Fuel filter 73 Centurion?

[Robert G. Smits]

Back working on the 73 Centurion this week end.  Should there be a fuel filter on the 455?  I have pulled the leaking radiator and have all new hoses to install.  Is there any way to tell if the fan clutch is working ?  What is the 3rd hose coming out of the fuel tank?  Sorry for all the questions, I am usually working on early Cadillacs.  Thanks Bob Smits

[JohnD1956]

The fuel filter is in the inlet housing on a Rochester Quadrojet carb. Hold the housing with one wrench while loosening the fuel line with a second wrench, then you can loosen the inlet housing and remove that. The paper filter will be inside pushed into place with a spring between the carb and the filter pushing it against the inlet side.

 

Have you ever replaced one like this before? If not, I would also recommend a lot of care when re-installing the new filter and housing.  Those inlet housing have a high probability of getting damaged threads, and then stripping when you try to overtighten to stop the resulting fuel leak.  The procedure I have practiced calls for aligning the inlet housing to the carb and then pushing the housing against the carb before beginning to turn the housing to install.  It seems to me that when that spring between the filter and carb is pushing the inlet housing outwards, the threads tend to rideon each other with excess friction which may cause misaligned and crossed threads when just turning the housing to install.  By pushing the whole inlet housing assembly into the carb and then turning, the threads have a better chance of aligning and catching without any friction. I follow this for several turns till the housing is seated and then you just need the wrench to seat the housing into the carb.  

 

If you already know about this then I apologize for the long response.

 

As for the fan clutch, there are two things to check.  with the engine off hold any blade and try to rock the fan. There should not be any movement front to back. If there is observe the movement closely. Is it the fan clutch, or is it the water pump neck. If there is no movement at all, then spin the fan blade and the blade should turn freely. If it does not turn at all or has significant drag, meaning the blade will not rotate a full rotation or more when hand spun,  then I would replace the clutch.

 

The third hose from the fuel tank depends on which two you already have.  Presuming the car has airconditioning, there is a fuel supply line, the thickest one  usually 3/8th line. That goes to one fitting on the fuel pump.  The second line at the pump goes back to the tank, this may be the same sized hose as the third line.  The third line should go to the charcoal canister on the drivers side inside front fender.

[NTX5467]

Usually, there is a thin, white/opaque clear plastic sealing washer between the metal fuel fitting and the carburetor inlet body.  It's thin and somewhat unassuming, but it needs to be there to prevent leaks.

 

Many of those filters were the "rock" filter, although the pleated paper(with metal end caps) filters will go in the same place, too.  There is also a Mercury Marine nylon mesh filter, which is claimed to be "self-cleaning".  Either way, they all work.  There were some of those filters which were longer in length than the other ones, but the one you have is probably the "short" one, about an inch long.

 

Fan clutch?  It should be "tight" on its shaft.  Not able to rock it front to rear.  As noted, the "play" could be from the clutch itself or the water pump shaft it's attached to . . . IF there is any play.  Does it still work?  if you feel a drag when you spin the fan/clutch assembly on the car, it'll probably be ok.  If it spins too long, then it's probably lost some of the silicone fluid in the clutch itself -- there is a "shadetree" method to compensate for this.  PM for information.  IF for some reason, the clutch has "locked up", time for replacement.

 

Should you need a new clutch, the fan clutches now sold for older vehicles will look a little "universal" compared to the earlier production units.  But as long as they have the same shaft length (between the mounting flange and the clutch body), they'll probably work decently well.

 

An operational check . . . when you first start the engine in about 80 degree ambient temperatures, the clutch will normally kick-in upon start-up, with more fan noise which will diminish as the clutch determines it isn't needed right then . . . determined by the thermostatic spring on the front of the clutch.

 

Hope this might help,

NTX5467

 

[Robert G. Smits]

Thank you for both replies.  As you can tell I have never replaced one of these filters.  Has anyone installed a filter in front of the fuel pump and is there any reason not to?  Thanks, Bob Smits  #43855

[JohnD1956]

Speaking of my 72 Electra, I put an inline filter right in front of my pump for a day.  Then I saw the center link had hit it at least once.  I removed that filter and did not try to find anything else to replace it with. 

