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1989 Jeep YJ Wrangler Sahara 4.2L Engine Missing Parts


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#1 Alberto_YJ

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Posted 07 May 2014 - 05:35 PM

Hi, my name is Alberto, this is my first post here. Recently bought a Sahara Edition YJ 89. It has a 3 speed automatic transmission. I did a trip of about 700 miles from the city where I bought it. At the beginning I was at 1700 meter over the sea level, went almost 3,000 meter over the sea level where I felt a total loss of power, even at full throttle it didn't raise more than 2,500 rpm.

 

I'm at sea level right now... when going lower the engine was feeling too much powerful and now it seems to run like a dragster. The bad thing is that the fuel consumption is too high. During the trip the floor was getting really hot, under the rear seat on the right side the paint looks burned and the carpet a little melted, the RR wheel well  is melted...

 

So after the trip I've been reading a lot about this engine and found that there are a lot of things that have been replaced and removed. I will like to have this engine working as it should and as stock as possible. 

 

To start with, there are two hose connections under the air cleaner base, found those openings without hose or plugs, completely open to the atmosphere. Some wires are hanging out, some vacuum hoses disconnected, don't know if the PCV valves are the right ones, the heater hoses are not in place, and at the thermostat housing it seems to be a plug sealing where one of those hoses should be connected. There is a vacuum reservoir under the battery that only has one hose connected, the other one under the water reservoir seems to be with all the hoses connected.

 

Where the exhaust pipe is leaving the engine to the cat, there is an opening at the side that is sealed.  The fuel filter is not the stock one, it only has one input and one output instead of 3 total, in addition is not on the right side close to the carb, but is down on the left side next to the fuel pump.  I have a plastic fuel tank, I think is 20 gal. maybe that worried me due to the overheating that the exhaust is experiencing.

 

Is the rear axle upside down? or is the plug right at that height? I've checked oil level on both axles and seems to be a little low, the rear one is dark brown. I'm feeling a strange noise when I drive very slow, like human walking speed, there is a knock noise from the rear and I feel the car moving side way when it sound, suspecting that there is something wrong in the diff gears or the bearings.

 

Look at the pictures and please help me find out that are the things that I'm missing, if you think that more detailed pictures are needed to identify something else I can take some more...Thanks in advance.

 

Regards from Cartagena, Colombia.

 

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#2 Moses Ludel

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Posted 07 May 2014 - 09:54 PM

Welcome to the forums, Alberto! Your photos are very helpful, and so is your description of the problems...Here are some observations:

 

1) The floor getting hot and the high altitude lack of performance are related to the catalytic converter and exhaust system.  This engine uses a Pulse Air catalytic converter, and the air tube from the exhaust head pipe to the catalytic converter has been eliminated.  This prevents complete burn in the catalytic converter and also eliminates the pulse air system's cooling effect at the converter.  (Lack of a Pulse Air hookup would fail a U.S. emissions test.)  In your case, the catalytic converter, if still intact, is either not functioning properly or is likely getting extremely hot from a rich fuel mixture and the missing Pulse Air function.  (Tip: The Pulse Air catalytic converter should have an air inlet pipe that works with the pulse tube system.)

 

2) You have valid concern about the exhaust heat and the plastic fuel tank.  In many cases, the heat you describe melts the fuel tank.  In a worst case scenario, this could cause fuel to leak onto a super hot exhaust pipe and either set the vehicle on fire or cause the tank to explode.  From the tailpipe's "rich" burn signs (black and sooty at the exit), plus your poor fuel mileage, it's quite possible that the carburetor is running way too rich.  This could be either a carburetor issue or the wide open throttle/limp mode may be operating all the time due to a wiring or vacuum circuit defect or tampering. 

 

3) Click on this link for the detailed 4.2L BBD carburetor rebuild articles at the magazine.  The BBD carburetor requires careful attention to detail during a rebuild, Alberto.  You will also find a number of articles related to 4.2L engine tune and troubleshooting at the Search box keyword "BBD".  To save you time, here is a link to the lengthy list at the magazine:  http://www.4wdmechan...rch-results.php

 

4) The previous owner of your Jeep Wrangler apparently disconnected and eliminated a number of vacuum hose and coolant features.  Here are the vacuum circuit diagrams for your engine, you can compare what you have with these PDF diagrams: 1) for the 1989 4.2L Jeep Wrangler with a manual transmission Attached File  YJ Wrangler 4.2L Vacuum Diagram.pdf   554.59KB   7 downloads and 2) Attached File  1989 Wrangler 4.2L Engine Vacuum Auto Trans.pdf   40.47KB   10 downloads for your automatic transmission equipped model.

