1989 F-250 with ZF-5 Speed. For as long as I've owned the truck, I've needed to press down on the clutch ridiculously hard to get the starter to activate. Over the years it has gotten more and more difficult, to the point where now I pretty much have to put on my steel toed boots and stomp down on the clutch pedal with both feet practically giving myself a hernia in the process. I tried taking apart and rebuilding the switch to no avail. Then tried replacing the switch with a brand new one. Still have the same problem, even with the new switch. Today I went to start it and now I can't get it to start at all.

Keep in mind, my truck has a non-adjustable switch. Some different years have a different style adjustable switch.

I tried to make some modifications to the switch but have failed thusfar. Any suggestions on how to fix the switch or bypass it by jumping some wires together on the harness. If I were to bypass the switch, I'm assuming my cruise control wouldn't work, since the computer would think that the clutch was always pressed in. Anyways I could live without the Cruise Control working for the time being, I really need the truck to be functional for my work.

Any suggestions are much appreciated.

 

People will yell at you for defeating a safety feature, but I always start in neutral anyway.

I bypassed it on an 89 for the same reason. I don't recall the wiring anymore, but there are 2 circuits -- although only one matters. Get a schematic and find the wire colors that link up the start. Short them together. There are other ones that go to the computer and probably the speed control -- I hooked those up with a switch because I wasn't sure what they did. But, it didn't make any difference ( although I never tried the speed control).

Sorry I don't have more info. But, you should be able to figure it out from the schematic. Easy enough to test -- PUT IT IN NEUTRAL and try the starter.

(probably should disconnect the batt while you're wiring it up)

I also don't know why it isn't adjustable. Mine also required some real pedal pressure -- makes no sense.

Good Luck,

hj

ps I'm not against safety, but this always seems like overkill -- it would be tolerable if it would at least let you start it in neutral.

 

I'm not sure when it changed from the pedal mounted white plastic 'rack' on my '87 and the master cylinder mounted 'mushroom' interlock of the '90's trucks.

Connect the two red/blue stripe wires.

 

Thanks a lot for the tips. Rather than modify the wiring, I decided to solder the connections together on the switch itself, but far enough down so that it didn't affect the wiring harness fitting into the switch. The truck will now start without the clutch pressed in at all, though I still choose to start with the clutch fully pressed AND in neutral, just out of habit. I have yet to test the cruise control, but I imagine it will still be functional, since it's on a different circuit which I didn't modify.

I really needed my truck functional by tomorrow morning for work. Thanks again for the very helpful advice!

 

My dad bypassed that silly switch on the 1990 F250 a month after buying the truck brand new in 1990. I did the same to my '94 F150 when I got it. Saves alot of wear and tear on the firewall, master and slave not having to step on the step when it's -15*F outside in winter, pushing all that thick cold fluid on the seals.

He used the switch to make a dead man switch with it. Neat idea.

 

If you go to the junkyard any automatic truck of a similar year will have a jumper block that plugs right into the harness connector.

I just went though a bunch of hassle with my truck. Whenever the truck was started it would rev to 2300 to 2500 rpm, and the poor old six didn't like it at all.

After getting rid of the ignition/starter bypass from the po I noticed the clutch switch was bad. I jumpered the the red w/blue tracer wires together and the truck started, but over revved like always.

On one of my trips to the jy I grabbed one of those jumper blocks and plugged it in, and low and behold the truck quit over revving on start.

I believe this is because on a manual truck the computer is expecting a ground on the signal return circuit which runs through the clutch safety switch. This is according to the wiring diagrams and pinouts from OnDemand.

In any case the truck has started normally since I put the jumper in about 6 months ago.

I haven't tried the cruise control since I never use it, but whether or not it would work would depend on if the circuit is open or closed when the cruise is activated, and whether or not the jumper is open or closed. I would guess closed for both, but that's just a guess.

If this is the case, the cruise would work, but wouldn't kick off when you pushed in the clutch and the engine would rev way up with no load on it, not a good thing.

Also, have you checked for firewall flex? If the firewall is moving out when you press the clutch the rod doesn't move enough to activate the switch. I had to fix this on my truck as well.

 

I used the same method as ford2go when I put a mechanical clutch in my truck (also made it adjustable. 2 birds with one stone on that one. I don't think my cruise works anymore though. I guess I'd have to check again to make sure.

 

Meh! Safety-schmafety!

I've got the same issue as Geoffunkel on the F150 I just bought (although not as bad). Being a Limey by birth and upbringing, where 95% of vehicles are stick shift WITHOUT clutch interlocks, the whole routine of 'check shift in neutral, parking brake on, clutch down, turn key' is second nature.

And just how the hell are you meant to do the emergency maneuver of moving a vehicle on the starter (if flooded out in deep water, for example) with a clutch interlock switch?

 

Do not assume that your cruise control will not work. I did the same modification on my 89 with factory cruise and it had no effect at all.

 

Yeah my cruise control works just as it did before. Everything is working great after the mod. And yeah I agree with you Adrian. I would never even attempt to start any stick-shift vehicle without the clutch pressed in and in neutral. The clutch-interlock switch is for people who don't know how to drive a stick. And frankly, I'm sure as heck not going to let anyone drive my truck unless they know how to drive a stick well. Man it really irks me when I see people start their cars in gear...

Or one of my friends who just bought a brand-spanking new Toyota truck and his method of turning it off was to just let the clutch out in gear so it would stall out every time (instead of just turning the key to off). I had to give him a stern talking to...