Edited May 31, 2016 by JohnD1956 (see edit history)

[NTX5467]

7 hours ago, Robert G. Smits said:

Thank you for both replies.  As you can tell I have never replaced one of these filters.  Has anyone installed a filter in front of the fuel pump and is there any reason not to?  Thanks, Bob Smits  #43855

 

One of GM's orientations on fuel lines, in the general time frame when your car was designed, was to use as much metal tubing for fuel lines as possible.  That made the only rubber hoses in the system at the fuel tank (connecting the tank lines to the chassis fuel feed line) and at the fuel pump (chassis line to the pump inlet).  The orientation then was to decrease the possibility of underhood fires due to leaky rubber lines.  Now that we have ethanol'd gasoline, it makes much more sense than it might have back then.

 

The rubber line at the fuel pump also serves to accommodate engine movement (from torque reactions) more than anything else.  Current production high pressure fuel injection lines also have a "flex length area" where they quick-connect to the chassis feed/return lines.  The rubber at the tank unit was probably for ease of assembly, as the current production vehicles also have a quick connect style line attachment back there.  1980s era fuel injected cars had metal lines with rubber O-rings . . . SPECIAL fuel-rated brown O-rings.

 

When I was getting my '68 5467 going again, the old mechanic put a clear inline fuel filter on the inlet side of the fuel pump, with short lengths of rubber fuel line connecting the line to the filter to the pump.  As he knocked some of the "accumulation" lose in the fuel tank, the extra filter was to see if any more accumulation was coming through the tank "sock" and fuel lines.

 

You could do similar on the pump inlet side, but if you want a filter between the pump and the carb, then you'll need to build a new line, with a blank section, between the pump and carb.  The :"blank section" would accommodate an inline filter (as Chrysler always used, or as Chevrolet did on some 1960s cars, with metal lines).

 

NTX5467

[Robert G. Smits]

Thank you again. Is there a source for the paper filter at the carb?   Bob Smits BCA 43855

[Robert G. Smits]

JohnD1956, Thanks for the "heads up" on pre-fuel pump  filter placement.  Is there a filter associated with the fuel tank pick up and do I need to drop the tank for inspection?  Thanks,  Bob Smits BCA 43855

[JohnD1956]

Yes, Robert, there is the filter sock.  There is a few pictures of the fuel pickup in my 72 Electra thread here:  http://forums.aaca.org/topic/242584-72-electra-aka-the-queen/?page=3 

 

Look for post # 69.  It is not the best picture but it shows the sock. The sock is pressed on and holds the canister casing together.  Also, NAPA or any decent auto parts store should be able to get you the right filter for the carb. It's only a few bucks.
May I ask what the specific concern is? 

[NTX5467]

The "sock" is something like a nylon mesh, whose alleged intent is to keep water out of the fuel system.  It has metal ends and is a tight slip-fit on the intake tube of the sending unit.  There can be several lengths for the same pipe diameter, so what you find as a replacement might be a little different than what's now on the car.  Also don't be surprised if the one on your car is somewhat deteriorated and fragile.  When you remove the sending unit from the tank, while you're there . . . plan on replacing the rubber fuel line(s) going to the sending unit from the chassis-mount fuel lines.  You'll probably need to also have a new fuel sending unit O-ring.

 

Please keep us posted,

NTX5467

[Brad Conley]

...and make sure those new fuel lines are ethanol compatible.  :-)

 

[Robert G. Smits]

JohnD1956, my 73 Centurion with 55K was purchased from an estate along with a 90 Jag about 10 years ago and has been sitting in my CC car building ever since.  I am vacillating between going through the entire fuel system verses installing a inline filter and waiting to see what comes out of the furl tank.  I would like to drive the car locally for a while and am not too concerned about a mechanical failure.  Down the road my wife and I will use it to tow our vintage 1970 Airstream Bambi.