Oyaji

. Nothing... short... of... brilliant! . I read in your post there you had thoughts of making... more than one? ;)

Anybody ever try (and succeed at) making his own fuel gauge sending unit, or modding one from another application?

Per the title. . Looking at getting a 1988 that is missing the fuel tank, so will also need fuel gauge sender and a fuel pump. I am not at all averse to cobbling something up. . One thing I thought of was going with any tank that would fit between the frame rails - a good and big one, like 40-50 gallons if available. To get away with that, I would need to relocate the exhaust pipe to the outer side the frame rail, and probably have it exit to the side somewhere ahead of the rear wheel (maybe cutting a round exit hole for the tailpipe through the lower bed valance). I'd still need clearance for the drive shaft, so such a tank would have to be either really shallow, or be saddle-shaped on the bottom with a "notch" for shaft clearance. I know it would be doubling my expense but if I could get them cheaply enough, dual tanks might be a desirable option. At minimum I would need stock fuel capacity. I only know of one MJ in a junkyard around here, and it is a 4 cylinder so I know the fuel pump wouldn't work for me because the '88 has an I-6 4.0 L. . Please put on your thinking caps and post up any solutions you have found or ideas you have. Thanks in advance.

The biggest thing you can do to improve economy is to tighten up your driving habits with an eye toward achieving better economy. . Beyond that there a number of tweaks you can do for improvements. Running tire pressure at the maximum reduces rolling resistance. Making sure of your wheel alignment not only potentially reduces drag but also extends tire life. Use of synthetic lubricants throughout your drive train reduces frictional losses by way of lower viscosity while retaining lubrication value (best check the experience of other owners on this for specifics regarding your application though). . Good maintenance of your vehicle counts for a lot. When I bought my 92 4x4/auto XJ, for example, the first thing I did was to go fill it up and start a logbook. My baseline highway fuel economy was only 14.5 MPG, so I went hunting for faults. First up were the plugs: not only were they terribly worn but 2 of them had broken center electrode insulators. Replacing them improved economy by 1.5 MPG. Next was removal of the catalytic converter... +2 MPG (if disallowed in your locale, replacing a plugged cat with a free-flowing metal substrate type would yield only slightly lower results). Wheel alignment gave a plus of 0.5 MPG, balancing the tires and running them at max pressure gave 1 more MPG. Tracking down a vibration that wasn't tires turned out to be a bad left front axle U-joint, that yielded another 0.5 MPG. There was something else I am forgetting, but ultimately I went from a baseline of 14.5 MPG (3 checks in a row from fill-up to fill-up, logged miles divided by gallons consumed) to a consistent 20.5 mighway miles per gallon over 115,000 miles. Dropping my cruise speed from 70 MPH to 55 bumped up economy to 23.5 MPG, too. . Adopting Cruiser's idea of advancing the timing may be a good one (should ask him for his results), but swapping injectors to some with a lower flow rate is not a good one. Doing so would just cause the ECU to compensate by widening the pulse width and deliver the same fuel consumption under closed-loop running (using oxygen sensor feedback), and under heavy load demand under open-loop running conditions (near wide-open throttle [WOT]) would not deliver sufficient fuel to maintain proper air/fuel mixture and might damage your engine. . If you are interested in pursuing fuel economy, I suggest hopping over to the ecomodder.com forum - there is a wealth of information to be had from like-minded people there, some of whom are quite expert on the subject. . Your fuel economy of 15-16 MPG is not really poor unless you drive like a grandpa already. I do, and I get 19.5 MPG under combined city/highway driving... but I do take a perverse pleasure in holding up traffic in the interest of maximizing fuel economy - especially when I keep passing the guys who are stopped at the next signal but who roared past me at WOT when leaving the previous one. I find I arrive at my destination at just about the same time as the guys who "drag-race" between traffic signals, but I do it on half the fuel. ;) . PS - Frank's question above about drive train details is one that needs to be answered in order to provide you with more complete advice... and you should provide tire size and type as well.

