Hard starting when cold
Thread Starter
|
Senior User
Joined: Nov 2010
Posts: 146
Likes: 0
From: Air Capitol, KS
Hard starting when cold
I own a 1981 F100 4.9 I6 with a newly rebuilt 1bbl. carb. Ever since I had the carb rebuilt, it idles a little fast when warmed up. The real issue is that it takes a lot of cranking in the morning to start (especially now since it's bitter cold). I do smell a little fuel on startup. It will crank and crank for about 20 sec., then maybe try to catch a couple times, then finally catch if I crank a little more and force it. I've been told it could be timing, but I wonder if there might be another solution. I have a manual choke which I've tried opened and closed and can't tell if either setting helps. Any suggestions?
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
For starters, since you have a manual choke, I'd figure out right where you want to put it for cold starting.
Take the air cleaner off and adjust the choke so that the choke plate on top is only open about 1/8" - 1/16". That'll be where you want it to start in the morning. Then, obviously, open it up as/when the truck warms up.
Do you have a vacuum gauge? If so, you can use one to be sure that your timing and your idle air/fuel mixture are correct, which should help a lot with cold startups.
Lastly, its possible something wasn't tightened right, warped, torn gasket, etc. that could be causing an internal fuel leak as it sits, and when you go to start it in the morning, it's already flooded.
Take the air cleaner off and adjust the choke so that the choke plate on top is only open about 1/8" - 1/16". That'll be where you want it to start in the morning. Then, obviously, open it up as/when the truck warms up.
Do you have a vacuum gauge? If so, you can use one to be sure that your timing and your idle air/fuel mixture are correct, which should help a lot with cold startups.
Lastly, its possible something wasn't tightened right, warped, torn gasket, etc. that could be causing an internal fuel leak as it sits, and when you go to start it in the morning, it's already flooded.
Thread Starter
|
Senior User
Joined: Nov 2010
Posts: 146
Likes: 0
From: Air Capitol, KS
Yes, I'll check those. I don't have a vacuum gauge, unfortunately, but I can check the timing and I already want to slow down the idle. I'll re-check the idle mixture also and I'll check the carb for tightness and gaskets as well.
BTW, I used to live in Boise. I really liked it, nice town. I used to live in Old Boise across from the Hollywood market.
BTW, I used to live in Boise. I really liked it, nice town. I used to live in Old Boise across from the Hollywood market.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
I'd definitely recommend a vacuum gauge if you plan on doing any of your own tuning, they're invaluable, and not too expensive. You can tune your fuel mixture, idle mixture, and your timing perfectly with one. No guessing. 
The idle RPM speed is controlled by two screws on the back of the carb (hard to reach when its on). The one that presses directly against the carb body is the normal idle, and the one that presses against moving linkage is the cold start idle. You want the cold start one adjusted so that it sits around 1500 RPMs when the engine's cold, and the other at around 700 when the engine's warmed up. (Not sure if you have a tachometer.)
I know the area you mean, quite the opposite end of town than me. A nice area though. Boise's great. Has the options of a big city, with the small town feel.
The idle RPM speed is controlled by two screws on the back of the carb (hard to reach when its on). The one that presses directly against the carb body is the normal idle, and the one that presses against moving linkage is the cold start idle. You want the cold start one adjusted so that it sits around 1500 RPMs when the engine's cold, and the other at around 700 when the engine's warmed up. (Not sure if you have a tachometer.)
I know the area you mean, quite the opposite end of town than me. A nice area though. Boise's great. Has the options of a big city, with the small town feel.
Thread Starter
|
Senior User
Joined: Nov 2010
Posts: 146
Likes: 0
From: Air Capitol, KS
Not perfect but better
After experimenting with my startup procedure, things are going much better, but still not perfect. I am more careful with setting the choke, pump it a few times before turning the key, and hold in the clutch until the engine runs for a minute or two (the clutch thing was making it die in the extreme cold at first). It will catch right away but die and I have to try a few times. After I make some more adjustments, it should start like it used to.
BTW, how do you get those cool signature notes at the bottom of your posts, if you don't mine me asking?
BTW, how do you get those cool signature notes at the bottom of your posts, if you don't mine me asking?
Last edited by krazeyelf; Jan 12, 2011 at 12:08 PM. Reason: wanted to add a question
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
It's amazing what the proper adjustments for cold weather can do. Before I did any on mine, it was a nightmare to get started in the winter. I'd have to start it about five times or so before it would finally run longer than 5 seconds, and then once it finally did, I had to brace the gas pedal with a long ice scraper to keep it running for a good ten minutes so it would warm up. If not, it'd die every time I let the clutch out.
