Jeep YJ won't start - JeepForum.com
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post #1 of 51 Old 07-25-2021, 03:59 PM Thread Starter
rudderhd
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Jeep YJ won't start

Hello.

I have a 91 YJ with a straight six and fuel injection. Have started to have problems with it starting and then dying on me or starting and I turn it off and won't start again. Once it dies, it will not start again. After a few days it would start and then die. Now it will turn over but won't start at all.



I have jumpered the relay and removed the schrader valve to see if the fuel pump will push fuel to the rail. No fuel came out of the schrader valve. I had 12V at the relay.



I am beginning to suspect the fuel pump is going. I haven't checked the fuel filter yet but plan to do that in the next few days. Is there anything obvious that I am missing? Should I be testing something else?


Appreciate any/all help on this. I don't want to drop the tank unless I absolutely have to, but starting to plan for that.


Thanks for any responses.


Chris

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post #2 of 51 Old 07-26-2021, 05:12 AM
fishadventure
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I chased a similar problem last winter in my 87 w/ 1994 4.0 et al.

A) your check engine light works, right?
B) you hear or don’t hear the fuel pump prime on initial key-on? I suspect no
3) when it won’t start: will it fire with starting fluid and then stall? I suspect yes.

Do yes it could be fuel pump- I bought one myself. But I replaced the ASD and fuel pump relay on a throw-parts-at-it whim snd viola! it started immediately.

Since then I’ve had to re-seat the relays a couple times (might have been the real issue!) when it stalls out but that was my cure. I’m pretty sure the oem relay just was old and needed to be new. The artozone chinesium relay I just think isn’t fitting tight like it should.

Either way that sounds like a similar issue and might get you fixed without the tank games.

Worth looking into.

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #3 of 51 Old 07-26-2021, 01:13 PM
laybackman
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Quote:
Originally Posted by rudderhd View Post
Hello.

I have a 91 YJ with a straight six and fuel injection. Have started to have problems with it starting and then dying on me or starting and I turn it off and won't start again. Once it dies, it will not start again. After a few days it would start and then die. Now it will turn over but won't start at all.



I have jumpered the relay and removed the schrader valve to see if the fuel pump will push fuel to the rail. No fuel came out of the schrader valve. I had 12V at the relay.



I am beginning to suspect the fuel pump is going. I haven't checked the fuel filter yet but plan to do that in the next few days. Is there anything obvious that I am missing? Should I be testing something else?


Appreciate any/all help on this. I don't want to drop the tank unless I absolutely have to, but starting to plan for that.


Thanks for any responses.


Chris
Pretty sure that this unit has an inline fuel filter. It would be the first thing I would replace, not knowing when or if it was ever replaced.

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Found out Grandpa is addicted to Viagra. No one is taking it harder than Grandma...
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post #4 of 51 Old 07-26-2021, 04:33 PM Thread Starter
rudderhd
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Quote:
Originally Posted by fishadventure View Post
I chased a similar problem last winter in my 87 w/ 1994 4.0 et al.

A) your check engine light works, right?
B) you hear or don’t hear the fuel pump prime on initial key-on? I suspect no
3) when it won’t start: will it fire with starting fluid and then stall? I suspect yes.

Do yes it could be fuel pump- I bought one myself. But I replaced the ASD and fuel pump relay on a throw-parts-at-it whim snd viola! it started immediately.

Since then I’ve had to re-seat the relays a couple times (might have been the real issue!) when it stalls out but that was my cure. I’m pretty sure the oem relay just was old and needed to be new. The artozone chinesium relay I just think isn’t fitting tight like it should.

Either way that sounds like a similar issue and might get you fixed without the tank games.

Worth looking into.
Thanks fishadventure.

Answers to the questions are: Check engine light works, don't hear the fuel pump, I haven't tried the starting fluid. Will try this and post later this week or weekend.

I tried the jumper on the fuel pump relay and it didn't start (there was 12V there). When I tried to jumper the relay and removed the schrader valve, nothing came out of the schrader valve, no fuel. I didn't try anything on the ASD because I didn't know about it. I will look into that this week.

Thanks again for the response. Really appreciate it.

Chris
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post #5 of 51 Old 07-26-2021, 04:39 PM Thread Starter
rudderhd
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Quote:
Originally Posted by laybackman View Post
Pretty sure that this unit has an inline fuel filter. It would be the first thing I would replace, not knowing when or if it was ever replaced.
Thanks for the response laybackman.



The next thing I was going to try was to remove the fuel pump connection on the fuel filter to see if fuel comes out when I try to start it. The fuel filter is a few years old. Will end up replacing it I'm sure. The one other thing I've seen about the fuel pumps in the ground connection. I don't have any idea what that looks like. I was hoping to try everything else before I drop the tank.