I'll take your comments under advisement - thank you for offering. Regarding proportioning valves: the idea is to reduce pressure to the rear wheels to avoid lockup, of course. Load in the rear allows more braking from the rear axle, but the Cherokee valve doesn't have a clue as to load. I don't know what is dialed in on them as a preset relief pressure, but at best and of necessity it is a compromise. Seems like an adjustable prop valve would be desirable for someone interested in maximizing brake performance there. That is a fine advantage of the Comanche load-sensing valve... provided it is properly adjusted. If brake performance is not what it should be on either vehicle, I reckon a hard look at the prop valving on them could yield some gains. Incidentally, it's pretty typical for rear shoes to last 3 times longer than front pads, even when the brake system is functioning optimally. It's just how it is, since so much of braking depends on the front axle. Braking performance is probably somewhere around 75% front/25% rear on Cherokees, with front bias even more pronounced on the (unloaded) Comanche. Lifts on either would raise the CG and potentially increase nosedive as well (depending on spring rate), further reducing the braking contribution from the rear axle. Since braking depends on load on the axle, you just cannot expect much rear braking from either vehicle. If the proportioning system is functioning properly, ABS cannot be expected to net any better results except under lockup conditions, and even then depending on whether the ABS modulating routine can actually outperform the driver (and with early-generation ABS, this is by no means certain). Reece146's and Eagle's comments about Chrysler's sampling rate and and hard braking are particularly apt here. (By the way - does anyone know what supplier provided the ABS system on Cherokees?) What I would be seeking in particular is to improve braking under panic-stopping conditions under a variety of load conditions, especially when pulling a loaded trailer. Traffic has gotten ten (or more) times heavier around here over the years, and unfortunately idiots on the road are not in short supply. It has become so bad these days that I have to pick and choose my times to tow a load to minimize risk. Anything I could do to improve safety is a plus; perhaps getting a better truck is the best option. All things considered, I am not averse to the idea of considering a later-generation better-performing ABS system from an entirely different truck as an option. It's just that I really do like the Comanche (for many reasons), and it seems that adopting the Cherokee ABS might be an easy way to go to achieve my goals. It's a shame I never tested any Cherokees equipped with ABS - I think some driving experience with some old ones would be worthwhile, provided I can get or make the opportunity. I do plan to do some reading about the specifics of that system, provided I can get my hands on the material. I'd also like to talk to some of the engineers who designed that system, if I can track any of them down and we can find the time and desire to talk shop...

Why would you need to reprogram anything? You would need to use the XJ axles, in order to get the tone rings, but the system works by sensing when the wheels stop turning. Why would it matter if the wheels are under an XJ or MJ chassis? Different wheelbase and load conditions, and possibly lift (if so equipped) would all combine to make a different baseline than the donor vehicle had. ABS calibration is quite a task in the design phase for every vehicle so equipped, and tweaking goes on for months for each vehicle before production starts (and sometimes for months afterwards, too!). All depends on the programming; it might compensate adequately for the differences between vehicles, but then again it might not. I am a pessimist by nature, and so before I dived in I would want to be sure I could cover all the bases before I start. I am also unfamiliar with the ABS as equipped on Cherokees. Early-generation ABS (and their early yaw control derivatives) on other vehicles was not that great; though some were better than others, I used to be able to out-brake (and out-handle) all of them on all the vehicles I tested in the 1990s. The main reason was the duration and frequency of the brake pulses (and possibly the modulation routine too), but a custom chip and reprogramming just might offer significant improvements for someone knowledgeable and patient enough to do such modifications. I have to ask myself if I am up to the task now, though.

If it had 172 miles on it instead of 172,000, then maybe... No, not even then, not for me. Even if it was a 91 or 92 4.0L with a thousand or less miles on it, I'd be on the fence - it would be more of a museum piece and I couldn't afford to just put it up and not drive and use it.

