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Jeep YJ Wrangler 4.2L Really Hard to Start

4x4 repairs mechanical tips

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#1 Alberto_YJ

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Posted 20 May 2014 - 02:05 PM

Moses, a friend of mine is having a hard time with his YJ when he tries to start the engine.  He said that some times take more than 10 attempts cranking the engine but it wont run. When we had luck and get the engine running, it suddenly dies when driving, becoming a critical safety issue as it loses power steering and brake boost.

 

A mechanic took the ignition components to a lab for testing, he said that everything is OK. (Coil, Distributor, Wires and Ignition module).

 

Please share some of your wisdom that can help him to find where the problem is. ;)

 

Thanks in advance.



#2 Moses Ludel

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Posted 20 May 2014 - 03:35 PM

In my Jeep Owner's Bible and other books and writing, I break down engine troubleshooting to basics.  First, the engine must meet these four criteria before you consider tuning:

 

1) Normal compression at each cylinder.

2) Correct valve lift at each valve.

3) Correct valve timing.

4) Normal oil pressure and no engine knocks.

 

If the engine meets these basics, then any problem related to starting would be outside the "long block" (the block assembly with all internal parts and the cylinder head with all valve mechanism pieces). 

 

There must be no intake manifold leaks or vacuum leaks at the carburetor base gasket, throttle shaft and vacuum circuits or EGR valve.  Vacuum leaks can be tested with the engine idling and use of a lower-volatility penetrant like WD40.  (Warning: Avoid spraying this on high heat surfaces or near sparks!)  A light mist sprayed at the fittings, intake manifold gasket, the carburetor base gasket and near the throttle shaft will cause engine speed to change if there is a vacuum leak.

 

Now we can address "tune issues".  The tune must meet these basic requirements: 

 

1) Adequate fuel supply, both fuel volume and pressure. 

2) Adequate spark and ignition at the correct time.

3) Normal air/fuel mixtures from the carburetor.

 

Breaking these tune needs down to trouble areas, the fuel supply must provide enough gasoline to the carburetor.  Poor fuel supply to the carburetor can be caused by a clogged tank sock, a dirty/clogged fuel filter, a defective fuel pump or a camshaft fuel pump lobe that is flat. 

 

Overall fuel flow to the carburetor can be tested with a "T" fitting placed at the carburetor side of the fuel filter.  The pump can be tested by cranking the engine with the coil wire removed (completely) from the coil and distributor cap.  With a fuel pressure test gauge attached, you can check the pressure at the "T".  Add a piece of fuel hose to the "T", and you can test fuel volume by running fuel into a safe container (away from heat or sparks).  If pressure and volume test low, move to the fuel pump side of the filter and repeat your tests.  Normal pressure and volume at the pump side of the filter means a clogged fuel filter. 

 

Note: If you need to know the fuel pump pressure and volume required, I can furnish these details. 

 

Air/fuel mixtures are usually either correct or not with a carburetor.  If the BBD Carter has a Sole-Vac metering system, however, a defective Sole-Vac system can throw off the A/F ratios.  (Non-U.S. versions of the BBD may not have this setup.)  A sticking carburetor needle or low float height can also create fuel supply or mixture issues—and fuel starvation.  I would look at the fuel filter and pump volume first.

 

See my BBD Carter rebuild details at the magazine: http://www.4wdmechan...Carburetor.html.  There are many details and additional carburetor tuning comments at this illustrated article. 

 

Spark, as you share, should not be an issue here.  If you do not find a problem with the fuel side troubleshooting, we can go into ignition troubleshooting.  The magazine has a number of 4.2L carburetor, tuning and EFI conversion articles to study.  Type these words into the Search box:  Carter BBD.

 

Lastly, don't overlook checking the spark plugs for either a rich or lean condition, gasoline fouling and other signs.  If the engine won't start, turn off the ignition and remove a spark plug.  (Protect your hands from heat!)  Look for a wet plug, sooty plug or completely dry plug, each is a clue...

 

Moses



#3 Alberto_YJ

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Posted 26 May 2014 - 04:39 PM

Hi Moses, finally a good mechanic found the problem... It was something stuck inside the carburetor, he fixed the problem but said that it is better to rebuild the entire carb. 

My friend is checking his carb for the ID number, Mine has a big 4 and 6-2373 upside down, I've looked to a rebuild kit but I'm not sure which one will fit.

 

Do you have any suggestions for this.

 

Thanks in advance.



#4 Moses Ludel

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Posted 26 May 2014 - 05:24 PM

Glad you found the problem source, Alberto...You should have no problem finding a rebuild kit, and there should be an identification tag (triangle shaped) on the carburetor to confirm the model number.  There were U.S., Canadian, Egyptian and Venezuelan applications.  Look at the build sticker for your Jeep and confirm the market of origin.

 

For identifying your carburetor and any parts you need, here is the factory parts listing and illustrations:

 

Attached File  YJ Wrangler 4.2L Carburetor Details.pdf   91.5KB   6 downloads

 

The part numbers will help, and the illustrations will be of use to your mechanic.  So will my step by step rebuild instructions for the 4.2L Carter BBD carburetor.  These steps are at the magazine.

