what could it be?
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Junior User
Joined: Jan 2012
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what could it be?
Alright i've got a 78 f150 with the 300 i6 stock carb. When i tap the gas pedal it either hesitates or just dies. If I ease into the carb it acts like nothing is wrong at all. If i'm driving in 3rd or 4th gear and tap the gas petal, it does not hesitate. It seems to do it when it isn't under much of a load or any load at all. It also seems to get a little better when it warms up but it's still bad. I've adjusted to it and drive it almost daily but its still a pain in the @$$. I have given up trying to diagnose the problem since I feel like it could be any number of 150 things. Anybody have this problem before? Any advice or help would be appreciated.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
That sounds like the accelerator pump is bad. Look down the throat of the carburetor and you should see a stream of gas spray into the barrel as you pull back the throttle.
Also make sure the vacuum advance is functioning and can hold vacuum.
Also make sure the vacuum advance is functioning and can hold vacuum.
Elder User
Joined: Mar 2013
Posts: 559
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From: In Hastings Delton area
Check and see if lead plug is missing on accelerator pump,I have fixed a lot of these .If the plug is missing you can make a new one out of a piece of lead wheel wieght Trim to fit tap in with hammer
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Elder User
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Lead Driver
Joined: Nov 2006
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From: Pa.
if the motor is the same year as the truck and the EGR was removed and nothing done to compensate in the dizzy then it needs to be worked on because the timing will be off .. The carb will also need to be rejetted for the change also
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Junior User
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To the others, where is a good location for my vacuum advance line?
The motor never had EGR. It is an 82 motor with all 78 external parts ergo eliminating the problems associated with removing the EGR.
I already thought about the timing factor. I will most likely time it with a vacuum gage, but I'm not entirely sure how to do that - where should I attach the vacuum gage, what am I looking for as far as readings and etc.
Thanks guys the help is appreciated
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
yes that is correct.
To the others, where is a good location for my vacuum advance line?
The motor never had EGR. It is an 82 motor with all 78 external parts ergo eliminating the problems associated with removing the EGR.
I already thought about the timing factor. I will most likely time it with a vacuum gage, but I'm not entirely sure how to do that - where should I attach the vacuum gage, what am I looking for as far as readings and etc.
Thanks guys the help is appreciated
To the others, where is a good location for my vacuum advance line?
The motor never had EGR. It is an 82 motor with all 78 external parts ergo eliminating the problems associated with removing the EGR.
I already thought about the timing factor. I will most likely time it with a vacuum gage, but I'm not entirely sure how to do that - where should I attach the vacuum gage, what am I looking for as far as readings and etc.
Thanks guys the help is appreciated
To answer your vaccum gauge question see here Classic Inlines - Tuning with a Vacuum Gage
You still might have to recurve the dizzy
Ford Truck Enthusiasts Forums - Search Results
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Junior User
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The EGR plate may have been optional in 78, but the motor that I took the parts off of did not and it is a 78. The Dizzy probly does need a recurve, but I don't have a clue how to do that or where to get the kit. Links or info for that would be awesome. Thanks for the Vac gage link and to everyone else.
Lead Driver
Joined: Nov 2006
Posts: 5,217
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From: Pa.
On the EGR it was more than likely already removed on the 78 motor there are several threads on removing the EGR on the 300 six and the pros and cons .. My suggestion is to read through them and make sure the EGR removal was completed properly so future damage to the motor won't occur.. Here is good article on the whole timing process and recurving and how it's done and the reasons why ..
Classic Inlines - Ignition System & Timing
Classic Inlines - Ignition System & Timing
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Junior User
Joined: Jan 2012
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Hey thanks a ton. I'll look into the recurve. I rebuilt the carb and timed the engine and it misses while cold, but when it is warm it runs better than it ever has in all the years that it's been in the family. almost NO hesitation, plenty of power, and I've been calculating the mileage in the high teens. Thank you.
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