4.0 head and EFI on a 4.2 block

Swaping 258 to 4.0, 4.0 parts to 258 etc!
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Jeep-Power
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Re: 4.0 head and EFI on a 4.2 block

Post by Jeep-Power »

Hey Jim-

I don't think boring it or not will have any significant effect on the outcome. The first head swap I did was on my block, that was bored the 0.030 over. This article was on Toms Jeep, which was stock bore.



Differently, well, on mine I didn't rebuild the head-- I just bolted it right on. I'd be sure to rebuild the head, as we did with Toms Jeep.

If you are going to be pulling the engine-- I'd consider putting in a 4.0 HO flywheel & bellhousing (Advance Adapters makes a really nice one)-- this will allow you to run the crank position sensor (CPS) in the factory location. The bellhousing is the key to it, so if that is going to be a hassle for you, don't fear. The balancer mounted CPS works just fine!

Please keep us posted & post your work here!
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Re: 4.0 head and EFI on a 4.2 block

Post by EFIeagle »

I just recently got mine running, but it's got some quirks. I'm using the same yellow top injectors you originally had, though with a stock fpr, and a return style fuel rail. The exhaust gets extremely hot within just a few seconds of running, and the throttle is very responsive unless opened completely. I'm certain it's running lean, everything else checks out. I have all of the stuff needed to make an adjustable MAP, but will that be enough, or will I end up overdriving the injectors to richen it up? My motor is bored .030 over, with a 92 HO cam. The motor was rebuilt very shortly before I bought my Eagle, so I don't know what's stock and what's not as far as bottom end goes, though I know everything is brand new. Also, I noticed you added the starter relay to your PDC in your later posts, how did you eliminate the 258 starter solenoid? I'm using an AX15 so I am using a 4.0 starter....If you could help me out on this I would greatly appreciate it!
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Re: 4.0 head and EFI on a 4.2 block

Post by Jeep-Power »

Yeah, I was lean too--

I tried the adjustable MAP sensor-- didn't see any significant results from it.

The adjustable fuel pressure regulator solved a bunch of issues for me!

I'm not sure of what you are asking about the starter relay. (The relay for the starter on Tom's YJ is on the fender, it is big and is not in the PDC-- on my CJ I'm using a Powermaster Starter, with it's own relay that is built into the starter). Please elaborate!
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Re: 4.0 head and EFI on a 4.2 block

Post by EFIeagle »

I was considering going junkyard diving to find a set of 88-96 Ford 460CID V8 injectors, those are around 24lbs at 39.5 psi, it looks like that's my option, I don't have anywhere near the cash to get a fuel rail gauge and adjustable Fpr.

As for the starter, I'd like to try and wire the starter into the starter relay on the pdc, and get rid of the solenoid and wires in the engine bay. I'm so close to having it right, but I can't find any wires that match the gauge of the black/green one coming off the starter, they're all significantly smaller...
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Re: 4.0 head and EFI on a 4.2 block

Post by Jeep-Power »

as for the regulator-- do what you can-- I know the adjust-ability of it is worth the trouble & $$.


The strter relay is big and has those heavy wires for a good reason. Are you saying that you will like to replace it with one of the smaller relays that reside in the PDC?
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Re: 4.0 head and EFI on a 4.2 block

Post by vortec23 »

I HAVE AN 84 CJ7 I PUT A 7120 HEAD WITH 94 ZJ EFI AND HARNESS I AM GETTING THE CPS RELOCATING KIT SOON I NEED TO KNOW IF I HAVE THE WIRING HOOKED UP RIGHT . ALL THE WIRING ON HERE IS BASED ON THE XJ WIRING AND THEY ARE DIFFERENT CAN ANYBODY GIVE ME THE LOW DOWN ON WHAT WIRES I USE OUT OF THE PDC... THIS POST AS BEEN A GREAT HELP TO ME . I HAVE NO POWER AT THE FUEL PUMP WIRE OUT OF THE PDC WHEN KEY IS ON OR OFF
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Re: 4.0 head and EFI on a 4.2 block

Post by Jeep-Power »

Vortec-
I'm not familiar with the ZJ harness--

my thoughts: With no voltage at the fuel pump, are you sure the ASD relay closing? The ASD supplies voltage to the fuel pump, injectors, alternator, , and a few other things I can't remember.
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Re: 4.0 head and EFI on a 4.2 block

