84 F250 460 2wd Auto

A short history:
Orig owner. 150k mi. Some years ago developed a hard/slow turn over/no start problem after reaching operating temp. Typical deal, wait 15-30 mins and starts up nice as you please. Cold starts were fine.

Current history:
Just rebuilt engine. 9:1 comp, stk dist., stock heads,blah, blah.
10 deg. initial timing.
NEW 800 ca battery, starter, alt, coil, starter relay, 2 ga. battery/starter/ground cables, ign. module.
Grounds run from battery to block and block to frame.
Still having the same issue.

Disconnected the R/LB starter wire from the solenoid, connected a bump switch between that terminal on the solenoid and the battery terminal on the solenoid and it turns over just fine.
WTF?

Reinstalled the old parts(starter, solenoid etc) and did the same thing. Turns over just fine.

Went back to the new stuff and repeated. Turns over just fine when jumped.

Could it be the ignition switch? That and the wiring which supplies power to the switch are the only things that have not been replaced.

BTW I have tried a different eng/ start harness... still no change.

Any Ideas...Thanks

 

What type of ignition do you have?

 

Stock. New cap, rotor, wires

 

Make sure you have 12 volts on the white wire going into the module when you are cranking the engine. The module will retard the spark when it sees 12 volts on this wire, making the engine easier to crank over.

 

try checking the r/lb wire the see if there is a bad spot u can also try running a new wire from the ing switch to the solenoid it may have a burnt spot in it

 

I actually have the ford wiring and vacuum manual which gives a quicky guide to ign. problems.

It says that the white wire test should show voltage within 1 volt of the tested battery voltage. Well I've got a 3 volt discrepency. So I checked at the ign. switch and there's a voltage drop across the switch.

I don't know if there is supposed to be a drop, but I'll try replacing it and go from there.

Has anybody else found the ign. switch to be a culprit?

Thanks

 

You may try another ignition module. Just get a used one from a junk yard. Heat causes starting/running problems with these things. Later on Ford put the module in the distributor with the same result.
It sounds like the ignition switch is fine, they either work or they don't.

 

I have three ign modules, two new and the orig. All three do the same thing.

 

That's not 100% accurate. These switches can develop all sorts of intermittent faults. Most comon with worn out switches, on this model, is they either won't start your truck every time, or you will not have any accessories like Radio, heater etc, unless you wiggle or play with the thing...

IATSE44: When you did the White wire test like it say's in the manual, did you make sure all the accessories were off? Heater, Radio, etc... etc... It does sound like the three volt descrepency between the battery and the white wire at the module could be the culprit.
Try cleaning the contacts. It should only be within 1 volt as the manual states.

Also you did not mention the engine block to Firewall Ground cable. How is this cable? With this cable being bad, or missing, it can cause grounding problems with dash components. This includes the Ignition switch, dash lights being dim, among others. Just a few thoughts...

 

that ground is new also. Took care of that when I re-installed the motor. ground the paint away attached the wire and coated that attached wire to prevent rusting.

Just got back with the switch. gonna try it now.

 

Finally got the switch installed a couple days ago.

Seems to have fixed the starting issue. Although there still is a voltage drop greater than the 1 volt spec. About 2-2.5 volts. Weird.

I checked the input voltage to the switch. 12volts. In the start position it drops 1.5-2 volts. At the switch.

Did the circuit check thing. Didn't find any appreciable resistance in any of the circuits.

Now I get to tear the front of the motor off to figure out what the dipwad that installed the cam screwed up.