Thanks for the reply and the comment.


Chris
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post #6 of 51 Old 07-27-2021, 05:12 AM
fishadventure
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The ground is usually a spade tab at the fuel tank and it home-runs to a screw at the ebrake bracket location.

The starting fluid (or 1/4 cup of gas poured in the throttle body) trick sorta eliminates a whole lot of ‘other’ diagnostic moments when it starts right up.
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[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #7 of 51 Old 07-27-2021, 05:13 PM Thread Starter
rudderhd
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Quote:
Originally Posted by fishadventure View Post
The ground is usually a spade tab at the fuel tank and it home-runs to a screw at the ebrake bracket location.

The starting fluid (or 1/4 cup of gas poured in the throttle body) trick sorta eliminates a whole lot of ‘other’ diagnostic moments when it starts right up.
fishadventure,
thanks for the information. I'll give the starting fluid test a shot in the next few days. As always, appreciate your time and the help.

Chris
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post #8 of 51 Old 07-28-2021, 03:55 AM
JD Blaine
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With all the stats given, I would have to say I’m with the prognosis that it’s the fuel pump. Not hearing it (or it running loudly) is a sign of a bad fuel pump. If it has 12v at the connector at the tank, and you can’t hear it, that’s another sign. No pressure at the shrader valve is another tip. If you do drop the tank, do the “fuel pump mod” to make it easier to get to next time. Aftermarket fuel pumps don’t last nearly as long, usually, as factory OEM pumps, so there’s a chance you’ll be replacing it again if you keep her long enough.

This are just my observations…not absolute facts. Take them for what they are…lol. Good luck!
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post #9 of 51 Old 07-28-2021, 06:30 AM
fishadventure
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We’ll see if it runs on starting fluid, see if it has power to the fuel pump, see if it has good relays, see if it has adequate neg(-) connection. Those are the shortcuts to diagnosing this.

[size=“3”]Shackles & D-rings are different things.
Cranking IS turning over
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post #10 of 51 Old 07-29-2021, 07:04 PM
Boojo35
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You are on a good path with your diagnosis. You have 12V on a relay but relays require 12V at two different places to operate. They also require the ground circuit on the control side to be worthy and a complete path through whatever they are controlling. You said you jumpered the relay and I am skeptical of what you jumpered because relays confuse the stuffings out of a lot of people and a lot of misdiagnosis begins right at a relay. I do this for a living and have seen it over and over and it really complicates things.

As pointed out already. Simply spray starting fluid, carb cleaner or brake fluid into it and see if it fires. Brake cleaner will also start an engine but be aware that it cannot be NON FLAMMIBLE Brake cleaner such as some CRC brand and others are.

If it starts when sprayed, a whole lot of the diagnostic tree is eliminated.
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If you cannot fix it with a hammer then it has to be an electrical problem.
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post #11 of 51 Old 07-29-2021, 07:11 PM
Eunit1979
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How do I check the relays is I find a relay right next to it that's working and I'll swap them out if the object works with that fuel pump relay in there then you know it's not the relay
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post #12 of 51 Old 07-30-2021, 06:46 AM
laybackman
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Quote:
Originally Posted by Eunit1979 View Post
How do I check the relays is I find a relay right next to it that's working and I'll swap them out if the object works with that fuel pump relay in there then you know it's not the relay
Using the horn relay is an easy way to check out a relay.

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Found out Grandpa is addicted to Viagra. No one is taking it harder than Grandma...
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post #13 of 51 Old 07-31-2021, 07:07 AM Thread Starter
rudderhd
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Thanks fishadventure. I'm going to check the starting fluid today. I'm also going to replace the fuel filter this weekend. I'll report back what happens.


Thanks again for the help.
Chris
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post #14 of 51 Old 07-31-2021, 07:10 AM Thread Starter
rudderhd
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Hi JD Baine.
Thanks for the info. When you say do the "fuel pump mod" do you mean cut the hole in the body so the pump can be fixed easily without dropping the tank?


Thanks.


Chris
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post #15 of 51 Old 07-31-2021, 07:17 AM Thread Starter
rudderhd
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Hi Boojo35.
I really appreciate the help. When I jumpered the relay I soldiered two spade connectors to a 12 gauge wire and inserted them into the relay socket. I will say the back connection on the relay didn't go in as far as the front, but when I measured the back connector there was 12v there, so at least the front connector made contact. I made the assumption that the back connector also made contact. Probably something I need to check again or verify someway else.


I'll do the starting fluid test today. Also will get a new fuel filter, but will only make one change at a time while I try to figure this out. Really appreciate the comments.


Thanks.


Chris
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