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| carb STILL backfiring...Mechanic gives up on me. https://slantsix.org/forum/viewtopic.php?t=48198 |
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| Author: | RogerDodger [ Thu Mar 15, 2012 8:31 am ] |
| Post subject: | carb STILL backfiring...Mechanic gives up on me. |
So after keeping my truck for 2months the mechanic calls me this morning and says that his technician gives up. What to do now? Backfiring through the carb and wont hold an idle while in gear without foot on gas. New carb, new ignition wiring, plugs, wires, cap, button, etc., took off timing cover and chain is good. Anybody got anything that can help me on this '85 Dodge D100? Getting tired of bumming rides and not being able to work. HELP!!! |
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| Author: | ESP47 [ Thu Mar 15, 2012 8:56 am ] |
| Post subject: | |
What type of carb is on the engine? Also does it have a Lean Burn computer? |
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| Author: | RogerDodger [ Thu Mar 15, 2012 9:08 am ] |
| Post subject: | |
Its a brand new Holley 1945 from BFIC carbs only. No learn burn computer. |
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| Author: | Reed [ Thu Mar 15, 2012 10:04 am ] |
| Post subject: | |
Does your distributor have a vacuum advance pod? |
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| Author: | Doc [ Thu Mar 15, 2012 10:13 am ] |
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Is it the factory 1985 hydraulic lifter engine? Has any head work been done? DD |
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| Author: | RogerDodger [ Thu Mar 15, 2012 10:23 am ] |
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Will have to check on advance pod when I get it back. un familiar with what a hydraulic lifter is but its the stock motor to my knowledge and no head work has been done. |
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| Author: | SlantSixDan [ Thu Mar 15, 2012 10:54 am ] |
| Post subject: | |
Timing chain is good (not too stretched) but is the cam timing correct? That's a basic and important question. Same goes for ignition timing; it's important to make sure the timing mark lined up with the "0" line on the indicator actually indicates top dead centre on the frontmost piston. The crankshaft pulley (where the timing mark is) is a two-piece item; the outer ring is held to the inner hub by rubber. Over years and miles, the rubber can lose its bond and the outer ring can slip relative to the inner hub, so the timing mark is no longer accurate. All of these things need to be checked. But your symptoms could also loudly point to a significant vacuum leak or a carburetor problem. If the carburetor is "brand new from BFIC", then it's probably got some kind of a warranty, so check for vacuum leaks where each intake manifold runner meets the head, where the carb meets the intake, and where the EGR valve meets the intake. None of this is secret special knowledge; it's all completely basic. I don't think much of a "mechanic" or his "technician" who doesn't know that these are the places to start checking. |
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| Author: | ESP47 [ Thu Mar 15, 2012 11:57 am ] |
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I vote for vacuum leak being the most likely culprit. Check the vacuum with a gauge and let us know what you're getting. If you aren't sure how to check, let us know and we'll give you step by step instructions. |
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| Author: | RogerDodger [ Thu Mar 15, 2012 12:09 pm ] |
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I have sprayed all connections with wd40 and no change. Possibly where the intake and exhaust manifolds go together?? I understand that is a common problem. |
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| Author: | RogerDodger [ Thu Mar 15, 2012 12:14 pm ] |
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And yes ESP any instructions would be great. And what kind and where to get a gauge to check. |
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| Author: | Reed [ Thu Mar 15, 2012 12:28 pm ] |
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At this point it will really help us diagnose your problems if you can post clear pictures of all sides of your carburetor, your distributor, and the vacuum hoses and routing of the vacuum hoses on the engine. |
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| Author: | Junior [ Thu Mar 15, 2012 3:36 pm ] |
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Wd40 in my experience doesn't work very well in revealing a leak, you want to something more combustible like carb cleaner or ether. do you have power brakes? If so you might want to look at the check valve and the booster.also make sure the mechanic hooked the vacuum lines up to the correct ports. |
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| Author: | Junior [ Thu Mar 15, 2012 3:39 pm ] |
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Has the distributor been out recently? If by some chance it was put back in 180° out it will run and give the symptoms your describing (i know form experience). |
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| Author: | slantzilla [ Thu Mar 15, 2012 3:52 pm ] |
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The symptoms are classic vacuum leak or weak ignition. Does it run well when revved above idle? Did they do a compression check? Burnt intake valve will bang through the carb, but you should also have a dead miss. |
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| Author: | THOR [ Fri Mar 16, 2012 3:32 pm ] |
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Quote: The symptoms are classic vacuum leak or weak ignition. Does it run well when revved above idle?
A "partially" burned intake valve will also backfire through the intake, but not necessarily create a miss... had that happen to me.Did they do a compression check? Burnt intake valve will bang through the carb, but you should also have a dead miss. ~THOR~ |
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