Fuel tank rattle...LOUD

[gathermewool]

Car: '97 LGT

 

Mileage: 185k miles

 

Problem: A rattling of varying amplitude coming from beneath the car. It ranges from barely audible to very noticeable, even with the radio on. I've had the car since 173k or so and have dismissed it as old car rattles.

 

Symptoms: The car runs fine. It will hesitate from a start once every 50 stop and goes or so. Nothing bad and it never continues to hesitate after that one time...well, until 50 times later or so http://forums.nasioc.com/forums/images/smilies/wink.gif

 

1st check: I got the car on a lift while doing an oil change and took a look around with the car running. I pinpointed the area of the rattle to above the heat shield, just forward of the axle back exhaust flange. I grabbed a rag and held on to the exhaust. No change. I grabbed onto the heat shield. No change. Although the sounded wasn't as far aft as the trunk, I lowered the car and checked the spare tire well. No change.

Gave up! http://forums.nasioc.com/forums/images/smilies/confused.gif

 

2nd check: A transmission fluid change later I detached the heat shield and started the car. The rattle was almost completely gone. BINGO! The aft end of the head shield had rubber mounts while the forward end was just shield to metal. I cut up a glove and put it on the car side of the shield, figuring that would cut out the rattle.

 

Rattle's back!

 

3rd check: I spent a little more time pinpointing the EXACT location of the rattle and I think I've figured it out. When I started the car this time there did not seem to be a rattle. When I lifted the car, I put my ear as close to everything as I could, minus the exhaust http://images.nasioc.com/ubb-files/smilies/eek.gif i finally put my ear on the left fuel tank and BINGO. I heard what sounded like a light hum and a very apparent rattle. As I moved my ear away the rattle diminished and then increased as I came back to that original spot. I checked the right tank at that spot and heard the same hum, but not as much of a rattle.

 

According to the Haynes Manual, both tanks are accessible with the rear passenger seats removed. An access cover for the right tank houses beneat the fuel pump/sending unit assembly while the left tank has a second sending unit. There is also an uptake (I think) line from each tank, with a filter at its end. Could it be that this filter has come loose and is rattling? It seems to me that this rattling would be dampened out by the fuel in the tank. The rattling does NOT get worse when the tank is near empty and is just as loud and noticeable with the tank full

 

How do I fix this? Please help!

 

Here's a clip from earlier:

 

FuelPumpNoise.flv video by gathermewool - Photobucket@@AMEPARAM@@http://vid381.photobucket.com/player.swf?file=http://vid381.photobucket.com/albums/oo251/gathermewool/FuelPumpNoise.flv@@AMEPARAM@@vid381@@AMEPARAM@@381@@AMEPARAM@@oo251/gathermewool/FuelPumpNoise

[gathermewool]

Does any one have any ideas?

[KnifeyMcShanker]

It shouldn't be hard to pull the sender out of the fuel tank. To be honest I'm not sure what all is in there, as the only Fuel tanks I've taken apart were Miata and RX-7s, but there were definitely things in those that could cause rattling.

 

I'd crack open the tank from the top (you may be able to access the cover from the trunk with the spare removed and the upholstery taken off) and see what you can find.

[jonklein611]

Not sure how they are mounted (haven't torn down the wagon that far yet), but it could be a mount it loose so the tank has some form of vibration?

[gathermewool]

The tank access cover is under the rear seats in the sedan. the right side houses the fuel pump primary uptake and sending unit. The left has a separate sending unit and the secondary uptake. This is at least how I interpret the Haynes diagram, although not every component is labeled in the diagram.

 

The tank also seems to be properly mounted. I've grabbed and pushed and prodded all over with out a bit of change in the amplitude or frequency. The tanks do not move at all.

 

I guess I'll take off the cover some time soon and see if anything obvious jumps out. I just don't want to mess with or possibly break the sending unit while monkeying around in there. : P

[KnifeyMcShanker]

Just be careful and remember how it all goes back together and you'll be fine.

