Hello all! First time post, but have been referencing LRF for a few years now for sure. So I finally have an issue that I cant see anyone else having..I have a 2001 Disco with about 93k miles.

So I've always had the on-again, off-again check engine light and it has, until recently, always been for P0455. Infamous I know, and yes, Ive already went through like 3 gas caps and that ain't it.

Recently though, i have been getting individual misfire codes (one cylinder, 8 was last I think), poor acceleration (modestly, still smooth just weak shifts and not as punchy) and rough idle once shes warmed up, like noticably shakey. All this along with the P0455. I replaced the purge valve last week, no effect whatsoever (and I was able to fit the Hyundai one, big savings).

I really don't think its a leak; if that's all it is from what Ive read its not supposed to affect performance and it obviously does in my case. Also, I am 99% sure it (CEL) comes up after passing half-tank; Ill drive 100+ miles on a full tank and NOTHING wrong. I have read that the system only activates after half tank.

Having said that, Im leaning towards the fuel pump. Not only does it only happen at half-tank, my gauge has not gone all the way up, even when completly full, for over a year now (though i rarely fill her all the way up; 91 octaine in Cali ain't cheap). That, compounded with the issues above make me think fuel pressure sensor. Now, and here's the kicker, I have a 2001, serial 1A291***, WITHOUT secondary air injection. Even my mechanic assumed it had secondary air, but it don't. Confirmed (when I replaced the radiator). Now I think my particular truck fell right between some big changeover and that will dictate a lot as to which fuel pump I have/need. I believe it will have the black plug on top and includes the pressure sensor on the pump.

Any ideas??? Thanks and sorry for the lengthy first post; obviously Im totally lost!

 

Since the gauge is driven by a float (at least in older models), seems like physical inspection of the pump assemby might be in order, don't do that with a full tank. And don't work on the fuel pump with open gas tank unless you have help nearby, wear eye and face protection. You might like Elvis, but you dont want to be a "hunk of burnin' love". But could you also have a line of some sort pinched? If you get to half a tank, does remove/replace the gas cap make any difference, like it was relieving pressure or such? Small outboard motors will literally stop running if the vent on the fuel tank is closed off.

 

If you want some help, send me your number and I'll be glad to walk you thru what to do and check.

 

Thanks for the ideas guys. DiscoMike, Ill be sending you my contact info (Thanks). I haven't tried removing the cap while she's running, but I'm assuming that would reveal a sizable leak. I'm not too concerned about the accuracy of the fuel gauge; its still roughly accurate enough to tell when its low, I just thought it might be associated with the other problems since its located on the pump itself.

 

Like I said im a noob and I cant figure out how to reply directly to you DM...Thought I would be able to send an email or message to your inbox or something.

 

Click on his name on the post he wrote to you. A menu will come down, select "PM" option, and there you go.
Good Luck, I hope you get the help you need. (and it doesn't cost you much, if anything!)

 

Cool thanks disc-o-no. It worked. Coulda sworn I tried that last time i logged in and that wasn't an option...I might not have had permissions yet.

 

Yeah, if you're not loged in for whatever reason, you can't do anything but read posts as far as I know. Sometimes if I leave the computer for a little while and come back it boots me off and I have to log back in.
Anyway, that's enough space wasted by me. Good Luck with your troubles, with DiscoMike you're in good hands. He's clearly been around these trucks for a good long time, nice guy too, and always willing to help!

 

OK, so did a bunch. Swapped the plugs from one cylinder to the next, did not change anything on the computer or performance. Hesitant to pull the fuel pump and since recent top end was done took it back to the tech.

Tech had it for like 4 days, tells me no leak (I'm assuming he pressure tested, he "sorta" indicated he did) and gave me a new (used but different) fuel cap, told me he did a injector service. Didnt get a chance to drive it himself much though, so gave me the truck back and tasked me with it (cool since he didn't charge me a thing yet).

Took the truck, drove for maybe two days, still rough as hell idle, but took a while for the check engine to come back up (he cleared the codes). Finally did today. NOW, only two codes, but one is for cylinder 8, the other for another cylinder (3 i think, but not 6 again.)

SO now two cylinders misfiring. Thats all that's reporting. Performance seems worse then before, but only a little. Still no real noticablility when on it. No more "large leak detected" though

 

Blade Rover, did you ever get this fixed? I've been struggling with the same problem for several months now. Truck runs rough, and when it throws a code, I usually get 0455, 0304, 0307, and 0300. So far I've replaced gas cap, fuel pump, evap canister and hoses, ignition wires, and igniters. And I still have the problem. My very good shop people also seem at a loss. I was hoping you could point me in a helpful direction. Any help would be greatly appreciated. Thanks!

Tom Whedbee