Anyone have detailed instructions on how to test the fuel pump pressure on a Detroit Diesel 3-53? I read that you should place the gauge in between the Secondary filter and the engine block but when I do I get a vacuum of 5 - 10 psi. I did read a forum stating that that the fuel pump should produce 45 - 70 psi at 2400 rpm.
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Fuel Pump Pressure Testing
- Thread starter csalerno
- Start date
Is the engine running for you? I don't think it's possible to get a vacuum with the gauge between the secondary filter and the block.
The fuel flow should be tank-primary filter-gear pump-secondary filter- head. You can confirm or deny, I don't have an engine handy and I'm the last guy you want to try to remember a detroit. Any chance you have the gauge between the first filter and the gear pump on the block? Even then it shouldn't have that much vacuum. Is the vacuum gauge labeled in " inches possibly?
The fuel flow should be tank-primary filter-gear pump-secondary filter- head. You can confirm or deny, I don't have an engine handy and I'm the last guy you want to try to remember a detroit. Any chance you have the gauge between the first filter and the gear pump on the block? Even then it shouldn't have that much vacuum. Is the vacuum gauge labeled in " inches possibly?
Right, that's good. I think THAT much is standard on a detroit.
I still can't see how it's pulling a vacuum. I'd start at either the tank or the gear pump and work toward the other one. Or start at the fuel strainer, blow back towards the tank with air to clear it out, then remove the line to the gear pump and clear that out.
Is the engine loosing power or stalling?
I still can't see how it's pulling a vacuum. I'd start at either the tank or the gear pump and work toward the other one. Or start at the fuel strainer, blow back towards the tank with air to clear it out, then remove the line to the gear pump and clear that out.
Is the engine loosing power or stalling?
No, I'd start with the pump back to the tank. Unless there's a rubber line that feels soft or funny.
Does your tank have a drain? Drain some fuel out before you start it up every time until it comes clean with not a speck in it. The state of the primary filter/strainer should give you an idea of the amount of junk in the fuel tank. It's also possible for something like a plastic seal from the a bottle of fuel additive to get caught in the wrong spot and cause issues. Sometimes draining and rinsing the tank is the only way to figure it out, "suckbucket" will do the job if there's no drain. The fuel is fine most likely, just let it settle and put it right back in. If there's a screen on the intake in the tank, then that saves some trouble with little bits plugging up the line, but a screen will plug with other stuff too.
If you want to diagnose the system rather than cleaning it, move that gauge around to see where it's plugged. 5-10 inches of mercury (HG) is too much in my mind. If the gauge goes from 0-30" then it's mercury.
Does your tank have a drain? Drain some fuel out before you start it up every time until it comes clean with not a speck in it. The state of the primary filter/strainer should give you an idea of the amount of junk in the fuel tank. It's also possible for something like a plastic seal from the a bottle of fuel additive to get caught in the wrong spot and cause issues. Sometimes draining and rinsing the tank is the only way to figure it out, "suckbucket" will do the job if there's no drain. The fuel is fine most likely, just let it settle and put it right back in. If there's a screen on the intake in the tank, then that saves some trouble with little bits plugging up the line, but a screen will plug with other stuff too.
If you want to diagnose the system rather than cleaning it, move that gauge around to see where it's plugged. 5-10 inches of mercury (HG) is too much in my mind. If the gauge goes from 0-30" then it's mercury.
thepumpguysc
Senior Member
I don't work/diagnose Detroits but.. when checking a 4 stroke diesel for low power, I use a pressure/vac combo gauge.. hooked into the inj. pump inlet.. it "should" show pressure.. IF it pulls a vac. anything over 4 inches, while reaching full rpm's, 9x outta 10 its a collapsing rubber line..
Macks & Fords are FAMOUS for it.. they have that soft, fabric covered hose, that collapses internally..
Macks & Fords are FAMOUS for it.. they have that soft, fabric covered hose, that collapses internally..
Birken Vogt
Charter Member
It seems unlikely, but possible, that the fuel pump is not working.
If all the fittings were super tight, and the fuel tank return is submerged in the fuel, then the pumping action of the injectors themselves could be keeping the engine running either backwards through the return line, or somehow pulling fuel through the dead pump, especially if the tank is uphill of the injectors. And pulling vacuum as they do.
This is a far fetched idea but it seems like you have covered the other things.
