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Charge Pump Pressure


AZB755V8
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I've been having an issue with my E9 Superliner. It starts and runs fine and if just put around don't skip a beat. If I step it a little, blow a little smoke, it noses over and start missing and sputtering, like running out of fuel. I get out of it for 10-15 seconds and it recovers. It ran Great before being garaged for 2 years. Now issues and I want to take it cross county this year. Getting to the point it has a fuel pressure gage, broke since I got the rig. I put a new gage in it today and got 20 psi. I wonder if too low and putting air into the injector lines. This gage reads galley fuel pressure, what the charge pump is putting to the injection pump. The broke gage was stuck at 80psi. So I took out the return restrictor and took out the copper seal ring and got 30psi. it seems that this part is losing the spring pressure over time. Have any of you had experience with the return restrictor going bad? My thought would have been the charge pump but it is returning a steady stream to the fuel tank even with the increase in pressure.

What is the the normal galley pressure for a Bosch pump. I don't think it is different for V or inline E9 pumps.

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To check fuel pressure it should be done under a load.I have seen many problems with fuel pressure and found years ago to check under a load this way you are checking for restictions in the lines as well the condition of the filter.I always connect a 10 ft hose to the gauge and tie it to a wiper arm and take it down the road then pull it down with the brakes.If the pressure drops more than 5 psi that means it cant get enough fuel to the injection pump or were ever your testing it from.When you check the pressure sitting still no load you are only testing the pump and over flow valve but not any thing else. Yes I have seen the valve go bad and some times you open it up and find the spring is broken.Way to test it is if the pressure is low sitting still use some vice grips and pinch the return line to the tank some but not all the way shut then the pressure should come up more.This is telling you your supply pump can pump more if it had a way of holding it from going to tank.

glenn akers

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Thanks, I'll have to get it out on some deserted road out here and wick it up. Any place else the Fire Dept would be called for the smoke...LOL I did exactly what you said with the gage already to make sure it was not something in an old line, it is wire tied up by the windshield. The pump at idle really puts a good stream back in the tank, plenty of flow.

There would be a point that the volume of fuel will not flow through the valve and pressure will rise. I have the govenor RPM's raised so the charge pump should keep raising pressure, good point. :thumb:  Maybe the miss and stubbly was due to old fuel that I did drain already. 

On the PT pump Cummins pinching the return line was the 2 cents way of putting more fuel to the injectors if I remember right. Not the right way but drivers did it to get more power. More than a few burnt pistons and valves I am sure.

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2 hours ago, Back In Black Pulling said:

Can't close return these V8 will blow seal out of filter tried it once.

With my 13mm pump lift pump will not keep up with my foot in it i have fass pump right at tank to feed lift pump. been working so far.

Are your fuel lines really old that might be sucking shut?

I heard that if the charge pressure gets much more than 100psi it will blow the secondary fuel filter right off the engine. I just replaced the gauge to see pressure. That filter is just like the construction of a oil filter and seen those blow off at 120psi. That would be REALLY bad hanging right over the right exhaust manifold.

Still would like to know the range that the galley pressure should be. Know so far 20psi seems low and 100psi is too high.

I got a 13mm pump as well that has been worked on. It does return a lot of fuel to the tank. I could only see it running out of fuel running wide open maybe, not normal driving. The engine has only 12,000 miles on the complete rebuild and all lines were replaced then, 1/2 inch to and 3/8 from pump... but could still be bad from sitting. 

Looking back at when it was missing and spitting. I had below a 1/4 tank of fuel and was getting on it. The fuel pick-up is in the lower front bung hole in the tank. From what I have seen a lot of fuel is running out and into the tank. Probably got all the fuel to the back of the tank, accelerating, and was sucking air. Guess I have to have over 1/2 full tank to go drag racing or change the pick-up, I'll change that when the truck is restored in a year or so. A working gauge would have shown that I think.

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Anywhere from 18-25psi at idle and 45psi under load. Need good pressure to fill the barrels of that 13mm pump.  The overflow valve can get weak on the return side causing low and sometimes intermittent fuel pressure problems. Need to check it under load as said.  This is for inline pump.

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