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tbloid 04-27-2013 07:46 PM

91 yj with 2.5 won't start? help!!!!
First off, I'm new here so please be nice. This is my first jeep in over 20 years.lots has changed.
ok here's my issue. I just bought this yj yesterday. It has the 2.5 liter. And I picked it up cheap. The frame has minor surface rust, the springs are junk, and it only has 108000 miles. The fuel tank had fallen off for the previous owner and busted a fuel line. I fixed that issue and have good pressure to the injectors. And the jeep wouldn't start. I replaced the cap, rotor, wires and plugs. Same thing, won't start. It turns over nice, good compression and sounds like it wants to run. I can get it to run if I intentionally flood it then pull the fuel pump will run for about 30 seconds then die like it's supposed to. During those few seconds it sounds good.
Any suggestions, or paths to take would be greatly appreciated.

Wrangleriffic 04-27-2013 09:17 PM

try turning on the key let it sit for ten minutes then try to start it.

Keymo 04-28-2013 04:41 AM

x2 for Wrangleriffic's response... Though I would think that if you are getting proper fuel pressure, your regulator is working properly and you would not need to "prime" your fuel pump - which is basically what he is telling you to do. But it's worth the try!

How are you intentionally flooding an EFI system? I'm not doubting you - but if you're trying to start it up like you would a carb'd engine - it's not going to work and you're going to cause yourself even more problems... As long as the regulator and pump are working properly - you shouldn't ever really need to mess with the gas pedal on an EFI motor while starting up...

With EFI, if you hold the pedal all the way down while starting the computer is programmed to shut off the injectors to clear a flood. Now, I believe - other than a flooded condition, where you hold the pedal down so the computer shuts off the injectors - don't give it any gas when you start it. EFI vehicles will figure it out on their own. If you have been giving it gas when you start it, it will take a while for the computer to "unlearn" the start conditions that you've screwed up. Even if it starts and then dies, don't give it gas - let it learn the proper idle to keep it running.

Have you checked/ran any codes?? Have you checked your sensors? I believe it is necessary, or at least in your best interest, to have all of those working properly in order for your EFI system to be working properly... I'm no EFI pro - I like my carbs... But I'd at least check my O2 and TPS sensors for sure, among others, if I were you...

tbloid 04-28-2013 07:37 AM

Thanks for the idea, I will try that when I get home tonight. What I meant by intentionally flooding it was after multiple attempts at starting, strong smell of gas. I would pull the fuel pump fuse and hold my foot to the floor, I've never heard that the computer would automatically shut down the injectors. I'll repost tonight if that helped.

Garyk 04-28-2013 12:36 PM

If you are getting a strong smell of gas, I would suspect the pressure regulator or as Keymo says, check your sensors.

tbloid 04-28-2013 01:22 PM

I'm going to check them tonight. Any pointers on good ways to check them would be helpful. I don't want to just blindly replace things

Garyk 04-28-2013 04:34 PM

You might also check the connection (vacuum) at the MAP thats on the firewall. If that is not connected or bad vacuum it will not run but may start for a second or two.

tbloid 04-28-2013 07:40 PM

Ok, I tried to turn the key and wait 10 minutes. It does the same thing. I also checked over the vacuum lines. They all look good. I'm stumped, how can I check the sensors without just replacing them? Any other ideas? Good spark, good airflow and fuel should equal running engine.

Keymo 04-28-2013 09:53 PM


Originally Posted by tbloid (Post 3693773)
Ok, I tried to turn the key and wait 10 minutes. It does the same thing. I also checked over the vacuum lines. They all look good. I'm stumped, how can I check the sensors without just replacing them? Any other ideas? Good spark, good airflow and fuel should equal running engine.

"LOOKING good" can be a very different thing than them actually being in good condition. You have to remember, these lines are trying to hold an AIRTIGHT vacuum...

A lot of sensors (and other electrical components) can be checked using a multimeter. Do you have a Haynes manual? It might be in your best interests to get yourself one to check values against and to use as a quick reference for these types of things (testing and troubleshooting small things).

Another, EASY way for checking over your sensors and whole system for that matter is to check for "Trouble Codes." Have your checked for codes yet?? This would be another situation where having a Haynes manual would come in handy....

(First, get yourself a piece of paper and a pencil)
You do this by putting the key in the ignition and turning it in this order: ON, OFF, ON, OFF, ON - then leave the key on. The ECU will go into "self diagnostic mode" (or something) and the "CHECK ENGINE" light will come on for a few seconds and then turn off. After it turns off for the FIRST TIME you'll want to count the number of times it flashes from then on.

This gets kind of tricky...
It'll flash X number of times and then pause for a second and then flash X times again and pause for about two seconds before starting the next code.

