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Thread: Questions, issues with my CUCV

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    Default Questions, issues with my CUCV

    Ok, So...

    I have a new-ish to me 1986 CUCV... When I first bought it less than a year ago, it ran and shifted as it should. Accelerated how a 6.2 would be expected to. Still had good throttle response, shifted strong and firm...
    NOW... It shifts very soft, if even sometimes noticeable at all... Its hard to accelerate... When I really press the accelerator, it just seems to bog down, doesn't want to pick up and go at all, it really only gets moving if im going downhill. Even on first take off, it just isn't what it used to be. I have looked around for air leaks, I have looked around for fuel leaks. This is the first "diesel" I have ever owned, and have no experience with CUCV's or their motors. From what I understand my CUCV Is all stock, it does have 33inch tires, and a K&N air filter. It has roughly 124,400 miles on it. I am hoping everyone may be able to give me some ideas on what the issue may be (seems starved for fuel maybe, slow to response) also, some upgrades that would help reliability, performance, and things of that nature.

    Thank you, Mike

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    4 Star General cucvrus's Avatar
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    Check into an injection pump, fuel filter, lift pump, clogged fuel sock, fuel return lines, sounds like it is fuel related. Tough one to call. Check what I listed and not in that order. But Good Luck. Knowing things about a diesel is helpful.
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    4 Star General Barrman's Avatar
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    Do all he listed above since they are common maintenance items you should be doing anyway. Also check your vacuum line from the vacuum pump to the throttle position valve on the side of the OP and then both rubber and metal vacuum lines all the way to the transmission. Plus the vacuum can on the side of the transmission.
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    I would put my bets on fuel or transmission.

    Easiest first though. When you start from a stop, can you hear/feel it shift from 1st, to 2nd, and then to 3rd? Drop the shift lever all the way to 1st, then when it's rolling good bump it (carefully) into 2nd- did it shift? Then do the same to 3rd.
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    Make sure the air filter is clean. One big difference between gas and diesel motors is the airflow. Where gas motors regulate air flow via throttle plates and fuel flow is based on air flow, diesels have full air flow all the time and regulate fuel flow via the injectors(a very simplistic explanation). So for the same miles traveled, the air filter on a diesel will see a LOT more air go by and fill up with crap a lot faster.

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    Of the things already mentioned, the fuel filter is most likely. These should be changed regularly anyway, and a clogged fuel filter would cause most of your symptoms.

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    Sergeant Major sneekyeye's Avatar
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    That sounds to me like you may be getting full vacuum at all times to the transmission. Mine does a similar thing, where it starts off and immediately slips into second and hits third about 15 mph. Test it by manually shifting into second at a stop and then it should shift 1-2 properly when you take off. Then pop the shifter into third at thirty or so, it should drop right in. If that is the case, you may have a bad vacuum regulator on the side of the injector pump.

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    Thank you everyone, I'm currently ordering a bunch of new parts to do do a full pm on the truck. I'll ho out later to check what was mentioned for the vaccum situation to see what happens!!
    I'm ordering a new fuel filter, new fuel lift pump, new trans filter, new in tank fuel pump. Im also going to replace both belts.
    So next question does anyone the sizes for both belts? Mine are extremely stretched... so getting an accurate measurement is gone for me.
    I'm positive all of these things haven't been done in quite awhile. I would replace the glow plugs but the truck starts really easy I've not had an issue with those.
    I'm going to do the PMs for the ; transmission fluid and filter, oil and filter, both differentials, the majority of the fuel system. And check all of my vaccum lines. I'm certain the fuel filter clogged but might as well go through a bulk of maintenance for my own piece of mind.

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    Welcome from SE Missouri!

    Is the truck smoking more than normal? When you change fuel filter dump out old fuel in filter into a clear glass jar without lid and look at the fuel. Look for water, and black specks, fuel hose deteriorating. Also rust, color is hard to see but flakes aren't.

    A lot of good advise but one thing to consider is that try to do one thing at a time to cure the problem that you seek. Fuel symptoms are different than shifting firmness, mph shift points.

    Good Luck and I get to Cuba now and then to the farm, 19 north of town 15 miles.
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    Agree with everything the guys have already mentioned.

    The CUCV stickies will have the belt sizes.
    Replace them all at same time. Not just two.

    If you haven’t already, replace every single rubber fuel/vacuum line.
    Including the 2” piece on the transmission vacuum modulator.
    The rubber gets hard and cracks with age.
    Cracks= leaks, debris

    Also a can of SeaFoam every third tank will help keep fuel system happy.
    Helps with keeping water out of fuel tank also.
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