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MPG Problem

Discussion in '1982-Present GM Diesel' started by ZuluNashun, Sep 26, 2001.

  1. ZuluNashun

    ZuluNashun Registered Member

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    I have an 84' 6.2 Diesel. I drive it about 45 miles a day. Good engine, strong enough for a daily driver. But my problem is that I'm getting nearly 11 mpg with it. It has 230k miles on it all of wich have been serviced very well. Why would it be getting such awful mpg considering I'm hearing that every one else is near 20. How do I fix my or problem or even, where do I start checking? Thanks
     
  2. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    First of all, replace your air filter. the #1 cause of poor performance and mileage is a lack of air. While you're at it replace your fuel filters.

    You may have an injector problem, or a pump problem. Most of the time an injector pump will fail at the throttle seal, but that will be obvious because you'll start to leak diesel. I have heard of worn pumps putting out too much fuel, which could be your issue. If you have plugged injectors, some of the fuel that's supposed to go towards driving could be being wasted.

    I get around 25 MPG on the highway and about 19 in the city. Heck, I even get 18 towing!!!!

    Change out your filters and see if that helps. If you're blowing lots of black at high throttle that's a sign of either not enough air(dirty air filter) or too much fuel...........



    <font color=blue> WE WILL NEVER SURRENDER<font color=blue>
     
  3. ZuluNashun

    ZuluNashun Registered Member

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    Ok but here is the thing. I thought of that filter thing. So There is a brand new air and fuel filter on it. My guess would be a pump. Everything else is good. Is there any way to check the pump and injectors? And it doesn't blow any large amounts of smoke.
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Your truck should have TWO fuel filters.....Did you replace both?

    Take it to a reputable diesel shop and they should be able to check the fuel presure coming out of the injector pump. It might be worth it to pull a couple of the injectors and take a look at them, too. I haven't had any injector problems myself so I can't tell you what to look for, but I'm sure DieselDan might have an idea..........<font color=red>CALLING DIESELDAN!!!!!!!</font color=red>[​IMG]



    <font color=blue> WE WILL NEVER SURRENDER<font color=blue>
     
  5. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    TWO?!?! ON my 84 engine there is only one....the BOX filter. On an 83 there are two spin on filters.


    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
    If it wasn't for bad luck I would have no luck at all!!
     
  6. DieselDan

    DieselDan 1/2 ton status

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    You've quite a few mile under her, how many miles are on the pump and injectors? Rule of thumb is injectors are good for 80K, injection pumps 120K, after that performance may start to deterate. Another thing, was the injection pump timed correctly? The marks on the pump and timing cover are only "ball-park" timing.

    Real trucks don't have spark plugs!
     
  7. ZuluNashun

    ZuluNashun Registered Member

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    Well, from what I can tell from previous reciepts, the injector pump was replaced at 105k and the injectors at 120k. So I guess it's time to replace them. I've only driven it 10,000 miles in the last 4 years. The rest of the time it's been up on stands without suspension or no tranny or drivelines. So, I'm going to take it to a diesel shop down by work and see if they can tell me for sure. Thanks
     
  8. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    Since it wasn't driven that much..maybe you need to run some Stanadyne Diesel Treatment through it?

    <a target="_blank" href=http://www.stanadyne.com>http://www.stanadyne.com</a>

    Or maybe it just needs ran. My "new" used engine kinda was a dog...but after driving it for a bit and running good Stanadyne through it it started to show its power.

    Also...get rid of the air system....too restrictive. I just built a new air system from the radiator support to the air breather out of PVC pipe. Much more power after that. And I can convert it to a snorkel in about 15 seconds because I put a female connector on the front. I have a male connector with a 90 deg and a length of PVC to get it out of the water!!

    Also...change that air filter. Spend some money ONCE and goto the GM delaer and get a new air filter...it comes with a foam filter around the air filter itself...gets all the big stuff...tree limbs, frogs, fingers, sockets....etc. And you can reuse that foam thingy again...

    Change the oil...use the good stuff...I used to settle for "good"..now I go for "BEST". WIX, AC Delco, or K&amp;N oil filters.

    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
    If it wasn't for bad luck I would have no luck at all!!
     
  9. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    My bad........I assumed that all 6.2s had the same filter setup. I've actually relocated both my filters with aftermarket products to make changing them out a lot easier......

    One of these days I'll have to post pics because I've had more than one person ask about it.



    <font color=blue> WE WILL NEVER SURRENDER<font color=blue>
     
  10. chevyracing

    chevyracing 1/2 ton status

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    This is not a tech answer but do you always buy your fuel at the same place? I live in a small town in Colorado and we have two places I buy fuel. One is Flying J, the other is Texaco. With Flying J my fuel milage is around 13, with texaco my fuel milage is around 16, sometimes 17. Diesel is like gas, gas has octane, diesel has cetane, .
    Disclaimer: The above results were from my 1999 one ton dually Dodge pickup with a Cummins H/O Diesel. Your actual results may vary depending on usage of the aformentioned product. In no way is chevyracing guaranteeing you will get 17 MPG by using Texaco fuel. Chevyracing has not been paid by Texaco to endorse their products. Chevyracing is not owned by Texaco corp or any of its subsidies. If you are still reading this that means you have a sense of humor and have a good day!

    Like to go sloppin' 'round in da mud in a rapid fashion....=) [​IMG]
     
  11. ZuluNashun

    ZuluNashun Registered Member

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    I usually buy my fuel from Phillips 66. It's closest and cheapest. I bought a case of the stanadyne fuel system cleaner. It seemed to really have helped. It blew a bunch of white smoke for the first little bit. It's become a second driver for me now so I'm not too worried about the mpg a whole lot.
     
  12. chevyracing

    chevyracing 1/2 ton status

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    This takes you right to standynes additives
    <a target="_blank" href=http://www.stanadyne.com/dsg/dsg_dfa.asp>http://www.stanadyne.com/dsg/dsg_dfa.asp</a>

    Like to go sloppin' 'round in da mud in a rapid fashion....=) [​IMG]
     
  13. JORGE

    JORGE 1/2 ton status

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    25,19,18 mpg? Sure?Mine this last time,has eaten 70 ltr in 206 miles, running for the muntains,climbing hills,etc. How many liters is a U.S gallon? 3.78 is true?
     
  14. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Those are pretty accurate numbers, brother......... Keep in mind that my 6.2 is in a half ton 2WD pickup truck. I'd imagine that you'd get worse mileage with a Blazer.



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  15. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    Somewhere I remember someone saying something about driving a barn?!?!

    edit: Found it...
    "of course it has the aerodynamics of a barn"
    by tRustyK5
    End edit


    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
    If it wasn't for bad luck I would have no luck at all!!
    <P ID="edit"><FONT class="small">Edited by SK-15 on 10/21/01 01:33 PM.</FONT></P>
     

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