So a few times this has happened now, I go to start my truck after it has sat for a week or so and I turn the key and get nothing. No clicks not anything, no lights dim or anything, it just doesn't even turn over. But the minute I put the gas pedal down it will fire up instantly, just wondering if anyone has come across anything like this before? After it has been run you can start it without issue until its parked for around a week or so. Someone mentioned possibly a neutral safety switch or an ignition safety switch.

Thanks

 

Cue the Twilight Zone music. This is a strange one. Let me make sure I understand this correctly. Please note I'm only asking about the starter operation for the moment, not whether the engine actually starts when you release the key.

1) When driven daily, or nearly so, the starter engages and spins normally when you turn the key to Start. Pressing the gas pedal has no effect on the starter operation. The starter always works normally if the truck hasn't been sitting for more than a few days.

2) If the truck sits for a week or so, and you do NOT press the gas pedal, the starter does nothing with the key turned to Start. Not even a click, no lights dimming, a nothing sandwich.

3) When this fault occurs, if you press the gas pedal, the starter operation then returns to normal.

Is all of that correct?

When the fault occurs, what if you continued holding the key to Start and then simultaneously pressed the gas pedal? Would the starter run?

Do you have to hold down the pedal for the starter to run? Or is it sufficient to just press and release, as if setting the choke?

I'm having trouble thinking of any portion of the starter circuit that is dependent on the position of the gas pedal. That's why I keep expecting Rod Serling to step out from around the corner.

What engine?

Fuel injection, feedback carb, or plain carb?

Transmission?

Ginger or MaryAnn?

 

Embrace the power of "AND" !!

 

So you are correct. But I do have to hold the gas pedal down to keep the starter going and then it will start. It's a 400, auto, c6 transmission. If I step on the gas and take off it will stop turning over after it has sat.

 

And it's an edelbrock 1406 carb if I remember right

 

Really odd, I mean other than the part about me being correct.

The only thing that comes to mind is if your body position changes while reaching for the gas pedal. Maybe you're holding the steering wheel a certain way, and it flexes slightly as you reach for the pedal. And IF the ignition switch was slightly out of adjustment, that extra pressure might be just enough to prevent the starter circuit from completing.

Still doesn't explain why this only happens after the truck has been sitting.

 

I agree, I just didn't want to be suddenly stranded somewhere. At this point I'm thinking replace the few accessible parts and see if it helps

 

I say check all grounds battery to motor and to frame and to body.
Dave ----

 

Look for any wires affected by the movement of the throttle linkage....

I wonder of the throttle linkage is providing an occasional ground path from the engine to body....

I'm with Dave, check and clean all of your ground connections.

 

Excellent advice. It would be easy enough to test the ground theory by running a long jumper lead from the cab to the battery's (-) post.

Any chance the throttle movement isn't what actually lets the starter run? Maybe it's a matter of a marginal ignition switch barely making contact. Without daily usage, light corrosion builds up on the internal contacts. You hop in the seat, turn the key to start, and nothing happens. But leave the key in Run, and press the gas pedal, and now the starter engages like it should. But grasping at the thinnest of straws, the extra time with the key to Run is what "fixed" it, not pressing the gas pedal. It just coincidentally happened at the same time as pressing the gas pedal.

Just thinking out loud, trying to make sense of this very strange problem.

Are there any electrical connections at all on the carb? Electric choke, for example?

 

I am going to my parents place today and will check all my grounds. I know the only ground I have off the battery goes to the engine and mounts to the bracket where the alternator was on. It does have an electric choke, and after all the other little electrical gremlins I've had to fix, this is the last one I really need to work on. Does the jumper wire have to be anything big or just a smaller wire will work?

I would say it was coincidence that pressing the gas gets the starter going, but this has happened 6 times now and every time I hit the gas it fixes the issue. So you're right there is probably a ground somewhere being affected by the linkages.

 

I want pictures. Could you snap a photo under your dash and then anywhere the gas pedal linkage and cable runs?

I'm gonna make a few suggestions based on assumption that it is actually not the gas pedal.

1) I've had problems in the past with starters having a sticky Bendix. (possibly the problem) Occasionally, the Bendix in a starter can stick in the position as if the starter were engaged. When this happens, the solenoid and ignition switch are all operated correctly, but the starter makes no noise or has any effect at all, because the Bendix is already engaged, but stuck. And it's very intermittent usually. Pulling the starter and greasing the Bendix shaft will fix it.

2) My 86' has a dual brake warning system which starts at the ignition switch and goes through a series of hydraulic sensors and the clutch pedal. It prevents the Red/Blue wire from getting power unless certain conditions are met, like the clutch pedal pushed in or pressure on the brakes, etc... Your truck with an automatic so I don't know if it would even have the system. What year is your truck? Is it possible that the truck ever had a manual transmission? To clarify if your truck ever had this system, we would have to know the year, and then we can look at the wiring diagram and see if there are any possible safety systems wired in to prevent starting in any way. On my 86, the dual brake warning system starts at the ignition with Purple/White wires, now deleted of course.

 

I'd say a medium sized wire would be plenty. Maybe 10 gauge?

I think the factory ground for the cab was just a short wire from the back of the intake manifold to the face of the firewall. This piece often gets lost if the engine was replaced or if the intake manifold was ever removed.

It's not the best ground path, in my over-inflated opinion. Too many connections along the way. It goes from the cab to the intake manifold, which sits on gaskets and is kinda insulated from the engine block. The conductive path is via the mount bolts to get around the gaskets. From there, those electrons have to make it out to the alternator bracket you had previously mentioned, so that is several more connections along the way.

For troubleshooting, I'd recommend running a longer single ground wire between the firewall and the battery's (-) terminal. If the starter circuit now behaves, just leave it there.

You're going to be a disadvantage for troubleshooting as the problem seems to clear itself once the engine is started. You'd have to wait at least a week to know if you've fixed it.

 

So I tried to start it today, no such luck. So I started tracing ground wires after confirming there are no wires entangled or touching the the gas pedal. However my ground wires both from my battery to engine were completely rusted and same with the one from the block to the solenoid. After sanding both down to clean metal I tried starting the truck without touching the gas pedal and success it started instantly. So I'm wondering if touching the gas shook things in the truck just enough for a ground connection somewhere. But the truck had sat for two weeks and started right away after cleaning those grounds.

 

It could have and why I said check all grounds.
I have heard of cars with autos that use a cable from floor shifter to trany welding the shift cable because of bad ground.

You keep saying ground from battery to motor (alt bracket) do you also have a ground cable from motor to frame? If not you should add one.
As for the body ground as said a 10 ga wire from motor / in take bolt if v8 to the firewall will be good.
Some battery NEG. cables have a wire & crimp connector off it, this can be run the inner fender side maybe to a bolt holding the regulator?

On my 81 with a 300 six the factory battery ground cable was long. About half way there was a tab soldered to the copper and went to the frame then on down to 1 of the starter bolts.

Frame ground with that tab and a cable loop to hold the positive cable from hitting the exh.

Here you can see the red 10 ga. ground wire

The 10 ga wire is off a boss on the left side to the back of the block to the fire wall.
Oh I forgot the ground from the hood to firewall, this is a braided cable.
Dave ----