[edit: just noticed the above post made while I was composing this one and HAD to comment] WOULD YOU JUST LOOK AT THOSE LONG VELOCITY STACKS ON THOSE WEBERS!!! WOOOOOOOOT!!! My 914 cam has 285 degrees duration (Scat C-35), and, though not wild, is much in excess of the stock 234 degrees. It still makes great low-end torque with 4 barrels for 4 cylinders on individual intake runners - so much so that on dirt or gravel even when I release the clutch gently I still get some wheelspin at a 900 RPM idle. Just sayin'... I started out trying to save money on jets by getting just 3 sets total, setting aside the baseline jets untouched, keeping one set as a reserve, and using a jet reamer and micrometer to incrementally increase size until I got my working set dialed in. My local speed shop made me a deal that saved me much headache: they sent me home with their entire stock of jets, and told me to just pay them for the ones I used when I returned the rest. I was shocked to have to step up to from the baseline 1.15mm mainjets to 1.65s before I got it right! Their more-than-kind and trusting offer saved me immense headache and many many hours work hand-reaming, measuring, and polishing the orifices of my own (finish is important because it affects flow). During the years when Webers were popular that offer would have been unheard of, and that level of trust is even more astounding today. (I suppose that has to do more with the current low demand for carbs than with retention of traditional values and personal integrity.) I hope your jetting adventure will be as serendipitous and happy as was mine. I'll suggest that you be very methodical and take copious notes as you go; you'll probably overshoot and undershoot a number of times before you arrive at the ideal setup.

:hijack: As an aside, I've been toying with the idea of adapting an ABS system to a Comanche. I was thinking that a custom chip with one-off programming would be required. But it occurs to me that a Cherokee system might be a good place to start... Thoughts, anybody?

Maybe in the future, but for now just need as many reports of failure as possible. Some details would be nice, at least the year of manufacture for starters. If a bunch of people complain, I'll go ask my metallurgist contact how to proceed. As I mentioned before, I'd guess a metallurgical study would need to be made of the parking brake pawls to determine if they are within spec for hardness. There would probably be some sort of procedure to go through to disallow tampering with evidence as a possibility - I am sure he would know about that as it is part of his specialty. Just need to see how widespread the problem is, first. Post 'em up, guys - don't be shy!

There isn't much you had to do besides hooking up power and antenna. Since it powers up, you should probably start and end with your antenna connections, then.

You didn't by chance also have the spark plugs out too, while you were working on it? If you did, double-check the firing order of your plug wires...

Yes.

Thanks, Eagle. No manufacturer includes items or function without good reason. Cost is so much a factor in design and manufacturing that every single nut, bolt, washer, weld, and dab of sealer has a purpose, and wouldn't be there if it didn't. You can be sure that the A/C running with the defroster is no exception.

Oh yeah, forgot to mention - those carbs are gonna be LOUD through the air cleaners when you open 'er up, too! :)

Frontal area and coefficient of drag are the 2 numbers to pay attention to - weight only matters much in city driving. Since the advent of fuel injection (FI), power on tap is the main gain from newer engines, though better engine mapping and an eye towards continually improving efficiency has shown some improvement in economy. Variable valve timing allows better efficiency across a wider range of engine speed which allows better performance from a smaller engine (yielding weight savings elsewhere on the entire vehicle as well), but older FI engines still showed remarkable economy. Case in point is my brother's 1989 Honda CRX, which, even with its short legs that result from sporty overall gearing, still consistently returns 43 MPG at 70 MPH.

The carbs are what grabbed my attention. . I used to be well-familiar with the IDA and IDF Webers, and still run a pair of 40mm IDFs with 32mm primary venturis on my 2.0 liter 4-cylinder 914 (that's 4 independent barrels, 1 for each of the 4 cylinders). [edit - added pic and vid - found these on Google and added them to illustrate] The really great thing about Webers is that when you have them set up on individual intake runners with 1 barrel per cylinder, they allow independent tuning for each cylinder. If you are patient and have access to a full range of jets, you can tune the engine so that it is pulling to the max. Also, with that level of tunability, you don't have to merely settle for great power at the top end whereas low-end drivability suffers - to the contrary, Webers will tame an engine so that even with wild cams you can get street performance out of it. This is really unusual for carbs, and is part of what gave Webers such a stellar reputation back in the day. . The other part that made Webers shine is how much they flow. Coupled with a good intake manifold, tuned scavenging exhaust headers, and match porting, the damn things will flow enough to unleash the top-end power potential of any engine... which is doubtless why they were original equipment on Porsches, Maseratis, Lamborghinis, and Ferraris (among many others) back in the day. . The downside is that, being carbs, they have no idea about the power demand you are placing on the engine, and they just dump fuel in analog of the flow and vacuum the engine generates regardless of load. This means they will cost you fuel (probably a third more than you would use on the same fuel-injected engine) plus have a tendency to carbon-foul your plugs when the engine isn't running fast enough to keep them hot and clear. You should tune the carbs on the rich side of the stoichiometric ideal for power (~ 12.5-13.0 : 1), but for street if you lean it out a bit to keep the plugs from fouling and your fuel economy somewhat more tolerable (as if! *lol*) then power suffers and you run into ping problems too. Either way, you will never pass an emissions test, and you will have to remove your catalytic converter (and a lot of other stuff). Interestingly, you can get an air/fuel ratio gauge that uses your oxygen sensor... that and multiple sets of spark plugs (plus a sandblaster-type spark plug cleaner) to read between jetting changes will help a lot getting the carbs dialed in. . I am not familiar with the particular setup you have traded for, but just by looking at them I can see you won't be getting the full potential out of them that you would with triple side-draft 2-barrels breathing through a 6-independent-tube intake... [edit - added pic] ... but if you have the right mindset, what you have got should give you many hours of enjoyment both getting and keeping it set up properly (I highly recommend investing in a 4-tube mercury column manometer to assist in synchronizing them). ;) . Also, you get to become a Weber snob, plus you have an excuse to be blipping your throttle when idling (like at traffic signals) to keep your plugs from fouling! :D

