98 XJ new fuel pump... knocking !!

[HeliDriver]

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Well this is pretty weird... I finally broke down & replaced the in tank 'fuel module' because of a faulty check valve (& pressure was a little low (5psi). After going through the major pain of getting the old one out, and the new one back in (plus skid plate), it fired up & showed 49 psi, which is right on the money - and pressure holds after shutting it off. BUT ... after about 15 seconds of running there's a loud knocking coming from underneath that sounds like a piece of sheet metal rattling against the exhaust pipe, or something similar - but it's coming from the fuel tank ! I can get underneath it & actually feel the knocking coming from the tank, and it's LOUD - loud enough to hear over the engine running.
I called the manufacturer of the pump - they have a tech support line - and they've never heard of this. He just said 'you'll have to take it out again & check it'......

I'm thinking maybe it's some kind of air lock situation, as I've read about this problem with other vehicles . . . taking off the filler cap makes no difference.
Looks like I'm going to be tearing it out again I guess

. . . any ... ideas ???
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[Tim_MN]

What brand of fuel pump did you buy, Airtex ? If necessary buy a Bosch or genuine Jeep Fuel Pump Assembly. If you bought an AirTex pump, expect to replace it again in about 18 months.

 

[birchlakeXJ]

What brand of fuel pump did you buy, Airtex ? If necessary buy a Bosch or genuine Jeep Fuel Pump Assembly. If you bought an AirTex pump, expect to replace it again in about 18 months.

Or much LESS than 18 months. I've had them fail right out of the box and fail prematurely.

I won't install Airtex fuel pumps or recommend them.

 

[HeliDriver]

Yep, it's an Airtex... that's all I could locate locally....
Another thing that's got me worried is that I put exactly 5 gallons into a fresh, clean tank - that we know is 20 gallons - and the gauge shows almost half tank . . .

Looks like I'll be dropping the whole assy out again

 

[HeliDriver]

What do you think of Crown Automotive ? I found a pump module by them on 4WD Hardware's site.

 

[sidewaysstarion]

I picked up a carter from NAPA to replace my airtex, IIRC it was $200 but was worth it.

My airtex was 3 months old when the check valve failed and 5 months when the fuel gauge died.

 

[weebur]

Maybe it's a dumb question but is your new skid plate tight? Have you put a hose down the filler neck and put it to your ear to make sure it's coming from inside the tank? Just a thought before you go through all that work again.

 

[Tim_MN]

What do you think of Crown Automotive ? .

EVERY Crown Automotive and Omix-Ada repair part I have bought has been total garbage. Poorly constructed, poorly fitting, and short lived. Cheap parts are cheap for reason.

Buy a Carter or Bosch fuel pump unless you enjoy dropping the gas tank frequently.

 

[JrTxJ]

Every Jeep I've owned and fixed has used almost exclusively Crown parts and they're all running fine.

Their fuel pumps come from various sources depending on the application. Some are Bosch, some are the Pierce Company made in USA, some are from MTS, all reputable sources. I wouldn't hesitate to use them.

 

[HeliDriver]

I think the vibration was coming from an exhaust clamp that was about 1/8" away from the skid plate, between the RR leaf spring - I think... I reasoned that after it started & idled about 15-20 seconds, it would begin running rough, just rough enough to maybe make the clamp ding against the steel and yes it felt just like it was in the tank (arrggghhh). I repositioned the clamp and replaced the O2 sensor ($) and now it seems OK - except that the fuel gauge may be off . . . so I may be replacing it after all, cause I gots to have an accurate fuel gauge. Bosch next time.
I put in 14 gallons & it says its almost full - I'm pretty sure the ABS plastic tank is 20 gal...

Thanks for all the info about different types/brands )