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Thread: Stupid quick question...

  1. #1

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    Stupid quick question...

    ok so cannot get my 2.0 to run right after reman head, weber and generally a full overhaul. It is dieseling like a mo fo. Checked timing multiple times and played with full on the carb over and over. Compression is eh.. sitting at 150, 140, 139, 136. Appears to be getting oil blow by in all the chambers as the plugs are wet and black. Since being a new head and fully cleaned engine, i am suspecting warped deck on the block. Head was put together by a local machine shop that knows these mitsu's pretty well and also checked for warp. Previous head cracked on cyl 3 between valves so guessing ran hot at some point warping the block thus getting blow by and causing the dieseling. BUT one thing i did not account for is that i slapped the mech fuel pump on the block as a temp block off until i visit the machine shop to make some nice goodies for it. Would the unused fuel pump with no rocker and open ports cause the dieseling? Would that act like a massive vac leak in the head? I have another motor i just pulled from a wrecked 87 that ran great so swapping that in after a tune up and throwing some much needed gaskets on it until I can pull the head and send the block to get checked.
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  2. #2

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    As long as the fuel pump recess was blocked off there is no way it will cause issues. What did the bores look like and how many miles did it do before you tore the head off it? Your bottom end might be tired (it is unlikely however not impossible that the block deck is no longer true). Other than those I would start simple - is your electric fuel pump running a low enough pressure for the Weber? Remember these suckers like 3-5 psi - you go higher on fuel pressure and it'll overfuel (causing the dieselling problem you're encountering). I hope you did some nice port work on your head to make the most of your carb!

  3. #3

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    Block had about 115 on before new head. Not sure about the recess question, Rocker is out and i just slapped a mech fuel pump unhooked to stop an oil leak. Using an electric fuel pump with holly reg for weber looking about 3psi at idle. Have some blue/black smoke from exhaust and plugs are black and a little wet. Think its just a fuel problem?? It almost runs decent on a cold start then warms up and goes to hell
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  4. #4

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    Fuel pump recess is the cavity where the pump rocker arm/actuator rod goes into the head. I have a tendency to think your core problem is overfuelling. Maybe your Holley regulator is faulty and isn't dropping the fuel pressure (I read somewhere the Holley regs sometimes have this particular problem). At 3 psi on idle it should be running fine.

  5. #5

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    Im going to swap intake manifolds with a makuni on it from a running motor on the stand tonight and see what happens. I dont have any more carb gaskets laying around easier to swap manifolds. lets see how it works with the electric fuel pump and then try with the mech on the makuni
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  6. #6

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    ok finally traced it down, auto choke on and carb reset fuel at 2.5 at idle as soon as i touch the throttle and it releases the autochoke, it dies. What in the hell is happening?
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  7. #7

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    got it, linkage came loose and had some gum up from sitting
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  8. #8

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    ...a squirt of WD40 can perform miracles. So how's it running now?

  9. #9



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    Australian translation: Squirt = Spray


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  10. #10

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    runs pretty good, need to swap plugs as they got fouled from gas dumping through the carb that was stuck open. drove it to a gas gas station and cvs. First time it has seen a gas pump since 99
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  11. #11

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    Quote Originally Posted by BradMph View Post
    Australian translation: Squirt = Spray

    Attachment 17654
    haha glad i wasnt the only one that thought that was dirty
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  12. #12



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    Quote Originally Posted by Rymar Garage View Post
    runs pretty good, need to swap plugs as they got fouled from gas dumping through the carb that was stuck open. drove it to a gas gas station and cvs. First time it has seen a gas pump since 99
    Be sure no gas got into your oil when fuel dumping alot through carb. Smell the dipstick. Blow by fuel can contaminate oil.

  13. #13

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    Quote Originally Posted by Rymar Garage View Post
    haha glad i wasnt the only one that thought that was dirty
    Really guys? I expected that from Brad though

    It's amazing that it hasn't caused you more grief considering how long the trucks been off the road. The valve stems must be hard as rocks by now. Bet the belts are sketchy too...

  14. #14

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    ^new head and fresh errry thang. It's still dumping fuel somehow and idles rough. crazy part is after heavy throttle it falls on its face and cuts off. Carb issue? I made damn sure when ordering my 2nd attempt at a weber that is was legit. maybe float not at right height?
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  15. #15

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    Between bad gas and Carbs Unlimited not selling a new carb like stated and having remains of a gasket of some sort blocking up to ports we got it figured out. slightly pissed about the carb being a reman and not new like they promised it was. o well.
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  16. #16

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    Not cool they misled you into buying a rebuilt carb + the fact it wasn't done properly either by the sound of it. Keep away from regular and ethanol (if you can - sounds like even that is difficult in the states...) I have recommended attempting to perform a 'dynamic' tune on a couple of occasions on the site but never heard any feedback.

  17. #17

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    I will be swapping fuel tanks tomorrow and replacing filters and see how she does. You should have seen the float position, damn near touching the top cover. There are a few stations around that sell non ethanol and I stocked up on some. My gmc gets filled with it too but the recent little gas crisis left me getting 2 tanks from not normal stations and wouldnt yea know i got some crap gas. Doing plugs, filters and small amount of seafoam on it tomorrow too.
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  18. #18

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    update. Having to pull an old cronie mech from work over this weekend as I cannot get this thing running right and all fingers point back to the carb yet again. Pretty sure I am about to have a slighty heated phone call with carbs unlimited.
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  19. #19

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    slightly stumped the old cronie too but dialed it to a possible faulty distributor so ordered one and it should be here tomorrow. The carb guru named tom over at redline pointed me in the direction of timing but i was dead on and fps was tested perfect at 2.5 we shall see if he is right. I have a cali truck dist here i knew was good but its got the vaccum advance and retard lines so ran without a misfire, but had to feed the fuel manually. Anyone ever had the same symptoms when your dist went out??
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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  20. #20



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    Remember as a coil goes bad you will need to dump in more advance. Just tossing that out there for it to sit in your Data Base of a head.
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  21. #21

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    Quote Originally Posted by camoit View Post
    Remember as a coil goes bad you will need to dump in more advance. Just tossing that out there for it to sit in your Data Base of a head.
    Aha! Maybe that is why I have the dist almost max advanced.

  22. #22

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    Its a new coil, but have ordered one as last night threw in the new dist and no spark.
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  23. #23

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    Check that the distributor is in stalled correctly. If it is, then the distributor may have a bad ECM. The ECM's either work or don't so you may have to install the original distributor and test it out.

  24. #24

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    Needed new coil and distrib. old ones were throwing spark, just not enough
    09 Sierra RC 2.5/Zone 1.5. on 295/70 18s
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