91 Cherokee starts then dies right away

[Alocatelli]

Well I have already tried before to just keep the engine cranking with the key past the run position but it still does that same thing "runs for a second then dies, runs for a second them dies, with the starter cranking the whole time." I think that rules out the switch. I'm just confused as to why when I jump the pump at the ballast resister with a battery charger that the pump runs in the acc but not start position. I want to try applying 12 volts directly at the pump bypassing any other wiring to see if it stays running. I guess I am going to just go out in the rain and try it. I really want to get this figured out and get my Jeep running again.

 

[Alocatelli]

Another note, I figured out today that my pump is running like it should and I seem to be getting good volume out of it. I rechecked for spark and I am getting spark. Also i'm getting 12 volts on the fuel injector nearest the firewall and only 0.02 volts on the front injector. I can't help but think it is something screwing up the signal to the injectors and they are just not firing right. Can anyone confirm what voltage I should see at all the injectors?

 

[89xjgrey]

Perhaps something happened to the injector drivers in the ECU. have you tried swapping the ecu with a known good one?

 

[Flash]

Did ya replace the the ballast resister.......i now you by pasted it but did ya replace it? they really are dirt cheap!.......fuel filter?

you said you have 12v on one inj wire but not an ether? when it starts dues it run all all the cylinder

dues it start smooth and then die or dues it barely start chug and die.

how about the spark is it still sparking while the eng is dieing or could it be the spark that causes it to die..........NO it has to keep the spark going because you said that you could keep it running on starting fluid......right?

If you don't have power to 1 or more inj........thats were you have to find out the why.........if it was a fuse they all would be 0v you my have a bad wire some wheres go double check the voltage at the inj with the key in the run position.


Flash.

 

[xjpheonix]

your injectors should have no noticable voltage if you got 12 v at any injector
you might need to try a new ecm... your injectors pulse according to where #1cylender fires due to the crank possition sensor sending a signal to the ecm and goes from there

 

[Alocatelli]

I am going to replace the fuel filter and the ballast resistor just to be on the safe side, will try that tomorrow. I have also changed out the ECU with a known good one and it had no effect. Before I was able to keep the jeep running by spraying starting fluid into the throttle body but since I jumped the fuel pump directly today it now doesn't really kick over at all. I tought it was flooded then so I tried to start it with the throttle held open and it did run for a few seconds then died again. I checked my plugs and they are dry so I don't think that flooding is the problem. I have been through all the injector wiring and it seems to be ok. Also checked over the rest of the wiring and found no obvious problems. This is the longest I have ever been stumped on an engine problem, although this is my first fuel injected ride. I love my Jeep but it's sure giving me hell this past week.:bawl:

 

[Alocatelli]

Also to clarify. The jeep only runs for about one second so I can't really tell if it is rough or not, but it seems to sound normal for that one second. It's like it fires on the initial shot of gas then nothing. Well you guys are pondering that problem, can someone tell me how to get a custom avatar, like a pic of my jeep to show up in my profile? Thanks again for all the help so far.

 

[xjpheonix]

alright i have called all my mechanic buddys 4 of them and 3 of them mentioned that the pick up in the distributer could be bad and they have ran into this problem before no they didnt read the posts but i read the important things to them so i dont know what its worth but you seem to need some help it doesnt explain being able to keep it running with starting fluid though
(at keast to me ) have you checked your pressure since you hard wired the pump?

 

[Flash]

Also to clarify. The jeep only runs for about one second so I can't really tell if it is rough or not, but it seems to sound normal for that one second. It's like it fires on the initial shot of gas then nothing. Well you guys are pondering that problem, can someone tell me how to get a custom avatar, like a pic of my jeep to show up in my profile? Thanks again for all the help so far.

The only way to put your own personal avatar on is to become a paying member. when your name is in red:thumbup: you can!

I could be wrong on this but i thing......that you should have 12V on one of the two wire of each inj when the ign is on......the ground wire is the signal wire from the computer to tell it to fire.......you will never see it with a test light(Ground polts or fire of the inj) you will need a Noid light for that!