Example: flash, flash, flash (pause) flash, flash, flash (two second pause) - this would indicate a "33" trouble code...

a "55" code will always indicate the "end of trouble codes" but you'll also know because the engine light will completely stop flashing... There are, I think, three codes what will ALWAYS be present when you check for codes - but the others should give us a good indication of what needs a closer look...

(Oh man, I hope I worded all of that right. :p )

You should check codes on your Jeep and then post back with what you found. It might give us a better starting point in helping you find out what needs testing and how. :thumb:

Keymo 04-28-2013 10:01 PM

I'm an idiot - I don't know why I didn't just search for this in the first place. This video is a walkthrough for checking Trouble Codes from Chrysler:

ECU-key.mp4 - YouTube

tbloid 04-29-2013 08:31 AM

Thank you keymo,,, for the info on getting the codes. I just checked them and got these. 12....33....55. From what I can tell, 33 is for the air conditioner. And 55 is the end of code signal. What is 12? I picked up my copy of the Haynes manual yesterday. And there's no 12 in there.

I will figure this out!!! Its a vendetta now. Well with help from my new friends on here that is. Hopefully I will have the opportunity to pay back your help.what I lack in knowledge of computerized engines, I make up for with my fabrication skills. If nothing else, you'll get to see some of my crazy concoctions

turdhurdler 04-29-2013 08:47 AM

12 is stating that the battery has been disconnected within 50 key turns of the ignition.


Keymo 04-29-2013 08:58 AM

That makes sense on the 12 code.... 12 is super common unless you haven't disconnected you battery(or had a dead battery) in a while... So it's really not an indicator of anything, to be honest. I think it's something like "battery has been disconnected within the past 50 startups" or something similar to that...

33 makes sense too - as I don't believe you would have AC. :p And obviously 55 is the end code... So dammit... All "normal" codes... Hmmm...

Now, I know you said that you got her to fire a bit when you did your flooding and pulling the fuse trick... But are you CERTAIN that your fuel pump is functioning properly? Can you hear it engage when you turn the key to ON? If not, you could have a bad ground or relay... If you hear it - you COULD have insufficient fuel pressure... Have you tested that?

Even if you DO hear it engaging and you know you have proper pressure in the line, you should get under the hood and try seeing if you can physically see fuel coming out of the valve on the fuel rail. I forget the exact name of the valve.. Sorry... But you should be able to press it and see fuel coming out... If so, we know that you at least have fuel getting to your injectors...

Also, in preparation for not finding the problem yet... Are you familiar with how to use/test with a multimeter?

Don't worry - we'll get this baby figured out! :thumb:

tbloid 04-29-2013 09:07 AM

The fuel pump sounds good, when key is turned. Runs for about 2secs.I'm not sure what you call that doohickey on the fuel rail either, but when I test for fuel there is good pressure. I don't have a fuel pressure tester, but as it squirts across the engine compartment. I am not real familiar with a multimeter, but I'm a fast learner. sounds like I'm going to have to be.

Keymo 04-29-2013 10:04 AM


Originally Posted by tbloid (Post 3695798)
The fuel pump sounds good, when key is turned. Runs for about 2secs.I'm not sure what you call that doohickey on the fuel rail either, but when I test for fuel there is good pressure. I don't have a fuel pressure tester, but as it squirts across the engine compartment. I am not real familiar with a multimeter, but I'm a fast learner. sounds like I'm going to have to be.

Hmmm... I'm not sure exactly but it seems like that would be enough pressure - though it (and your previous information) makes me wonder if maybe it's too much pressure...??

This may be barking up the wrong tree - but the reason I think this is that your fuel pump DOES come on and engages and is getting fuel to your injectors because it's firing up. But only when you pull the fuse to the pump which is cutting the pump off. I'm thinking your pump could be sending too much fuel - essentially flooding your engine when you crank and when you pull the fuse it's cutting off the pump which will stop the pressure on the fuel - under which condition your engine is finally firing and then running until it's starved of fuel... This is all just theory right now, but it seems like it could be a good possibility as you aren't showing any relevant codes either...

Were your spark plugs new when you started this process? Have you checked your plugs since all of this started? You might be able to tell if they've been experiencing a rich condition just by pulling them and seeing what they look like... Generally, the business end of your plugs will look dark brown/rusty looking if it's running too rich...

I know that if your return line (to the tank) is blocked it can increase your fuel pressure.. I don't KNOW if it can increase it enough to flood your engine - though it's a possibility... Have you checked your return line and made sure it's clear and hooked up properly?

Also - a stupid question: Is this the same tank of fuel that you got the Jeep with or did you drain and put new fuel in it?

