Stumble
Mountain Pass
Joined: Sep 2004
Posts: 127
Likes: 28
From: s/e iowa
Also, you might check the carb to intake manifold hardware, make sure its tight. If the carb has not been off for a long time both gaskets probably need replaced. I like to put a light layer of white lithium grease on each side of both gaskets to help ensure a good seal.
Stumbles and hesitations sometimes hurt the powervalve also.
Stumbles and hesitations sometimes hurt the powervalve also.
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Also, you might check the carb to intake manifold hardware, make sure its tight. If the carb has not been off for a long time both gaskets probably need replaced. I like to put a light layer of white lithium grease on each side of both gaskets to help ensure a good seal.
Stumbles and hesitations sometimes hurt the powervalve also.
Stumbles and hesitations sometimes hurt the powervalve also.
I actually bought new gaskets, but I sprayed a lot of carb cleaner all the way around the base of the carb with the truck running and not so much as a hiccup. I really don't think I'm pulling any air in there.
Mountain Pass
Joined: Sep 2004
Posts: 127
Likes: 28
From: s/e iowa
yeah used a lot of carb cleaner trying to get it figured out also. Mine was the gaskets and powervalve and throttle shaft wear. I even stroked a file across the pull off spacer and carb base plate, none of it was perfect.
I often try to remember how these things ran off the show room floor. So spoiled by FI.
I often try to remember how these things ran off the show room floor. So spoiled by FI.
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Good deal...we'll all be waiting to see what you've found.
Any manifold vacuum will do for setting the carb's mixture.
For checking the distributor's vacuum advance can's diaphragm and breaker plate.... you can pull the line off the can's nipple and attach the vacuum gauge's line to it, or, pull the vacuum line off the ported nipple on the carb and use it. The engine doesn't have to be running to do this.
Any manifold vacuum will do for setting the carb's mixture.
For checking the distributor's vacuum advance can's diaphragm and breaker plate.... you can pull the line off the can's nipple and attach the vacuum gauge's line to it, or, pull the vacuum line off the ported nipple on the carb and use it. The engine doesn't have to be running to do this.
ok. i pulled the vacuum line off the distributor and hooked up a clean hose to it. popped the cap and sucked through the hose. there is no movement on the arm inside the distributor. i then tried blowing on the line. i can hear the diaphram in the canister when I do this. so is it time for a new distributor, or can you service this.?
seems that arm in there should move freely when vacuum is applied. hope this is the cause of my issues. im also getting a backfire put the carb if I really stop it down in 3rd gear... truck stumbles, backfires, and then it goes. this thing seems like it wants to make good power but it just wont.
checked timing. 800 rpm appears to be 15 degrees or better...hard to get a good reading in bright sunlight.. timing does advance as ms increase so mechanical advance is working. no ping whatsoever.
lastly, where are the mixture screws on this carb? nothing on the front near the accel pump.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
ok. i pulled the vacuum line off the distributor and hooked up a clean hose to it. popped the cap and sucked through the hose. there is no movement on the arm inside the distributor. i then tried blowing on the line. i can hear the diaphram in the canister when I do this. so is it time for a new distributor, or can you service this.?
seems that arm in there should move freely when vacuum is applied.
checked timing. 800 rpm appears to be 15 degrees or better...hard to get a good reading in bright sunlight.. timing does advance as ms increase so mechanical advance is working. no ping whatsoever.
lastly, where are the mixture screws on this carb? nothing on the front near the accel pump.
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
was only able to suck it by mouth (that didnt read well....lol). Cant imagine engine vacuum would be much stronger. Will look for an advance can. Seems I could replace it without pulling the distributor....maybe. AC compressor bracket might be in the way.
I ran out of adjustment trying to get the idle below about 750. 15-16 degrees of tining there if my pointer is accurate, but no ping. I need to vheck early in the day tho when I can see the timing marks a little better.
Will look for the adjustment screws to try to maximize vacuum. What do you think is causing the carb backfire? Too lean?
I ran out of adjustment trying to get the idle below about 750. 15-16 degrees of tining there if my pointer is accurate, but no ping. I need to vheck early in the day tho when I can see the timing marks a little better.
Will look for the adjustment screws to try to maximize vacuum. What do you think is causing the carb backfire? Too lean?
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
It's easier to replace the can without pulling the distributor, in my book. Glad you "procured" a substantial vacuum....hehe.
Ok, good on the checking the timing.
Ran out of adjustment to get the idle down? Definitely play with the mixture, timing and check for vacuum leaks.
Back firing through the carb can be an indication of a too lean a mixture, vacuum leak, timing, a faulty accelerator pump, crossfiring - plug wires # 5 and 6 being old and leaky would do it - or a cracked distributor cap or all of the above.
Ok, good on the checking the timing.
Ran out of adjustment to get the idle down? Definitely play with the mixture, timing and check for vacuum leaks.
