5 Series Fuel Pump in '74 tii: Unusual Sounds

[2002#3]

1974 2002tii...

I (1) prophylactically replaced the original fuel pump (which was working perfectly, albeit characteristically noisily) with a new 5 series Bosch (16 14 1 179 232) fuel pump and (2) installed new in/out hoses, expansion tank, and SS clamps.  Pump and tank seemed to be mounted well and isolated by rubber from the floor and body.  No leaks.  No vibrations.

• The new pump worked flawlessly during 1,500 miles.  However, it's promised newly pleasant low volume hummmm was constantly interrupted by a rougher, different-pitch lower sound.  The expected and the unusual sounds seemed to alternate back and forth every couple of seconds.  

 

I thought "bad pump", so I installed another one.  Same pump, same OEM number, also made in Cech; however, different supplier.

• The second pump also has performed performed flawlessly during the last 2,000 miles.  However, same alternating sounds.  Now, I can feel the sound as vibrations not by feeling the pump, but rather by touching the inlet of the tank where the unwanted vibrations (and resulting sounds, I assume) seem to have their genesis. In the photos, this spot is at the most obvious SS clamp which attaches the braided line to the tank inlet.  NOTE:  Don't be concerned with all the exposed electrical connections.  They were weather-sealed after the photo was taken.

 

All seems fine in '02 Fuel Suppy Land except for those unsettling alternating sounds.  Something doesn't sound or feel right...

 

Any thoughts?

 

Larry

 

PS:  Thanks Mike and Andrew for listening to this issue at '02 Fest.

 

 

 

 

[Glen Karr]

Larry,

The original pump had a cone screen in the pump inlet which stopped rust particles and whatever that made it past the tank pick-up screen.  When I replaced my original pump with the new style pump I put a small canister fuel filter (NAPA 3299) between the tank and the pump.  What may be happening is contaminants which were previously caught by the inlet cone filter are now free to enter the new pump and after awhile damage/erode the new pump internals.  Good luck on your diagnosis.

 

Best,

Glen

[2002#3]

Thanks, Glen.  Certainly might be the case.  As I recall, both new pumps have inlet screen filters.  Go figure...

 

[MatthewCervi]

Have you checked the screen on the fuel pickup in the tank?

[PaulTWinterton]

I had that happen "once" shortly after I installed the 5-series pump.  I went for a test drive and when I got home I heard that sound.  Freaked me out.  I started the car a few minutes later and the sound was not there.  I still think it was pump cavitation caused by air trapped inside the reservoir (tank). Once the air was replaced with fuel the sound never returned. To test my theory I guess you would have to prime the pump or fill (bleed) the reservoir manually.

 

I also wrapped my pump with rubber "flashing" mostly to get a better fit in the bracket. Smaller diameter pump.   Kinda loose metal-on-metal without.

 

 I hope that adds some positive information.  Good luck.

 

 

[2002#3]

Matthew, I have not checked the screens within the pump or inside the gasoline tank.  Will do so.

Paul, I, too, wrapped the pump in bicycle tire inner tube to secure it and to fit the bracket.

Thanks, guys.

 

[dlmrun2002]

  A  late model e30 fuel pump will drop and fit perfectly into a 1974 gas tank. Fuel sender will be spot on too. Less pump noise when in the tank also.

hth

dlm ny country

[Son of Marty]

If the screens or air leak don't solve the problem maybe the fuel jar has lost it's air bladder and is not damping pulses, not the first thing I'd suspect but it's on the list.

[OriginalOwner]

+1 Glen Karr.    When I did the change to the 5-series pump (early 2010) I saw no pump inlet screen, so I installed a small nothing-fancy fuel filter between tank and pump inlet.  No problems to date.

    I used a "take apart" style so I could disassemble, clean, reassemble ..... Something like this .......

Cheers,

 

Carl

 

[2002#3]

dlmrun2002:  Always a good option.  

Original:  You got a source for your tidy, take-part filter?  Several are available on eBay.

Son:  Fuel jar?  Air bladder?

 

Thanks to all.

 

Larry

 

[Son of Marty]

The black can, it acts as a accumulator and has a bladder in it to damp out fuel pulses from the pump and provide a reservoir of fuel at pressure so you don't lean out when you suddenly floor it. 

[2002#3]

Thank, Son.  I knew its function but had no idea it had a bladder in it.  It's new so I assume the bladder is OK.  Maybe trapped air...

[Son of Marty]

Yeah I've never cut one apart so I'm assuming a bladder, if not then it's shape and position will keep some air trapped. But the use/reason remains the same.

[otisdog]

No bladder in my recently refurbished '74....

[SydneyTii]

I had a tiny air leak, same weird sound, eventually it leaked fuel and I found it, back to normal now, my leak was in the pipe which feeds the pump, I assume it was drawing tiny amounts of air in.