new idi engine

[bigblue85]

so i picked up a 7.3 to replace an 6.9 engine out of my 85 and the 7.3 came out of a 91 pickup and i wondered ifthere was anything that i had to change out to make everything to just right in place. i noticed the glow plug controller was different than the one out of my 6.9 and that the fuel filter pedistal had a wire on it which made me wonder if it was for heating the fuel? all in all i picked up a 7.3 with 140k for 500 bucks which didnt bother me it was a tad oily because of the valve cover gaskets being shot. is there anything i should be aware of before i throw the engine in? i planned on puttin new head gaskets on it just in case you never know though.

 

[Knuckledragger]

You have already noticed the two main external differences between the two engines. The 7.3 had a 12 volt GP system, is much more reliable than the 6.9 (and more popular as well), and the filter head acted as a water separator, removing the need for the sometimes faulty 6.9 firewall mounted unit. I'm not sure if it also acted as a fuel heater.

 

[bigblue85]

ok so will it hook up to my stock serperator wiring? after i remove the fire wall mounted one? because thats what im stumped about because i know it will bolt to my 4 speed and all but i am concerned about the wiring differences mainly what i will have to mod and all

 

[Knuckledragger]

You may have to splice some wires, but yes, the separator wire should work the same. No mods here, just a little extra wire.

The GP system is different and should be transferred totally from the donor of the 7.3 while removing all of the 6.9 stuff. The GP connectors are even different. If you got the GP wire harness with the engine, all the better. Indicator lights and wiring is the same, just the voltage going to the GPs is different.

 

[hesutton]

Eh.... I just used the 6.9 stuff on my 7.3 during the swap. I didn't have any usable 7.3 glowplug harness stuff, so, I just put the spade type ZD-1A glow plugs in the 7.3 and have run it that way for the last 5 years without any problems.

I did, however, ditch the firewall water separator and just ran the 7.3 filter head on the truck.

Heath

 

[mabc926]

I used all the 6.9 wiring too when I did my 7.3 swap, but my glow plugs are on a push button, don't trust the 6.9 controller.

And I'm using the 6.9 style filter head by choice, filters for it are cheaper, and they have a higher micron rating.

Just need to mount an aftermarket water separator.

 

[Diesel_brad]

Just be mindfull of the cavation problems the 7.3s have

 

[Agnem]

Probably just syntax, but since it was implied, be advised both systems are 12 volt, and both use 6 volt plugs. The 7.3 system is intelligent, where as the 6.9 system is not. Both have their weaknesses, but adapt the 7.3 system to your truck if you can. It's failure mode is prefered.

 

[bigblue85]

ok thanks alot guys! i planned on using my 6.9 glow plug controller and using my 6.9 fuel filter pedastal assembly just to make it easier because i need a truck to drive and by the way im gonna pull the heads off and change the head gaskets just in case there might be problems. is there anything i need to look for during this process that is common on these 7.3's? the engine seems to be a good runner the guy said it had 140,000 miles which i thought was great im just gonna throw some new gaskets on it before i throw it back in

 

[bigblue85]

and ill have it on an engine stand to start it before i put it in to make sure everything is alright while i check the valves and lifters. do you guys think the engine stand would be able to withstand the vibration? or should i start it on the cherry picker instead? and what all do i need to get it to start


a. fuel in a jug and line running to mechanical pump.
b. a battery to turn i tover
c. ? that it? i plan on running it for only about 30 seconds to a minute without antifreeze.
d. how would i get the glow plugs to work with it being out of the truck???

 

[riphip]

Don't forget the oil cooler re-ring & oil pan (Wacker T442) seal. Much easier with it out.


Rick

 

[bigblue85]

ya i think im gonna use the oil cooler off my 6.9 on it. its in better shape than the one on the 7.3. what do you mean by the wacker t442 seal? i bought a fel-pro oil pan gasket

 

[mabc926]

ya i think im gonna use the oil cooler off my 6.9 on it. its in better shape than the one on the 7.3. what do you mean by the wacker t442 seal? i bought a fel-pro oil pan gasket

Return that gasket, either use wacker t442 (google it) or a bead of RTV.

 

[bigblue85]

so the t442 is a make a gasket type stuff?

 

[Diesel JD]

Icanfixall usually advises people not to use the oil pan gasket. I forget what his sealer of choice is, but from what I understand from the factory these engines ha sealer and not a gasket and the gaskets tend to leak sometimes. It is pretty hard to do anything to the oil pan with the engine in frame so now's the time to get it right, same with the head gaskets and oil cooler, though these can be done in frame. I avise you to reconsider the 6.9 glow plug system. Mel didn't elaborate, but failure mode for the 6.9 system is often burning out your glow plugs by sticking the relay in the "on" position whereas the 7.3 style usually just won't heat the glow plugs very much if you have a dead glow plug or a loose wire. If you really are dead set on using the 6.9 system your best bet is probably some 12V glow plugs and a manual momentary toggle. You can get 12V "slow glow" plugs for a 5.7 GM 1978-80. They are rated around 11-12 V where our ZD-1A berus and similar are rated at 6V. These would heat much more slowly but they should live a long life even if by mistake you leave them on for a bit too long. Honestly I'd figure out some way to give the engine a feed of water so you can run it on the test stand long enough to get it up to temperature to make sure everything is in order. I haven't done it so I'll defer to the guys who know better. I'm sure you could run it with no coolant for a minute or thirty seconds but I don't know if that will tell you what you want to know.