I recently bought my grandfather’s old F-150, its a 1983 model with the 351w and the 7200VV carb. I replaced the distributor cap & rotor, plugs, wires, and fluids. The truck idles just fine in park/neutral, but when I shift it into reverse or drive, it stalls out. There is a valve of some kind attached to the carburetor, and it opens and closes rapidly as the truck dies (in time with its sputtering) so I think it may be the cause of the problem. I have not been able to find much info on that carburetor, but I think that valve is a fuel temperature system that meters the amount of fuel going to the carb depending on is temp.
Has anyone run into a similar problem? Can I replace that part without having to replace the whole carburetor?
Much appreciated.
This truck is burdened with a nightmare emissions control system that’s 30 years old…If emissions testing is not necessary, if the truck was mine, I would replace the feedback “smog carburetor” with a similar one from an earlier vintage truck, 1972-1979 which are simple to maintain and adjust…I would “de-smog” the whole truck but that is probably not an option for you…
The part you hear clicking on your carb is PROBABLY some sort of idle-air control solenoid that supposed to maintain a constant idle speed…But I’m just guessing…See if there is a throttle-stop adjustment screw that sets the position of the throttle plate at idle and adjust it up a little to stop the stalling…Also, check for any vacuum leaks, those 30 year old vacuum hoses are all way overdue for replacement, as that will destroy the engines ability to idle…How many MILES on the truck?
Is the valve the choke plate? Try blocking it open with a wooden clothes pin and see if the truck dies then. You may want to look for vacuum leaks as well. A picture of the “valve” would help.
It has 78,000 miles on it, and I’ve checked the vacuum lines but have not replaced them. I can’t find an IAC on the truck or in any of the manuals I have, and the only indication of what the valve I’ve seen act up is from an article from Popular Science in 1976 that google pulled up. I’m trying to find a manual for that carburetor as well. If I were to replace the carb with a more traditional model, I think I’d have to replace the ignition system as well because the computer that controls the carb also controls the ignition system (EEC-III), which is why I have not given it serious thought. If I’m wrong about that, I’d be more willing to get rid of the POS VV carb that’s on there.
As far as the specific issue I’m having, I’ll post a pic of the part that seems to be giving me the trouble as soon as I can.
Yes, Caddyman. That carburetor is virtually unrepairable . The problem sounds like a vacuum leak and may be anywhere in the intake system but most likely it is the carburetor. My best success has been to replace the VV model with an earlier model Ford carburetor. It is a fairly simple swap. And when the carburetor is off pull the EGR spacer plate and examine it and replace all the mounting gaskets and check that the EGR pintle is seating.
And for the purists who think I am rushing to judgement on the carburetor, there is an array of solenoids controlling carburetor functions through a spaghetti plate of hoses that is virtually impossible to comprehend without factory training and the carburetor is a nightmare to set up properly. Dealing with that setup is a losing proposition in my experience.
How many electrical wires are connected to the carb? Yes, the ECM will notice a carb change and the CEL will come on, but that should not effect the other systems…The electronics back then were pretty crude, especially on trucks…Farmers routinely de-smogged these vehicles without too much trouble…
I appreciate the quick responses for this…
I don’t have the truck in front of me to check, but I know of at least 4 electrical connectors that run to it. I’ve more or less determined that it is a fuel issue because I can keep the motor running for about a minute after shifting it into drive but it requires constant feathering of the gas pedal, although it could be a vacuum leak causing the fuel issue. I read just now that I might be able to disconnect the wire harness at the valve I’m looking into and it may let it run (albeit a little rich), but the forum post was for a truck a couple of years newer than mine. I’ve checked the PCV and bowl vent solenoid, and all the vacuum lines. Everything that should be getting vacuum as best I can tell, is, but I have not put a gauge on it to check the vacuum levels, and its still possible I’ve missed a leak somewhere. When I get home I’m also planning on double-checking the vacuum lines, but since the problem only shows up when its shifted into drive and only runs for 2-3 seconds (unless I’m in the cab), I’m out of ideas on how to isolate the problem. I’d rather not replace the carb until I either get this one running right or find the actual problem so I don’t replace it and still have the issue.
Good luck CM400. But the carburetor is part of the “system” and it is difficult to isolate a problem because a minor malfunction in one sub section will manifest itself as a significant malfunction in another area. I would suggest that you inspect the carburetor base gasket and the EGR spacer gasket as they are prone to failure. The EGR spacer itself was notorious for cracking and/or burning out.
Rod, I’ll certainly replace the gaskets, it can’t hurt… Could a failure at one or both of those points cause the motor to die only under load? The most confusing part of it for me is that it runs fine in park/neutral no matter how far I put my foot to the floor, but in drive, it dies almost instantly…
A carbureted, pre lock up converter engine that idles smoothly in neutral but dies as soon as it is shifted into gear unless the throttle is pressed is a text book case of vacuum leak.
Thank you, sir. That’s what I’ll focus on.