zrtwooo

just got back from a road trip and used my cruise control flawlessly on the way there however on the return trip it would stop holding my speed after about 1/4 mile. cruise light still on but not able to set any speed. If i shut the truck off it would repeat the same process of light on, cruise set to a speed, and then would release that speed and wouldnt set to speed again. I think there is a thread on this somewhere but i couldnt find it...vacume leak?
thanks in advance...
Mike

MikeyB

Yep, check the vacuum pump under the passenger side battery and the hoses for leaks. I assume your truck is an automatic?

MikeyB

zrtwooo

yes it is...thanks ill take a look!

domehead

Just had my truck into the dealer about the crusie control. If I try to accl with it it would start and than would shut off completly. The dealer could not find the problem.

The truck is a 6 sp manual.

Spooler

What year is your truck???? If it is an 03-04.5 then you don't have drive by wire and have a vaccum pump. If you have a vaccum pump, then check for leaks. Vaccum pump is right behind the passenger battery. Follow the nylon vaccum line, it will go under the drivers battery to the cruise control dashpot.

johnh

for some reason some guys assume that everybody knows what vehicle is having a problem....not so, please fill out your signature

domehead

Sorry about no sig.

Truck 2009 3500 dually, SXT 6 speed manual. QC, LB

nsxt

Anytime cruise control has issues I first check the clutch switch (if its a manual) and the stop light switch.

zrtwooo

how do you check those switches, more specifically the brk switch. what are you looking for and how?

nsxt

The cruise control deactivates when the brake pedal is pushed. If the switch is too sensitive a bump in the road could wiggle the pedal enough to trip the switch and deactivate cruise.

This can be tested with the engine off. See how sensitive the switch is by wiggling / pushing on the brake pedal with your hand and watch for the brake lights to come on. There should be about 3/8" or so pedal movement.

zrtwooo

thanks Ill try that...

zrtwooo

If it has a leaky line why would it reset when the truck is restarted? I don't understand how the sys works... Is there a test to run on it that can confirm if its a vac leak? Has anyone had the same symptoms as i do? Sometimes it will engage and after about 10-15 sec it will disengage and won't re-engage untill truck is turned off. sometimes it works perfectly for as long as i want it to...?

underwoodbits

My truck was doing the same thing, it is a leak or bad vacuum pump. Mine was both. The vacuum leak will make your pump run all the time and burn it up. If your vacuum pump doesnt run right now, replace it first. If its working now or when you get a new one if needed, the leak will probably be right in front of and above the fuel filter. There is two big hoses there that rub the vacuum line. Go to Shucks, Checker, etc , etc and get a vacuum fitting and cut the vacuum line and put the new fitting in. You can get a new vacuum pump off ebay for less then $100. You can use a Ford diesel 99-07 vacuum pump, there the same pump. Just make sure it has the round electrical plug that your pump has, not the three prong. Mine was doing the exact same thing as your truck, wouldnt reset until you turned the truck off. But I replaced the vacuum pump and put the new fitting in where it leaked and now it works perfect.