79 bronco IDI 7.3 [Archive] - TheDieselGarage.com

: 79 bronco IDI 7.3

01-16-2007, 07:52 AM
hello all first post! I have a 79 bronco that i swapped a 7.3 ford IDI motor into and got everything on and put together but i have some problems. first i need to figure out what to do for a tach! anyone know a wiring diagram or somthing i can use to hook up a traditional coil style tach? and also since i swaped the motor and tranny out of a 91 ford truck i need to figure out a speedo. any one have any cheap sugjestions? and finially can anyone giv e me a link to turning up the fuel pump? thanks

01-16-2007, 12:39 PM
Can't help you on your problems but I am sure someone here can. Your project sounds very cool! A friend of mine has a '94 f250 stroke he rolled. We were thinking of finding a nice Bronco like a '96 Eddie Bauer & making it a stroke, ttb50, 10.25 & all. You have any pics?

01-16-2007, 01:41 PM
Here's the fuel article:
The coil style tachs dont work, unless you're really electronically gifted. There's a few diesel tachs out on the market that are decent. I think with a 91, you can still use an older style mechanical speedo, maybe even use the 79's. Just comb thru a bone yard and you'll find something. Make sure you bring along the wrong one to compare others to.

01-16-2007, 02:25 PM
The standard way to get a Tach signal on a diesel is from the alternator. Most Delco alternators have a "TACH" terminal, and some Motorcraft ones do as well.

The speedo could be more problematic. Your bronco used a mechanical speedo, and there is no provision for that on the '91 drivetrain you have, they were off the ring gear tone wheel. You may need to contact a local 4x4 shop to get a speedo drive for your transfer case.

01-16-2007, 03:23 PM
hey thanks guys the speedo is really a problem as i knew it was a rear end ring gear hall effect speedo pic up. i was just hoping that somene had a quick fix though. ill post up some pictures as soon as i figure out how. thanks for the quick response guys! and thanks for the link nevrenufhp

also on my front pump cover i have a plug a pickup on the driver side. can i use this for a tach and could somone give me a link or somthign to i can find a cheap tach?


first run in the mud after i got her together crawled into this hole and tried to sink it spinning just the back tires but when i got on it she came screaming out like a bat out of hell

01-18-2007, 02:17 AM
well guys tonight i think i may have a problem today while driving into town the oil light on the bronco came on and went off and it does so every once and awhile. was wondering what is the place place on the motor to measure oil press im really not looking forward to taring into the project so soon.:shrug: thanks

01-18-2007, 02:31 AM
The oil sender is an idiot light switch, they fail - OFTEN.

Verify pressure with a mechanical gauge, it is common for the 6.9L/7.3L IDI engines to idle at less than 10 PSI hot, and as long as it is 6 PSI or more, and it comes up with RPM, I would not be too concerned.

I would use the next heavier weight oil, if oil pressure is tending to the low side. I don't know where you are from, but since it's January, and I don't see any snow or ice, I would say that you should be running 15W-40 year-round anyway.

01-18-2007, 02:41 AM
thanks ill be slapping a mechanical i have at the house on tommarow and see what the result is. thanks for the info. ya im up in norther cali not much snow and the coldest it gets here is usually in the 20's and that has been this last week.

also john g do you have any ideas on the front cover pick up and making a gas style tach work off of it?

01-18-2007, 02:47 AM
There are THREE bolts that secure the IP gear to the IP shaft, you *could* use a magnetic P/U (like an ABS or VSS sensor) to read each bolt-head and a tach set for 6 cyliners I suppose.

Don't know if the signal is strong enough, but it's worth a try.

01-18-2007, 02:55 AM
hmmmm sounds like it would spare me time and painfull words coming from my mouth and just buy a diesel tach lol thanks for the thoughts. ill probly post some more pictures tommarow of the truck and the engine


01-18-2007, 02:58 AM
As I recall many Delco alternators are set-up for a Tach output just for diesels. Check with your local alternator/starter rebuilder, that would be the easiest thing to do.

01-18-2007, 03:10 AM
hmmmm do you know what kind of signal it puts out? im kinda far out of town

01-18-2007, 03:17 PM
I *think* it's a 12V pulse every 1/3 revolution.