If all the fittings were super tight, and the fuel tank return is submerged in the fuel, then the pumping action of the injectors themselves could be keeping the engine running either backwards through the return line, or somehow pulling fuel through the dead pump, especially if the tank is uphill of the injectors. And pulling vacuum as they do.
This is a far fetched idea but it seems like you have covered the other things.
John C.
Senior Member
It has been years but I always teed a gauge on the outlet end of the pump. I've never seen any Detroit run with a vacuum on the outlet side of the secondary fuel filter. I have seen a vacuum on the inlet side of the fuel pump. Having said that are you sure you have the outlet side of the pump.
kshansen
Senior Member
Something is sure sounding wrong here!
My first question would be are you sure the gauge is working right?
Next has anything been modified in this machine? Is this the original engine that came in it and all the hoses connected as they came from factory? Is this the original gear pump?
The only places you should ever see a vacuum in the fuel system of a Detroit are the inlet to the primary filter and in the line from the primary filter to the gear pump.
It maybe a little stretch of the imagination but if someone has been switching things on this machine I could possibly see where if the fuel lines on the gear pump got connected backwards this could reverse the fuel flow. Causing the engine to try sucking fuel in through the return line and past the injectors and then pushing it out through the secondary filter to the pump and then the pump would be pushing it back to the tank by way of the suction line.
There are both right hand and left hand rotation pumps made for various Detroits so even if the lines appear to be connected to ports labeled "inlet" or "outlet" the flow could be going in the wrong direction. As this is a 3-53 those engines can be built with more variations than I would want to try to imagine. Blower on right or left, exhaust right or left, not even sure if there is a real front or back to the block! About the only thing I have not seen is a crank on the top with the head on the bottom, but even that would not surprise me. I have heard of some detroits with the crankshaft standing up and down!
Just for fun I'd suggest disconnecting the hose from tank at the primary filter and crank the engine over to see if there is fuel coming out while cranking.
My first question would be are you sure the gauge is working right?
Next has anything been modified in this machine? Is this the original engine that came in it and all the hoses connected as they came from factory? Is this the original gear pump?
The only places you should ever see a vacuum in the fuel system of a Detroit are the inlet to the primary filter and in the line from the primary filter to the gear pump.
It maybe a little stretch of the imagination but if someone has been switching things on this machine I could possibly see where if the fuel lines on the gear pump got connected backwards this could reverse the fuel flow. Causing the engine to try sucking fuel in through the return line and past the injectors and then pushing it out through the secondary filter to the pump and then the pump would be pushing it back to the tank by way of the suction line.
There are both right hand and left hand rotation pumps made for various Detroits so even if the lines appear to be connected to ports labeled "inlet" or "outlet" the flow could be going in the wrong direction. As this is a 3-53 those engines can be built with more variations than I would want to try to imagine. Blower on right or left, exhaust right or left, not even sure if there is a real front or back to the block! About the only thing I have not seen is a crank on the top with the head on the bottom, but even that would not surprise me. I have heard of some detroits with the crankshaft standing up and down!
Just for fun I'd suggest disconnecting the hose from tank at the primary filter and crank the engine over to see if there is fuel coming out while cranking.
If you're sitting in the drivers seat the Blower is on the Left, fuel pump is on the Right. The backhoe originally had the Gear pump disconnected and an Electric Pump was in place. The engine would stop running after 5 minutes with the electric pump so I rebuild the Gear pump and reinstalled the square coupling to engage it again. Like I said some days it runs with power and other days it won't budge. Will follow your recommendations Monday.
Drained the fuel tank and found no debris, replaced all of the existing rubber fuel hoses with new and plumbed all of the suction side of the Primary with copper tubing. I did notice that the fuel return line was routed about 4 inches above the exit fitting in the cylinder head. Is this gravity fed back to the tank? If so I would think this would be a problem with fuel backing up and not flowing back into the tank. Ran the hoe for about an hour and it operated fine.
kshansen
Senior Member
Should not make any difference if the fuel pump is working it is pushed back to the tank.
Did you recheck the pump pressure at the inlet to the secondary fuel filter?
Also is the fitting on the head that the return line is connected to the proper restriction fitting? Should be stamped with some numbers like .080
kshansen
Senior Member
Yes copper will work harden and then crack, probably right at the end where it is flared or how ever the connection is made.
I would prefer a good steel line with ample hold-downs to support it or if flexible connections are needed something like an Aeroquip 1503 hose:
http://www.jgbhose.com/static/905480.asp
or and equivalent. Don't need the wire reinforcement for the pressures but helps in an application where it may be hit by things!