OK, I am not the most educated fella when it comes to electrical. But I think I have one for the best and brightest out there.

'99 Expy EB with 5.4 was running just fine with no indications of problems at all. Shut it off in the drive way and when I went to start it 30 minutes later - NO CRANKING at all. Not a cough, wheeze or even a clicking noise. Instrument panel shows no problems, gauges all work, battery is giving 12.6 Volts and PATS is not the issue. I repeat - PATS is not the issue. So I jump the studs on the starter solinoid and she fires right up. Runs like a brand new truck. I could drive it all day like this.

BUT...when I shut it off, NO CRANKING when I turn the key. I think massive sudden failure of the starter relay and replace it with a brand new one. NO CRANKING. Tried both relays twice with no difference. After searching here, I pull the starter and double check all the connections down under. I really didn't think that was the problem as it cranks like a mother when I shove a screwdriver between the studs. And sure enough, everything down under checks out.

All of the trucks electrical items work with ONE exception. While driving it today, I noticed that the radio does not even turn on. Stock radio MACH sound system and we have never had issues with it till today. All other electrical works like it should as far as I can tell.

Alternator is throwing 14.4 Volts at idle, I pulled EVERY fuse and checked them, AND EVERY relay in both power distribution box and drivers knee box was rotated to check for a fault. Did the last two items TWICE - FOR GOOD MEASURE. I even pulled the ignition switch from the steering column to check for electrical gremlins and found none.Starter OBVIOUSLY works well when I jumper the studs.

Now what? I can't ask the wife to start her truck with a screwdriver all day as she stands 4'9" in heels and can't even see into the engine bay on a good day.

 

Did you try starting the truck in neutral ?

Did you meter the small wire to the starter motor relay, before replacing it ?

 

I did try starting in neutral, no diff. I pulled the shift lever all the way up as some threads suggested, no diff.

When I shove a screwdriver across the posts - it starts in Park and Neutral and with the brake on or off in both gears. I rule out the brake overlock switch thingamabob.

I will go meter the small wire now. I assume I should find 12 V on the small wire when the ignition is in the start position???

 

Small wire has 3.94 V with ignition OFF and 12.82 V while ignition is in START. This is also the same voltage as the battery right now.

 

Actually the start in Neutral & checking for power are to see if the DTR ( Digital Transmission Range ) sensor is working.
Not too sure what brake thing you are talking abut, this is the transmission gear safety switch.

The small wire is the power to the coil, the ground for the coil is from the firewall ( or should be ). The other 2 are the normally open contacts.

What ground did you test with ? I would expect 0 V with the key in the off position.

Did you use the case on the starter motor relay ?

I would say another bad starter motor relay, but you can bench test the one you already replaced to see what it is doing.

Meter over the terminals in resistance setting.
Ground the case
Apply power to the lug for the small wire. The resistance should be low ( less than 200 ohms ).

Do you have any modifications ?
Trying to locate why you would be getting 3.94 V with the key not in the start position.

 

At work now but will check further later today

 

OK, I am back on the truck. I tested the small wire with the ground being the negative on the battery. Just unplugged it from the relay and stuck the red meter wire in and held the black one on the negative post while the key was held in the "start" position. Kinda weird that it shows almost 4 V with the key off. It shows 13+V with the key in start.

I was checking the #21 fuse in the driver knee panel for voltage on pin 2 with the key in "start" and all of a sudden, the radio starts to work! Since I could not find a good ground to test for voltage, I stuck the fuse back in 21 and tried to start engine again. NO CRANKING. And the radio does not work again. Bummer. I unhooked the battery again trying to recreate but no luck. I will measure resistance on the relay now.

 

According to the pinpoint tests in my '01 shop manual, everything tests OK up to test B7 which measures resistance between Digital Transmission Range Sensor pin C182-12 and starter relay pin 86. I will do a visual on the TRange Sensor and test resistance next

 

You already tested from CJB Fuse #21 to the coil on the starter motor relay by measuring 12.82 at the coil wire while in the start position.

Anything higher than 12.6 V should make the start motor relay normally open contacts close, but this is why I suggested bench testing the one you pulled out ( not the one that is installed ).

The new one you put in is a new one, not a pick and pull one, correct ?

Are there any other modifications ? Still trying to figure out why ~ 4V is on the coil with the key off.

 

«Fuse #20 in the CJB is a 5 amp fuse that feeds the radio and the GEM off of circuit 325. It becomes circuit 1000 after the fuse. Circuit 325 feeds the Starter Motor Relay Switch from fuse 21. The GEM grounds the circuit in start to turn off the radio. Pull fuse # 20 in the CJB and the truck should start. If it does start I suspect the GEM.

.

 

Jean Marc, I pulled #20 fuse and tried with no change. So I don't think it is the GEM.

Sculley, Yes, this is a NEW starter relay in the truck, I bench tested both and both are working fine. Now I have an extra as NAPA don't take returns on electrical

I too am puzzled by the ~4V at post 86 on the relay. Could I be getting a hot short from somewhere in the wire harness?

Got underneath and made sure the TR (transmission range) sensor was tight to the tranny and that the elec connector was tight as well. It is. So that should rule out the TR sensor as the problem as it hasn't moved since I got the truck.

I am beginning to think I have a worn/failing ignition switch or connector in the steering column. That is where I am going next.

Oh, BTW, there are NO electrical mods to this truck other than a GPS on the dash that is currently unhooked. The only other mod is Gotts intake. Pretty much stock.

 

Also, I did not test resistance on the TR sensor due to my thoughts that I would have to rig up longer wires to reach it and that would INCREASE resistance, wouldn't it?

 

10' of 14 AWG wire will have a very low resistance, so it would not be an issue, but once again you are getting 12 V at the starter motor relay on the firewall, so it is not an issue from the key to the DTR Sensor to the starter motor relay.

For some reason the starter motor relay is not closing the normally open contacts when power is applied to the coil.

Try metering the starter motor relay coil from the power wire from fuse #21 to the case on the starter motor relay, and see if you still have ~ 4 V with the key off, and 12V with the key on.

 

HE77S BELLS...I couldn't find anything wrong (no broken wires or unplugged connectors) in the steering column so I buttoned everything back together and tried to start it. FIRED RIGHT UP!!!! I shut it off and tried 5 more times. Works like it should. Even the radio.

Now I am mad and frustrated. What is wrong with it and why is it working now? I don't want to send the wife out in an unreliable rig.

Any ideas?

I will drive it today and keep notes.

 

How did you confirm PATS was not the issue ?