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Author Topic: sporadic misfire  (Read 12656 times)

Offline greenmonster

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Re: sporadic misfire
« Reply #15 on: September 09, 2010, 11:58:58 am »
I have 12.34 volt with key on and 14.59 volts at idle.
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Offline Irish_Alley

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Re: sporadic misfire
« Reply #16 on: September 10, 2010, 07:08:02 am »
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Offline greenmonster

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Re: sporadic misfire
« Reply #17 on: September 10, 2010, 04:11:30 pm »
A bolt on the a/c bracket.
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Offline Irish_Alley

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Re: sporadic misfire
« Reply #18 on: September 11, 2010, 12:27:19 am »
A bad ground from the bock to the frame or body can cause it not to but hot enough. What I do sometimes is grab the treads of the plug with a jumper cable and put the other matching end to the neg side of the battery and test from there.
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline greenmonster

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Re: sporadic misfire
« Reply #19 on: September 11, 2010, 08:14:34 pm »
I'll try the jumper cable thing and let you know how it goes.
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Offline greenmonster

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Re: sporadic misfire
« Reply #20 on: September 12, 2010, 08:53:51 am »
The spark is still orange even with it grounded to the battery.
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Offline Irish_Alley

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Re: sporadic misfire
« Reply #21 on: September 12, 2010, 06:55:08 pm »
Tell you the truth I have a miss my spark is blue. If you ground is good and you changed all your distributor parts I'm lost
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline TexasRed

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Re: sporadic misfire
« Reply #22 on: September 12, 2010, 11:19:40 pm »
What kind of HEI? Do you still have ESC hooked up? External or internal coil?
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Offline greenmonster

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Re: sporadic misfire
« Reply #23 on: September 13, 2010, 01:32:54 pm »
As far as I know it is factory from 1975.I don't know what esc is but the coil is in the cap.
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Offline Captkaos

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Re: sporadic misfire
« Reply #24 on: September 13, 2010, 04:21:10 pm »
ESC wouldn't be on a 1975 that is the first year for the HEI.  ESC started in 1981.
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Offline TexasRed

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Re: sporadic misfire
« Reply #25 on: September 13, 2010, 09:53:12 pm »
Is that voltage reading you gave of the battery or the wire going to the distributor? What kind of a plug are using to ground against the frame to check for spark or are you using that tester from Harbor Freight? Did your truck come with a governer?
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Offline greenmonster

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Re: sporadic misfire
« Reply #26 on: September 14, 2010, 06:22:47 am »
The volt reading is from the dis.I am using a ac delco plug gaped at .035.
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Offline TexasRed

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Re: sporadic misfire
« Reply #27 on: September 14, 2010, 07:59:23 pm »
20 in of vacuum is quite a bit. Has this engine ever been rebuilt? I'm thinking either fuel pump or maybe the strainer/sock in the fuel tank is clogging something up. What's fuel pressure like?
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Offline greenmonster

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Re: sporadic misfire
« Reply #28 on: September 15, 2010, 05:56:51 am »
When i bought the truck about 3 years ago the guy told me it had a fresh top end.I just put a new fuel pump on it when it started acting up but i never tested the pressure.It is just a cheap replacement pump.
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Offline TexasRed

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Re: sporadic misfire
« Reply #29 on: September 15, 2010, 04:40:56 pm »
I think there's anything but a cheap replacement pump that's mechanical unless it's a race pump.
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