Flash.


flash.

 

[Alocatelli]

I guess I'll become a paying member then. I'd like to help support such a great site anyway:yelclap: . As for the pressure when I hard wired the pump, it was the same, 39psi initial and then around 34psi sustained. After I realized that the pump was running in the on position I hooked it back up to the factory harness. I don't know for sure either but I would think I should see 12v on all the positive wires at one point or another.

 

[Flash]

I guess I'll become a paying member then. I'd like to help support such a great site anyway:yelclap: . As for the pressure when I hard wired the pump, it was the same, 39psi initial and then around 34psi sustained. After I realized that the pump was running in the on position I hooked it back up to the factory harness. I don't know for sure either but I would think I should see 12v on all the positive wires at one point or another.

Ya i only posted up a fue times and an felt it was worth it. Besides you get to vote for your chapter president and a lot more access to eater things to.

your spark plug are dry, so its not over fueling, if ya can keep it running with starting fluid then its not a cam sensor or crank sensor giving ya grief(You need to try and keep it running on carb spray to prove that they are NO the problem, or what ever is you choose of flammable spray)

if the connector is plugged into the inj there should be 12V on each side of the connector but unplugged there should only be 12V (Bat+) on one side and
and a quick strike of ground (bat -) from the ECM when that inj is to be fired. this ground path turns on and off to quickly for most test light. The noid(I now that I'm spelling it wrong:dunno: )light will flash every time the ECM sends a signal.

If ya can keep it running on carb spray .......it fuel related

If your fuel pressure stay up(in spec.) when it running on carb spray then its not the fuel pump.

if you put a noid light in place of the inj and they all blink while your crankeing.................then you have a bad or plugged inj.


Flash.

 

[xjpheonix]

hmmmmmmm i know this is way off line but what about bad fuel its happened to me before i fueled up and there was too much water in the fuel for my vehicle to run maybe its sepperating in the line while it sits so you are getting a good squirt of fuel to start the engine... i dunno seems like if you can keep it running w starter fluid its not a fuel rail or inj prob also wouldnt be a spark prob (unless spark is too weak to ignite fuel but not starter fluid which would indicate a coil) and you have sufficient fuel pressure and volume that rules out most things its worth lookin at at this point...
good luck ..

 

[xjpheonix]

ok i just read back on all the posts you said it seems to be getting good volume "SEEMS" now im my book that is a big thing becaus like i said i had this same exact problem in a 93 and i had what seemed to be good volume but it wasnt sufficient enough to keep the engine running once it started... seemes to me again like before that this is an issue that should be addressed completely befor getting too involved in everything else a filter wouldnt be a bad idea either
just MY .02

 

[Flash]

hmmmmmmm i know this is way off line but what about bad fuel its happened to me before i fueled up and there was too much water in the fuel for my vehicle to run maybe its sepperating in the line while it sits so you are getting a good squirt of fuel to start the engine... i dunno seems like if you can keep it running w starter fluid its not a fuel rail or inj prob also wouldnt be a spark prob (unless spark is too weak to ignite fuel but not starter fluid which would indicate a coil) and you have sufficient fuel pressure and volume that rules out most things its worth lookin at at this point...
good luck ..

thats a vary good idea run some gas into a glass clear container and let it set. if there is water in it you will now!!!


Flash.

 

[Alocatelli]

I will check for water in the gas today when I change out the filter. I also forgot to say that when the cherokee first wouldn't start I have barely any gas in it, low enough that at the start I thought I had just run out of gas in the driveway, and I may have at the start don't remember. But then I went and got about 7 gallons and dumped it in. Maybe I picked up some crud off the bottom of the tank and it plugged something or perhaps the empty tank some how got condensation in it. Not sure just throwing some ideas out there.

 

[Rust Heap]

When you are changing the filter and checking for water the fuel pump should be able to fill a 1liter container in less than 1 minute according to my '93 FSM.

