wiggles

Ok thanks, so 55 meant I have no codes? And I can check the o2 tomorrow

CoffeeCommando

Ok, I just typed a novel and I accidentally hit Back (I have one finicky touch pad).

I'm going to explain a no code and your condition... agian.

First, there isn't a code for a malfunctioning fuel pump. It has power, ground, and I'm guessing another wire that relays that it has power and therefore is operating to the ECU. As long as the circuit is there, it's pumping fuel and doing its job... to an extent.

As long as it has power, it basically is considered "working" by the ECU. Does that mean its operating at FULL power? No. Although electrically powered it's still a mechanical device in that aspect.

There are two parts to the fuel pump. The check valve and the fuel pump itself. The Check Valve maintains pressure in the fuel line. That's its sole job. If you have a failing check valve, some symptoms you would encounter are hard starts in the morning when it's cold. But then after warmed up it starts much easier, almost like normal.

Then there is the fuel pump. The fuel pump's sole job is to pump the fuel past the check valve. That's it. It's doing it... but when a pump starts to go south it has reduced pumping. It eventually gets to the point to where it doesn't pump at all and you got nothing. The fact that when you are under load it has backfiring/sputter would indicate a dying pump. The increased throttle means increased air and faster injector duty cycles... bleeding the pressure from the fuel lines. The pump, on its way south, can't keep up with it. That is how the phenomena works.

However, 02 sensors can cause the exact same problem. Hopefully that is your problem because it's much cheaper and easier to deal with. But.. you also don't have a code for it.

Something to note is although I had a bad 02 in the front once.. It wasn't revealed that it was bad until I replaced the one in the rear. Do a search for "Oxygen Sensor FYI" or "02 Sensor FYI". I posted it a few weeks ago. I'm not going to retype all of that. That will explain to you how the 02's work.

wiggles

Thanks man, that's a big help! It does take just a tad longer to start when it had been sitting for a little while. Is there a way to narrow it down to just the pump?

CoffeeCommando

I pretty much just did that for you. The only other things that will cause your symptoms are electronics.. and you don't have any codes.

It taking longer to start is the check valve, but I think that's still ok. It sounds like your pump itself is on its way out the door to me. And since your check valve is slowly losing pressure, I recommend scouring the internet NOW for an antire pump assembly, by Bosch, before it dies on you.

Delta

the problem is that my CEL isn't on and i know it works cause it came on a while back because of the compressor and now its gone

CoffeeCommando

I told you that you won't see a CEL for a failing pump that is still pumping.

CanadianJay

Check the condition of the wires from the CPS at the top of the bellhousing. Didn't have a chance to read all the threads on this post but I had a very similar issue in my old XJ. Turned out the wires from the CPS weren't routed well and hit the exhaust causing them to melt and short together.

Not sure if the 98 has the same CPS setup...

CoffeeCommando

CPS and exhaust are on opposite sides of the engine in the inline 6.

CanadianJay

Hmm coulda sworn the crank position sensor was mounted to the top of the bellhousing (exhaust side) and the wires passed around the exhaust side... I didn't mean the cam sensor in late model XJ's... well been wrong before.. wife reminds me of that fairly regularly...

96 xj mudslut

I'm having this same problem on my xj. I have replaced everything on the ignition and fuel system. Also engine will NOT rev over 3 1/2. I'm thinking map sensor or air flow sensor. Tps and cps are also new along with o2 sensors

CoffeeCommando

CPS is a camshaft position sensor, in the distributor, on the opposite side of the engine.

CKS is the crank sensor, which is by the exhaust like you said. Shouldn't be touching it though. The cord is just long enough to reach up to the manifold on mine... but I have the 97 and later era XJ.

CoffeeCommando

The only time I ever had my engine to where it wouldn't rev past 3 grand was when I had a collapsed lifter...

And if you have that, you should hear a ticking coming from the engine. It will sound exactly like a "tick" . Not a shick, and not a knock.

If you have that you need to not crank it anymore and pull the head off. You're going to need a new set of lifters. And pray to god it hasn't wiped out your cam if that's the case.

ooteedee

Well.... I seemed to have solved the problem by replacing the Fuel pump and ASD relays.
(I also replaced the cooling fan relay just for the heck of it.)

No more hesitations.

BUT now it tends to stop running when idling at 500-700rpm.

Plus, the passenger front door window just dropped down into the door. Apparently, disconnected somehow. Geez.....

CoffeeCommando

It shouldn't idle between 500-700. When I first installed my Airtex fuel pump it did that. Did that for a long time. Then would disappear and reappear every other day.

I just finished installing my new Bosch, and my lean code (p0171) is gone. It has better performance at WOT.

The airtex was running ungodly lean at WOT. I had an AFR hooked up so I could see that.

If you just installed an airtex... not good. What kind of pump did you put in there?

ooteedee

I didn't replace the fuel pump.... just the fuel pump relay.
(In the fuse bus under the hood.)