Starting truck

I've been called out to re-wire a lot of 39mt starters where people have done this. When they designed the 39mt they put that relay there for a reason, older trucks have starting systems designed to power up high resistance starter solenoids. The 39mt has a low resistance solenoid to reduce voltage drop which in turn dramatically increases current draw. What your saying may work on some trucks, but definitely not all.

 

You dont need a relay on top of another relay.
Delco did this to assure proper voltage and amperage gets to there seliniod. I get this. But when most all trucks nowadays have one already its over kill.

Ive had 2 trucks so far exhibit a click no start situation. After tossing that stupid relay on the starter and going direct all problems disappear. That was 8 years ago on one 1 of the trucks, still working great today.
Im just going off my own personal experiences with that relay. I toss them out the door right from new and dont look back.

And if the 39mt has a low resistance selinoid why did the put a relay on there??? Because they want no voltage drop between ign key and the selinoid. If your truck is already wired that way why do it again..

 

To the op.
Just grab a wire and go from pos post on starter to the small post on selniod and see if it engages the starter..

If it does , bypass that relay and g directly to the seliniod with that wire coming from the relay off the fire wall on your Columbia....
For gods sake just make sure your trans is in neutral first.
Trust me your problems will disappear after throwing that poor excuse for a relay as far as you can. There junk.

 

Glad i coukd help!

 

There is a reason to be in neutral LOL. Glad you got it started.

Those two bolts on the actual starter is also how you jump a truck from another with like 10 gauge cables. (Or larger if you got em...) Bypass all that relay crap. Kick that kitty or detriot or whatever.

 

It works on probably 95% of all trucks out there. No ones driving a 64 dimond reo with sub par wiring OTR anymore.
It wouldnt even be an issue if delco put a relay worth a grain of salt on the starter to begin with. Every truck now a days has a very good relay already, conventional will be on the firewall and a cabover will be the batt box behind the drivers steer tire.
Dont get me wrong, thses 39mts are fantastic starters and ive actually havent had one fail yet. But those cheap relays they out fit them with are garbage and totally not needed. Probley the root cause of a lot of miss diagnosed starter replacements also.

 

I don't know about the Diamond Reo with subpar wiring... ours had very good and it had to be hauling milk on a assigned route.

God to run a Reo all over again... (And a 5 gallon bucket of narcotics for the pain...).. one more time.

 

was just trying to get a visual, I thought it was the batteries, but the clicking persist. 2000 Volvo N14