Electric choke is cracked.
Thread Starter
|
Postmaster
Joined: Oct 2004
Posts: 4,402
Likes: 1
From: Delisle/Vanscoy, Sk.
Electric choke is cracked.
The electric choke on my 86 351 auto truck I notice it is cracked. But still together. My gas mileage sucks and I wonder if this would have something to do with it. It has been to 2 garages and they saw no problem with the choke the way it is. But I got to thinking if it is cracked and open. Won't it affect the bimetal spring that opens the choke. Instead of getting the heat it would be getting some cool air on it thus maybe causing the choke to stay closed and thus sucking more gas than it should. It has been to 3 shops and everyone of them said the truck was up to snuff and they could find nothing wrong. They were amazed to see a truck with all the stock parts still under the hood. It only has a 128,000 km on it, 70,000 miles. I'm the 3rd owner.
Oh my gas is about 6 miles per gallon.
I plan to get another choke anyways, I suspect it is possible problem to mileage.
Oh my gas is about 6 miles per gallon.
I plan to get another choke anyways, I suspect it is possible problem to mileage.
Senior User
Joined: Feb 2006
Posts: 479
Likes: 0
From: Sonoma, CA
If it's broken and the choke is stuck open, it will only be a little more difficult to warm up the engine, as it will be a little lean cold. Once warm the choke should be fully open. If it's stuck closed, it would cause a rich condition warm and make the mileage drop a bit. Probably some black smoke with this scenario too. Take off the air cleaner and watch the choke flap as it warms up.That will provide your answer.
Thread Starter
|
Postmaster
Joined: Oct 2004
Posts: 4,402
Likes: 1
From: Delisle/Vanscoy, Sk.
I have open the air cleaner after a jaunt to town and the choke is open. But the exhaust is black when you give some gas. The pipes are black soot and in the winter the ground is black on the snow. Yet the carb according to these gargaes is set right up. The float is where it should be. I just suspect this choke may fluctuate due to the crack. I still plan to get a replacement. The other problem up here is now trying to find a shop with a scope. Everything is Fuel Injected and computerised. Most shops do not have scopes anymore and when they break they just rather not fix them. I think a scope check would also help the truck.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
You need to replace the choke; they are wrong in saying it is okay to be cracked. Many stock 21xx carbs have manifold vacuum running into the choke cap. A crack can contribute to a vacuum leak. If you pull the choke cap off on a running engine with these carburetors, the engine will stall. You need a good seal here.
I don't think cool air is getting in there. Those springs get pretty hot, pretty fast, and stay that way for a while. If the cracked cap is contributing anything to the poor mileage, it would be related to a potential vacuum leak. But I'd imagine the biggest factor in your poor gas mileage is the condition of the carburetor in general. With 70,000 miles on an untouched truck, it is definitely time for a carb rebuild.
I don't think cool air is getting in there. Those springs get pretty hot, pretty fast, and stay that way for a while. If the cracked cap is contributing anything to the poor mileage, it would be related to a potential vacuum leak. But I'd imagine the biggest factor in your poor gas mileage is the condition of the carburetor in general. With 70,000 miles on an untouched truck, it is definitely time for a carb rebuild.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
(See above post.)
Also, if you are getting THAT much soot, the carb is not set up correctly. The shop is wrong; how can they say a truck that is shooting out black smoke has a perfectly tuned carburetor? That is ridiculous. There is more to it than the float. It's time for a carb rebuild. My money is on a ruptured power valve.
I'm confused what you need a scope for. Scope to me means oscilloscope. Do you mean a sniffer for the exhaust?
Best of luck!
Also, if you are getting THAT much soot, the carb is not set up correctly. The shop is wrong; how can they say a truck that is shooting out black smoke has a perfectly tuned carburetor? That is ridiculous. There is more to it than the float. It's time for a carb rebuild. My money is on a ruptured power valve.
I'm confused what you need a scope for. Scope to me means oscilloscope. Do you mean a sniffer for the exhaust?
Best of luck!
Last edited by fmc400; Aug 8, 2006 at 11:30 PM.
Thread Starter
|
Postmaster
Joined: Oct 2004
Posts: 4,402
Likes: 1
From: Delisle/Vanscoy, Sk.
A scope engine. It is hooked up and helps check all your firing is up to par and the it helps with setting the carbs for RPM's and that they can set your enginr up for maxium perform. These shops today have the suitcase computers for newer stuff. Very few now have the equipment that can help set up firing and carburations and timing any more. Everything is becoming powercoils and sensors. No distributors, carbs, points and condensors. The engine scopes helped the mech in solving some of the problems and setting the engine to run at it peak.
The carb was rebuilt at a garage just before I bought it. I think they put in a rebuild kit. The owner I got the truck from is not a mechanic and he took it to the shops for repairs.
A lot of the rebuild kits do not come with replacement check ***** or springs for power take off valves. Just some diapharms and gaskets. I don't like that. I rather go and buy another carb from a supplier. Problem is they are 500 to 600 a carb. I have a 4bbl Holley stock.
Anyways I suspect the choke is no help and it is an electric choke. Vacuum leak is a possiblity. There is so many vacuum lines on this truck it is hard to see the engine.
The carb was rebuilt at a garage just before I bought it. I think they put in a rebuild kit. The owner I got the truck from is not a mechanic and he took it to the shops for repairs.
A lot of the rebuild kits do not come with replacement check ***** or springs for power take off valves. Just some diapharms and gaskets. I don't like that. I rather go and buy another carb from a supplier. Problem is they are 500 to 600 a carb. I have a 4bbl Holley stock.
Anyways I suspect the choke is no help and it is an electric choke. Vacuum leak is a possiblity. There is so many vacuum lines on this truck it is hard to see the engine.
Thread
Thread Starter
Forum
Replies
Last Post
fmc400
1973 - 1979 F-100 & Larger F-Series Trucks
55
Jul 30, 2014 10:11 AM
highguy2012
1973 - 1979 F-100 & Larger F-Series Trucks
1
Apr 24, 2012 10:13 PM
Nathan Plemons
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
6
Jun 30, 2009 06:44 AM
sum_weirdo
Fuel Injection, Carburetion & Fuel System
5
Nov 12, 2007 07:03 PM
