Modern fuel pumps

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another Todd

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How does a modern fuel pump with a reservoir work? I am having issues with my 2000 Silverado in which it starves for fuel at about one quarter tank, it still runs but only will achieve about 30 MPH and acts like it is running out of gas. Adding fuel to the tank cures the problem. Again, this happens when there is still about 6-7 gallons of fuel in the tank. What is happening here? I intend to replace the pump, but I always like to know exactly what causes failures like this. BTW, the filter is fresh.
 
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I suspect its getting hotter when the fuel level is lower. IF its beginning to fail, that difference in temp might be enough to put it over the edge.
 
On Silverados, Suburbans, and Tahoes the fuel level sending units are known to fail. This problem is a little difficult to diagnose because the fuel gauge usually appears to be working properly. Also, on these three vehicles that are E85 capable, the alcohol concentration sensors are known to fail. Either/both of them somehow control fuel pump operation through the main computer and either/both of them can cause the problem you describe. Malfunctions with either of these components will usually throw a CEL (eventually).
Also, the problem that you describe and/or a hard-to-cold-start problem (unusually long cranking time after the vehicle has been sitting) can be signs of an impending fuel pump failure. This will NOT typically throw a CEL.
 
Originally Posted By: another Todd
I do not have the long cranking time issue. When at 1/4 tank and the problem is occurring, it does throw a code but it is only for random misfire detected.

A lean running condition can cause this. Have you changed the fuel filter? If not, I would start with that.
 
Originally Posted By: wag123
Originally Posted By: another Todd
I do not have the long cranking time issue. When at 1/4 tank and the problem is occurring, it does throw a code but it is only for random misfire detected.

A lean running condition can cause this. Have you changed the fuel filter? If not, I would start with that.


Please read his original post.
 
It's purpose is to keep the pump swimming in fuel all the time. Cooling is one benefit, but the primary reason is to keep the engine supplied at all times to reduce the number of misfires. Even though it's a lean misfire, it's still unburnt hydrocarbons out the tailpipe. You don't have to feel them or have the MIL kick on for them to be occurring either.

It's filled by a jet valve down at the bottom and retained by a check valve.
 
The fuel pump is like any other part..it wears out and needs to be replaced. Get it replaced before it leaves you stranded. Keep the filter changed and don't run it low on gas or else die prematurely.
 
Originally Posted By: Warstud
The fuel pump is like any other part..it wears out and needs to be replaced. Get it replaced before it leaves you stranded. Keep the filter changed and don't run it low on gas or else die prematurely.


^^^THIS!!

When I spoke to the Delphi techs about these pumps he said their 'design life' was/is about 100K miles, give or take, even if they are treated like gold.

The factory installed Delphi module I am replacing currently (with ANOTHER Delphi pump) owes me NOTHING at 165K HARD miles!!
wink.gif
 
Originally Posted By: another Todd
How does a modern fuel pump with a reservoir work? I am having issues with my 2000 Silverado in which it starves for fuel at about one quarter tank, it still runs but only will achieve about 30 MPH and acts like it is running out of gas. Adding fuel to the tank cures the problem. Again, this happens when there is still about 6-7 gallons of fuel in the tank. What is happening here? I intend to replace the pump, but I always like to know exactly what causes failures like this. BTW, the filter is fresh.


We have not had much issue with fuel pumps here, despite a lot of GM V8 powered trucks in the lot. BUT they do have weird symptoms when failing that include a strange hard to start issue that can be very intermittent. Usually you are driving along and they just quit, no sputter, the truck just stops running like you turned a switch.

Also note that no matter what the sending unit says the amount of fuel actually in the tank can be quite different!
 
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reservoir?

to my knowledge this word has been used to make it sound like there is "reserve capacity," but it's usually just a fancy way of saying the tank has a couple more gallons on tap after the needle gets low.

VW was the only MFR i've known to actually add external tanks as "reserve," but they were actually located above the gas tank and were, as far as I could tell, the first to drain after filling up!

I can't say for certain with your model, but from what I understand, most newer pumps are actually in their own capsule inside the main tank. The capsule is fed fuel from the tank via jet pump, so it's always full, even if the tank is nearly dry. The pump doesn't become uncovered until you're down to the last quart. So, I'd move pump, filter, and regulator thoughts down the list.

Reading the above about faulty sender and sensor, I'd start there.
 
Originally Posted By: dailydriver
There IS a 'well' depression in my plastic tank where the pump module sits, ALWAYS submerged, to help prevent starvation/pump overheating issues.

I don't know if the truck tanks are the same.
21.gif


Steve??


Yes, there is a depression to keep fuel available to the pump.

Add to that incredibly conservative fuel gauges. Even with the yellow warning light illuminated WAY after the E mark there is still 5 gallons or so in the tank.

In the last ten years across a lot of GM V8 trucks we have had one intermittent pump that we replaced and one outright failure. It just doesn't seem to be a huge problem.
 
Originally Posted By: dailydriver
Originally Posted By: Warstud
The fuel pump is like any other part..it wears out and needs to be replaced. Get it replaced before it leaves you stranded. Keep the filter changed and don't run it low on gas or else die prematurely.


^^^THIS!!

When I spoke to the Delphi techs about these pumps he said their 'design life' was/is about 100K miles, give or take, even if they are treated like gold.

The factory installed Delphi module I am replacing currently (with ANOTHER Delphi pump) owes me NOTHING at 165K HARD miles!!
wink.gif



How do you treat a fuel pump like gold? How do you run a fuel pump "hard"? With a fuel return I'm pretty sure it just pumps fuel in a relatively continous fashion. Unless if it bumps pressure under load...?

Also, 100k is on the short side, what with 100k warranties on the rise. Pretty sure they design for longer, and given how many troop well past 100k I'd have to think they do design for much longer life than 100k.

Who uses Delphi pumps?
 
^^^^^^^^^^^^^

I do. They offer pumps across multiple applications, with design changes to problematic pumps.
 
I find that running them low always tends to make them fail sooner as there is less liquid to cool them. Also, as mentioned, the sending units tend to give problems. The use of a PEA detergent based fuel system cleaner like Techron or Gumout with Regane can help solve that on some.

I make it a point to always fill up at 1/4 tank if at all possible.
 
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