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Detroit 3-53 Fuel Pressure:

old-iron-habit

Senior Member
Joined
Nov 22, 2012
Messages
4,233
Location
Moose Lake, MN
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Retired Cons't. Supt./Hospitals
New pump showed up today and it's a left hand rotation where I need a right hand pump. This was packaged incorrectly as the label clearly states "Right Hand" rotation. Located a rebuilt pump on ebay with the exact same part number and the gent shipped it today. This pump is a "Reliabilt" unit and never installed. I'll drop the incorrect pump back in the mail tomorrow morning.

You mentioned that some of the fuel lines have been replaced. Make sure the lines from the gear pump to the secondary filter are rated to hold the pump pressure. They were usually steel from new. I found one which had a rubber carburetor low pressure rated fuel line instead that collapsed on the inside. I have also seen the low pressure primary filters used in the secondary filter canister and they fail plugging the line to the head with little fuel and pressure allowed through. Sounds like you got it figured out, but wanted to share a couple quite common issues we found in the past.
 

1693TA

Senior Member
Joined
Feb 27, 2010
Messages
2,687
Location
Farmington IL
Occupation
FAA Radar Engineer, (Retired)
Hi and thanks. The suction line from the tank to the inlet of the first fuel filter is low pressure carburetor fuel hose. From this filter canister to the inlet of the gear pump is a hydraulic hose with crimped ends. From the discharge side of gear pump to the inlet of the second filter is another hydraulic hose with crimped ends. From this second filter cannister to the head inlet is yet another hydraulic hose with crimped ends. The return to tank from the restrictor fitting is a low pressure fuel line. I don't know what SAE hose it is but I've had it all off the engine and blown through it, (by mouth) and really didn't note any undue restriction.

When I replaced both filter elements I verified they were correct in the housings. They are WIX filters from Napa and all the gaskets/seal rings were replaced also. When I had the original pump removed I pulled the hex plug in the side, removed the spring, and when I turned the pump sideways, the relieve valve slipped out in my hand without a hesitation. I looked and seen nothing on either the valve, or seat which would cause constant pressure relief, or bypass. I didn't take the body apart but I did dunk it in the solvent tank, (mineral spirits) and gave it a good douche and degreasing and when clean nothing looks out of sorts. I then put it back together and remounted onto the engine with the same results.

The replacement pump is currently in St. Louis so should have it tomorrow and will get it installed and checked out shortly thereafter.

Really appreciate the help/guidance/ideas as it helps keep me motivated to work on this old crap. Besides being a lot of fun, it does a good job keeping me out of jail.

Thanks,
 
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1693TA

Senior Member
Joined
Feb 27, 2010
Messages
2,687
Location
Farmington IL
Occupation
FAA Radar Engineer, (Retired)
New pump took care of the problem. I built up and replaced the low pressure hose on the discharge side of the restriction fitting and installed a small hydraulic needle valve and gauge into this line for testing purposes. This is the hose returning to tank. The original pump would not build hardly any pressure at all remaining under 10psi with the needle valve completely closed just before engine stall. The new pump in the same scenario unloads at about 85-90psi and the engine stalls shortly thereafter. Normal operation pressure at about 1500 or so rpm, (no tachometer installed) is about 40psi with a gauge plumbed permanent.

The engine miss or high speed "flutter" is gone, and she screams as should.
 
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