Back firing through the carb can be an indication of a too lean a mixture, vacuum leak, timing, a faulty accelerator pump, crossfiring - plug wires # 5 and 6 being old and leaky would do it - or a cracked distributor cap or all of the above.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
It's easier to replace the can without pulling the distributor, in my book. Glad you "procured" a substantial vacuum....hehe.
Ok, good on the checking the timing.
Ran out of adjustment to get the idle down? Definitely play with the mixture, timing and check for vacuum leaks.
Back firing through the carb can be an indication of a too lean a mixture, vacuum leak, timing, a faulty accelerator pump, crossfiring - plug wires # 5 and 6 being old and leaky would do it - or a cracked distributor cap or all of the above.
Ok, good on the checking the timing.
Ran out of adjustment to get the idle down? Definitely play with the mixture, timing and check for vacuum leaks.
Back firing through the carb can be an indication of a too lean a mixture, vacuum leak, timing, a faulty accelerator pump, crossfiring - plug wires # 5 and 6 being old and leaky would do it - or a cracked distributor cap or all of the above.
LOL...that really narrowed it down.
You know all these symptoms have acted like a vacuum leak from day one, but I've replaced everything questionable and I simply can't find any other leaks with the carb cleaner method. The more I do, the more I'm leaning towards just slapping a new carb on this thing and being done with it, assuming I rule out everything else. My dad suggested fuel pressure could be an issue on the mechanical pump as well. Not sure how to check that though when the engine is falling on its face under acceleration.
Will get out and set mixture when I have the time to do so. Hitting Napa after work today to see if they have a new advance gizmo.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Alright! I'm happy I nailed the backfiring through the carb problem for ya! 
Fuel pump/pressure considerations might come into play if you had no "squirts" in the venturi while blipping the throttle on a cold engine....or hard starting.....or the smell of gas in the oil.
I don't remember if you said you rebuilt the carb....?
Let us know how the new advance can works....it probably will come with some springs...and mebbe a small allen wrench which is used for adjusting when vacuum comes in. We can get to that later.
Fuel pump/pressure considerations might come into play if you had no "squirts" in the venturi while blipping the throttle on a cold engine....or hard starting.....or the smell of gas in the oil.
I don't remember if you said you rebuilt the carb....?
Let us know how the new advance can works....it probably will come with some springs...and mebbe a small allen wrench which is used for adjusting when vacuum comes in. We can get to that later.
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Have not rebuilt the carb. going through all the easier stuff first. If it does come down to needing a rebuild, I may just go the reman'd route instead. I know it's more dough, but I'd probably feel better about it.
So Napa had two parts listings for the vacuum advance but they couldn't get either one. They ranged in price from $26-42, but an entire new distributor was only $59 so I just did that and will feel good having all new electronics inside. Will get that swapped hopefully Friday, and will reset timing and tune engine vacuum then and see where it goes from there.
Any other tips on finding vacuum leaks? I've gone through a full can of carb cleaner hitting the ends of all vacuum lines, around the carb base, side of the carb where the throttle goes through, etc.
Should I assume that the new distributor is adjusted properly or do you guys think I'll be needing to messing with spring tension, etc?
I don't have much drawing vacuum....EGR, Brake Booster, Distributor, and PCV. Most of the ports on the manifold tree are capped, and don't appear to leak.
So Napa had two parts listings for the vacuum advance but they couldn't get either one. They ranged in price from $26-42, but an entire new distributor was only $59 so I just did that and will feel good having all new electronics inside. Will get that swapped hopefully Friday, and will reset timing and tune engine vacuum then and see where it goes from there.
Any other tips on finding vacuum leaks? I've gone through a full can of carb cleaner hitting the ends of all vacuum lines, around the carb base, side of the carb where the throttle goes through, etc.
Should I assume that the new distributor is adjusted properly or do you guys think I'll be needing to messing with spring tension, etc?
I don't have much drawing vacuum....EGR, Brake Booster, Distributor, and PCV. Most of the ports on the manifold tree are capped, and don't appear to leak.
Mountain Pass
Joined: Sep 2004
Posts: 127
Likes: 28
From: s/e iowa
Carb rebuild kits are cheap, I would try the rebuild before spending the money on a reman. Just ensure that the carb is thoroughly cleaned and ALL passage ways are clear.
Just for the heck of it, spray some WD or carb cleaner along the intake to head gaskets while its running to rule out a bad gasket.
Just for the heck of it, spray some WD or carb cleaner along the intake to head gaskets while its running to rule out a bad gasket.
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
will see. Let me eliminate all other possibilities first. I know my vacuum advance is hosed...so that gets fixed first, followed by more tuning and timing adjustments.
Good idea on checking the manifold itself for leaks. I'll try that.
Good idea on checking the manifold itself for leaks. I'll try that.
Thread Starter
|
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
Word.
