Cranks but nothing - JeepForum.com
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post #1 of 36 Old 10-11-2020, 07:29 PM Thread Starter
BrkCaddy
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Cranks but nothing

Looking for some help on this 94. 4.0 5spd
Ive googled for a few days and still cant get it started.

This is what it does. Cranks but wont fire up. Has new distributor and coil.
Fuel pump does not work unless the relay is jumped. I have no spark either, also no CEL, horn dont work either lol.
I have replaced the capacitors in the ECU also.
I read elsewhere about unplugging the VSS as maybe the ASD is shutting it down from a bad VSS. But didnt start.

So im looking to you all for ideas. To me it seems to be a ground issue maybe ( I redid the grounds and added one) or maybe something is tripping the ADS. This is my first Jeep, but know my way around cars very well.

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post #2 of 36 Old 10-11-2020, 08:35 PM
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Sounds like you've got a ton of stuff wrong. Has this ever run for you?

Problem 1 is you have to jump the relay to get fuel. That's a separate issue if you're at least getting fuel pressure to the rail while you're testing other things. Unfortunately, no spark can be caused by a lot of things but you may want to start with the coil. How did you confirm no spark?

You may not be getting a CEL but are you getting any codes from the ECU?


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post #3 of 36 Old 10-12-2020, 05:28 AM
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I’d see if there is power to the ecu with key in run. Use a meter and prove it powers up and off when the key is cycled. Backtrack to the ignition switch if not.

If the ecu has power coming to it and it is on at the right time use a jumper and test light to mimic the CEL. No CEL? There’s a problem...Can’t go further until it’s solved. )Confirm ECU has basically zero ohms on its ground/neg(-) wire; use the battery neg(-) for this test because that is the longest path to the source and could indicate an issue.)

If you have an active CEL you can read the codes; write them down. Any next steps are too broad to imagine until you have an active ECU and read the codes.

Obtain online or on paper the ECU and 60-pin connector pinouts. If you have an active ecu you’re probably gonna want those wiring diagrams next.
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Cranking IS turning over
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post #4 of 36 Old 10-12-2020, 05:57 AM Thread Starter
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Quote:
Originally Posted by Waternut View Post
Sounds like you've got a ton of stuff wrong. Has this ever run for you?

Problem 1 is you have to jump the relay to get fuel. That's a separate issue if you're at least getting fuel pressure to the rail while you're testing other things. Unfortunately, no spark can be caused by a lot of things but you may want to start with the coil. How did you confirm no spark?

You may not be getting a CEL but are you getting any codes from the ECU?
Going to put scanner on it today, I keep forgetting to take it with me lol. As for no spark I put a spare plug in a wire and crank it.


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Originally Posted by fishadventure View Post
I’d see if there is power to the ecu with key in run. Use a meter and prove it powers up and off when the key is cycled. Backtrack to the ignition switch if not.

If the ecu has power coming to it and it is on at the right time use a jumper and test light to mimic the CEL. No CEL? There’s a problem...Can’t go further until it’s solved. )Confirm ECU has basically zero ohms on its ground/neg(-) wire; use the battery neg(-) for this test because that is the longest path to the source and could indicate an issue.)

If you have an active CEL you can read the codes; write them down. Any next steps are too broad to imagine until you have an active ECU and read the codes.

Obtain online or on paper the ECU and 60-pin connector pinouts. If you have an active ecu you’re probably gonna want those wiring diagrams next.
Thanks ill look fr that pinout. And try to get codes.


Also like to mention previous owner said " it just died then wouldnt start"
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post #5 of 36 Old 10-12-2020, 06:10 AM
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Quote:
Originally Posted by BrkCaddy View Post
Going to put scanner on it today, I keep forgetting to take it with me lol. As for no spark I put a spare plug in a wire and crank it.
Dumb question: Are you grounding the spark plug when you check for spark?

Josh
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post #6 of 36 Old 10-12-2020, 06:59 AM
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Quote:
Originally Posted by BrkCaddy View Post
Going to put scanner on it today, I keep forgetting to take it with me lol. As for no spark I put a spare plug in a wire and crank it.
Pretty sure a scanner won't do you any good. I think all YJ's has OBD I if they had any computer at all.
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post #7 of 36 Old 10-12-2020, 08:10 AM
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Quote:
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Pretty sure a scanner won't do you any good. I think all YJ's has OBD I if they had any computer at all.
Yes, they had an OBDI computer. You can cycle the keys to get the codes. See this article: https://www.quadratec.com/jeep_knowl...article-24.htm

I remember that being one of the few improvements over AMC when Chrysler bought Jeep. The AMC Jeeps I'd end up diagnosing the old fashioned way, or I'd jump connectors on the diagnostic connector to test the parts without removing them from the vehicle.