 

Note: The emission and carburetor circuits are closely linked together on this 4.2L engine.  The ignition is somewhat independent but also works through vacuum, coolant temp and ECU timing controls.  This is a complex system, the reason many owners convert to EFI.  Howell, Mopar and MSD have EFI systems as you will see in the article on the MSD Atomic EFI conversion for a 4.2L. (Click on the link—there are five detailed pages to this article!)  Howell is the easiest system to install and cost effective if you want to do a conversion to EFI.  You can restore the BBD carburetor, vacuum circuits, ECU circuits and such; however, it will take time and patience to sort out all of the modifications and tampering that the previous owner has done to this engine's vacuum, emissions and coolant circuits.

 

5)  The rear diff cover looks normal, it does seem like a low fill plug, but that's the Dana 35 design.  The noise and hop sound like a factory limited slip differential that's either defective or in need of friction modifier and an oil change.  Remove the diff cover to drain, do a thorough inspection, and if there is a factory multi-plate Spicer limited slip, there should be a tag specifying use of special lube or lube plus friction modifier.  Friction modifier breaks down, and fresh oil and modifier often eliminates clutch plate chatter and wheel hopping.

 

6)  Your engine's fuel filter should have three attachment points and fuel lines.  The third line returns excess fuel pump volume to the fuel tank.  This serves two vital functions: 1) reducing load on the carburetor needle and seat and 2) lowering the risk of fuel vapor lock by keeping fuel moving and not stagnating in hot lines at the engine.  Vapor lock is a common phenomenon on mechanical fuel pump systems without a third pipe (fuel return) to the tank.  High altitude driving and hot under hood or exhaust temperatures increase the risk of fuel vapor lock.  You need to restore the 3-line system, the engine could have been experiencing vapor lock at higher altitudes under extreme load.

 

Worth noting, poor engine performance at 3000 meters is also a function of altitude.  A naturally aspirated (no supercharger or turbocharger) engine loses approximately 3-5% of its horsepower per 1000 feet of elevation.  You're talking about 9,000-plus feet above sea level, so that could be as much horsepower loss as 45%!  This would create a very rich burn condition on a carbureted engine, too, since the carburetor has fixed jet sizing.  There is a primitive "wide open throttle" (WOT) fuel enrichment mode, which is not intended to compensate for altitude. 

 

You have an oxygen sensor on the 4.2L engine, designed to help regulate fuel enrichment (to a very limited degree) and spark timing, primarily for tailpipe emissions purposes.  It does not change the air/fuel ratio constantly like an oxygen sensor helps to do on an EFI or MPI system with electronic fuel injection.  In the U.S., improved high altitude operation is another reason why 4.2L Jeep owners convert from the BBD carburetor to an EFI system.  EFI will instantly compensate for altitude changes and air/fuel ratio demands.

 

This should get you started on troubleshooting and evaluating your Jeep's exhaust system, fuel circuit, vacuum circuits and carburetor.  Ask questions as needed, we can take this further.

 

Trust this helps, Alberto...

 

Moses



#3 Alberto_YJ

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Posted 08 May 2014 - 08:47 AM

Moses, Thank you very much for the input...I'll start removing the diff covers and replacing the fluid if there is nothing broken, actually there is a leak on the front diff housing, I thing that resealing could stop the leak. Do you recommend use of silicone or gasket for diffs? or both?

 

Another issue is that the shift selector lever is not locking in Neutral, Drive, 3...etc. It only locks in Park position. I'm missing the indicator needle, it came with a bended wire with red tape as indicator, it does work but I would like to see a picture of the factory one to see if I can make one similar...

 

About the heat from the catalytic converter and fuel consumption it seems to be a lot of work to get the whole system working as it should, as it involves the exhaust system, carb and vacuum.

 

I need to start writing down a list of parts that I need and I can not find in my country. So I can improve the engine's performance.

 

Thanks for sharing your knowledge.

 

Regards.



#4 Moses Ludel

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Posted 08 May 2014 - 11:45 AM

You're welcome, Alberto...The fuel/carburetor, emissions system and ECU is so interconnected that the whole system must be restored in order to function properly.  This will take time and careful evaluation. 