 

[Flash]

I will check for water in the gas today when I change out the filter. I also forgot to say that when the cherokee first wouldn't start I have barely any gas in it, low enough that at the start I thought I had just run out of gas in the driveway, and I may have at the start don't remember. But then I went and got about 7 gallons and dumped it in. Maybe I picked up some crud off the bottom of the tank and it plugged something or perhaps the empty tank some how got condensation in it. Not sure just throwing some ideas out there.

Thats what happened to my 89 XJ carried 5 g with me just to see were the inaccurate guage ran out of fuel. shut it of one day at a 1/8 of a tank and it wouldn't start................

MAN the more i think about it the more it resembles your probem.............any way to continue with the story!

when i went to start the jeep it would start and then stall over and over again. put the 5 G of gas in still nothing when and got 7 more.....no start!!!!

check for fuel at the shrader valve, got fuel flow, put a guage on it and had pressure, but not enough!
had my buddy Bang on the take while i cranked pressure cam up and it started!!!!
Has not failed me in 2 mounts(but i never go below a 1/4 tank any more!)

It's like ones you suck air into the pump it ......kind air locks:sure: I don't now but if it would have been a bad pump it should have died on me again!

when i talk to the previous own he told me that every time he ran it out of gas......every time??????:hang: every time that he ran it out of gas he would have to hold the srader valve open while some one else crank on it tell he got all the air out of it.........:wierd: operantly he had dune this many time so i don't thing that the pump is bad but there must be some sort of check valve in there that will not seat with out solid fuel.

I now this seam real strange and i can say for a fact why this fix it but ................if ya ran it out of fuel this could well be the answer!

I real want ya to try it and see if I'm just plane "NUTS' or if it will fix your problem.
I would have told ya this story earlier but.....I don't thing........that you had told us about the running out of gas

Dang I;m long winded:yap:


Flash.

 

[Alocatelli]

Ok, I replaced the fuel filter, fuel pump ballast resistor, cap, rotor, sparkplugs, and the plug wires. I also checked for water in the gas which there wasn't any and I checked for fuel flow into a bottle and made sure there was no air in the lines up at the fuel rail. I go to turn it over and nothing, same problem still and now I am officially out of ideas:gonnablow and want to push the jeep into the lake. It's looking like I may have to tow it somewhere because I am not sure what else to do.:tear:

 

[Flash]

Ok, I replaced the fuel filter, fuel pump ballast resistor, cap, rotor, sparkplugs, and the plug wires. I also checked for water in the gas which there wasn't any and I checked for fuel flow into a bottle and made sure there was no air in the lines up at the fuel rail. I go to turn it over and nothing, same problem still and now I am officially out of ideas:gonnablow and want to push the jeep into the lake. It's looking like I may have to tow it somewhere because I am not sure what else to do.:tear:

Take you frustration out on the fuel take(with a rubber hammer) and just, beat the crap out of it!!! while your buddy, wife.......some one is turning the eng over!........
did the fuel pressure come up or build up any fast sense the filter change.......did ya blow thru the old filter to see if it was plugged?

If that don't work were going to have to go back to the basic's and stay on one piece, like spark and check it thru all, until we are sure that it's not it and then to the next.

flash.

 

[needsrepair]

After reading most of the posts I would still want to know what is happening at the injectors. Do you have a noid? If the noid is hooked up on one of the injector harness's and you fire it and it dies you should see the noid stop flashing. This dosent tell you what is wrong but it narrows things down. If the noid quits flashing then its a matter of did it lose the pos or the neg? One guy said that one side is hot all the time? If that is true does it lose the pos when it quits. If its pos(hot) all the time then you should be able to connect a voltmeter or test light to that wire and see if it loses the pos when it quits. If it dosent lose it then obviously its losing the ecm signal. Now the question is why. Im going to bed soon or I would dig deeper. we might need to look at a print to see what its losing. If the ecm stops the signal to the injector. Why does it. Oil switch loses signal? Other input is not seen or not the correct voltage or resistance? Corroded wire (high resistance)? I would like to see a print. I have one on cd but I dont think its that year.