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post #1 of (permalink) Old 01-29-2007, 11:17 AM
transalpian
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1991 YJ starting (or lack thereof)

Greetings all!

I have a 1991 YJ wrangler with the 4.0L in-line 6.

And it doesn't run. Or more accurately, it won't start anymore.

I blew a heater hose on it last week. Upon replacing the hose, it wouldn't start without a LONG time on the charger. The alternator was bad (tests showed) and the battery was good. I replaced the alternator, and it still didn't start unless a LONG time on the charger. Even then, it would run for a while but not re-start when shut off.

I'm getting spark to the plugs, and fuel to the fuel rail (note to self, don't test these at the same time [img]/ubbthreads/images/graemlins/crazy.gif[/img])

I do not have a lit check engine light (or maintenance req'd), but have not yet checked for codes.

So, is it a sensor? My lack of knowledge is astounding here!

Thanks in advance

T'alp
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post #2 of (permalink) Old 01-29-2007, 11:39 AM
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Re: 1991 YJ starting (or lack thereof)

First check to see if there is voltage on the positive side of the coil. If there is no voltage then the ECM is shutting down the ignition and fuel system.
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post #3 of (permalink) Old 01-29-2007, 11:59 AM
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Re: 1991 YJ starting (or lack thereof)

I'm getting a spark when the engine turns over. Is this the same thing?
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post #4 of (permalink) Old 01-29-2007, 12:09 PM
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Re: 1991 YJ starting (or lack thereof)

Yes, this is what your trying to confirm. Now spray some starting fluid into the throttle body, past the throttle plate and see if the engine starts. If it does, the problem is about 99.999% a problem with the fuel pump. The engine will run until the starting fluid is expended.
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post #5 of (permalink) Old 01-29-2007, 12:41 PM
transalpian
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Re: 1991 YJ starting (or lack thereof)

I had tried dumping gas in with no success. Should I try it with starting fluid?

Also, I am getting gas from the fuel pump, verified by removing a fuel line from the injection system.
post #6 of (permalink) Old 01-29-2007, 01:50 PM
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Re: 1991 YJ starting (or lack thereof)

OK... so you've got spark. What's missing?
<ul type="square">[*]Timing[*]Fuel[*]Air[/list]Those are the three possibilities.

The fuel pump is turned on to pressurize the fuel line for 2 seconds by the ECM. Then it's turned off. From this point on, the CPS sensor must take over and send pulses to the ECM. The ECM sees the pulses and then turns on the ignition and the fuel pump. The ECM is turning on the systems, and you've got spark, but likely no fuel pump, or the injectors aren't pulsing. So, we're trying to figure out if the problem is in the fuel delivery.. where is the problem.

Dumping fuel in the throttle body throat may/may not help. Raw fuel can sometimes be drawn in and flood the engine. It's not atomized into a vapor, that's the job of a carb, or the fuel injectors. That's why I'd still suggest the starting fluid. It's already a vapor, not like the fuel you dump in.

So, if the engine doesn't start on the starting fluid, you can then bet the problem is timing. Have you checked the static timing?
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post #7 of (permalink) Old 01-29-2007, 02:02 PM
transalpian
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Re: 1991 YJ starting (or lack thereof)

Remember, this thing ran great until the heater hose blew and shorted out the alternator.

I'll try the starter fluid test and report back.

Thanks for all the help, I really don't want to take this into a $hop!

t'alp
post #8 of (permalink) Old 01-29-2007, 02:06 PM
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Re: 1991 YJ starting (or lack thereof)

Usually, when a coolant hose spews, it destroys the TPS sensor. You may want to check that! But often a TPS won't kill an engine, just make it run really lousy, but I've been known to be wrong. Also, if you squirt in the starting fluid, the TPS is... kind of taken out of the fuel delivery system.
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post #9 of (permalink) Old 01-29-2007, 02:10 PM
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Re: 1991 YJ starting (or lack thereof)

Stupid question, the TPS sensor is where; on the distributor or the bellhousing? Too many abbreviations for me [img]/ubbthreads/images/graemlins/laugh.gif[/img]
post #10 of (permalink) Old 01-29-2007, 02:18 PM
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Re: 1991 YJ starting (or lack thereof)

The TPS is the sensor on the Throttle body... above the Idle Speed Control Motor. May I suggest you take a look at the Autozone Repair Manual! It's a godsend if you need to know where stuff's at. There's a component locator too! It says the TPS is:[ QUOTE ]
On your 1991 Jeep Wrangler 4WD, the Throttle Position Sensor is:


Under hood, center, upper engine area, driver side of valve cover, mounted on rear of throttle valve assembly

[/ QUOTE ]


Also another good online resource is The Bradford Public Library, you don't need a library card to access the on-line Auto Repair Reference Center. Give it at try, they're both good references.
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