 

It's unfortunate that previous owners and some mechanics believe that it is useful to "disconnect" and discard various components.  In tampering like this, the function of the entire system suffers.  "Restoration" seems the only real fix with this complex stock system—or an EFI conversion like the Howell Engineering TBI package if you can afford it.  (Click on the link for details.)

 

As for the diff cover sealing, silicone RTV works well.  Use a type recommended for exposure to gear lube.  Do not overcoat, apply a uniform bead that will smooth out evenly and seal properly.  (3/32" to 1/8" bead size is plenty.)  Make sure the diff cover is flat around the bolt holes, and torque the bolts snugly to specification and evenly.  Do not over torque the bolts, or you will indent the cover at the bolt holes and risk a leak.  Snug all bolts to just seat the cover, then let the RTV set up slightly before tightening bolts to final torque.

 

There is no need for a gasket if you do this properly; in fact, average quality cut paper gaskets are more prone to leaking than silicone RTV alone.  The later factory use of RTV instead of a cut gasket suggests that RTV works better.  (An exception would be rubber gaskets like those found on the Ram truck's AAM axles.  These work very well.)  I use RTV for Jeep diff covers.

 

Keep us posted, Alberto, enjoy your Wrangler and be safe in your travels!

 

Moses



#5 Alberto_YJ

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Posted 08 May 2014 - 01:16 PM

Actually I can afford the conversion kit, but I really like to keep the vehicles as stock as possible, I like to make small modifications, eg. some fog lights that match the YJ style, some lift to give it a better off-road look, I really like to keep the 80's style things that you can add, a modern stereo will be necessary as the stock one is a cassette player hehe...

 

Mechanically I know that the engine can be more efficient with a conversion but I really like the carb and the idea that is "easier" to service. It's really cool to see a machine from '89 that can be close in mileage to my past '09 Toyota LC90, even with all the electronics improvements and sensors that should increase the efficiency.... It has a 2.7L 4 Cyl. that was running around 18 miles per gal at maximum. You can not compare the power of that 2.7L with the 4.2L that the YJ has and almost the same mileage rate...

 

I think some mechanics suggest to disconnect things and they argue that there is no difference doing that, and in addition the owner will save money avoiding spare parts purchase... anyway, my task now is to restore it to a good efficiency level, environmentally and economically talking.

 

I Will try to do the diffs inspection and fluid replacement and will post some pictures.

 

Thanks again.



#6 Moses Ludel

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Posted 09 May 2014 - 03:21 PM

Alberto, you'll find the BBD carburetor step-by-step article at the magazine helpful.  The vacuum diagrams, too.  As you proceed with the restoration, we can fill in other "factory" details.  Since you're willing to do this work, I know that you will be thorough.  Each of these systems overlap, and the only "right" way is a restoration to original equipment performance as you suggest...You always have the option of an EFI conversion if you discover that it is cost effective or if you simply cannot find the many parts you need for the restoration.

 

I am pleased with your enthusiasm and believe you will draw the correct conclusions about whether to restore or not, Alberto.  Looking forward to pictures of the Jeep.  The forums' Garage Photo Gallery would be a good place to share.

 

Moses



#7 Alberto_YJ

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Posted 10 May 2014 - 05:03 AM

Good morning Moses, yesterday I did another inspection to draw a sketch as the Vacuum System is now... Here are the results. Some pictures to clarify what the drawing is showing. Could you please let me know a good website where I can buy new Vacuum hoses, check and delay valves? which ones will meet the factory specs? which internal diameter hoses I should look for? which filter to install in the PCV rear valve?

 

There is a picture where you can see the Air cleaner cover, It has a crushed connector, What is this one for? 

There is a connection under the steper motor that is not connected, is that the one that goes to the EVAP SYS VAC MOTOR?

 

What I see is that the last mechanic that worked on this engine just plugged any hose where it reached...

 

Thank you and have a good day...Regards.

 

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#8 Moses Ludel

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Posted 10 May 2014 - 08:33 AM

In the U.S., NAPA retail auto parts stores have always been helpful.  Car Quest also has extensive catalogs of individual parts.  NAPA's Echlin line and catalogs are a good source.  Do you have retail chain stores like these in Colombia?  Is there an AC/Delco, Motorcraft or Bosch warehouse?  These would all be sources for the more generic parts like check valves and vacuum delay valves.  Otherwise, your best source, and many do this in the U.S. with older engines and emission control parts, would be recycling yards ("wrecking yards") that have older Jeep vehicles for dismantling and used parts sales.