[gathermewool]

Just thought I'd follow up with my minimal trouble shooting findings. The access cover was just behind the rear passenger seat back, beneath the carpet, and is held in place by four screws. Removed, the fuel return, supply and jet pump fuel lines are visible along with the fuel pump wiring harness/connector. The rattling noise was very obvious with the access cover removed, btw.

 

The whole sending unit/pump assembly is held in place by eight 10mm ( IIRC) nuts. Nuts removed, the whole assembly, including the top plate that was just loosened, pump bracket and send unit/level float slides, simply slides right up the studs and out of the fuel tank.

 

In a well ventilated shop, I slowly lifted the pump assembly with the motor running (and the fuel pump plugged in.) The vibration/rattling was still present, so the thought that the fuel pump bracket might be vibrating against the inside of the tank can be ruled out.

 

With the pump assembly detached from any structure - held in my hands alone - I assume the issue is with the pump itself. I completely removed the whole pump assembly and, after cleaning away all of the flammable fuel from the pump and letting it sit to dry, I very quickly bench tested the pump by applying 12V directly to the contacts for a brief moment. The pump whirred to live and sounded completly normal; however, the pump was only energized for a VERY brief time, so it may not have spun up to full speed. I wasn't gutsy enough to run the pump dry for any extended period - I was hoping for something gross and obvious right away.

 

I'm posting here with my BB, so if any of this is unclear I'll try to edit or adress it later.

 

Btw, since posting last I've replaced both CV shafts, and very shortly after have been experiencing a lot of vibration at idle in drive. Replaced one of the shafts again; no change. The fuel filter is also new; no change.

 

Any ideas???

[gathermewool]

Added a clip. I'm stil debating buying a new pump, but $100 to NOT fix the issue would suck

[gathermewool]

Cliffnotes: Fuel pump replacement solved the loud vibrating/rattling issue with the old pump. No change in performance. Vibration while stopped in gear still present.

With the ltd. Lifetime warranty, it was hard not to go with the Bosch fuel pump. I was hoping for a warm day to tackle this, but the rattle/vibration was getting on my last nerve! I’m also having a vibration issue, which I don’t attribute to the fuel pump, but was curious if replacing the pump might kill two birds with one stone.

The new guys on Limdu at the auto hobby shop refused to let me do any fuel work in the bays, so I was forced to drive home and replace the pump in the parking lot, in the cold! I’m actually glad I did. The last time I pulled the hanger assembly the pump to outlet pipe fuel hose looked fine. This time it was bulged in the center and very rubbery feeling; to the point where I could barely get the spring clamp off. I also needed a push nut, which holds the strainer to the pump suction. I drove the other car to the local Autozone and the guy cut a piece of hose for me for free; very nice!

Long story short, I froze my ass off, but made sure to take my time. I made a few simple mistakes during assembly – attached the bottom bracket before the pump strainer – but overall the replacement went off with out hitch. Started the car up, and the vibration/rattle was gone! I couldn’t believe it. The pessimistic part of me was expecting it to remain, and the $100 for the pump to have been wasted.

Lessons learned:

 

• Take your time. If you’re not in a hurry or are getting frustrated, take a break and grab a drink or bite to eat.
  

• Make sure to replace all parts that need to be replaced, even if it means a considerable delay. If it looks questionable, get a new one.
  

• If you’re working outdoors in the cold, like I was, sliding a heat pack under your gloves is a must. I can work with my entire body frozen, but as soon as my fingers are numb I’m useless.
  

• There’s an alignment stud on the pump that the strainer slides onto. A push nut is required to secure the strainer to the pump. One did not come with either the pump or the strainer, and it looked like removing the push nut from the old pump would destroy it. Unfortunately, the push nut I bought was too wide, and would not fit onto the alignment stud. I ended up having to tug, twist and pull off the old strainer to salvage the old push nut. It was a little beat up after I “gently” coerced it off the old pump, but was still in useable condition, fortunately.