Post by EFIeagle »

vortec23 wrote:I HAVE AN 84 CJ7 I PUT A 7120 HEAD WITH 94 ZJ EFI AND HARNESS I AM GETTING THE CPS RELOCATING KIT SOON I NEED TO KNOW IF I HAVE THE WIRING HOOKED UP RIGHT . ALL THE WIRING ON HERE IS BASED ON THE XJ WIRING AND THEY ARE DIFFERENT CAN ANYBODY GIVE ME THE LOW DOWN ON WHAT WIRES I USE OUT OF THE PDC... THIS POST AS BEEN A GREAT HELP TO ME . I HAVE NO POWER AT THE FUEL PUMP WIRE OUT OF THE PDC WHEN KEY IS ON OR OFF

If you have good search experience with google (I'm not being sarcastic), you should with a little digging, be able to find a ZJ owners manual to download for free. If you can find one, get it and go to the wiring diagram for the pdc. Look up the wires coming out of the fuel pump relay. There should be a wire for fuel pump+. My XJ harness has two of those wires, both green/white stripe, I only use one of them. That's your power wire. Run a wire from the - side of the fuel pump to a clean, exposed (not painted, etc) spot in your engine bay and attach, that's your ground wire. The ECM will power the fuel pump for about a second and a half in "run", then shut off, unless your engine is actually running. So, if you have one, use a multimeter to test the connection while you have someone toggle the key to "run", you'll have a second and a half to see whether or not you have power. When your fuel pump runs for the first few times, it will be really really quiet and hard to hear...

The main wire that will give power to everything is actually three wires, there are a few splices in the circuit. It should be a 10 or 12 gauge blue wire, there should be three of them coming out of the pdc, and some splices further along the wire. YOu should be able to find a cut end. Hook your yellow ignition wire that used to go to your CJ coil up to the blue wire. I had a lot of difficulty getting my wiring figured out as well, and had to research and ask all over the place, so I've got it down now...
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Re: 4.0 head and EFI on a 4.2 block

Post by vortec23 »

From the PDC....
14 OR/DB - Fuel pump (Positive)
16 YL/BK - To ignition switch (Crank)----------TO----------CJ- 14 LB
12 DB/GY - Ignition switch (Run)----------------TO----------CJ- 12 RD/WT
12 RD/WT - Ignition switch (Positive Feed)----TO----------CJ- 12 RD

THATS HOW THE 4.0 GETS HOOKED UP BUT I'M USING THE STARTER FROM MY 84 CJ7. I AM TRYING TO FIND A V-BELT PULLY FOR ME 94 ZJ ALT. I WANT TO USE THAT IS THERE DIFFERENT WIRING FOR THIS
I DO HAVE ALLDATA FOR BOTH
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Re: 4.0 head and EFI on a 4.2 block

Post by EFIeagle »

I'm using my 258 alternator, so I couldn't tell you on that one....
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Re: 4.0 head and EFI on a 4.2 block

Post by Jeep-Power »

vortec-- I'm not sure what info you are looking for... please clarify. 8-)
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Re: 4.0 head and EFI on a 4.2 block

Post by vortec23 »

TallPeter --- I wanted to know if thats the way to hook up the wiring and any suggestions on a v-belt pully that will fit the alt. from the zj :banghead:
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Re: 4.0 head and EFI on a 4.2 block

Post by Jeep-Power »

vortec23 wrote:From the PDC....
14 OR/DB - Fuel pump (Positive)
16 YL/BK - To ignition switch (Crank)----------TO----------CJ- 14 LB
12 DB/GY - Ignition switch (Run)----------------TO----------CJ- 12 RD/WT
12 RD/WT - Ignition switch (Positive Feed)----TO----------CJ- 12 RD
OK-- got it-- this is what I posted about the wiring from the XJ harness-- I don't have any wiring diagrams here(at work), in front of me.

The three wires that need to be hooked up are: the BIG (#4) red wire on the side of the PDC-- we downsized and lengthened it (with #12 wire). It runs right to the (+) side of the battery. The ground wires (the ones that bolt to the side of the engine block-- black with a brown stripe) get bolted back to the side of the block, and the solid dark blue wires get hooked to Ignition (+) power. Hook those three up and it is ready to run!

which wire do you have hooked up to un-switched battery?
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Re: 4.0 head and EFI on a 4.2 block

Post by vortec23 »

i hooked it up the way that chart told me too but i dont have a dark blue wire i have a dark blue with grey tracer. Is sounds like the same thing cause it comes out of the pdc three different places but it splices into one wire.I got my cps kit today i will hopefully have it running tonight
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Re: 4.0 head and EFI on a 4.2 block

Post by vortec23 »

Its me again got the cps in today still not getting anything out of the fuel pump nore do i have any spark any help would be great :boom:
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