curious situation
Thread Starter
|
Junior User
Joined: Aug 2006
Posts: 92
Likes: 0
curious situation
Hi gang. I have a curious situation here that has me stumped. Here is part of what i posted in a previous thread
So for the heck of it, I started pulling vacuum hoses off of the manifold tree. From the carb float bowl vent, there is a vacuum operated valve on the hose going to the charcoal canister. When I pulled that vacuum hose off, WOW. Idle rpm came up to normal, was idling smooth. Gave it some throttle and it reved right up, just a slight hesitation.)
Now today, whith that vacuum hose disconnected from the vacuum tree on the intake manifold, it runs like a champ. If I plug that port on the tree, it runs like crap. If I'm not mistaken, that open vacuum port is equivalant to a big vacuum leak. I'm thinking that maybe another component that uses vacuum could be malfuntioning causing my situation.
The tab,tad,egr solenoid, smog pump, diverter/bypass valve were all purchased at the junkyard.
Am I on the right track in thinking that another vacuum component could be malfunctioning or am I way off track in thinking this?
Any thoughts on this would be greatly appreciated.
Bill
So for the heck of it, I started pulling vacuum hoses off of the manifold tree. From the carb float bowl vent, there is a vacuum operated valve on the hose going to the charcoal canister. When I pulled that vacuum hose off, WOW. Idle rpm came up to normal, was idling smooth. Gave it some throttle and it reved right up, just a slight hesitation.)Now today, whith that vacuum hose disconnected from the vacuum tree on the intake manifold, it runs like a champ. If I plug that port on the tree, it runs like crap. If I'm not mistaken, that open vacuum port is equivalant to a big vacuum leak. I'm thinking that maybe another component that uses vacuum could be malfuntioning causing my situation.
The tab,tad,egr solenoid, smog pump, diverter/bypass valve were all purchased at the junkyard.
Am I on the right track in thinking that another vacuum component could be malfunctioning or am I way off track in thinking this?
Any thoughts on this would be greatly appreciated.
Bill
Senior User
Joined: Sep 2004
Posts: 351
Likes: 0
From: Richfield MN
Did you ever rebuild the carb ?
Its a ez job on your truck.
I would start there then go back to hooking up vac. lines.
There should be a diagram under the hood to guide you.
If it still acted like a vac. leak after that I would try to find it with starter fluid.
Spray around the tree and lines if motor races you found your leak.
Its a ez job on your truck.
I would start there then go back to hooking up vac. lines.
There should be a diagram under the hood to guide you.
If it still acted like a vac. leak after that I would try to find it with starter fluid.
Spray around the tree and lines if motor races you found your leak.
Senior User
Joined: Jun 2001
Posts: 121
Likes: 0
From: S.E. Alaska
If you apply vacuum to the vent line I bet is dies real quick! My Bronco had a fire (before I bought it) so all of that was gone. I could not decide what to do with that vent line from the fuel bowl. If your charcoal canister wasn't allowing the line to draw properly it would act very differently removed as there is a slight vacuum on the line. I would either look into replacing the canister, or just route it further away to be safe and put a breather filter on it (which is what I did as the canister was gone).
That is assuming I understand you correctly.
That is assuming I understand you correctly.
Thread Starter
|
Junior User
Joined: Aug 2006
Posts: 92
Likes: 0
little_mule, the problem in not the fuel bowl vent hose. But in that hose there is a vacuum operated valve. The vacuum hose for that valve connects to the tree on the intake maniflold. With that hose connected to the tree, the engine runs like crap. If I pull the hose off the tree, the engine runs fine. That port on the tree is now open. If I plug that port, the engine runs like crap. It's like it needs a vacuum leak to run good. The problem has to be some where in the vacuum system. Either a component or hose or something. This does not make sense to me the way its acting.
Bill
Bill
Senior User
Joined: Sep 2004
Posts: 351
Likes: 0
From: Richfield MN
Bill a truck will never run good with a Vac. leak.
I could be wrong but heres what I think.
The hose you are pulling off comes from the carb.
It has a one way valve the opens when you give the truck throttle.
Suck on the hose with your mouth and you will see what I mean.
That allows vac. to the tree.
I had a 85 with a 300 six.
When I rebuilt the carb It fixed alot of running and hesitation issues.
As I said before I would start there first.
Its a one hour job to rebuild that carb.
I could be wrong but heres what I think.
The hose you are pulling off comes from the carb.
It has a one way valve the opens when you give the truck throttle.
Suck on the hose with your mouth and you will see what I mean.
That allows vac. to the tree.
I had a 85 with a 300 six.
When I rebuilt the carb It fixed alot of running and hesitation issues.
As I said before I would start there first.
Its a one hour job to rebuild that carb.
Posting Guru
Joined: Aug 2000
Posts: 1,984
Likes: 2
Bill, could that carb vent valve be bad? Maybe try disconnecting the hose from the carb to the valve, and see how it runs.....
Trending Topics
Thread Starter
|
Junior User
Joined: Aug 2006
Posts: 92
Likes: 0
thelonerangerxlt, That is my dilema. I did disconnect that vent valve vacuum hose at the vacuum tree on the manifold. With that port open, the engine runs good, if I cap that port it runs crapy and dies. What seems strange to me is that the weekend before, it was running good with that vent valve vacuum hose connected to the tree. The following weekend it ran crapy untill I pulled that vacuum hose off. I'm trying to figure out why it runs good with an open vacuum port and crapy with that port capped.
Bill
Bill
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