Just the fuel pump? or something else..

[mattynicks3]

Quick update...

Other day we were out messin with it again and decided to put a CPS in it thinking maybe it would bring the fuel and amperage gauges back. Ive read that the CPS can cause these to fail as well as not letting the OBD II connect...3 problems that my Jeep is having. Before actually having the old one out I figured what the hell...and checked the shrader valve for pressure at the fuel rail, and for the first time since I've owned the Jeep, there was actual pressure there. The day before we replaced the fuel pump, but had no luck. Could it be possible that there could be a clog in the fuel line somewhere and it is taking a while for the fuel to get passed the clog? And what's the best way to clean out the fuel lines if this could be the problem?

 

[joe_peters]

Well, on the 97+ the filter/regulator/fuel pump is an assembly in the fuel tank, and the fuel tank must be dropped to get to the assembly.

As for the fuel taking time to get past a clog--unlikely. Counter intuitive that with the fuel pump not running that the fuel would be working its way past a clog over time--if I am understanding your post.

 

[Matthew Currie]

If you found ice when you had the pump out, perhaps there was still some you didn't find.

If there's a chance of something in the lines between filter and fuel rail, I'd disconnect the line near the tank first, and see if it pumps gas out, because I still think your first priority is to determine if the pump is coming on when it's supposed to, and if not, why not. If fuel comes out there, then the next step is to determine if there's ice or something else in the line between there and the fuel rail, because if there is, you don't want it pumping into the injectors.

 

[orange]

What is the P.S.I. fuel pressure ???

 

[mattynicks3]

Alright so we're finally getting pressure at the fuel rail, but only when we jump out the fuel pump relay. We tried starting it because now we're getting fuel, and we found we had no spark either. We checked and found that there was power getting to the ignition coil, but nothing coming out of it, so I went and picked up a new one and installed it yesterday. Tried starting it after that and it still didn't want to start. Not sure if we'll be out there working on it today but when we find new things I'll keep you guys posted.

 

[gradon]

I've had the shorted/bad cps cause the crank-no start, no connectivity to the obd2 port, no fuel to the rail, due to the shorted out asd relay. If you have the ignition on and then unplug the cps, you should be able to hear the priming of the fuel rail if it is indeed a bad cps. Also, you might want to trade the ASD and fuel pump relays for the A/C and starter relays.

 

[mattynicks3]

I've had the shorted/bad cps cause the crank-no start, no connectivity to the obd2 port, no fuel to the rail, due to the shorted out asd relay. If you have the ignition on and then unplug the cps, you should be able to hear the priming of the fuel rail if it is indeed a bad cps. Also, you might want to trade the ASD and fuel pump relays for the A/C and starter relays.

The CPS is brand new, just put it in on friday. The only way we could get the fuel pump to kick on was to jump the fuel pump relay. We did swap the relay with the other relays thinking it may be bad, but it made no difference. I highly doubt every single one of the relays in the Jeep are bad..so I'm guessing there is something else going on.

 

[kastein]

Where'd you measure for power at the ignition coil? The positive end is constantly powered while running, it's what's known as a negative side switched system. The ECU grounds and then ungrounds the negative side when it wants a spark.

Also - Leominster/Lunenburg, eh? That's right up 190 from me, basically. I'll be out of town this weekend but if you need another person to stand around and scratch their head I can head up that way sometime.

 

[Wallyman]

Shot in the dark here but it has happened
Pull apart some of these connections to see if they corroded. very poor electrical connection can cause phantom symptoms and intermittent ones to boot.bad grounds are a common issue as well. Also if it sat and a rat got up in there.... well you know...

 

[Matthew Currie]

Shot in the dark here but it has happened
Pull apart some of these connections to see if they corroded. very poor electrical connection can cause phantom symptoms and intermittent ones to boot.bad grounds are a common issue as well. Also if it sat and a rat got up in there.... well you know...

I mentioned this before, but second it again.

 

[Wallyman]

I mentioned this before, but second it again.

I see that now. sorry it was late and i was skimming.

 

[mattynicks3]

Ok so I know its been a few months but I know you guys want updates when shit gets done sooo.... the beast is finally running! I haven't had time to tinker with it until the past few days. I found an ECU, got it this morning, plugged her in, and my Jeep fired up with no hesitation. All my gauges are working, the fuel pump is kicking on and priming as it should, and I obviously have spark now...cause it runs. So after all the bulshit and time put into this thing tracing wires and testing grounds, checking/buying sensors, and jumping relays, the ECU was the culprit. I did replace the fuel pump, but the old one was shot anyways so it needed it.

Just a heads up for people that say ECU's never go bad.....here's another one.

 

[kastein]

Huh. Glad you got it fixed!

How much would you want for the toast ECU? I've got a '99 on my desk gutted and I'd be interested in comparing the hardware to the '98 to see what they changed between the two years, just don't feel like paying $50+ for a perfectly good one at the junkyard when I'm going to tear it to pieces anyways.

 

[mattynicks3]

Idk what did you have in mind for a price? The junk ECU I have has been opened up, but is untouched. We opened it to look at it to see if there was anything physically broken inside, but everything appears fine.