I'm pretty new to the diesel world so please bear with me. I am transplanting a 92 cummins and getrag into my 73 crew cab project. What wiring do I absolutely have to have to make this engine work correctly? I don't plan on putting cruise control on the truck so I know that I don't need that. I've heard that you can put the grid heaters on a momentary switch and use that. I know that I'de need the alternator and starter for sure. I think the alternators are regulated through the computer right? If so I could convert it to work through the old style regulator right? Thanks for the help.

 

You can convert the alt to old style regulator. Grids can go on a switch like you think. All you need for the engine it self is a 12 volt supply for the fuel solenoid.

The orginal feed wire to the gasser coil will work for that.

 

That is the beauty of these engines, purely mechanical.


The grid-heaters can be left off; you will never ever need them; same with the water-in-fuel sender and fuel-heater.

If you still have the engine out of the older truck, you can use pipe adapters, if necessary, and mount the gas-burner gauge-senders in the Cummins block, so the factory gauges will work.


I am not certain just when they went to the communist alternators; the wife's truck is an inter-cooled 1991 and it has the externally-regulated alternator.

If you use the externally-regulated alternator off of an earlier Cummins, it should bolt right in.


HOT wire on the starter and GROUND on the block, "start" wire to the little terminal on the starter, and ignition ON to the fuel-solenoid.

I think that covers it.

If you really want to connect all the other un-necessary stuff, do the vitals first and work the other out later.

 

You can also "GUT" the fuel-solenoid, add a KILL-CABLE, and do away with the IGNITION ON wire, if you so desire.

 

I think I'll have to go to that 91 alternator like you were talking about. I plan on putting all new gauges in. I was thinking autometer, but after reading about some peoples problems here I might not use autometer now. I just want: oil pressure, water temp, voltage, fuel X 2, boost, pyro, and a tach. The speedo is mechanical off the divorced 205 so that won't be an issue. Of course I will want AC, interior lights, radio and such, but that's unrelated to the engine wiring. Will I need the grid heaters at all? It doesn't really get that cold here in central texas. Maybe 5 or 6 days out of the whole year it dips below freezing. I was planning on driving the truck to northern new mexico one winter for some snow skiing and I don't want to be left stranded. I'de like to be able to start and stop the truck with the key.

 

Although trendy and politically correct, I am not at all impressed with Autometer gauges = too much use of flimsy plastic.

I like good old brass-plated-housing Stewart Warners or Sun-Pros.

A decent SunPro gauge can be had for a mere portion of the cost of Autometer.

I get mine from a place called Tradervar on E-Bay and Amazon.com.

Also, Surplus Center usually has quality gauges at salvage prices.



I have four Cummins trucks in drivable condition; not one of them has the grids connected; any one of them will fire before you can get off the key, no matter how cold of a place I have been in.

If one did hesitate to fire, a small snort of ether will bring it to life.

The grid-heaters are a tremendous drain on the electrical system and I honestly believe a contributor to many of the electrical difficulties many have with these trucks, as they put everything else in a strain for lack of current when they are on.

You can wire them to only function on demand, if you so desire.

 

Not in Texas or New Mexico. I wouldn't worry about the grids until you stay at 0* on a regular basis. I never wait for them in the summer.

 

I know I wouldn't need it in Texas most of the time. I'm heading up to new mexico awhile after I get this truck finished to do some snow skiing. It's near the colorado border at 8,000 foot elevation. I just didn't want to have any difficulty starting it there and leaving me stranded with the snow bunnies.

 

Well the question is where in NM. At altitude and in the winter you could need them. Say around Taos or other high areas.

In UT the truck starts fairly well year around. I usually am glad for the grid heaters when the temp has been <30*F for a while. And we are only at 4200'

My recommendation is to wire them to a HD momentary switch, that way you don't accidently leave them on.

 

All the alternators are externally regulated, you can use the '73 regulator and wiring and it will charge.

The grids aren't strictly necessary. When I got my truck the grid relays were fried, it started OK at 17 degrees unplugged. If you want to use them, Rich's suggestion is perfectly fine.

The KSB is already wired unless you've pulled every wire off the engine. The fuel heater is not hard, it needs 12 volts switched and a ground. Some will argue with me, but if you are going to drive the truck in cold weather it should have a fuel heater.

All the engine needs to run is 12 volts to the shutoff solenoid - and if you gut the solenoid and use a shutoff cable you can don't need power for the engine at all.

 

It only gets really cold here in texas about 5 days out of the year. The rest of the time it's easily above freezing. Where would I find a momentary switch that I could use for the grid heaters? And what is the KSB? I'm a newbie and still learning diesels. The complete engine is still in the donor and still driveable for now. I'm assuming that the fuel heater is around the fuel tank heater right? I'm running dual ramcharger gas tanks.

 

Hi Ramman -
I agree with everyone on the grid heaters. I put a cummins into my 75 and wired them up on a button. I only use them in the winter, other wise I just light it up.

The 12v ignition feed to the pump was a little tricky. The way the gassers were wired in 75, there is not a single ignition wire that is powered during both the start and run position of the key switch. (It has to do with bypassing the balast resistor during the during the start function, which of course you don't need anymore) You can't just put the two feeds together because they will backfeed each other. What I did was put diodes in line to prevent the backfeed.

As far as the external regulator goes, it will work with the newer alternators. You need to keep in mind that the charging current in the older trucks goes through the bulkhead connector to the alternator guage and then back through the bulkhead connector to the battery. The newer alternators put out a lot more current than the old ones, so you definately want to bypass the bulkhead/alt guage. If you don't, the heat from the higher current could melt the bulkhead connector. I just ran a heavey guage wire from the alternator directly to the battery positive post.

Good Luck! I can tell you that the conversition made all of the difference in my truck. It is a pleasure to drive - lots of fun - and the fuel economy is awesome. Hope this helps - Fred

 

The fuel-heater is directly on top of the fuel-filter, about an inch thick, and the same diameter, held in place by the hollow fuel-filter stud; some are slotted and some accept an Allen-wrench.

On the donor, you should be able to see the electrical plug to the heater, just above the filter.

 

I was planning on eliminating the amp meter complete and installing completely new gauges. I did a mod to my gauge cluster that a departed friend showed me how to do. He cut out the oil, fuel, amp, water gauges, but left the speedometer. He then installed brand new autometer gauges in place of all those and wired them up to work with the factory wiring. I'm also planning this upgrade
http://www.madelectrical.com/electri...p-gauges.shtml
I'de be really interested in seeing pics of your 75 conversion. Does that fuel heater need continuous power to work properly?

 

If you grab the grid heater relays from the donor (look like lawn tractor starter relays) any old momentary switch will work, it doesn't take much current to run the control side of the relays.

The KSB is the wire on the side of the injection pump. It gets 12 volts from the shutoff solenoid through a switch on the intake manifold.

Yes, it needs 12 volts off a switched ignition feed. It pulls more current the colder the fuel gets. At 0 degrees it pulls around 7 amps, at 100 degrees it's not really doing anything at all. I'd run it off a standard 30 amp relay.