howdy fellas,

I got a long story but I'll condense it. After a 9 hour day (w/ some beer drinking of course) of maintenance the truck wouldn't start back up. The maintenance included:

-Installing a new battery and cleaning existing cables
-New fuel filter
-New air filter
-New plugs, plug wires, distributor cap and rotor
-Changing the oil and oil filer
-Removing the A/C compressor and the hosing that ran from it to the evaporator/drier and to the condenser then plugging the holes w/ epoxy to prevent crap from getting in the system so I can eventually reinstall new components.
-Seafoam in the brake booster vacuum line

After all this I was thinking I was ready to take on the coming winter. I buttoned everything up and went to start her up and no go. First try she tried to turn over but never succeeded. Every time I've tried since then she doesn't even turn over. The mechanic I took it to found out that all wires were good and the culprit was a part called the "clutch interlock switch jumper." All fine and dandy but he can't find the f'n thing. He says it's supposed to be just above the accelerator pedal but it's not there. If he jumps it (I assume at the solenoid) then it fires right up and runs great. My question is wtf is this part and where might it be located and, if it can't be located in a reasonable amount of time, what harm could come of bypassing it and putting new wiring in that would exclude it? By the way it's an auto tranny.

Thanks for reading my book and any input is appreciated.

Josh

 

The Clutch Interlock switch jumper is mounted on the clutch pedal support.

But I doubt the Clutch Interlock switch jumper is your problem.
Either your starter solenoid is not wired right or your neutral safety interlock switch has a problem.

 

Is the neutral safety interlock located on the steering column? and if the solenoid was wired wrong, why would it just now be going bad after working for all these years?

 

WTF indeed,,,, a clutch interlock switch on an auto trans????

Now I could understand if you said the neutral safety switch...

So which is it, auto with a neutral safety switch of a manual with a clutch interlock?? I'm not trying to be a smart a$$ with this question, just trying to figure out what you have...

Neutral safety will most likely either be low on the steering column near firewall OR on the side of the automatic trans where the shift lever connects...

 

No it is located on the side of your transmission where the column shift linkage enters the transmission.
It is also called the Manual Lever Position Sensor (MLPS) and the safety contacts are inside of it if you have an E4OD Transmission.
If you removed the battery cables and cleaned both ends you have not have gotten all the wires back under the stud nut on the starter solenoid. I do not how far you went in the cleaning.

You could also have a bad Ignition switch or Ignition switch linkage on the steering column.

If you have an E4OD:


IF you have a Transmission other than the E4OD (C6 or AOD):



/

 

We talking about the clutch interlock switch jumper and most if not all automatic transmissions trucks have one.

I think you need to re-read this thread.

 

The cleaning I did on the cables only involved the ends that go on the battery posts so they were never taken off the solenoid.

Also, thanks for all the help. I'll go over this info with my mechanic when they open back up tomorrow morning. Hopefully I can get this problem fixed so I can tackle the rough shifting tranny next. Thanks for the help.

Josh

 

If you have an E4OD a new MLPS sensor may fix both problems.

 

that would be awesome...not lookin forward to the time and money needed for a tranny fix. let's hope

 

You may also have bad wiring or plug at the MLPS.

Testing the MLPS:


/

 

Alright, well i just found out that we're not getting power to the MLPS. Could that be the wiring at it is bad or that the Neutral safety switch is bad?

 

So I think what we're gonna do is bypass the neutral safety switch and just splice in on either side. Whatcha all think?

 

If you are not getting power to the MLPS Bypassing it is not going to do you any good.
The MLPS is also the neutral safety switch.

If you are not getting power to the MLPS then you have a problem with the clutch Interlock switch jumper or the Ignition switch. I am betting on a bad Ignition switch or the two screws are loose at the bottom of the shifter in the cab. That is if you have the two screws on a 1990 or did they start with the 1992?

The two screws:


/

 

FOUND IT!!! the damn kill switch. The actual switch was bad. Dang that was alot of work for that. Thanks for all the help subford. learned alot about my ignition crap along the way so at least I got something out of it.

 

What are you calling a "kill switch"?