And THAT reminds me of the "names" of the flight crew of that Asiana Airlines flight that came up short of the runway (at San Francisco, wasn't it?): Sum Ting Wong, Wi Tu Lo, Ho Lee Fuk, and Bang Ding Ow! http://www.youtube.com/watch?v=nFKd7BDNO-U

Need to keep in mind this effort will be to get dysfunctional parking brakes repaired under recall. Anything else that might accrue is incidental. . With that in mind, we need to have reports with a brief description of incidents of parking brake failure. Once it seems a general and similar failure is commonplace, the next step will be to see if other parties (like my metallurgist contact and NHTSA) are willing to carry this to the next level. . Post up how your parking brakes work (or how they don't work) for your MJs of any and all years, guys.

If the manifold bolts were loose, you'd be having trouble noticing the smoke because you would be concentrating on the all the noise instead!

40 miles! Good deal - sounds like you got it whupped then. . I'm curious - was that trip before or after your transmission fix? I'm wondering if the transmission problem was part of the overheating problem?

:agree: Just go drive it as normal (an hour at highways speeds should do it) and see if the spilled oil doesn't all just burn off enough to stop smoking. Keep an eye on your oil pressure gauge (just like you always do, right? ;)) and you'll be safe enough. Wouldn't hurt to keep an eye out for leaks elsewhere, too.

Awwwww hell yeah! Congratulations! Now need to see if it is done with the overheating problem... ;)

Could definitely be that. Was talking to them in the shop so it was loud. The guy even told me that tire balance has no chance of causing wobble in the front end, but I know that it does because new tires fixed my wobble for a little bit until they got wore in. Sure it does - tires out of balance can provide the initial wobble input that gets amplified by other front end faults. There is often a trigger event though, like hitting a bump, that sets the stage by cocking all the slack in the front end to one side, then the tire imbalance wobble starts oscillating harmonically to the limit of travel allowed by all worn suspension components. (There are other harmonics in the front suspension that can oscillate independently of tires, though, but tires are the initial big offender here.) Balancing your tires of course will not repair the faults in your front end, but it will reduce or eliminate "death wobble" for some amount of time.

Also the 86-92 MJs had the same part number for the parking brake assembly throughout the years, 52000803. Usually when a subpart modification or design change is made to an assembly, the part number changes to indicate the mod or change. That right there is some pretty damning evidence when combined with the other reports in this thread of MJs of all years experiencing the same parking brake failure. I think this is worth pursuing, especially by the 2 guys (so far) who reported losses: 1 MJ that ended up with a smashed front end, and the other who not only had his truck totaled but also got his arm mangled in the bargain. Need to collect all reports of failure here, then bundle them and ask NHTSA to investigate. The fact that the same part number is used across all years of production is the key. A metalurgical study of failed parts would clinch the deal, I think, and set the stage for a class-action lawsuit. Every law firm in the country that handles such actions would be salivating over the thought of getting a slice of that pie.