66 Bronco 170 Engine Problems

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Dec 1, 2003 | 08:49 PM

dpalmer

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From: Seattle/Tacoma

66 Bronco 170 Engine Problems

Just recently tried to get my Broncos 170 engine running better. Pretty much did a complete tuneup with wires/plugs/cap/rotor/points etc. Also because of the way it runs, rebuilt the carb with a carb kit. The problem remains that the engine will only idle with at least half choke pulled on it. Any further in and it's idle becomes rough to the point where it dies. No difference with the idle circuit screw and no timing is set at factory specs. I isolated both vacuum fitting from the intake manifold and no difference. Sounds like a vacuum problem to me but cannot find anything obvious. Any suggestions for me where to find the problem? Thanks in advance.

Dec 1, 2003 | 09:57 PM

broncoman66

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From: Columbia, Illinois

Are you getting enough fuel? Maybe a weak fuel pump. This may sound dumb, but do you have a new fuel filter? Is your idle setting set too low? What about mixture? Just some ideas, hope they help. I can relate to your frustration as my 66 used to have a 170 too.(not any more)

Mike
66 Bronco 5.0 SEFI, 3 speed, Dana 44 front 3.54, Big bearing 9" posi 3.50 rear, Bushwhacker cut outs, 3" lift, 32x11.50-15 Mud Kings

Dec 2, 2003 | 09:48 AM

spartamouse1

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if you have checked thououghly for a vacum leak and there is none i would go back through the carb. did you soak the carb when you rebuilt it? was it sitting for along time w/ fuel in it?

Dec 2, 2003 | 08:42 PM

dpalmer

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From: Seattle/Tacoma

The fuel filter was one of my first attempts...well before the tuneup and carb rebuild. As far as fuel pressure goes, I have not hooked up a gage to see what exactley I have for fuel pressure, but I do get quite a lot of fuel from the pump when the fuel line is disconnected and routed into a can. I would imagine that 3 to 5 fuel psi for this engine would be normal huh? The intake manifold is cast right into the head but has two "freeze" plugs, one in each end. Are they common problem areas for vacuum leaks? What is normally used i.e. wd-40/starting fluid for checking for vacuum leaks? And yes, the idle speed screw is for sure set fast enough and I see no difference in engine operation adjusting the idle mixture screw. Again, thanks for any help.....Dave

Last edited by dpalmer; Dec 2, 2003 at 08:46 PM.

Dec 2, 2003 | 10:08 PM

broncoman66

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Joined: Jan 2003

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From: Columbia, Illinois

I doubt the caps on the ends of the intake would be bad, but you never know. I would use carb cleaner to check for vac. leaks. However, I bet you need to get into the carb again. Spray every little passage down with carb cleaner and blow through it with a rubber tipped air gun. It sounds like to me there is some crap in the carb yet. Make sure float is good, and adjusted properly, and needle and seat are clean.

Mike
66 Bronco 5.0 SEFI 3 speed

Dec 2, 2003 | 10:46 PM

johnarahill

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From: Jacksonville

Not much help for you, but I have the same problem with the same motor. Does it have a 1bbl carb? If so, it may be an Autolite 1100 or 1101. I have found a website called ponycarbs.com where they have rebuilt ones and will rebuild yours. If I don't fix mine in about the next week, I'm thinking about getting one of theirs. They say that they hook each one up to a motor and tune it just right so you shouldn't have to make any adjustments when you get it. Since you seem to think you have a vacuum problem (as I suspect I might), does your vacuum advance unit have two vacuum hoses? Mine does, but one has been cut off and plugged. What do your hoses hook to? Thanks dude.

Dec 2, 2003 | 10:46 PM

dpalmer

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From: Seattle/Tacoma

Thanks for the suggestions. I will check for vacuum leaks and if nothing shows, then go back into the carb. The problem was first noted after sitting for a few months. The float did check fine although I wasn't sure about the little weight attached to the float. Never saw that before.
And Johnarahill, thankyou for the post and website. Hadn't considered spending much on this engine with future plans to install a mild SBF. The carb is a single barrel although not sure of the model. Went to the local parts store for the carb kit which as I was told, covered a wide range of single barrel applications in the kit. Gaskets and such fit my carb so I guestimate it was the right one. My vacuum advance has only one connection on it. I verified it worked by sucking on the vacuum line and listening to the engine speed/sound change. It ran great a few months ago before sitting so I don't believe it to be too much of a problem now. Will keep looking. Thanks for all the help.....Dave

Last edited by dpalmer; Dec 2, 2003 at 10:59 PM.