 

The vacuum hoses should be the easiest items to find, as these hoses are "universal" and come in specific sizes for the diameter of the vacuum nipples and pipes.  A vernier caliper (even an inexpensive plastic one) is helpful for determining the correct diameter needed.  You want the hose to fit snugly on the pipe or vacuum nipple, so some experimenting with samples of vacuum line would be helpful.  In the PDF I have provided below, the Mopar listings show actual vacuum and fuel hose sizes for the various locations on your engine and vehicle.  These measurements are for bulk hose that you can buy locally.

 

To save you a great deal of time on your Jeep 4.2L Wrangler project, I combed through the factory Mopar parts catalogs for your model era.  I gleaned out pages that provide both detailed illustrations and also the part numbers.  You can see the relationship of the parts. 

 

Some (very few) of these parts are still available from Chrysler/Mopar.  The Mopar part numbers will help you cross-reference to other manufacturers that may still offer the parts.  Hose sizes are noted in "I.D." (inside diameter) and shown as "bulk" source.  This means they are generic and can be purchased as bulk hose for vacuum or fuel hose in these sizes. 

 

Make sure you use hose that is specified as vacuum or fuel grade.  Always use fuel-grade hose for fuel lines or for lines exposed to fuel vapors.  Your 4.2L Wrangler with carburetion does not require fuel injection rated pressure hose.  (If you convert to EFI, you must upgrade the fuel supply line hose for the added fuel pressure.)

 

Note:  The fuel tank for your vehicle is either 14.5 or 20 gallon.  The 2.5L TBI/EFI engine uses an electric pump in the tank, your 4.2L carbureted engine does not.  At the tank, your Jeep has only the fuel gauge module without the electric pump unit. 

 

This will speed your search along.  Both the PDF text and the images can be "zoomed-in" for great detail.  I trust this will make your project much easier.  You can determine what you have, what you need and the part numbers for each item. 

 

In the page footnotes and model references, Mopar labels your Jeep YJ Wrangler as a type "81".  I am unclear whether your vehicle was for U.S. (North America), Canada or the export market.  In some cases I provided sets of information for both U.S. and export market vehicles.  You will need to compare the illustrations with your vehicle's actual equipment:

 

Attached File  4.2L YJ Wrangler Fuel & Emissions Systems.pdf   373.29KB   8 downloads

 

From experience, I know that if you do not have this "big picture" information, the project can become very challenging.  With the extensive information provided in the PDF, you will be able to identify the parts you have and those you need.  At that point, you can try to source the parts by part numbers or from generic sources.  You will discover what is still available as new replacement parts.  You will also know the relationship of the parts and how they fit together.

 

I trust this helps, Alberto...

 

Moses



#9 Alberto_YJ

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Posted 10 May 2014 - 11:00 AM

Of course it helps much more than what you can imagine, I want to thank you for sharing all this information that is not easy to get in short time... I hope I can take good pictures when performing all this restoration to share them and retrieve some of your help.

 

That last PDF has really detailed and accurate diagrams, very helpful. I'm sure I can find some hoses and parts here, but I will need to order some more, and it will be easy to order almost all from a single vendor.

 

Will keep you posted.

 

Thanks a lot.



#10 Moses Ludel

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Posted 10 May 2014 - 11:27 AM

You're very welcome, Alberto.  These kinds of issues come up frequently for restorers of the 1981-90 Jeep CJ and YJ Wrangler models with the 4.2L inline six-cylinder engine.  In the U.S., it is often a state-required emission inspection that turns up the "troubles" with the emissions and fuel system...I trust that the information provided in the PDF will help you and many other Jeep members and guests at these forums. 

 

Colombia must be a wonderful country for four-wheel drive access.  You mention "3000 meters" elevation, and that is much like the Sierra Nevada Mountains near our home.  Snow, permanent snow packs on the north slopes, this can be great country.  At Colombia, you have access to the Pacific Ocean, the Caribbean Sea, Ecuador, Panama, Venezuela, Peru and Brazil!  Lots of rivers and mountains, too.  I imagine that the magazine's Honda XR650R dirt motorcycle would be a great way to explore Colombia. 

 

Photos would be great with your Jeep at these kinds of backdrops...Please share photos when you can.  Enjoy your 1989 Wrangler Sahara, Alberto.

 

Moses




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