After I adjusted the choke, cold idle, etc. properly, it'd start with the first turn of the key, idle on its own, and was driveable immediately.
After I adjusted the choke, cold idle, etc. properly, it'd start with the first turn of the key, idle on its own, and was driveable immediately.
Thread Starter
|
Senior User
Joined: Nov 2010
Posts: 146
Likes: 0
From: Air Capitol, KS
I think I'll invest in a timing light that has a built-in tach; I think they make such a thing. Some day, possibly this summer when it's warmer, I'd like to install a dash-mount tach.
So, I have to ask, how does a vacuum gauge help to set fuel mixture, idle mixture, and timing, and how does one do that?
So, I have to ask, how does a vacuum gauge help to set fuel mixture, idle mixture, and timing, and how does one do that?
Trending Topics
Postmaster
Joined: Dec 2006
Posts: 3,603
Likes: 10
From: Spokane, WA
Unplug the vacuum line running to the distributor and plug it. Attach the vacuum gauge to a full manifold vacuum source. With the engine running, turn the dizzy one way or the other until the highest steady reading on the gauge is obtained and back off 1-2hg. Lock down the distributor. Do the same with the idle mixture screw to obtain the highest steady reading. Adjust the idle speed screw. Go back and forth between the idle mix and speed screws always adjusting to the highest steady vac reading. Hook up the distributor vac line, drive and try. Make sure the engine is fully warmed up before you start the adjustments.
A good read on vacuum gauge use can be found here: http://www.secondchancegarage.com/public/186.cfm
A good read on vacuum gauge use can be found here: http://www.secondchancegarage.com/public/186.cfm
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Yup, that's pretty much it. What you're looking for is bringing up the vacuum reading at idle.
The better the timing and the better the fuel mixture, the higher the vacuum reading will be, since its running better.
The better the timing and the better the fuel mixture, the higher the vacuum reading will be, since its running better.
Thread Starter
|
Senior User
Joined: Nov 2010
Posts: 146
Likes: 0
From: Air Capitol, KS
much better starting
Well, I got the procedure down as good as I'm going to get it. Got her to start on first turn this morning. Still plan to do the tuning when I can get the tools and the time together.
The only other real issue I notice now is at highway speed when under load, when I really get into it she comes almost to the brink of bogging down. It never really bogs down, but it starts a sort of "rhythmic vibration" which never happened before when I got into it at high speed under a load, and doesn't really do much for keeping her up to speed. I'm guessing tuning will fix this as well as possibly changing plugs and wires, but I wanted to throw this out in case you fellas have any thoughts.
P. S. Thank you for the vacuum gauge tuning procedures.
The only other real issue I notice now is at highway speed when under load, when I really get into it she comes almost to the brink of bogging down. It never really bogs down, but it starts a sort of "rhythmic vibration" which never happened before when I got into it at high speed under a load, and doesn't really do much for keeping her up to speed. I'm guessing tuning will fix this as well as possibly changing plugs and wires, but I wanted to throw this out in case you fellas have any thoughts.
P. S. Thank you for the vacuum gauge tuning procedures.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
Awesome on getting the cold startup going better. 
As for the bogging, that's difficult to say. When was the last time it had new plugs, wires, cap, rotor, etc? I would say if its been a while, give it a fresh tuneup and then tune it with the vacuum gauge. If after all that it still bogs, then you at least you know you've eliminated a lot of variables.
As for the bogging, that's difficult to say. When was the last time it had new plugs, wires, cap, rotor, etc? I would say if its been a while, give it a fresh tuneup and then tune it with the vacuum gauge. If after all that it still bogs, then you at least you know you've eliminated a lot of variables.
Thread Starter
|
Senior User
Joined: Nov 2010
Posts: 146
Likes: 0
From: Air Capitol, KS
Tune-up
Yep, a tune-up (plugs, wires, cap, rotor, oil, filter) is my next planned "project." I'll let you all know what effect that has. I'm not sure when the last time it was done, definitely not since I bought her back in September. It's probably about time.
Thread
Thread Starter
Forum
Replies
Last Post
charecter1
1994.5 - 1997 7.3L Power Stroke Diesel
5
Apr 28, 2016 06:29 PM
Handegard
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
4
Aug 6, 2011 06:09 PM
