Wrangler a bit hard to start - JeepForum.com
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post #1 of 22 Old 07-11-2020, 10:16 PM Thread Starter
JohnW63
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Wrangler a bit hard to start

After getting the wires and wipers and fuel pump and all the other issues straightened out, I've gone down the tune-up road. Replaced the plugs, distributor cap and rotor , cleaned out the throttle body, and put some Lucas injector cleaner in the tank. The Jeep still doesn't fire up like I want it. Most of the time, it takes a try or two of cranking it to fire up. On race occasions,it will fire up right off.



I'm trying to figure out what is next. The plug wires are original 1992 ones. I could change those. Anyone know the resistance values I should see on them ? How does the engine set a " choke " fuel mixture when cold starting ? Is there a sensor I need to clean or check ? It runs fine once it starts up. It's a 4.0 fuel injected engine. It should fire up like a modern car, I would think.

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post #2 of 22 Old 07-12-2020, 05:03 AM
fishadventure
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Look up the threads on capacitors in the ECU to eliminate that possibility. Old capacitors giving extended cranking isn’t unusual and as YJs get older I suspect it will become more common as time goes on.

You say you did tuneup stuff. Plug wires are part a tuneup. Good one’s aren’t that expensive- $30-$80 on amazonian. Air filter, some throttle body spray cleaner, clean or check battery and block connections, etc. Use plain old copper Champion plugs as the former favorites have become junk and and aren’t even assembled correctly for the last two sets I bought. The Japanese brands and the more expensive fancy modern plugs don’t usually provide good results in a YJ.

Mpfi and tbi don’t ‘choke’ actually. They use a static base map to send fuel down the intake in a richer condition than it would at operating temperature. As the motor warms up the ecu starts listening to the sensors and based on the O2 sensor it begins to select fuel delivery volume, going full-ecu control that is based on the split-second information.

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #3 of 22 Old 07-12-2020, 08:14 AM
jtec
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thoughts

fuel pressure test AND a pressure leak down test with KOEO.
Look at fuel pressure regulator - check to see if any evidence of fuel in vac line.

Try to prime fuel at first start of day and see if it improvrs. Turn key to on count to 5 turn key off then try to start jeep - any change?
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 22 Old 07-12-2020, 12:26 PM Thread Starter
JohnW63
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jtec,


Wouldn't a fuel pressure issue effect the running of the Jeep as well as startup ? I'll have to look up how to do the tests. I assume KOEO is Key On Engine Off.

I'll try the prime test.
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post #5 of 22 Old 07-12-2020, 12:30 PM Thread Starter
JohnW63
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Fishadventure,


"Good one’s aren’t that expensive- $30-$80 on amazonian. "



Do they have ones that are actually the correct length and boot shape ? Any favorites out there ?
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post #6 of 22 Old 07-12-2020, 02:13 PM
mikewiz38
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Quote:
Originally Posted by JohnW63 View Post
Fishadventure,


"Good one’s aren’t that expensive- $30-$80 on amazonian. "



Do they have ones that are actually the correct length and boot shape ? Any favorites out there ?
I bought some AC/Delco Professional wires off Amazon about two weeks ago. They were the correct length and boot shape. I'm not a spark plug wire expert, but they work and didn't have any issues with them.

1994 Wrangler YJ - 4.0L - 5 Speed
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post #7 of 22 Old 07-12-2020, 03:20 PM Thread Starter
JohnW63
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OK. I ordered some from Summit Racing. Amazon wasn't going to deliver them until Friday, even with Prime. Summit has a warehouse in Las Vegas and I get things from them in two days most of the time. I went with Taylor ones. I'll report how well they fit.
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post #8 of 22 Old 07-12-2020, 03:21 PM Thread Starter
JohnW63
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jtec.


The "prime" step was not fully successful. First time of the day, I thought it was. The second time was not.



John
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post #9 of 22 Old 07-12-2020, 03:27 PM
jtec
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I suspect fuel but another issue could be ECT - that is the temp the PCM is seeing not the gauge.

the fuel pressure tests will get the WHOLE fuel pressure picture, to easy if you have the gauge. And the prime test is easy enough.

We will get it. Let us know about the wires, if they help.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 22 Old 07-12-2020, 03:57 PM Thread Starter
JohnW63
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I can get a gauge. I work on enough cars in our stable, to make it useful.


Is the ETC just the temp sensor near the thermostat ? That should be easy enough to test. If the book has the resistance range listed. I'll check.
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post #11 of 22 Old 07-12-2020, 08:15 PM Thread Starter
JohnW63
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Watched a video on testing the fuel system and ordered a decent, not Harbor Freight test kit. I'll post when I have some readings. I am a little concerned that I don't here the fuel pump priming, like the video showed.
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post #12 of 22 Old 07-13-2020, 04:03 AM
Chrisnvegas
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My friend, Rich, his Jeep started crappy too. It was a fuel pressure issue. Once it was running, it was fine. I wondered how long his starter would last.

"Alferd Packer: “Stand up, you voracious, man-eating son of a *****, stand up! There was seven democrats in Hinsdale County and you up and ate five of them."
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post #13 of 22 Old 07-13-2020, 05:45 AM
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I believe my current plug wires were ac delco as well.

I had a set of Belkin before that which failed quickly (lots of stumbling at speed and/or under load. Took me a while to figure out it was the wires but lots of other stuff got up to snuff before the unexpected plug wires failure was discovered)

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #14 of 22 Old 07-14-2020, 07:25 PM Thread Starter
JohnW63
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I think it's the fuel pressure regulator. I turned it to key on a few times and it built up to about 30-35 psi, but once I left it like that, with the key on, the pressure started dropping pretty quickly. I'd guess it would go to zero in a minute. When the engine was running, and I pulled the vacuum line, the pressure did not go up. I had suction on the line, like I'm supposed to.
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post #15 of 22 Old 07-15-2020, 05:50 PM
Boojo35
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If there is any sign of at the fuel pressure regulator where the vacuum line disconnects it is a dead giveaway that the regulator is bad.

If you cannot fix it with a hammer then it has to be an electrical problem.
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