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04-21-2015, 12:34 AM
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#1 |
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Registered User
Join Date: Jul 2014
Location: Lovell WY
Posts: 93
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Gas engine "dieseling" and back/after fire
Just because my BBC is doing such only when warmed up to temp ~190 degrees, what are the causes of such events and possible fixes. I do intend to rebuild the engine, but I'm just wondering.
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1979 GMC Sierra Grande Crew Cab C25, 454/TH400/4.10-Project truck/ DD 1985 Chevy K5 Blazer 700r4/4.10/8 lug- in search of new engine 1993 GMC Sierra K1500 4L60E 2007 Suzuki Forenza- her DD and the family vehicle |
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04-21-2015, 12:38 AM
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#2 |
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Registered User
Join Date: Jan 2009
Location: Calgary, AB
Posts: 1,181
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Re: Gas engine "dieseling" and back/after fire
Carbon build up is usually a big reason.
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04-21-2015, 02:02 AM
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#3 | |
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Registered User
Join Date: Jan 2009
Location: Winfield, Kansas
Posts: 54
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Re: Gas engine "dieseling" and back/after fire
Quote:
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04-21-2015, 09:23 AM
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#4 |
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Registered User
 Join Date: Nov 2013
Location: Fowler California
Posts: 140
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Re: Gas engine "dieseling" and back/after fire
Carbon, again, is often guilty. I've also had this problem before when my coil and/or coil wire (if you don't have coil in cap) is going south.
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1967 CHEVELLE MALIBU 427/700R4 1971 CHEYENNE 10 350/350 1983 GMC K3500 454/400/205 1987 R10 TBI 350/700R4 2014 CRUZE 2.0 TURBO DIESEL |
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04-21-2015, 09:53 AM
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#5 |
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Registered User
Join Date: Dec 2014
Location: Mulberry, AR
Posts: 222
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Re: Gas engine "dieseling" and back/after fire
idle to high, vacuum leak, timing off.
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1981 Silverado C10 LS/4l60e My truck may be loud and ugly but I love her like bacon |
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04-21-2015, 05:21 PM
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#6 |
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Registered User
Join Date: Oct 2014
Location: Spearfish South Dakota
Posts: 407
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Re: Gas engine "dieseling" and back/after fire
To low octane gas or idle set to high. that's why carbon cleaning can help upped the compression to point you need hi test or premium these days . I would try higher grade gas or different station.
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83 c10 long Box Daily Driver 90 Jimmy parked 98 Road King/ 06 Road Glide In memorium 63 impala SS/ 65 Chevy Panel 65 GMC Short Box/ 68 Camero |
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04-21-2015, 09:08 PM
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#7 |
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Registered User
Join Date: Jul 2014
Location: Lovell WY
Posts: 93
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Re: Gas engine "dieseling" and back/after fire
Well after doing some work on it today I found the dizzy cap needed replaced and the advance was on ported vacuum so I switched to manifold vacuum and the high idle was set way to high. I guess I just need to learn how to tune a carb properly. Runs better and has more power. So this spring / summer I will just do head gaskets and put a dual plane intake on and run it till it needs rebuilt or I decide it's time
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1979 GMC Sierra Grande Crew Cab C25, 454/TH400/4.10-Project truck/ DD 1985 Chevy K5 Blazer 700r4/4.10/8 lug- in search of new engine 1993 GMC Sierra K1500 4L60E 2007 Suzuki Forenza- her DD and the family vehicle |
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04-21-2015, 09:14 PM
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#8 |
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Registered User
Join Date: Feb 2015
Location: Bonham, Texas
Posts: 241
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Re: Gas engine "dieseling" and back/after fire
Isn't dizzy advance supposed to be ported? Thats how my vac diagram shows it.
A worn out carb can do the backfire/after fire too. Mine did it forever till I replaced it. |
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04-21-2015, 09:47 PM
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#9 |
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Registered User
Join Date: Jul 2014
Location: Lovell WY
Posts: 93
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Re: Gas engine "dieseling" and back/after fire
Yes dizzies are supposed to be ported but I do need to replace mine and putting it on manifold advances it sooner. My carb is a fresh rebuild edelbrock that I haven't really messed with alot, I bought it and installed it and then I got my blazer and really haven't drove the BB. The truck dieseled badly with the quadrajet on it. I do plan on rebuilding the q-jet when I do the head gaskets and put a new intake on, I found a dual plane spread/square bore for $250 so I can run either or, I just need to find an electric choke for the q-jet and I will be good to go.
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1979 GMC Sierra Grande Crew Cab C25, 454/TH400/4.10-Project truck/ DD 1985 Chevy K5 Blazer 700r4/4.10/8 lug- in search of new engine 1993 GMC Sierra K1500 4L60E 2007 Suzuki Forenza- her DD and the family vehicle |
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04-21-2015, 09:49 PM
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#10 |
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Registered User
Join Date: Dec 2007
Location: Kimberley, BC, Canada
Posts: 799
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Re: Gas engine "dieseling" and back/after fire
About the vacuum advance, have a read of this:
http://www.bangshift.com/forum/forum...vacuum-advance
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Greg 64 GMC Suburban - 283, NV3500, 14 bolt 77 C10 swb - 292, SM465, 12 bolt |
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04-22-2015, 12:38 AM
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#11 |
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Registered User
Join Date: Jul 2014
Location: Lovell WY
Posts: 93
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Re: Gas engine "dieseling" and back/after fire
I stand, well sit, corrected. Thanks for the information Greg. You learn something new everyday.
__________________
1979 GMC Sierra Grande Crew Cab C25, 454/TH400/4.10-Project truck/ DD 1985 Chevy K5 Blazer 700r4/4.10/8 lug- in search of new engine 1993 GMC Sierra K1500 4L60E 2007 Suzuki Forenza- her DD and the family vehicle |
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04-22-2015, 06:02 AM
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#12 |
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Registered User
Join Date: Feb 2015
Location: Bonham, Texas
Posts: 241
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Re: Gas engine "dieseling" and back/after fire
That was a fascinating read.
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