Did a LOT of both in school back then.

We also had a big scope on wheels with OBDI connectors and different analyzers; could make a printout of the spark, and timing curve, and things like that.

The shop I worked at had a SnapOn scanner that I loved. Old Chryslers would trip the CEL at 60,000 miles whether or not something was actually wrong The head bossman of the shop was thrilled when I showed him how to reset those lights with the scanner, because he could make $45 a pop doing practically nothing.

But yeah, cycle the key and it'll pull codes by flashing the CEL.

Josh
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post #8 of 36 Old 10-12-2020, 09:54 PM Thread Starter
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Well tried to get codes by key cycle and no luck there. I did find the pinout for it. What pins should i be looking at ?
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post #9 of 36 Old 10-13-2020, 04:23 AM
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Quote:
Originally Posted by BrkCaddy View Post
Quote:
no spark can be caused by a lot of things but you may want to start with the coil. How did you confirm no spark?
put a spare plug in a wire and crank it.


Quote:
Originally Posted by fishadventure View Post
I’d see if there is power to the ecu with key in run. Use a meter and prove it powers up and off when the key is cycled. Backtrack to the ignition switch if not.
Also like to mention previous owner said " it just died then wouldnt start"
Quote:
Originally Posted by Wabatuckian View Post
Dumb question: Are you grounding the spark plug when you check for spark?
Josh
Don’t use the key to test ECU. Use the pinout diagrams and see if it’s getting power like i described.

And same for CEL: you don’t know if there’s a wiring or other problem like an underhood PDC fuse. So you have to prove pos(+) power and neg(-) ground with a meter and the CEL in a way that eliminates a bad bulb or poor connections at the cluster. Randomly doing anything won’t do ... or prove anything unless by some infinitely small stroke of luck something heals itself.

Even the Haynes manual has a rudimentary diagnosis chart you can follow iirc

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #10 of 36 Old 10-13-2020, 07:41 AM
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If you don't get a Code "55" at the CEL (completion of code list) then you do have bigger problems and need to move on to what FishAdventure covered.

Josh
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post #11 of 36 Old 10-13-2020, 12:04 PM Thread Starter
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How do I get codes without using the key. Like what wires am i looking for ? Cause when i tried to key cycle nothing happen
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post #12 of 36 Old 10-13-2020, 05:50 PM
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Quote:
Originally Posted by BrkCaddy View Post
How do I get codes without using the key. Like what wires am i looking for ? Cause when i tried to key cycle nothing happen
I'm not sure you can.

Let's back up a bit.

1. Turn key on. Does CEL illuminate?

If yes, go to 2.

If no, check bulb. If bulb is bad, replace and repeat step 1.

If bulb is good, skip 2 and go to 3.

2. Turn key on-off-on-off-on. Count flashes of the CEL for the code. For example, a code 12 will be FLASH (pause) FLASH FLASH. When the codes are complete, a code 55 will flash (5xFLASH, 5xFLASH).

3. Verify voltage at ECU. Find ECU power on pinout measure using a digital multimeter. Some use test lights and those work OK; I prefer the DMM because it'll tell me if the voltage is low.

Report back with findings.

Josh
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post #13 of 36 Old 10-13-2020, 09:05 PM Thread Starter
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Quote:
Originally Posted by Wabatuckian View Post
I'm not sure you can.

Let's back up a bit.

1. Turn key on. Does CEL illuminate?

If yes, go to 2.

If no, check bulb. If bulb is bad, replace and repeat step 1.

If bulb is good, skip 2 and go to 3.

2. Turn key on-off-on-off-on. Count flashes of the CEL for the code. For example, a code 12 will be FLASH (pause) FLASH FLASH. When the codes are complete, a code 55 will flash (5xFLASH, 5xFLASH).

3. Verify voltage at ECU. Find ECU power on pinout measure using a digital multimeter. Some use test lights and those work OK; I prefer the DMM because it'll tell me if the voltage is low.

Report back with findings.

Josh
Ok ill check that bulb for sure.
As for for to the ecu im seeing pin 3 is labled battery so I assume thats power going into the ecu
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post #14 of 36 Old 10-14-2020, 07:32 AM
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Safe assumption. I've not worked on these in years and forget just how they're labeled, but that sounds right.

Josh
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post #15 of 36 Old 10-14-2020, 07:35 PM
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There is a place to hook a OBD1 scanner up.
It is in the wiring loom driver's side.
It should have a cap on it.
Sorry not sure how to put a picture up without Photoshop.
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