Timing and Back Firing Issues. Pictures - The 1947 - Present Chevrolet & GMC Truck Message Board Network

donelan07 · 02-24-2009, 12:45 AM

I just got a clean gas tank and new fuel pump put in. Now my truck wont start it just back fires.
Fire out the top of the carb

Bottom of the Fuel Pump. Return line?

Return line?

Where it is back firing from.

Infanti · 02-24-2009, 01:07 AM

Did you fool around with the distributor?Looks like timing is out.

68gmsee · 02-24-2009, 10:04 AM

As Infanti mentioned, it's possibly a timing issue. Other thing that can cause it are bad valves, badly worn timing chain or gears or even the cam/crank gears out of adjustment.

I would check the timing and have a compression check done.

72chevyk10 · 02-24-2009, 12:06 PM

SWEET *cough* i mean ow thats bad

Infanti · 02-24-2009, 08:46 PM

Give us more info on what you did so far.Was truck running fine,then you changed gas tank and fuel pump and this all happened?Or did you have issues before you changed parts out.

texanidiot25 · 02-24-2009, 09:22 PM

Looks like the 1st fire-ups on my motor before the timing was set

**americanmusc1e** · 02-24-2009, 10:57 PM

TRY THIS
do you have a points distributer still?

i managed to put my distributer cap on backwards one time (i put the little peg in the vacumn advance slot and fit and looked alright) and it backfired out of the carb just like that,

we even poured gas into the carb trying to get it to start, all it did was catch my carb on fire

68C15 · 02-25-2009, 06:13 AM

looks like you do in fact have the correct pump for a non-return system, good.
it is back firing from the throat, timing way off. unfortunately I bet the power valve is now toast. I'll check with wifey and see if I can get parole for this weekend.

first I need you to hit Advance and get a 6.5 power valve and possibly a bowl gasket. I'm all fresh out of both. all I have left is 3.5, a couple 2.5s and 3 plugs (hi-perf stuff).
power valve
http://holley.com/125-165.asp
gasket
http://holley.com/108-83-2.asp
BTW, this would be a good idea. not necessary, but would be nice.
http://holley.com/108-98-10.asp

do not, I repeat DO NOT use these
http://holley.com/26-113.asp

donelan07 · 02-25-2009, 01:55 PM

I can't work on my truck this weekend. My brothers wrestling up in Aberdeen for state.

68C15 · 02-25-2009, 10:33 PM

OK, now I dont have to feel guilty for not being available. my leave was pulled because I went to Harbor Freight last weekend. she is upset about what I spent.

02-24-2009, 12:45 AM	#1
donelan07 Active Member Join Date: Dec 2004 Location: Brookings, SD Posts: 202	Timing and Back Firing Issues. Pictures I just got a clean gas tank and new fuel pump put in. Now my truck wont start it just back fires. Fire out the top of the carb Bottom of the Fuel Pump. Return line? Return line? Where it is back firing from. __________________ _________________________________ 1972 Chevy SWB 4x4 350 4speed

02-24-2009, 01:07 AM	#2
Infanti www.infantimachine.com Join Date: May 2007 Location: Delta,BC Canada Posts: 311	Re: Timing and Back Firing Issues. Pictures Did you fool around with the distributor?Looks like timing is out.

02-24-2009, 10:04 AM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Timing and Back Firing Issues. Pictures As Infanti mentioned, it's possibly a timing issue. Other thing that can cause it are bad valves, badly worn timing chain or gears or even the cam/crank gears out of adjustment. I would check the timing and have a compression check done.

02-24-2009, 08:46 PM	#5
Infanti www.infantimachine.com Join Date: May 2007 Location: Delta,BC Canada Posts: 311	Re: Timing and Back Firing Issues. Pictures Give us more info on what you did so far.Was truck running fine,then you changed gas tank and fuel pump and this all happened?Or did you have issues before you changed parts out.

02-24-2009, 09:22 PM	#6
texanidiot25 Eat My Rust Join Date: Jan 2007 Location: Cypress, Texas Posts: 3,362	Re: Timing and Back Firing Issues. Pictures Looks like the 1st fire-ups on my motor before the timing was set

02-24-2009, 10:57 PM	#7
americanmusc1e Senior Member Join Date: Jan 2009 Location: Austin, TX Posts: 1,079	Re: Timing and Back Firing Issues. Pictures TRY THIS do you have a points distributer still? i managed to put my distributer cap on backwards one time (i put the little peg in the vacumn advance slot and fit and looked alright) and it backfired out of the carb just like that, we even poured gas into the carb trying to get it to start, all it did was catch my carb on fire __________________ -- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted

02-25-2009, 06:13 AM	#8
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	Re: Timing and Back Firing Issues. Pictures looks like you do in fact have the correct pump for a non-return system, good. it is back firing from the throat, timing way off. unfortunately I bet the power valve is now toast. I'll check with wifey and see if I can get parole for this weekend. first I need you to hit Advance and get a 6.5 power valve and possibly a bowl gasket. I'm all fresh out of both. all I have left is 3.5, a couple 2.5s and 3 plugs (hi-perf stuff). power valve http://holley.com/125-165.asp gasket http://holley.com/108-83-2.asp BTW, this would be a good idea. not necessary, but would be nice. http://holley.com/108-98-10.asp do not, I repeat DO NOT use these http://holley.com/26-113.asp

02-25-2009, 01:55 PM	#9
donelan07 Active Member Join Date: Dec 2004 Location: Brookings, SD Posts: 202	Re: Timing and Back Firing Issues. Pictures I can't work on my truck this weekend. My brothers wrestling up in Aberdeen for state. __________________ _________________________________ 1972 Chevy SWB 4x4 350 4speed

02-25-2009, 10:33 PM	#10
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	Re: Timing and Back Firing Issues. Pictures OK, now I dont have to feel guilty for not being available. my leave was pulled because I went to Harbor Freight last weekend. she is upset about what I spent.



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