LeRoy90laredo

dead fuel pump is my conclusion

F1Addict

You appear to have a vacuum line in your hand and I'm quite certain it goes somewhere. But I'm not sure where, someone else will have to chime in.

No hum is bad. That noise is your fuel pump priming the fuel rail (creating pressure at the injectors). If you don't hear the hum from the fuel pump then it's not priming and you're not getting fuel pressure. That could be either your pump or the fuse for the pump.

Keep in mind, the fuel pump primes based on the pressure it senses in the fuel rail. If the rail already has sufficient pressure, the pump won't prime. This is normal. So if you've cycled the ignition a few times the pump may not prime. Without a fuel pressure gauge, the only way to test this is to let the engine sit for a few minutes in order to allow the pressure to bleed off then try again, listening for the pump to prime.

mmj1111

OK so I need to first get a fuse for the pump test that out- Then if that doesn't work, replace the fuel pump. Sound about right? Are there threads or tutorials for how to change a fuel pump fuse? Thank you all for your help and expertise.

mmj1111

Cool- I connected the loose wire to the loose fitting on the air filter. So that is solved.

F1Addict

I believe there are tutorials on fuel pump replacement both here and on YouTube but don't go crazy replacing stuff yet. More needs to be known before you start throwing parts at it. Did you try priming the pump again, after your Jeep sat for a little while? If it's still not priming, it could just be the fuel pump relay (sorry, thought it had a fuse).

mmj1111

So you prime it by leaving the key in it turned for a minute or so? I did that to no avail. I will try the relay before I go replacing the pump!

beijingjeep

(im not a super expert) but there should be a cap on the end of the fuel rail on the driver side of the engine (silver tube in your pics). you should be able to take a black cap off or something like that and it should look almost like a tire valve stem (the thing you put air in your tires with) you can push the middle of that in just like you do if you want to let some air out of your tires. you can do this to the fuel rail and gas should squirt out for a little (not much at all) and then your pressure will be zero.
then, you crawl under the gas tank of your jeep (right under the rear hatch) and have a friend turn the key 'on' but not trying to start the jeep, just to where the radio comes on... if you hear a hum from the gas tank your pump/relay is good.

correct me if im wrong guys... it is like this on all the Chevy trucks i have owned... my Jeep has a carb and mechanical fuel pump... lol

beijingjeep

it will hum as soon as you turn the key to 'on'... and only for 2-4 seconds...

beijingjeep

In this picture is your coil... it gives the spark to your spark plugs... if you want to test it (most do it a different way, but this works) pull the wire off it that is highlighted green in this picture. Then you can touch the back of your hand to the copper post and have a friend try to start the Jeep... it should shock you... it won't feel good, but that way you will know you are getting spark to the distributor and we can go from there... if you want to test it a different way im sure someone will chime in how they do things.

beijingjeep

if you want to, take 3 pictures for us...

One of the engine from the front of the jeep

One from the driver side of the jeep

One from the passenger side of the jeep

If i can find time i will try to label some things for you so you can know more of where things are... Im not a Jeep expert by any means but i can do my best.

mmj1111

Anyway I can use a voltage meter instead of my hand? haha, I will test this tomorrow and get back to you, thanks!

beijingjeep

should be able to... ground and copper post on coil would be my guess. not sure if it will fry your meter or not...

But (this is the problem i am having with my Jeep) in order for the coil to produce the large amount of voltage it needs to lose voltage for the electromagnetic field to collapse. i don't know what your system uses, but some have computer controlled ignition modules to produce this 'pulse' or contacts on the distributor cam. so with the ignition on, the coil will not produce proper voltage... mine only gives 6V, however when you try to start the engine your voltage should spike if you are getting the 'pulse'. Maybe use your meter to check the voltage to your coil first and see if you can see a 'pulse' while trying to start the Jeep,(should be 12V and then drop every time a spark plug should spark, might be very hard to spot if you have a digital meter) then see what you have coming off the coil. If the coil is working properly, it should throw a spark is there is grounded metal close to it. (My Jeep has no 'pulse')

these might help:
http://auto.howstuffworks.com/ignition-system3.htm
http://auto.howstuffworks.com/ignition-system.htm
http://auto.howstuffworks.com/ignition-system4.htm

F1Addict

Remove one of the plugs, connect the plug wire to it, hold the ground electrode against a ground (like a bolt on the block or head) and have someone crank the engine. You should see a bright blue/white spark between the grounding electrode and center electrode and you won't get the crap shocked out of you

sam24th

Ok so we already confirmed that the starter turns over, so this is either a fuel delivery issue or a spark issue. Personally I think the fuel peump is the most likely culprit since you say you dont hear the humming sound anymore.

1.) To test for fuel pressure go to your local autozone and rent a fuel pressure tester. You can rent it for free. You have to put a deposit down but get the full deposit once you return the tool. Remove the cap on fuel rail. (red thing in picture) attach fuel pressure tester on it and turn the key to run position, turn off, then turn to run again, then off. You should see pressure build up on the gauge and hover around 29psi if I am not mistaken, nevertheless you should see pressure build up. No pressure is no good. If you have pressure then its probably a spark issue.


CREDITS: Picture was taken by Shawn, just using it for reference.

2.) To test for spark, pull a sparkplug, I suggest the 3rd plug just because it is easiest to get to. Ground out the end of it to the engine block and crank it. You should see it arcing a bit. If you have spark then it is not a spark issue.

DFlintstone

That is a fine way to check spark.^^ (about the first thing you do if it cranks, but doesn't start). By "Hold the ground electrode", he means the metal part of the plug. The threads, the hex part ect. Holding that metal against metal on the engine it can't shock you. If you lift it up, it can. (no big deal).

You should hear the pump a couple secs when you turn it on. (as said!) You can swap your FP relay with the AC relay. See>http://autorepair.about.com/library/images/bl347lib.htm

There is a ceramic fuel pump ballast resistor on the inner fender near the air cleaner. The front gets battery voltage, and a little less goes out the rear directly to the pump. That resistor is only to quiet the pump a bit. You can try bypassing it The resistor, and it's connections are a known problem! So you need to see if there is power there at the rear of the resistor. If there is, and you don't hear the pump, the pump is probably shot. There should be power for a couple secs when you turn it on, and also while it's cranking.

If it fires and runs a second with starting fluid, you'd know its a fuel issue and it's sparking OK.