'82 E-350 - Cruise control surging
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From: Wyoming
'82 E-350 - Cruise control surging
Got a new problem with 1982 E-350 RV with 460 - cruise control is surging. Even on level stretches, it will climb 3 mph over setting, then lurch back to setting, repeat, repeat. It's happy going up hills, but is really bad going downhill.
I've fixed a fair amount of problems with the cruise before, including:
-soldered broken connection on 6 pin servo connector plug
-replaced broken wire between servo and throttle with cable from bike shop
-replaced too-stiff throttle return spring with aftermarket double-spring setup.
If I were to guess, I'd go after a vacuum leak first. Maybe an EGR related issue? I have no problem maintaining smooth speed control with my foot alone.
I've fixed a fair amount of problems with the cruise before, including:
-soldered broken connection on 6 pin servo connector plug
-replaced broken wire between servo and throttle with cable from bike shop
-replaced too-stiff throttle return spring with aftermarket double-spring setup.
If I were to guess, I'd go after a vacuum leak first. Maybe an EGR related issue? I have no problem maintaining smooth speed control with my foot alone.
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From: Wyoming
How does that tie into the cruise control? I have no reason to believe my speedo is not functioning properly.
There are two hoses coming from the servo. One goes from the servo to the engine vacuum port behind the carb, and it's fairly new. The other one goes from the servo to the firewall by the parking brake - what's this one tie into? It's got tape all over it from a previous owner.
There are two hoses coming from the servo. One goes from the servo to the engine vacuum port behind the carb, and it's fairly new. The other one goes from the servo to the firewall by the parking brake - what's this one tie into? It's got tape all over it from a previous owner.
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From: Wyoming
A quick check on RockAuto shows 3 replacement servos for around $70-$90. Not too bad, but not so cheap that I'll just throw one at the problem. Is there a way to check the servo on a bench or electrically?
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Got this from an old thread on the 80-86 F-150 forum (actually was an answer to my own question):
"The cruise control switches in the steering wheel is where I've had the most problems, especially "on-off" and "resume". If your cruise will engage but lurches or hunts badly and then drops out; there is a 50,000 ohm potentiometer (variable resistor) internal to the servo unit that can cause this symptom. My local Ford products dealers and parts houses couldn't supply or even identify the part. Got mine from u-pull-em junk yard out of an old Lincoln servo. I think most of '70's and '80's Ford products used the same basic cruise control design with differences primarily in switches, carburetor linkages, and component mounting arrangements. "
Sorta points to the servo, eh?
"The cruise control switches in the steering wheel is where I've had the most problems, especially "on-off" and "resume". If your cruise will engage but lurches or hunts badly and then drops out; there is a 50,000 ohm potentiometer (variable resistor) internal to the servo unit that can cause this symptom. My local Ford products dealers and parts houses couldn't supply or even identify the part. Got mine from u-pull-em junk yard out of an old Lincoln servo. I think most of '70's and '80's Ford products used the same basic cruise control design with differences primarily in switches, carburetor linkages, and component mounting arrangements. "
Sorta points to the servo, eh?
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Lead Driver
Joined: Feb 2003
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From: Oak Harbor, OH
The bad thing about the servos is that they're either good or bad. There really isn't a way to fix them once they start the dreaded hunt game. Replace it, the speedo cable runs to a speed sensor. It's a round thing in the middle of the speedo cable, usually close to the transmission near the firewall. Check the wires. If the insulation is starting to wear it will cause this too as the servo is sensing strange values from it. It may just be time to use an aftermarket cruise unless you've got a good junk yard close with a lot of low mileage older fords that are stored inside.
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I traced the other hose from the servo through the firewall back to a small valve over the brake pedal. Looks like a vacuum break valve that pops open with only a small movement of the brake pedal. It's threaded, and was pretty easy to spin in it's mount. I turned it about 1/4 turn tighter against the brake pedal armature. The rubber hose itself doesn't look too bad. maybe that'll shut the valve a little tighter to prevent vacuum leakage. I'll test drive it this weekend on a short trip.
While I can see how this valve would dump vacuum and release the cruise, there doesn't seem to be any electrical connection associated with it. So is there another switch on the brake pedal that turns off the cruise from the electrical side of things?
While I can see how this valve would dump vacuum and release the cruise, there doesn't seem to be any electrical connection associated with it. So is there another switch on the brake pedal that turns off the cruise from the electrical side of things?
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
Yes your brake light switch and if the speedometer drops below 30 MPH it will also drop the speed control out.
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The cruise is working OK again. Other than twisting the brake dump valve slightly tighter, I didn't do anything significant.
I pulled the hose to the brake dump valve off at the servo and sucked on it - seemed to hold vacuum fine. Pulled off the air cleaner and checked the little chain at the throttle - just a little play there. Then I pulled the hose off the brake dump valve and plugged in my vacuum gauge and went for a drive. The cruise held fine at 65 mph, no surging. I was a bit surprised to see very little vacuum on the gauge. I figured I would see intake manifold vacuum, but it stayed around 1 to 2", and would top out at only 3". The gauge also moved funny, in little spurts like a quartz watch. Like the servo was getting info in pulses. On the drive back, I plugged the dump valve back in. Still smooth cruise action. I find it hard to believe that turning that chintzy plastic dump valve a touch tighter against the brake pedal armature did the trick, but maybe it did.
I pulled the hose to the brake dump valve off at the servo and sucked on it - seemed to hold vacuum fine. Pulled off the air cleaner and checked the little chain at the throttle - just a little play there. Then I pulled the hose off the brake dump valve and plugged in my vacuum gauge and went for a drive. The cruise held fine at 65 mph, no surging. I was a bit surprised to see very little vacuum on the gauge. I figured I would see intake manifold vacuum, but it stayed around 1 to 2", and would top out at only 3". The gauge also moved funny, in little spurts like a quartz watch. Like the servo was getting info in pulses. On the drive back, I plugged the dump valve back in. Still smooth cruise action. I find it hard to believe that turning that chintzy plastic dump valve a touch tighter against the brake pedal armature did the trick, but maybe it did.
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I gave the RV to my inlaws in 2013, and it's never moved from where I parked it since. The cruise control gave me trouble quite a bit after the last post, so no, it wasn't the final solution. I have a 2007 E450 class C with a 6.0L diesel now. I think the old cruise control was mainly a victim of time.
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Sep 14, 2015 08:09 PM
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