mhuppertz

Resume hasn't worked in years, but I lost cruise completely a month ago. Checked the fuse and linkage. Power brakes are working, so not a direct vacuum issue (although I think the pump is probably weak causing my RWAL to set a CEL).

Do the vacuum motors ever give out?

thrashingcows

The vacuum pumps don't generally die on these motors. They are a vane pump and unless the vanes are worn right out, then it will generate vacuum.

My guess is that some part of the electronic cruise system has died. Could be the steering wheel switches, or maybe the clock spring...or any number of other components in this overly complicated system.

Crack out your FSM and a multi meter and start following the cruise diagnostic procedures.

mhuppertz

Just ordered a clockspring "http://www.amazon.com/Dorman-525-104-Air-Clock-Spring/dp/B000EQ2KT4" from Amazon because I know mine is wounded. It probably happened years ago when my Borgeson came loose and I went through a chain link fence!

Ok, ok. Have the FSM right in front of me, going to work the trouble tree.

bigragu

Also, somewhere on YouTube, I saw a step by step tutorial on so one taking apart the cruise vac actuator. FSM said this is a non serviceable item. There are 2 screws to remove and plungers and springs in there if my memory serves me. All I did was follow that dudes tutorial and clean/lube the plungers and cruise worked great to this day. If someone knows how to post that link if found please do so to aid everyone. Should be a sticky item, for sure

Philip

Mark check the vacuum switch by the left hand hood hinge. If it doesn't see vacuum it will set a CEL and CC doesn't work eather.

MrFusion

So THAT'S what that thing is!!! Been pondering that one for awhile. Thanks!

westcoaster

Funny,
Google Cummings diesel and all you get are Cummins websites...

cougar

I had to disconnect mine a year or so ago. It would be working fine then go full throttle all of a sudden. What is scarier is it takes a while for the servo to bleed off and release the throttle after you turn it off. I've had to kick the trans into neutral and shut off the engine.

j_martin

My two cents.
There are many components in this system. All can be tested, most with a common multimeter.

The quickest and least expensive path to a repair is proper diagnostics. Throwing parts at a problem is the slowest and most expensive.

Some failures have common symptoms, which makes parts selection based on anecdotal advice almost worthless.

Get the manual. Read it, and follow it's instructions.

thrashingcows

I have done all the checks and procedures in the FSM for the cruise control and everything has checked out properly, but the system still accelerates slowly or quickly when in use. I have replaced every component with used spares except the PCM and the clock spring in the steering column.

j_martin

The clock spring goes to the switches on the steering wheel. If they work, the clock spring is OK. Checking out the clock spring is a simple matter with an ohmmeter.

I can see a scenario where the accel switch is noisy causing unexpected acceleration. The proper operation of that switch can be checked out with an ohmmeter as well, though it would be easier with an analog (needle) meter because you'd be looking for leakage and random very short contact.

Just a thought, if the mechanical part of the above mentioned switch were knackered, then road bumps would cause said acceleration. I think I've actually seen that happen.

It's not like these are top shelf switches. All three actual switches in the cruise control switch set cost less than $2,00 combined. They are actually of the type like the pencil push reset switch in a modem, expected to work properly 10 or 20 times in the life of the modem.

Though it is possible the PCM is the culprit, it's not likely.

peckens

Mine keeps accelerating when it is cold out, but goes away after I turn it on an off again. It used to accelerate hard on and off while cruising until I found the wd40 straw mod in the 2nd gen forum. Helped a ton. There is also a pcm relearn TSB procedure believe it or not if I find it I will post it.

peckens

Speed Control - Surge at highway Speeds

NO.:

08-07-93 Rev. A

GROUP:

Electrical

DATE:

Mar. 19, 1993

SUBJECT:

Speed Control Surge

NOTE:

THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 08-07-93 WHICH SHOULD BE REMOVED FROM YOUR FILES. ALL REVISIONS ARE HIGHLIGHTED WITH **ASTERISKS**.

NOTE:

THIS BULLETIN APPLIES ONLY TO FOUR WHEEL DRIVE VEHICLES EQUIPPED WITH THE CUMMINS DIESEL ENGINE.

MODELS:

1992-93 (AD) Ram Pickup/Ram Cab Chassis

SYMPTOM/CONDITION:

Some vehicles may exhibit a speed variation at highway speeds while the speed control is engaged.

DIAGNOSIS:

1. Perform the speed control system test as outlined in Section 8H of the service manual. If no problems are found during the test, proceed to step 2.

2. On 1992 vehicles verify that the vehicle is equipped with the correct speed control servo and cable for the Powertrain Control Module (SBEC) that is installed, Refer to the chart below and make sure that the Powertrain Control Module, servo and cable match.

POWERTRAIN CONTROL MODULE REFERENCE CHART

SBEC Part No. Servo Part No. Cable Part No.

56027570 53007954 (Zemco) **4428787**

56027571 53007954 (Zemco) **4428787**

56027572 53007954 (Zemco) **4428787**

96027573 53007954 (Zemco) **4428787**

POWERTRAIN CONTROL MODULE REFERENCE CHART CONT'D

SBEC Part No. Servo Part No. Cable Part No.

56027081 53009315 (Eaton) **52078330**

56028082 53009315 (Eaton) **52078330**

56027083 53009315 (Eaton) **52078330**

56027084 53009315 (Eaton) **52078330**

3. If no problems have been found to this point, the speedometer drive gear on the output shaft of the NP 205 transfer case may be at fault. Remove the speed sensor, adapter and the speedometer drive gear. Carefully inspect the speedometer drive gear while rotating the output shaft. Any cuts or irregularities on the gear can cause a speed sensor signal variation. If any irregularities are present, proceed to the repair procedure.

PARTS REQUIRED:

1 Speedometer Drive Gear 3732038

REPAIR PROCEDURE:

Replace the speedometer drive gear using the procedures outlined in Section 21 of the Rear Wheel Drive Dodge Truck Service Manual.

POLICY:

Reimbursable within the provisions of the warranty.

TIME ALLOWANCE:

Labor Operation No. 21-97-10-91................................0.6 Hrs.

FAILURE CODE:

58 - Internal Defect