Sorry if it seems like I'm all over the place with asking you to check things and my suggestions... I'm just trying to tally everything up in my head and telling you what to check as it seems relevant...

Keymo 04-29-2013 10:14 AM

Here's a decent little chart that might help with checking out your park plugs...

Attachment 242690

tbloid 04-29-2013 12:11 PM

Ok, pulled the return line to the tank, good flow no signs of blockage. I did run the tank empty this way and replaced with new fuel again. Also at this time I hooked up a pressure gauge and it's just below 40psi. So that looks good. I replaced the plugs, wires, cap and rotor right away when I began this. I have not pulled the plugs again yet to check them. I'll do that tomorrow after work. Again, thanks for the help and suggestions. The Jeep was running in December, I found an oil change receipt.

tbloid 04-30-2013 07:32 AM

Just pulled the plugs this morning. They look good to me. I have a few pics if someone could help me figure out how to post them. Tomorrow I'm going to replace all the vacuum lines. Then next step will be pulling all wire connections. I'm going to give it the once over, before throwing the parts store at it. I know it'll run, just got to find the right problem.

Keymo 04-30-2013 09:18 AM

Are you on a computer? Or a phone?

For a computer - when you are in the reply window there's a paperclip looking thing in the top of the reply window with a small arrow pointing down... You'll click that and then you can select your picture(s) from there.

On a phone (assuming it's a droid) - when you are replying to a post you can hit the button next to the home button (I believe) and it'll bring up "post" "attachments" and "cancel", I believe.. You'll hit the attachments button and then select your picture from there.

Now for the problem... Haha!

I think you should get yourself a multimeter before you go pulling wire connections... Then you can test for continuity and may be able to isolate the problem quicker and it can also help you with testing various sensors and relays to make sure they're working. If I were you, I'd start off checking my sensors to see if they're getting power and if they're functioning properly.

First - when you have your multimeter, you should check your AutoShutdown Relay and the "fuel pump shut down" relay. Not sure if that's the official name, but when that goes bad it can cause the Jeep to shut down immediately after starting. I was thinking about suggesting it earlier - but the whole pulling the fuse thing made me wonder if it wasn't something else. I believe they should be in a box under the hood - the horn relay should be in the same location as well.... They also have fuses that you might want to check out as well...

If those aren't the culprit you should definitely check the connector to the CPS. Supposedly if your CPS is bad - your Jeep isn't supposed to start at all. But I did some looking into it and a lot of people are having similar problems at you where their Jeep will start and then after a minute or so it'd just shut down. They weren't showing a code for the CPS either - but a few said that if they checked codes after 4-5 no-starts THEN the code would show up. I believe it's 32...

tbloid 05-01-2013 11:48 AM

Good news!!! There's life in the little beast.

Finally got it running, and took it for a drive. I'm not sure what was going on or if it's fixed yet. What I did was pulled the return fuel line and plugged it off. A mechanic friend thought it may be the regulator starving the injectors. That immediately flooded the poor little engine. So with the help of another this time. I replaced the return line to normal and pulled the fuel pump relay. I had her turn over the motor with the accelerator to the floor. As soon as it started running I put the relay back in and out a few times to try to keep it going while she played with the accelerator. After about a minute of this it began running smoother. It idled out around 700 RPM, I let it come up to operating temp and shut it down. Then tried to start it again, popped right off like a trooper.

Cross your fingers that the gremlin died in there. Now the real fun begins. Putting the lift on, repairing the rusted floor, and fabricating all the what nots.

I really appreciate all the help you have given me here and I'm sure there will be more advice I'll be asking for, as well as giving hopefully as time goes on. Keep an eye out for my builds in the various threads here.

Thanks again!!!!

Keymo 05-01-2013 11:18 PM

WOOHOO! Glad you got 'er running! :thumb:

I'll stay sub'd to this thread and you should put up a link to your build thread when you start it! :D

tbloid 05-02-2013 05:54 AM

Will do!!! Thanx

tbloid 05-17-2013 05:26 PM

Ok, I got it started. Not sure how to post the thread link, but it's named " the cheaper jeeper, my Craigslist build "

Thanks again for the help

tbloid 05-17-2013 05:27 PM

Ok, I got it started. Not sure how to post the thread link, but it's named " the cheaper jeeper, my Craigslist build "

Thanks again for the help

tbloid 05-17-2013 05:28 PM

The build thread is named " the cheaper jeeper, my Craigslist build"

Thanks again for all the help

james-bile91 03-06-2015 06:40 PM

I having a similar problem with my Jeep I get gas, air, and spark. I replaced distributor, cap, rotator, CPS, spark plugs,and wires. Also replaced the fuel pump relay and still nothing happened. Need some help

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