1990 f150 no crank

[831152]

Alright, bought the truck with the knowledge that it has a bad clutch interlock switch. P/O has put on a new starter, and new solenoid. this morning I stuffed myself under the dash as best as I could, located the safety switch and bypassed it until I can get the part I need. So, when I go to start the truck now, I hit the key and get a single "clonk" from the solenoid. nothing else. I can still get under the hood and start it by bypassing the solenoid, so I know that the starter's fine.

There's a little bit of hackery going on with the wiring - so I'm not 100% sure what's supposed to go where. I'll snag some pictures here in a bit, but thought I'd get opinions here.

[Will W]

Don't take me for an expert on this subject, there are some great people on this site that know massive amounts
more than I, but let me ask a few questions.

When you "bypassed" the safety switch, do you mean to say that you shorted it out, or did you unplug it?
Shorting it out would be the correct thing to do I think.

The other thing I would ask is why the PO replaced the starter & solenoid. You are still having that same problem
that he seemed to be having and it wasn't caused by the starter & solenoid.

That "Single Clunk" you hear makes me immediately think bad cable connection. Have you actually taken the
battery cables off and cleaned them, not just looked at them? Have you checked the ground cable connections
to the frame and block? How good is the battery? Do the head lights dim out on cranking?

Do you have a volt meter, or even a 12V light that you can put across each connection when you crank the engine
to see if the connections are good?

[831152]

Yes, by bypassed I mean shorted it so the truck would crank. I was told by P/O that they suspected starter/solenoid when they first got the truck, but diagnosed it as a bad clutch interlock switch. I put a jumper between the two red/lt blue wires and this is where we're at.

Solenoid picture -


As far as battery cables go, I know they both need to be replaced, as they're in rough condition. just wanting to make sure everything's wired up correctly before I dive in too deep.

Battery is good, sits at 12.4-12.2 resting.

[Steve83]

Battery cables get replaced a LOT more-often than they need to be - it's better to just replace the terminals, as explained on this page:

(click this text)


That alone will probably solve this problem.

[Will W]

IF I understand correctly, you can jump the little stud at the top of the relay in the picture you posted to the
positive side of the battery and the truck cranks over. If that is true then you can eliminate connection
problems with the high current path. Then the problem probably is a break in the path to the little stud on the relay
in your picture.

But you said that you can hear that relay clunk when you turn the key. That says there is not a problem in that
path to the little stud.

So I must have miss-understood something.

You said you bypass the solenoid and the engine cranks. Do you really mean to say that you jumped the two
big terminals on the relay in the picture above and the engine cranks, or did you mean that you took the little
stud to 12V and the engine cranked. There's a big difference there.

[831152]

You said you bypass the solenoid and the engine cranks. Do you really mean to say that you jumped the two
big terminals on the relay in the picture above and the engine cranks, or did you mean that you took the little
stud to 12V and the engine cranked. There's a big difference there.

I jump the two big terminals on the relay and it cranks. I was able to get it to crank by jumping the little stud to 12v and it worked twice. At this point I'm suspecting that the solenoid itself may have gone bad

[Will W]

I suspect that you are right.

The engine should crank EVERY TIME you take that little stud to 12 Volts.

The thing in the picture you posted was the RELAY. The solenoid is the big bulge mounted to the starter.
A solenoid is a relay, but it is also a electric piston that shoves the starter gear into the flywheel before
applying power to the starter motor. When the PO said he had replaced the starter & solenoid he probably
meant that he replaced the big starter motor, with the bulge on the side containing the solenoid, at the time.

However, the relay in the picture, even though it looks clean, maybe the only culprit in this whole story.

When you go into the parts store ask for a STARTER relay, not a solenoid.