4.0 issues

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Stuka
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Re: 4.0 issues

Post by Stuka »

I knew I had recalled it being in there. Some places call it the Distributer Plate Switch.

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tedlovesjeeps71
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Re: 4.0 issues

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I'll eat my crow and humbly apologize to all.


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jpswapmohn
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Re: 4.0 issues

Post by jpswapmohn »

Weren't the 98's OBD2? Throwing any codes?

This may help:
https://www.cherokeeforum.com/f2/jeep-c ... bdii-3341/

My 95 is OBD1 and i just use the ignition on-off-on-off-on to read the flashes
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Curly
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Re: 4.0 issues

Post by Curly »

Shagoneer wrote:Image
That sure sounds like a relay with a bad ground. Can you tell by touching the relay which one is making the noise?
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Curly
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Re: 4.0 issues

Post by Curly »

Can you get codes or data from the DLC (connector for computer that is normally under the dash)?
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Re: 4.0 issues

Post by Shagoneer »

Curly wrote:Can you get codes or data from the DLC (connector for computer that is normally under the dash)?
Already hooked an obd2 scanner up and it didn't have any codes.

I will double check all of the relays before I work tomorrow.

I will buy a multi meter Wednesday when I get paid so that I can check voltage at the plugs and at the coil.
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Stuka
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Re: 4.0 issues

Post by Stuka »

Shagoneer wrote:
Curly wrote:Can you get codes or data from the DLC (connector for computer that is normally under the dash)?
Already hooked an obd2 scanner up and it didn't have any codes.

I will double check all of the relays before I work tomorrow.

I will buy a multi meter Wednesday when I get paid so that I can check voltage at the plugs and at the coil.
No need for a voltometer, most wont handle that voltage anyway. Just pull a plug, hook it back to the wire, ground threads, and have somebody turn it over. It should spark. If not, we know the issue is in the ignition someplace. If it does spark, its either fuel, or sparking at the wrong time.
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Curly
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Re: 4.0 issues

Post by Curly »

I think your problem is going to be related to that buzzing relay. Identify the relay, check its wiring and it will most likely be the cause of the no start.
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Re: 4.0 issues

Post by Shagoneer »

Curly wrote:I think your problem is going to be related to that buzzing relay. Identify the relay, check its wiring and it will most likely be the cause of the no start.

Well I still haven't had time to go outside and check, however, as (in stock form) two relays power the ABS, one is the fuel pump (which in my case doesn't matter as the pump is hard wired instead of being on a relay), one is for the horn, and one is the AC unit. That leaves two possible culprits that could actually affect starting 1. The auto shutdown relay, and the starter relay.
As they are $5-$10 each I may replace both, while I am following wires to figure out which one is having problems.
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Re: 4.0 issues

Post by Curly »

The ASD relay controls the fuel pump and coil in stock former. Since you seem to have no spark, it's most likely that ASD relay buzzing.
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Re: 4.0 issues

Post by Shagoneer »

I'll probably try it with the horn relay in the asd relay location, to see if it's just Abbas relay or if it's a wiring issue.
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Re: 4.0 issues

Post by Shagoneer »

Ok after switching the relays it's no longer buzzing, but it still won't start.

So now I'm going to check spark
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Re: 4.0 issues

Post by Shagoneer »

So my genius #?*! broke one of the spark plugs while removing it to do a spark test. The plug appears to be in decent shape (other than being broken in half), however the model of plug was discontinued somewhere between 2007 and 2009 (reading different dates different places).

So I guess I will change out my decade old plugs while I'm doing everything else:
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Re: 4.0 issues

Post by Cecil14 »

Is it a stock ECU? Have you tried swapping that out? I've killed an ECU or two in my truck over the years. They're generally pretty cheap anymore.


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Re: 4.0 issues

Post by Shagoneer »

I've got spark, and I've got fuel, but still won't start
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tedlovesjeeps71
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Re: 4.0 issues

Post by tedlovesjeeps71 »

Did you only test one plug or do all 6 have spark?


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Re: 4.0 issues

Post by Shagoneer »

I only tested number one. I guess I ought to check all 6.
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Cecil14
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Re: 4.0 issues

Post by Cecil14 »

If you know anyone else with a similar year 4.0L, just swap the ECU. Or, if there's a cheap pick n pull around, grab a spare. I think ECUs are like $25 at my local yard, I keep a known good spare behind the seat.


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Re: 4.0 issues

Post by Shagoneer »

Will a Cherokee Ecu for a wrangler? I know here we're some years with minor differences.
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Re: 4.0 issues

Post by tedlovesjeeps71 »

Shagoneer wrote:Will a Cherokee Ecu for a wrangler? I know here we're some years with minor differences.
I think it would have to be pretty similar. Within the same year spectrum, same transmission type, etc.


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