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Hesitation when accelerating


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#1 Matt_V

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Posted 10 September 2008 - 05:21 PM

I was trying to think of the reasons the hesitation was happening when I accelerated. I first thought vacuum leak. I dont think that so much anymore. Then I was thinking distributor, which it could be, but I have a good vacuum advance now. Then I got to thinking... fuel pump.
If I am thinking correctly, the fuel pump is a mechanical fixture near the front of the engine, right? If it sat in a barn for about 4 years, would it have a diaphragm in it like the vacuum advance that might have deteriorated and causing such an issue?
Matt
1982 Ford Bronco 4x4 351w, 2bbl carb. - LOTS of work needed.... Project truck
2007 Chevy Silverado 1500 Classic 4x4 Crew cab, Daily driver
Wichita Falls, TX

#2 JLasvegas

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Posted 10 September 2008 - 06:27 PM

accel pump in carb possibly

do you get any back fire or pop thru the carb?
1989 FORD BRONCO XLT 5.0 302

#3 BroncoJoe19

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Posted 10 September 2008 - 06:37 PM

I am pretty sure that there is a diaphragm in a mechanical fuel pump as you discribed. Could it be dry rotted, cracked, and leaking? I don't see why not.
According to Haynes one should get 6 to 8 psi for all except the in line six cylinders
and 5 to 7 for the inline six.

volume (at idle RPM) 1 pint in 20 seconds.

IF the hessitation is just while accellerating, and you fixed the vac advance, then the more likely culpret would be a poorly functioning accellerator pump in your carb.
BroncoJoe19... I am not a professional mechanic, nor an engineer.
One should always obtain professional advice before attempting a repair or modification.

1990 Tan on Black Eddie Bauer - resides in North Jersey
302 with 33's on 15s E4OD Speedometer corrected trans
Auto hubs with manual transfer case snorkel

#4 Matt_V

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Posted 10 September 2008 - 06:37 PM

already replaced the accel. pump in the carb. Before I got the vacuum advance on the distributor, I had borrowed a timing light and 'timed' it and prior to that it used to backfire bad...

I guess it could still be a distributor/ignition issue.. just exploring possibilities right now.
Matt
1982 Ford Bronco 4x4 351w, 2bbl carb. - LOTS of work needed.... Project truck
2007 Chevy Silverado 1500 Classic 4x4 Crew cab, Daily driver
Wichita Falls, TX

#5 Matt_V

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Posted 10 September 2008 - 06:50 PM

I've got lots of time to sit and think of what could be wrong... facing a back surgery soon to fix a herniated disc... so when I think of something to ask, I ask. Not necessarily meaning I have the time, ability or money to fix it.. and hoping I dont have to sell it to help pay medical bills before I get to at least get it running well enough to have some fun in it... in my mind I dont see a fully restored Bronco, although it would be nice... I just want a dependable knock around rig that if needed could double as a spare vehicle.
Matt
1982 Ford Bronco 4x4 351w, 2bbl carb. - LOTS of work needed.... Project truck
2007 Chevy Silverado 1500 Classic 4x4 Crew cab, Daily driver
Wichita Falls, TX

#6 JLasvegas

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Posted 10 September 2008 - 08:10 PM

replace the mechanical fuel pump, they are cheap and easy to install, they will also help with any hard start issues if its leaking back into the tank and not supplying enough pressure
1989 FORD BRONCO XLT 5.0 302

#7 BroncoJoe19

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Posted 11 September 2008 - 04:35 AM

Matt,
Just curious, is it a really significant delay? Like you hear it bog, and then it finally winds up and goes?

Or is it like a single cylinder miss and then it takes off?
BroncoJoe19... I am not a professional mechanic, nor an engineer.
One should always obtain professional advice before attempting a repair or modification.

1990 Tan on Black Eddie Bauer - resides in North Jersey
302 with 33's on 15s E4OD Speedometer corrected trans
Auto hubs with manual transfer case snorkel

#8 Matt_V

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Posted 11 September 2008 - 04:58 AM

Matt,
Just curious, is it a really significant delay? Like you hear it bog, and then it finally winds up and goes?

Or is it like a single cylinder miss and then it takes off?


It bogs, then if you slowly accelerate it will wind up and go. Press the pedal too fast and it will stall completely if the engine isn't already somewhat revved up, like going down the road, even then it is sluggish.

Haven't taken it on too many trips down the road yet. I think I am going to have to replace tie-rod ends and such... its a little loose up front. :P
Matt
1982 Ford Bronco 4x4 351w, 2bbl carb. - LOTS of work needed.... Project truck
2007 Chevy Silverado 1500 Classic 4x4 Crew cab, Daily driver
Wichita Falls, TX

#9 BroncoJoe19

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Posted 11 September 2008 - 04:37 PM

Matt,
Do me a favor and try this.
Pull the hose to the vacuum advance, and plug it and see if makes any difference at all.
joe
BroncoJoe19... I am not a professional mechanic, nor an engineer.
One should always obtain professional advice before attempting a repair or modification.

1990 Tan on Black Eddie Bauer - resides in North Jersey
302 with 33's on 15s E4OD Speedometer corrected trans
Auto hubs with manual transfer case snorkel

#10 Matt_V

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Posted 11 September 2008 - 11:24 PM

Joe, I'll try to do that this weekend if weather permits.
Even though I'm in North Texas near Oklahoma border, I think that little storm thingy in the Gulf that someone nicknamed IKE :P is gonna dump a lot of rain on us here.

Edited by Matt_V, 11 September 2008 - 11:24 PM.

Matt
1982 Ford Bronco 4x4 351w, 2bbl carb. - LOTS of work needed.... Project truck
2007 Chevy Silverado 1500 Classic 4x4 Crew cab, Daily driver
Wichita Falls, TX

#11 BroncoJoe19

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Posted 12 September 2008 - 04:22 AM

LOL... just remember... if you turn your back to the wind and rain... you'll get an instant upside down umbrella!
:o
BroncoJoe19... I am not a professional mechanic, nor an engineer.
One should always obtain professional advice before attempting a repair or modification.

1990 Tan on Black Eddie Bauer - resides in North Jersey
302 with 33's on 15s E4OD Speedometer corrected trans
Auto hubs with manual transfer case snorkel

#12 Matt_V

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Posted 14 September 2008 - 12:24 PM

Joe,
I tried what you said, and it didn't seem to make much of a difference. Might have actually made it stall out a little less? Either way, it still stalls out when you first mash the gas.... not always stalling all the way to quit running.. just sometimes.

Edited by Matt_V, 14 September 2008 - 12:25 PM.

Matt
1982 Ford Bronco 4x4 351w, 2bbl carb. - LOTS of work needed.... Project truck
2007 Chevy Silverado 1500 Classic 4x4 Crew cab, Daily driver
Wichita Falls, TX



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