 

Moses



#5 Alberto_YJ

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Posted 27 May 2014 - 03:55 AM

Thanks for the information Moses, actually we are missing that tag, I've tried to find the tag but there is no tag on my carb or my friend's one. Is the number that I gave you saying something about the carb?

 

Is a 2BBL Carter for sure, but is there too much difference between the models for the rebuild kit? or there is a kit that fits all of them?

 

Regards, have a good day.



#6 Moses Ludel

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Posted 27 May 2014 - 07:33 AM

Alberto...Most carburetor kits have wide coverage.  A BBD Carter kit often fits a variety of applications.  To help determine your carburetor, look for items #25 and #26 in the Mopar parts breakout that I shared.  Does your carburetor, or your friend's BBD, have these parts?  This is a Sole-Vac system for the North American emissions applications.

 

Also, I commented that your build stickers (should be on the door tub sills, forward, driver's side) will indicate the market for these Jeep vehicles.  Determine your Jeep's original market, that will help with parts identification.  The Mopar list shows several parts that fit specific market engines. 

 

At a quick glance, the common "types" for your Jeep year and engine, each a BBD Carter, would be 8383, 8384, 8394 or 8366.  Do you have the Sole-Vac system with stepper motor?  This is carburetor #8383, #8394 or #8384.  The 8383, 8394 and 8384 are common North American applications.  The 8366 (no stepper motor for Sole-Vac) is Venezuelan.  For which market was your Jeep built?

 

The vehicle build date and market will determine which carburetor originally came on the engine.  As for carburetor rebuild kits, Echlin is my brand of choice, and the NAPA/Echlin kit fits every BBD Carter carburetor used on a 1989 YJ Jeep Wrangler, regardless of the market.  Here is the NAPA kit description:  http://www.napaonlin...207B_0064194887.  In NAPA's system, the part number is MPF 31207B.  (Other kit makers use different part numbers.)   As you will see, these kits have enough gaskets for each of the variations.  There are many aftermarket carburetor kit sources online.  All kits that I found fit a range of Jeep/Carter BBD 4.2L engines.

 

Also, here is a very useful catalog for restoring both your fuel and emission system.  It is the actual Echlin catalog. (NAPA stores at North America handle Echlin.  You may have other sources for Echlin products.)  You want to restore your engine's fuel and emissions features, and this can help:  http://www.napaechli...B_NA980_HQr.pdf

 

Moses



#7 Alberto_YJ

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Posted 27 May 2014 - 10:10 AM

Moses, I don't know how you can retrieve all that helpful information, I'm very grateful.

 

About the carburetor, mine has the stepper motor and sole-vac system. From the VIN number I can decode that the wrangler was assembled in Brampton, Ontario...The VIN decoders that I've seen only have the number 1 for the first digit, Indicating United States... Mine is starting with number 2. I have a concern about the engine because my VIN number has a T instead of an M that it should have regarding the year (89) that is a K on my VIN#, not an L for (90).

 

Anyway, now I have cleared my question about which rebuild kit to order.  It has been very helpful that NAPA catalog that you have shared as there are some vacuum valves that I'm missing and didn't find a source to buy them, but there are some of those that they do not have listed. Don't know if they are hard to get.

 

By now I've identified and founded: 2-950 and 2-1015 valves...

 

Still trying to hunt the rest of the valves that I'm missing for the Pulse Air System and vacuum system for restoring...

 

 

Thank you again. Regards.



#8 Moses Ludel

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Posted 27 May 2014 - 11:09 AM

You're welcome, Alberto.  I have worked at many levels within the automotive industry, including dealership and aftermarket parts and service departments and machine shops.  This helps when finding data and information.  I'm pleased that you and other Jeep owners can benefit.

 

Here is the Mopar official VIN decoder for the early Jeep YJ 4.2L Wrangler years (1987-90):

 

Attached File  Jeep YJ Wrangler VIN Decoding.pdf   64.39KB   5 downloads

 

For 1989 and 1990, the "T" and "M" in the 8th position of the VIN (see the chart) does indicate a 4.2L unleaded fuel engine.  Looks like you have the appropriate engine for the chassis.  And yes, the original build was for the Canadian market, not Venezuela, which explains the Sole-Vac system and stepper motor. 

 

You'll find the attached chart helpful, this is what Mopar parts personnel used to identify vehicles, markets, and the right parts for customers and service personnel.  I thought the Echlin catalog would be useful, too.  The illustrations and details provide items that can interchange and meet your vehicle's needs. 

 

Use the NAPA online catalog, too.  See the parts listed for your specific Jeep year, model and engine. 

 

Your "library" is growing!  In addition to the internet, my print resource library consists of four six-foot tall bookcases lined with shop manuals and other automotive data dating back to 1917.  I constantly research for my journalism, books and other publishing outlets—and today, even for HD video how-to productions.

 

Moses





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