1987 Ford Corsair Carb Problem ?

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jamie2666

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Nov 23, 2019
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Hi,

Hoping someone out there might have a few ideas about the issues I'm having with this motorhome. The symptoms are:

- high idle, won't kick down when warm
- some times it diesels after shutting it off
- lack of power up any hills
- transmission won't kick down when you step on it
- off the start, like at a traffic light, if you step on the gas it would stall....you have to feather the gas to get it going
- hard to start cold

Everything, to me, points to a carb issue and for the price of a new carb I thought i'd just buy one and slap it on rather then rebuilding. But just wondering if there is something else i should be looking at instead.

Any ideas would be greatly appreciated!

Thanks!

Jamie
 

tote

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Sep 14, 2016
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Might try running some Seafoam through it first.
I replaced the carb on my '87 Lindy. World of difference.
I've also done the Seafoam thing and I swear by it.
 

wae

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It's been a hot minute since I've really done anything with a carb, but it sounds like a vacuum leak.
 

8Muddypaws

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wae said:
It's been a hot minute since I've really done anything with a carb, but it sounds like a vacuum leak.

Transmission not kicking down is usually a pretty good indicator of that.
 

jamie2666

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Nov 23, 2019
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Thanks for all the replies, I can't believe I forgot the engine and type of carb, that would probably be helpful when asking for advice. It's the 460 engine with the Holley 4180 carb, four barrel. I did a visual look for vacuum leaks but I suspect its not something I could even see. I believe I read that you could spray something around the base of the carb and if the engine revs up it means there is a vacuum leak so I suppose I should try that first. Soon as we're done with our fourth and fifth winter up here in Canada I'll fire it up and give it a try.

Thanks again for anyone who's taking the time to post!

J
 

Gene50

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Check all of your vacuum lines that go to the carburetter from other components including the brake booster if it is vacuum operated and not run by the power steering.

That would also include a vacuum line to the transmission modulator valve which is also operated by vacuum. And the modulator valve itself as well as the PCV valve and related hoses And any distributor vacuum advance that the engine might be equipped with

The rubber in the lines degrades overtime and cracks
 

Gene50

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The ?dieseling? after shut off is likely due to the high idle speed although there are other factors that could contribute to that symptom as well.
 

jamie2666

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Nov 23, 2019
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Thanks again! Yea I thought the high idle was just the choke not kicking off, but maybe it's just been set really high by the previous owner....I'll have to check that out too.
 

TheBar

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Sounds like you may have more than one problem. One could be the carb choke. If it is stuck that's causing everything but the transmission kick down. Depending on the year it could be an electric choke that just has the 12v wire disconnected or the heating element is burned out. Hold the throttle open and make sure the choke moves freely and that the choke is closed when cold and completely open when hot. If it doesn't open completely the high idle cam or the linkage may be stuck.
 

jamie2666

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Nov 23, 2019
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Thanks, that was my first thought, that the choke was stuck open because it would explain a few of those symptoms. It is the electric choke I believe so I'll try tracing all the vacuum lines and then checking the choke...hopefully its as simple as one of those problems, a lot less expensive then replacing the whole carb.

Thanks again!
 

jamie2666

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Nov 23, 2019
Posts
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So its finally gotten warm enough to get the RV uncovered and start looking into this problem. The first thing I noticed is that the carb choke isn't closed when cold, its basically just fully open all the time. It's getting voltage at the electric choke. You can move the carb choke by hand very easily open or closed, no resistance at all to it which leads me to believe the spring in the electric choke is busted, or the linkage. This is kinda the opposite of what I thought was happening. If that's the case, is this problem only affecting the cold start ( it is hard to start when cold ) and wouldn't be the cause of the other problems ? Next is tracing vacuum lines. Thanks again for all the help!
 

Lou Schneider

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You can use an unlit propane torch (carefully) or WD40 or starting fluid to find a vacuum leak.  Spray it on the suspect hose or joint - if the engine speeds up as the vapor is sucked in you've found a leak.
 

