ghetdjc320

Half a cam is 6 cyl at TDC just either on the exhaust or comp stroke.

Since the crank is spinning twice as fast as the cam and the cam sensor is “open” half the time and “closed” the other half of a single revolution, then crank 2 triggers would equal one cylinder. Since cylinders 1 and 5 go off in close sequence, it would seem like the oscilloscope is registering each 2 triggers as a cylinder. The 3 groups of 4 triggers would represent the sequential pairing of cylinders 1-5, 3-6, and 2-4. At least, that’s what I’m basing my trigger info on lol. Ultimately the crank pattern for the 4.0 HO is 18-2-2-2

One caveat I had not anticipated was that this particular ecu mode cannot natively control the GM style IAC valve in the throttle body. Even the stock ecu never did a great job of that. So I removed the throttle body set screw and flipped it over for easy access from above. Set my idle to a nice 850-900 without load. Since our temps are always the same I don’t need any extra idle anyways. Actually works remarkably well even on the stock injection! So if you iac is acting up try this. I’ve done this with motor sports vehicle before as well with great results.

Well it’s time to just go for it and build the ecu harness. I tested the ecu today as I wanted to be sure it would recognize the stock 4.0 HO cam/crank triggers. How these triggers functioned was always a bit odd to me as I’m used to seeing a missing tooth flywheel that would always indicate #1 cylinder is at TDC. The cam sensor would then tell you if it was on the compression or exhaust stroke. The HO flywheel is nothing like that. It has 3 sets of 4 holes in Y pattern on the flywheel/flex plate. Here is what that looks like: The cam turns only 1 Revolution for every 2 revolutions (720*) of crankshaft rotation. Because of this, the cam sensor can help you determine when the engine is at TDC on the compression stroke. Here is what the HO cam sensor looks like on a 94-99 distributor: It’s worth noting that all the HO years ultimately give the same signal. Even the later model distributorless systems introduced in 99 had a cam sensor that fits in that same distributor hole to give the ecu TDC timing. This new ecu can handle sequential 6 cyl spark using either coil on plug or a wasted spark system using that later model sensor. You could just leave the old distributor in also but I like the cleaner look of the 99-03 cam sensors. 04-06 had a bit different looking and somewhat failure prone cam sensor/opda unit. So I wanted to make sure the ecu would read these stock sensors before I moved forward. It does! Here is the oscilloscope it was reading from the cam and crank triggers: the top readings in orange are the crank trigger and they correspond to the holes on the tone ring on the flywheel/flex plate. Every 2 “spikes” represent 1 cylinder. The lower blue line is the cam sensor. You’ll see that it goes low for 12 crank triggers and then goes high for 12 crank triggers. Every 2 crank triggers is a cylinder event. It’s pretty simple when you think about it. 1,5 3,6 2,4. The cam triggers high on compression stroke and triggers low on the exhaust stroke. Thus you can find TDC on either stroke at any given engine RPM. Note also that the original supply voltage for these sensors is 8v from the ecu bu I am supplying them with 5v from the new ecu and the readings are just fine.

Need the door lock cylinder clip/retainer for my 91. Somehow mine is gone and I can’t find it anywhere. Also need the coil electrical connector. It’s just the 2 wire connector that plugs into the coil. Should be the same for most all HO 4.0’s. The tab on mine broke off and it doesn’t hold on well anymore. Thanks!

On another note, the ecu and all wiring and adapters are in. Not sure exactly when I’m going to be installing it just yet but hopefully soon. Having a slight overfueling issue when trying to restart once the truck has been sitting a few minutes after driving. I suspect the fuel map for cts is off for the injectors I’m running. I have to start the truck and immediately open the throttle to clear out the fuel.

And here are some pics of the truck for kicks. You’ll notice there is no more body seam between the cab corners and cab back.

here are some of those pics:

I know some have successfully installed new seatbelts from both eBay and other online suppliers. I believe they were listed as fitting a 4dr XJ but are not oem. They look quite nice though

It would be nice if there were an insert for the cup side of the hinge to take out the side to side slack. I know the tailgate strap bumpers hep align that but it’s not quite enough to eliminate the slack.

@Pete M any chance we could get some more eyes on this post? Good info!

Yeah the step downs are only a few bucks on Amazon for a fully potted waterproof version. Actually just ordered a couple more for my stand alone project

Maybe stronger R&P than an original MJ 44 but not an HD 44 by any means. I suppose if you have an 86 mj and you want an oem upgrade. But if it’s just a strength perspective, I wouldn’t spend time hunting down an axle that only comes on one production year and will be hard to find and/or expensive. And if your going FSJ amc20 route than grab an Isuzu or passport D44 rear from a 98+ Which is a much stronger option not to mention easier to find and typically cheaper.

The bolt pattern is the same as that 95/96 booster. They were the same bolt pattern on XJ’s from 91-01. All 91+ boosters will require some slight mods to the brake pedal connection so your pre 91 brake light switch will work properly. Make sure to hold onto the little aluminum 1/4” spacer that’s behind your booster if you still have it. It will provide the spacing needed for the 97+ booster to clear the pinch seam on the firewall. I run an 01 booster and MC on my 91 MJ. Was a bolt on for me since i have the newer style brake light switch. However, before you go that route, could it be that you just need to replace the check valve in your existing booster?

Don’t think Tim is going to reply. Looks like he hasn’t been on the site in over 12 years. I’ve come across many amc 20’s in full size Jeeps. Decent axle but I wouldn’t spend much effort hunting one down.

Make sure to grab the shims also if you don’t have adjustable control arms.

The tps voltage input is 5v. You can get a nice little 12v to 5v step down transformer online. You should be able to nix the renix ecu and just use the tcu stand alone. A super nice albeit expensive option is a compushift tcu. Gives you full control over all shift points which may be very helpful in adjusting those shift points for a Diesel engine

Ill take some pictures of that setup from different angles for you.

Wondering if @Minuit has any insights on this circuit. Just getting the inputs and outputs mapped and setup in the software

Potting fully cured. Ecu on the way. I’ll be using some unused cavities on the 60 pin connector and adding the ignition outputs to the harness for the extra 2 coils (3 total coils driving 2 cyl each). If anyone has a simplified description about what the heck the difference is between the “ac request” and “ac select” inputs on the stock ecu are that would be perfect. I’ve studied the wiring harness diagrams and I don’t see what the difference is between the two. For now, I’m just going to setup the “ac request” input and wire in the “ac clutch activation” output. This ecu also has full alternator control which is a plus. Only thing I need to add now is a coil igniter/amplifier.

Potting curing

Just google “euramtec Comanche” and look for posts from this site. I’d do it myself if i had the time. Can’t remember what the euramtec part number is but it will pop up in one of those threads.

Here are some pics… Working on the stand alone ecu. Settled on MaxxECU Sport. I desoldered a harness connector from and old ecu I had laying around. I’m now adding pigtails to each terminal. The idea is to have my MaxxECU plug into the stock harness. I recently replaced my 60 pin harness connector as well with a new one from Mopar. At the moment I plan on just getting a plug and play setup working. I will eventually switch to a wasted spark system and delete the existing coil and distributor. The ecu is compatible with all stock cam and crank triggers and will even control the alternator field requires on obd1 setups. More info coming in the next few weeks.

Sounds good, please do.