. If it is, have a good look at the fuel lines to see that there are no kinks in the rubber hoses. If the electric fuel pump works fine and is not causing any problems I would leave it. If you want to go back to the mechanical pump it is not hard to do.

  4. #4

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    thanks for the replies. first off the electric choke is unhooked, and turned open. as for the fuel pump, its one of the universal pumps from autozone. i looked it up and its rated at 4 to 6 psi. it is mounted right under the battery and is hooked to the resistor for the coil. i first thought that was the problem but i hooked it up with a relay and a different power source but no luck. i wanted to hook the manual pump back up but it looks like its right under the intake manifold. i downloaded a repair manual but it dont show how to get to it.

  5. #5

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    Chances are that's why the previous owner put the electric one in. The mechanical pump my have worn out and it was easier to put the electric one in. If you want to hook it back up and try it you may be able to get at it by removing the wheel and going through the wheel house.

  6. #6

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    ill just replace it and hook it back up. ill post back one i get that done!

  7. #7

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    Or drive up on ramps and reach up from under.

  8. #8



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    Sounds so much like a starving fuel issue. Electric choke being disconnected shouldn't effect driving after warmed up, unless the flap is closing and opening from lack of tension to keep it open. Your vacuum advance ok? Got a good line to some vacuum pressure to turn that distributor when accelerating, probably do, just a guess. Check for vacuum leaks around carb or any smog devices or intake manifold, another guess. Does 88 have a computer connection to check codes? If so maybe run it by a auto parts store and see if you can capture some codes. Air Cleaner good? PCV valve ok? Make sure your accelerator pump is spitting fuel when ya twist the throttle linkage. It maybe shooting too much or too little. I like to check at tail pipe for mixture settings, If fumes burn eyes real quick, its rich, if you feel just heat and no fume smell your ok or lean. Plugs will usually tell you this though. Crossed plug wires can do weird stuff also. Manual fuel pump replacement is simple, Don't loose the pushrod when you take the pump off though. The rod is about 2 inches long and it can fall quietly and not be noticed.

  9. #9



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    Also check the vacuum lines over to the box on the drivers side inner fender - those lines go to a unit that controls the electronic carb and will go nuts when they are not connected. Mice and old age will cause them to split or disappear. Also check the EGR valve for carbon buildup, PCV valve, and make sure the carb is tight to the manifold.
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  10. #10



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    Quote Originally Posted by 88maxine View Post
    as for the fuel pump, its one of the universal pumps from autozone. i looked it up and its rated at 4 to 6 psi. it is mounted right under the battery and is hooked to the resistor for the coil.
    There is the problem. The pump is to far away from the tank. It must be with in 12 inches of the tank or it will not work correctly. As you drive it do you here it get loud? If so it's sucking to hard. They are made to push fuel not pull fuel.
    Once you move the pump see how it drives and let us know. But my bet is on the location.

    If you go with the mechanical pump you will need to drain the radiator and pull the carb.
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  11. #11

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    i havent had a chance to mess with it since its fathers day weekend. but i hope to next week if the rain holds off. i got to thinking the other day that the owner said he replaced the timing belt on it. im just wondering if he got it a tooth off or something as i have done that back when i was working in a shop and had almost the same identical problem. idk ill check and see and get back to yall. thanks.

  12. #12

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    I'm interested to see if you've found the problem or if its been fixed. I've got the exact same thing with mine.

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