TheBar

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The previous owner likely set the idle speed high to compensate for the open choke. The electric choke isn't expensive but check the linkage before you replace it. Fix that first and see what difference it makes. If you still have problems then it sounds like you have a vacuum leak. One trick is pinch off all the vacuum lines coming off the carb and intake manifold with needle nose pliers one at a time. When the engine runs better you have found the source. Also less likely to start a fire. It may be old enough to have a vacuum power brake so it could be a leak in that line or the booster so pinch off that line also. If they are original all the vacuum lines need to be replaced anyway. Which isn't expensive but very frustrating on that big block in a tiny space. And your carb may be gummed up so try Seafoam in the gas for a couple hundred miles before replacing the carb. Seafoam works miracles on both carbs and fuel injection but it can't fix everything. Before replacing the carb make sure the bolts holding the carb to the manifold are tight but just snugged down not over tight. I would replace that gasket first because they can cause a huge vacuum leak. Also make sure it is the right gasket for that year. Many auto parts stores carry the same gasket for that model of carb but the intake manifold can change by year. I had the wrong carb gasket for 25 years on my 73 truck. I bought 3 rebuilt carbs and nothing helped until I bought one from an old parts guy at Napa. He said try this gasket first and it has purred like a kitten ever since.
 

jamie2666

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Nov 23, 2019
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You're definitely bang on with the big block in a tiny space! It's so tough to find and see anything. The choke, even though not the main problem, is a head scratcher, after I posted I went out to start it cold and it was snapped shut. Started it up and watched it slowly open while it warmed up, then tried to move it by hand and I could feel the tension against the spring....then the next time i went out to start it when cold it was right back to the way it was before, wouldn't close and you could open and close it no problem with no resistance....

I found two really small vacuum lines, one red and one white that were snapped in half....the white one didn't seem to have any suction when the motor was started but it was connected to a tree that was on the same line as the distributor vacuum hose. The red one had quite a bit of suction so plugged both seemed to run a little better when I ran it up and down the road, would down shift when I hit the gas but was only doing around 80km/hr. I doubt the answer is that simple though, going to clamp the brake booster next to see if that does anything and then onto the gaskets. I can't find a line to the transmission, is it possible there wouldn't be one on it ? The transmission has a linkage to the throttle which is intact.

Will also try the Seafoam and see if that helps too.

Thanks again for all the help and suggestions! Appreciate it.
 

TheBar

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If the choke doesn't close when cold then the bi-metal spring inside has a problem. You may just want to replace the choke assembly since they aren't expensive. But sometimes you can fix it. If it is an electric choke it probably has a removable cover. There should be markings on the cover so make sure you know where it is set before removing it. The choke is adjustable and these marks show you how much and how long it stays closed. If it is not electric then on most older models the adjustment is by bending the rods attaching the spring to the choke plate on the carb. Too much choke and the engine will "chug" and blow black smoke. Too little and it will be hard to start and try to die when you accelerate. Setting a choke correctly may take multiple tries. Every engine is different. Slowly remove the cover and note how one end of the spring attaches to the cover and the other end attaches to the housing. The spring may be broken, out of place, sticking, or it may have been reassembled wrong.

Your transmission likely has a vacuum modulator but I think the linkage from the carb to the transmission would control the downshift. This is probably adjustable. See which direction the linkage moves when you open the throttle. Adjust the linkage to move it a little further in that direction to make it downshift quicker.
 

donn

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Depends, but if it were mine and I planned to keep it for a few more years I would do a fuel injection conversion and not look back. Improved fuel economy, improved drivability.
 

jamie2666

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Nov 23, 2019
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Hoping there are a few people left on this thread that can help me out one last time! After two years I've fixed most of the problems I was having. Went on a 2000 km trip this past summer and the thing pretty much ran great with lots of power but still having a confusing problem at idle. Just to recap, this is what I've done so far:

- compression test and replaced all spark plugs
- new fuel pump assembly and fuel filters
- new carburetor
- replaced all broken vacuum hoses

Now just have a problem with the idle which isn't consistent, so that makes it a lot more difficult to diagnose I think.

After driving for awhile and coming to a stop it either:

- is barely idling and you have to feather the gas to get it going or it will stall
- is idling way too high
- is idling right where it's suppose to be

Doesn't seem to be any rhyme or reason to any of these......you never know which it's going to be when you stop.

If anyone has any thoughts I'd love to hear them! All the help on here has gotten me this far and I think this is the last mystery.

Thanks again everyone!
 

donn

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Vintage Ford 460s were notorious for timing chain wear. The rest of your issues are likely carbon build up and/ burned valves.
 
Last edited:

uchu

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Ontario, Canada
You were given some good advice in your related thread here:


Based on what you describe about the idle, my vote is for the timing chain acting up.
 

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