7.5 w/ manual won't start - help! - Ford Truck Enthusiasts Forums

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7.5 w/ manual won't start - help!

 
  #1  
Old 09-04-2011, 01:40 AM
ta2rob
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7.5 w/ manual won't start - help!

The patient: 1993 Ford pickup w/ a 460 cid gas motor, 5 speed manual w/ granny low 1st gear, 4x4, dually, standard cab, & standard bed.

The problem: hot or cold, turn the key w/ the clutch pedal to the floor, and ... nothing. Won't even crank over.

Repeated slamming of the pedal to the floor violently with the key turned to crank the motor eventually starts the beast.

Sometimes, though rare, she'll just start up like a normal vehicle.

Recent tune up (problem existed before tune up), including new plugs, wires, distributor cap, oil/filter change, K&N air filter cleaning/oiling, tranny/t-case/axles drained and filled, etc. New battery terminals/cables. Negative cable's ground checked. Wal-Mart battery, not new, never load tested, unknown age, but seems like there's another problem. This battery passes volt meter tests standalone w/o the motor running and also at idle.

I feel the clutch kill switch is bad, maybe corrosion of the contacts, and isn't letting battery power to get to the starter. The repeated violent clutch pedal slams to the floor (then start) point that way.

The ignition key turns freely, and always powers up the truck in the 'run' position. All the accessories work, too.

Can anyone help? How do I bypass the clutch kill switch? I am the only one who drives the truck, and would obviously be aware if I defeated this kill switch.

Truck runs superb otherwise.

I searched the site, but no joy on this issue.
 
  #2  
Old 09-04-2011, 07:05 AM
ArdWrknTrk
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There are many threads about the clutch interlock... this image from the manual is hijacked from one.





Jump the red and light blue wires and see it you can't start the truck then.



.
 
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Old 09-04-2011, 07:41 PM
ta2rob
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Thanks!

Hey, jumping the red/blue & red/blue wires did the trick! She starts every time now on the first try!

Question: the connector has other wires, which are now not hooked up to the faulty interlock switch. Using the wiring diagram in the shop manual, it looks like one of them goes to the 'engine controls system'. Is this true, and if so, does it need to hooked up to anything anymore?

What about the other wires?

I simply unclipped the connector from the switch, squeezed out both red/blue wires, and spliced them together. I then used electrical tape to wrap everything up and a zip tie to the plastic dashboard.

Are there any negative consequences if I leave the connector uncoupled to the interlock switch?

Thanks again.
 
  #4  
Old 09-04-2011, 07:52 PM
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Sorry, I can't answer that for certain.
I have an earlier (carbureted) 460 with no ECM at all.
My safety interlock is actually over on the clutch pedal itself but the harness colors are common.

As I said there are a number of threads.
If you go to -advanced search- and choose your era of truck, then put whatever term "clutch safety interlock" for example -in quotes- in the query box i'm sure you will find the answers.

Glad it worked for you!
 
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Old 09-05-2011, 03:45 PM
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The other wires on the clutch switch are for the cruise control.
 
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Old 09-05-2011, 10:04 PM
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Originally Posted by jas88 View Post
The other wires on the clutch switch are for the cruise control.
OK ... the wiring diagram I have does not even show the 2 solid green ones. Those are the ones I'm wondering about.

Anyway, like I said in another post about this subject, I got it fixed with a new $30 Autozone switch. I replaced the worn out pushrod bushing while I was there.

The truck starts on the 1st try every time, without splicing the red/blue stripe wires from the switch's connector together.

I will test out the cruise control tomorrow. It worked previously, but acted kind of weird ... once set at whatever speed, it would hold that speed properly, then seem to loose speed, then compensate for the loss in speed by accelerating. This was quite obvious, and annoying to say the least.

Maybe the new interlock switch will cure my cruise control issue, too? One can only dream ...
 
 
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