2.8 into 3.1 Bighorn.

[HarryVL]

As I mentioned on my re entry post we recently bought a 95 Bighorn with a cooked motor with a view to fitting the 2.8 from my old truck into it.Seemed like the easiest and cheapest way to upgrade.I knew the electronic injection could be a problem but expected it to be the injectors, thinking they would be like petrol ones, but they"re not.The changeover was very straightforward, thanks to mr isuzu drilling all the holes the same for both motors.True.you can even convert a 3.1 to gear timing if you've got the parts.I'd say Rodeo 2.8 bits will do.
The Problem.I used the 95 electronic injector pump because I wanted to stay with the computor for any other little jobs lt might be involved in, like the auto trans [has it's own computor] but the two probably talk to each other.This pump doesn't have a throttle cable and has plugs and wires all over it.Power is a little down on the old truck partly due to the auto but also the fact that it's running really rich.The computer thinks it's still feeding a 3.1 and there's no feedback anywhere other than throttle position and manifold pressure.Exhaust gas sensors and things were added later.It's not too bad cruising but put your foot and you'd think it was burning coal.I'm using 1/3 more fuel than in the old truck.
The plan was to run this setup till I overhauled the 3.1 but I pulled the head off the other day and found the 2 outer bores had aluminium welded onto them and the 2 middle ones badly scored.And the head's got a big crack in it.The crank might be ok though.So plan B was to Chip the computor down but apparently that's not an option.
So fellow Isuzu enthusiasts,any other ideas.I've already thought should've bought a 94.Too late now, and we wouldn't have got TOD [that could be a double edged sword too] but it was pretty handy a few weeks ago when we crossed the desert road in a blizzard.Last resort is to put the manual pump in while we save for a second hand motor but they're a risk too.
Thanx for reading this far.I wish I'd seen some of the other questions as they happened.I've 'been there done that' myself with quite a few of them.
Regards,Harry.

[geeves]

You have to use the 4jb1 injectors but otherwise I cant see any easy answers.
I would suggest from other stories including the Wizard that we went up Thompsons with that that motor failed because of injector pump problems.
Also the fuel curve would be very different between the 2 engines
For this reason I would say use the 4jb1 injector pump but its not going to talk to the auto correctly.We had a member in Botswana that had this problem I dont think he ever solved it. The auto ran in permanent kickdown. Why not use the manual trans. I know the trooper uk site has delt with quite a few of these issues through swapping 4jx1s out for 4jb1s

[geeves]

A random thought. I dont know if this can be done Consult an expert first before attempting. Marry the electronic top of the 3.1 pump with the mechanical bottom of the 4jb1 pump. This would give the actual pump section of the 4jb1 and the electronics of the 4jg2. It might work but I might also hear the result in Wellington

[justinw]

I would suggest from other stories including the Wizard that we went up Thompsons with that that motor failed because of injector pump problems.

Hi Alan

The engine failure wasn't an injector pump issue, it hadn't been modified at the time it went bang. It was leaking exhaust joint heating the oil cooler turning it into an oil heater.

The Wizard is still going strong, I drive it to work nearly everyday, although it is technically sold. The young guy that brought it is buying it on layby at the moment. He is going to use it as his tow/hunting wagon while he builds his 3.1 Mu with Patrol axles, Rodeo body and ultimately a V8.