01-18-2007, 04:18 PM
that sender on the pump housing is the factory tach sender for the 7.3 in the original truck so if you can find a comperable tach from the original or make one from an 84 or newer diesel f250 fit in your dash you can use that .

as for the speedo you have 2 choices use the bronco t case with the speedo drive in it or find a tcase from a 90 or older f series truck and use that one


01-19-2007, 10:48 PM
today i jumped under the hood very slowly (broken tail bone and such) but i did get some new pics and have a video of my mechanical oil that made me very happy to see but still think it may be a bit low you guys be the judge

oily but not bad for a 400$ swap.
and oil pressure just cranking no start up

also i checked the voltage that i was getting to my glow plugs and there each getting 12.46 volts and im having a hard time starting, and i think my glowplugs are shot. any quick tests i can use?

sorry for all the questions this is my frist diesel and want to keep it alive i looooooooooooooooooooove all the power of it.
thanks guys


01-20-2007, 12:09 AM
You can go to this site the have what you need alittle pricy but good .


01-29-2007, 11:41 PM
Autometer makes some nice ones, I just installed the 3" ultralite in my truck, they come complete with the pick up and hoseclamp to attach it to your alternator for $130.00
:Thumbup: On the conversion

01-30-2007, 06:59 AM
thanks! could you maybe show me some pics of your tach and where did ya get it online?
at least somone else thinks its cool.

01-30-2007, 01:29 PM
Check out e-bay # 270084927919, $118.00. I bought mine at Advanced auto locally, I don't mind paying a little more for if something should happen to it I can personally take it back for a return. Sorry I can't post pics from this loaner computer, Mine suffered a motherboard meltdown and is in the clinic right now. As far as your spedometer goes What transfercase are you running? I kept my 205 and everything works as it should. Also where did you find a bronco that clean? I would travel far to find a rust free piece such as yours.

01-30-2007, 07:28 PM
well i used the 91 truck t case i thought i would be better off and the tcase that came with the bronco looked about as good as if i had dropped it off a cliff. its been cored out and tossed away. and the bronco i bought locally here (northern cali) for 500 bucks and its really not that bad at all the grill has some problems and it has one dent you can barely see in the pics and thats it. i did have to notch the frame a bit to get the engine in but. overall it was worth it. i tell ya its a screamer i really really really enjoy every second i get to drive it. i have a video of it and me just playing in this clay mudhole might impress some. thanks for the tach info too. im really looking into doing the same thing you did.

01-31-2007, 01:02 AM
ok go bone yard hopping you need the rear snout and the speedo drive componants out of the t case on a 88-91 truck f150 250 bronco ect ect .. preferable a 150 with the same gears you have so you have a better chance of getting the correct speedo drive gears for your ratio I did this when I put a 94 tcase into one of my 88 trucks

01-31-2007, 09:09 PM
check! have cable and snout installed next problem well. lol the speedo is trash next option. im thinking i might just make a whole new instrament cluster cause the old one actually came apart in peices. any ideas ? and suggestions? thanks for the info

02-11-2007, 06:35 AM
If you run an aftermarket speedo and tach you can just install a sender or use the existing transmission sender. They plug right in where the cable goes. I did this on my 71 Mustang. I got a sender off a modern Ford then am running a SW speedo, it has a calibration proceedure you do that is pretty easy and you have a nice simple speedo that has just 2 wires intead of a cable.

02-11-2007, 04:33 PM
If you look in the first engine photo you posted you already HAVE a tach sender! It is the two wires on the left front of the engine laying on the un-occupied bracket next to the PS pump.

All you need now is a diesel tach for the dash from a scrapper.

03-18-2007, 03:31 PM
Hey scratcheynum1, nice tk! I have a idi 7.3 that I would like to put in a similar tk. How nice did the oil pan fit the chassis? Were there any other clearance issues? Did you use any stock motor mount components, or fab everything? thanks, curious.

03-18-2007, 04:53 PM
acutally not much has to be done. the oil pan is no problem. and the motor mounts you can use the stock bottom half of the broncos mounts and i just welded up to the top half of the 7.3's mounts its kinda a hit and miss game untill you get it just right. also you will probly have to notch the frame on the pass side exhaust and starter clearance issues.

thanks for the comments
thanks for the questions i like them.

also i have tooooooooooooooooooooooons of pictures of it if you want. let me know