No Start And No Search

[jagray85]

I tried searching but maybe I'm searching for the wrong thing.

Anyway, I have a 84 and a 89 Jeep in my driveway. Both Runs, one wont move and the other one wont stay running. The 89 is the problem child right now.

The 89, well it will start, but die once I let off of the Starter. It will stay running if I hold the starter, but that obviously will eventually kill the starter. I have already tested power on the ignition switch and everything checks out... What the hell?

I know I'm new here, my friend Curtis told me to join cause you guys know everything about these things.

 

[Saudade]

If you're sure the switch is OK, then check the ballast resistor on the inside fender next to the aircleaner. It's the white ceramic block with 2 wires. Simply disconnect the two wires from the resistor and connect them together. Then try it.

 

[jagray85]

Ok, Did that and it wont even start now. Just cranks over constantly, doesn't start or even fire. Plugged it back and it started right up and died once I let off the starter.

I tested the wires on the Fuel Pump harness. The Pink/Black Wire gets power when you are cranking it over, but stops when you let off the starter... so I tried jumping that wire and nothing, still does the same thing... Which wire is the one to jump the Fuel Pump?

 

[birchlakeXJ]

Did you jumper the ballast resistor? (you mention you "plugged it back?? What do you mean by that) The ballast needs to be jumpered to still allow the fuel pump to work. Can't take it out of circuit.

How did you check the ignition switch out? If it's not the ballast, the next logical suspect is the ignition switch.

 

[jagray85]

Ok, I unplugged the balast, and connected the two wires together. IT didn't start at all. Then I plugged the wires back to the balast and it started and died once I let off of the starter.

I tested the voltage on the Red (12V Constant), Yellow (ignition) and Green (starter) and they all have voltage when needed.

 

[jagray85]

Anyone?

 

[Saudade]

When you first turn the key to ON but not Start, do you hear the fuel pump run?

 

[jagray85]

No, And I even tested the Voltage while messing with the ignition. The Fuel Pump doesn't get power until its in the Start Position. The On Position doesn't do anything, Acc doesn't do anything. Only when you try to start the vehicle does the fuel pump actually get power. Atleast thats what I saw from my tests. I'm still unsure as to the right wire. But Its the only one that got a normal power reading. There's 3 wires, Ground, Fuel Level and Power.

 

[Jess]

Have you checked the fuel pressure?

 

[VAwheeler]

No, And I even tested the Voltage while messing with the ignition. The Fuel Pump doesn't get power until its in the Start Position. The On Position doesn't do anything, Acc doesn't do anything. Only when you try to start the vehicle does the fuel pump actually get power. Atleast thats what I saw from my tests. I'm still unsure as to the right wire. But Its the only one that got a normal power reading. There's 3 wires, Ground, Fuel Level and Power.

It sounds to me like you just answered your own question. If your fuel pump is not getting power with the ignition in the on position, thats the culprit for it dying once you let off the ignition from the start position.

The general rule when this is happening is to check the ballast resistor. Your fuel pump recieves 12V when cranking. This is done through the fuel pump relay by-passing the ballast resistor. When the key is returned to the on position the relay then "directs" the power to run through the ballast resistor that knows the voltage down to 5V (I believe). This is done to satisfy pesky customers who complained of hearing noises from the rear of the vehicle.

Since you have by-passed the resistor and that made your problems worse rather than correcting them, I would guess that the fuel pump relay is bad. IIRC the fuel pump relay is on the passenger side fender along with three other relays. I am not sure which one is which. But you could try buying a new relay (only a couple of bucks) and swapping in the new relay with each of the old one at a time until your problem is solved.

If this doesn't solve your problem, I would then move on to tracing the wires from the relay to the fuel pump, and the wires for the relay over to the ballast resistor. If you have leads long enough or make some redneck leads from some other wire, you can just check the continuity of those two wires to ensure that they are not broken or grounding out somewhere.

 

[Saudade]

I would agree that the FP relay is the next suspect. The relays are under the cover behind the battery, just above the ign coil.

 

[jagray85]

Great, lemme pull some from my other jeep and try them out! The other jeep I got for 500 bucks, it has a 2.8v6 with NO BALLS! ITs scary to drive and I can't drive my fast car daily so the 4.0 jeep must be fixed.

 

[jagray85]

Ok, Replacing all 4 Relays failed... Can't I just do a fuel pump rewire so it runs 12v constantly through the Ign?

 

[VAwheeler]

Ok, Replacing all 4 Relays failed... Can't I just do a fuel pump rewire so it runs 12v constantly through the Ign?

If it was your relay that was bad, you could have tried this for a temporary fix. But since the relay isn't the culprit, jumpering power isn't going to solve anything either.

I am not sure which wire is supposed to get power and which wires are supposed to send power out. (I'll check this thread after work to see if someone else has already spoken up or not) But there should be one with that has 12v when the ignition is in the "on" position or in the "start" position. There should be one lead out with 12v with it in only the "on" position and a seperate one that only has 12v when in the start position. I would start there to figure out what wire is sending power where and trace them to figure out which one is the problem.


Another test you could try to isolate where your wiring problem is, would be to uplug both wires from the balast resistor and take a scrap section of wire and run it directly from the battery to the wire that is supposed to be on the forward most connector. This should cause your fuel pump to run. If it doesn't run your problem is the wiring between the resistor and the pump. If it does run the your problem is between the resistor and the relay.

 

[db10bo]

I would say trying another CPU if you can get a hold of one. I had a friend that was having similar problems and one of the connectors in the computer was going bad so see if there's someone near you that has a spare to drop in and see if that helps your problem.

Dane

 

[VAwheeler]

I would say trying another CPU if you can get a hold of one. I had a friend that was having similar problems and one of the connectors in the computer was going bad so see if there's someone near you that has a spare to drop in and see if that helps your problem.

Dane

I personally dont see how the CPU could cause the fuel to cut out once the ignition is returned to the "run" position.

Can you shed any light on how the CPU caused the issue? Which connector was it that caused your fuel pump not to work?

 

[jagray85]

Its freeeeeeezing balls right now, so I'm going to load up on some coffee and throw on a few pairs of clothes and try the jumping method on the resistor.

I hope and pray it works, cause its snowing

 

[jagray85]

JEEP RUNS! Ok what I did was I disconected a wire off of the Resistor, and jumped it. Nothing! Fuel pump was loud as hell but didn't run. So next I left the wires connected to the resistor and hooked direct 12v up to a wire and BOOM! But it ran iffy.... revs fine, but idles rough....

 

[jagray85]

While the Orange/black wire is jumped direct to 12v, it runs but idles rough. Once I disconect the direct power, it idles great and then dies a few seconds afterwards.

 

[VAwheeler]

If it runs while you have a wire jumped directly from 12v to the resistor then that means you have a faulty relay (which you checked and determined that wasn't it) or there is something wrong with the wiring between the relay and the resistor.