Losing fuel pressure, thoughts?

[alexbrown64]

Well done,
I hope the new o2 sensor sorts out the problem. Should really improve the open/closed loop situation. Amazing what a faulty o2 sensor can do to performance....

Cheers,

[rainman]

that plug look alot like the plug that is down by the coil on my XJ i have been told it is 2 things;
1- a plug for the DRB 3 FACTORY SCANTOOL
2- ac clutch switch for alternative AC compressor position.

[Sobek]

It's been a bit of a mixed bag so far...

I've had immediate and noticeable improvements after a few short drives, noticeable gains in power, for the most part a rock solid idle, easy instant starting. But it's still feeling pretty down on power, every now and then it's got substantially more, but then it'll just be fairly flat. So I'm up and down between "Hey this feels great!" and "Hey, this feels the same as before again" haha.

I'm getting intermittent lumpy idling, sometimes after an extended drive, sometimes even during initial start and warm up. It's the exact same ploppy lump that I had before too. Hard to describe, but it's unique. And today after I drove into town and was heading home, it did something new. I was stuck in a bit of traffic, and it practically died, for just a second. A real sudden harsh jerk and audibly the motor just about died, picked up and didn't do it again for the rest of the drive home. This is eerily identical to what it was doing a couple of years ago before I replaced my cam / crank sensors and my ignition coil... That same sporadic hard jerk and loss of power.

I'm kind of thinking, maybe this is my camshaft sensor playing up... again? I bought the best one available at the time, the Standard Motor Products camshaft coil for something like $40, although they do have pretty poor warranties of about 1 year on them so MAYBE it's just a dud? What do you guys think, or could a crank sensor cause this to happen to? I was thinking camshaft sensor because that might explain the roughness that feels / sounds like it's timing related, as we've discussed, as the camshaft sensor is more likely to cause that sort of poor running than a crank. Frustratingly I never did isolate whether it was my cam or crank sensor years ago as I just replaced a whole crate of parts all at once since I didn't have the freedom to dick around with it then.

So definitely making progress! Can't complain haha. At least it starts fine and runs far far better, but there's just still one gremlin left it seems. I might take apart my dist again and triple check that cam sensor and its wiring, make sure everything checks out. Hmmm dee hmm hmmm

[rainman]

i had problems with strong fuel smells, ordered all-new roll-over valves grommets and hoses for the fuel tank. turns out when i replaced the gas cap while waiting for the parts to turn up and the fuel smells stoped.

[Sobek]

I had been contemplating replacing my gas cap, what with it being... 26 years old. Thanks for reminding me, I'll put one on order with the next lot of parts I get.

I haven't had much progress due to life things, but I think I've narrowed it all down to the crank position sensor. Mostly, it's the intermittent and sudden power loss that can happen totally at random, as if someone had slapped the brakes on for half a second at highway speeds. This is what it was doing a couple of years ago, and back then I replaced the cam and crank sensors at the same time which resolved the issue. I've been deep diving old forum discussions in my spare time, and general consensus is that this kind of power cutout is without doubt to blame on the crank position sensor. Most people agree it generally either works or it doesn't, but that it CAN operate in a degraded state and cause not only the sudden power cuts, but poor idling, general lack of power, and misfiring (which all makes perfect sense anyway). I then also remembered that not too long after I replaced it, I had that incident where the cable was too close to the exhaust manifold, and it melted the outer ribbed protective cover, making the jeep totally die on me going up a hill in the dark one night. Re-routing the cable and letting it cool made it work again ever since, but for all I know it messed up something with the sensor internally and it's just now coming to fruition. I'm also finding that I can start the jeep and it will randomly idle awful, lumpy and ploppy and reeking of lean or richness, but if I shut it off and start it up again, 9 times out of 10 it runs perfectly. Like, almost all the power back perfectly. Does kind of make me suspect the crank sensor and perhaps an iffy reading of the flywheel or something. I broke out the multimeter and as per test procedure outlined in a thousand places online, I checked ohms over pins B and C on the sensor and found that if I set my meter to 2k ohms max, I have a reading of around 150. If I set it to 20k ohms max, the reading is about 600. I'm told it should read out of limits / open / 100k+ ohms... but mine doesn't. So it leans towards the sensor being a duddy.

So that's where I'm at. Ordering the new crank sensor tonight, along with the coolant temp and air intake temp sensors as they're all stock too. With any luck this will be the ticket.

Do we have any preferences towards crank sensor brands? Back when I bought it, the best option available besides the $200ish 'oem' was the Standard Motor Products sensor from Rockauto, and it looks like that's pretty much the best they still offer. If you guys have any other suggestions for brand, I'm open. I don't think I can do a $200 "Boy I hope it's this one this time!" sensor buy right now lol

Will update in due course!!

[Classic Boy]

I only use a mopar supplied sensor on my daughters WG. Her failure was typical p0340 and the Jeep just stopped only to restart 30mins later. I read a lot of forum complaints on US Jeep forums about problems with aftermarket sensors so I ordered genuine from rockauto.
Some months Later on she suffered poor running symptoms with a very rich exhaust that was somewhat difficult to isolate no codes etc, I discovered the cam sensor drive (no distributor on the WG) had flogged out, when replaced with a new drive unit it cured the problem. It’s been great ever since. The original crank sensor failed around 250,000kms the car now has 345,000kms without issue.

[rainman]

i have had luck with NTK/Ngk sensors