Losing fuel pressure, thoughts?

[alexbrown64]

I have the NTK sensor. Works great.
https://www.rockauto.com/en/moreinfo...=1180268&jsn=8

Ive heard to stay away from Bosch. Hopefully a new O2 sensor works wonders, as they really do a lot of work in measuring stuff and helping the computer make decisions on how the engine should run.

I can see my O2 sensor on my scanner doing all sorts of stuff between open loop and closed loop. The Jeep always runs in open loop until warmed up. This gives the Jeep extra fuel. This is why yours was purring when it was cold with the O2 sensor disconnected. Its when it warms up and goes into closed loop that the O2 sensor really starts working. The sensor will inform the computer how to set the air/fuel ratio.

Sounds like your basically running in open loop all the time. This is like running the Jeep with the choke on. Will run like shit!!

I think a new NTK O2 sensor for your OBD1 XJ will work wonders. Also, check the wiring around the O2 sensor, as its close to the exhaust and can melt.

Cheers,

[rainman]

ntk was OEM.

that's the beginning middle and end of it.

would be worth eyeballing the the wires going to the oxy sensor they can melt.



$5 bucks says that that the diaphragm in the top of the evap canister is torn. its just under the black cap....

[Sobek]

Originally Posted by alexbrown64

I have the NTK sensor. Works great.
https://www.rockauto.com/en/moreinfo...=1180268&jsn=8

Ive heard to stay away from Bosch. Hopefully a new O2 sensor works wonders, as they really do a lot of work in measuring stuff and helping the computer make decisions on how the engine should run.

I can see my O2 sensor on my scanner doing all sorts of stuff between open loop and closed loop. The Jeep always runs in open loop until warmed up. This gives the Jeep extra fuel. This is why yours was purring when it was cold with the O2 sensor disconnected. Its when it warms up and goes into closed loop that the O2 sensor really starts working. The sensor will inform the computer how to set the air/fuel ratio.

Sounds like your basically running in open loop all the time. This is like running the Jeep with the choke on. Will run like shit!!

I think a new NTK O2 sensor for your OBD1 XJ will work wonders. Also, check the wiring around the O2 sensor, as its close to the exhaust and can melt.

Cheers,

I guess that's the pitfall of online motoring... everyone has an opinion, and they're all absolute in their certainty. I've heard an overwhelming amount of reports that Bosch doesn't always play nice, so I have to assume there's some truth behind that. And just after I posted I also got reading that NTK were the OEM suppliers for O2 sensors anyway, so I agree and will go with that. My current O2 sensor still looks brand new, including the wiring. You'd think I installed it last week! When I installed it, I made sure to route the wiring down by the brake lines that are there, so it's as far as it can be from the manifold and exhaust

Parts are ordered, shouldn't take long to arrive and with any luck that will put this whole ordeal to bed!

Still jealous of that live data

Originally Posted by rainman

ntk was OEM.

that's the beginning middle and end of it.

would be worth eyeballing the the wires going to the oxy sensor they can melt.

$5 bucks says that that the diaphragm in the top of the evap canister is torn. its just under the black cap....

I've eyeballed that canister for quite some time, I replaced the vacuum lines for it as the old ones were brittle. I figure the contents of the canister are worthless as well at this point, but I haven't seen any R&R's on the thing. On the BMW's we remove them, disassemble, replace the filter material and refill it with a substitute charcoal material. Anyone do that on these Jeeps or are they another part that can be bought for next to nothing?

Also, how do you even remove that cap? Mine rotates freely like it has no force on it, but that's all. Is it a tight fit and you just have to pull up hard as you can?

[rainman]

the black cap just pulls up, be ready to catch the spring.

suggest u not use the vac line nipple as a lever to get the cap off fingertips under the lip of the cap is all u need.

[Sobek]

Thanks for that, I'll check that out today. If that diaphragm is rooted, is there a replacement to buy, or is it something we can just ghetto fix ourself with some alternative material? I'd wager too that mine is long since failed. Aside from fuel smells, will a leak at that diaphragm cause any other issues specifically?

Looks like big delays on shipments from the US, naturally, with all the weather they're experiencing. So sadly it may be some time before my new o2 sensor arrives. Oh well...

That being said, I've been doing some driving with it disconnected and man, is it bringing back some (good) memories or what! Just how smooth and happy it feels, and yesterday I had to hit the motorway for a bit and what do you know, it decided to do it's little "I'm a 4 litre rocket" routine and go like a stabbed rat. It's nice to have overtaking torque again lol, felt great to drive again.

Can't wait to get this sorted!!

[Sobek]

Diaphragm is as good as new. Soft, rubbery, no splits, spring is good. That's a nice surprise

I do have frequent strong fuel smells though, even with the car off. I recall reading about the vent valves in the back on top of the fuel tank failing, or the hoses from them rotting? Bugger dropping the tank, ugh.

[Sobek]

Well... There's your problem. No idea what happened to the rest of the end of it, and I was sure I bought a not-exactly-cheap part yet it's entirely unbranded. Huh. Well, new one is in, haven't had a chance to run it yet as I've been dragged away, but will tonight.





Also, while looking around and checking everything, I came across this single pin round blue wired connector just by the airbox, extending out of the same loom as the Oxygen sensor. Does anyone have any idea what this is for? If anyone recalls our XJ had a replacement motor put in somewhere in the late 90's and we suspect it may be from a Grand Cherokee given certain parts on it. My only concern is if there was a temp sensor somewhere that the stock XJ 4.0 uses that the GC one didn't have, and they just taped it up during the swap. The tape wrap on it was NOT factory, that much is certain.

I checked XJ and GC wiring diagrams and I swear I can't locate it ANYWHERE