Fuel pump 96 Chevy

[john k]

Been driving this 96 half ton since 2012.  Fuel pump quit on way to work back in 2015.  I discovered previous owner cut an access hole in the box, so putting in a new one was no problem.  Couldnt see it due to the bedline.  Truck now has 209k and running fine.  Has made several 900 mile trips without a problem.  A year ago in November drove it into town,  ate, then no start.  Was 5 degrees and stiff windchill.  Had no fuel pressure.  so had it towed home.  Got a new pump, but wasn't til Feb. got it in, as we had snowstorm one after another.  Only scoop out the box so many times til it gets old.  New pump, no start,  seemed to have fuel pressure.   In May, got back at it,  and bought a pressure gauge.   Pump put out 15psi, not the 45 it needs to run.   Can't find reciept.  got another pump, NAPA,  put it in, ran fine.  45psi at the engine.  drove it several hundred miles.   Then  when 59 miles from home,  no start, no fuel pressure.   Went back the next day,  30 degrees warmer, and fired right up.  Got home, put in replacement pump,  got about 250 miles on it, at home,  5 degrees and no fuel pressure.  Got 13 volts at the pump plug, so told girlfriend to tap the top of the tank,  bingo,  55psi.   moved it 50 feet,  restarted just fine.   Went out next day,  cold, no start.   First pump was ORiellys, as was second.  Now3 NAPA pumps.   now  looking to see if GM still has a pump for a 96.   Getting a little ticked off.  Anybody have such a run around?

[goodfellow]

Did you do a current draw check on the pump(s) when they were working? also, does it have an external fuel filter?  -- pumps usually don't fail that quickly unless they are stressed due to an overcurrent condition (mostly caused by restricted fuel lines or filters).

What does the inside of the tank look like?

[ron350]

According to Rock auto and Amazon.
AC Delco EP381 (GM 25163473) fuel pump is $75 from amazon or $84 rockauto.

AC Delco parts page:
https://parts-catalog.acdelco.com/catalog/catalog_search.php

 

[stokester]

Did you replace the pump electrical connector?

If memory serves me right, the AC/Delco replacement pumps include a new and improved connector. 

[slip knot]

Check your grounds.

[john k]

Traced wiring from the fuse box to tank, no damage I could see.  Tried a new fuel pump relay, no change.  Cleaned the original wiring connector with electrical spray.  Soldered on a new ground wire at the pump connection, cleaned the frame attachment point, 2 pumps ago.   The one common factor is temperature,  when the temp  falls below 15 - 20 degrees, the pumps fail to work.  Tank is very clean inside,  the only filter is the sock on the pump,  which was renewed with each change, because once pressed on cannot remove without destroying it.  Have  not tried to check the draw of the motor
.  Beginning to question the specs, quality of the pumps. 

[gtermini]

the only filter is the sock on the pump,  which was renewed with each change, because once pressed on cannot remove without destroying it. 

Does that not have the round metal inline filter along the frame rail under the drivers door?

I sometimes think all the non-oem parts are made by one outfit and packaged to suit, and sometimes that outfit turns out junk. So then you end up with junk no matter where you buy it.

[slip knot]

My 98 had a filter on frame under the drivers door. Do the pumps work again after they warm up? We see a lot of ethanol moisture issues in my area. Is it possible the fuel get slushy and won’t pump at that temperature? 

Maybe time for a dealer item pump?

[john k]

Found that there is a filter inline in the framerail,  hidden above the crossmember.    today ordered a pump, strainer, and filter from Rock Auto.  Sometimes it would start when it got above 30, most times it still took a tap on the tank. 

[gtermini]

The threaded fittings on those filters are always tighter than the dickens for some reason. Flare nut wrench/crowsfoot is a must.

Hopefully that filter is just gunked up and get's her going again.

[john k]

Sunday was the first warm 55! Day in weeks.  Got under the pickup,  replaced the filter,  steel line fittings were really tight.  Poured some dirty gas out.  Will cut it apart later.  Then replaced the pump with sock.  Fuel pressure back up to 55psi.  High today was 29,  going to put some miles on it soon.  Truck always started easy,  plenty of power, could easily get up to 85,  am thinking the pump had enough power to push through a clog, until it failed.  Funny it always happened when temp was below freezing.  Got the parts from Rock Auto.

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[geneg]

How often do you run low on gas?  Some say that running low is hard on in tank pumps since the liquid dispels heat from the pump motor.  Also the water/ethanol problem becomes worse at lower tank levels.  Granted the water is always at the bottom, but driving agitates the liquid in the tank so you may get more gas than water as long as there is enough gas in the tank.  The cold weather issue makes me think of water in the tank freezing up.  Keep the tank full (or over half full) with at least mid grade gas.  Also, change the filter once a year!  Good luck.  You should be alright now with everything replaced.

[bonneyman]

There's very few things I despise more on modern cars than in-tank fuel pumps!    (OK, power window regulators are right up there).
Yeah, replacing the fuel filter along with the pump is a must. I'd also replace the pump relay, cause if the pumps runs hot it'll likely draw more amps and can damage the relay. For $12 I carry a spare relay, just in case I get a no start. Quick and easy fix - if it doesn't help, no big loss.

I've toyed with cutting an access port in the Astro van to get around the ridiculous cost of dropping the tank for replacement ($600 last time around), but a guy who did it on YouTube said watch out when using a cut-off wheel (lines and wires are tight up against the bottom of the floor).
I take care to not run the tank below half, and add 4 oz of MMO per 10 gallons to get some lubrication to the pump. They do not like running when the tank is empty. Apparently when they run hot for extended periods the plastic housing gets darker, and the dealers can tell what's happened and deny warranty.

[john k]

every pump I have pulled out was just as shiny as the day installed.   Usually keep the tank at least half full,  a habit when living out in the country,  not keen on walking.   put on 120 miles today,,,,, ran well.  keeps up with traffic good, at 213K

[john k]

 300 some miles on the latest pump.   Last week at 22 degrees, no start zero fuel pressure, relay clicked, did not hear the pump run.  Next day 35 degrees, ran normal.  Ran a new 14 ga wire from the fusebox to the pump.  Soldered both ends.  Was in town, no start, thumped the bottom of the tank,fired up.   Today 50 degrees, no start.  Next stop is to pull the pump again, minutely check the in tank wiring, which has always appeared good.

[strik9]

At the shop we simply changed out all the connectors with fresh ones to eliminate the chronic problems.  From the tank to the chassis usually.  Not suprising that all were 90's GM products either.    Had some wonky after market pumps but mostly it was goofy wire connections.

[Heiny57]

I vote for bad grounds somewhere.

[john k]

Fixed it!  Bought a new gas tank,  the current tank seeps a bit when over half full and parked.  Pulled the pump out first.   Looked things over real careful.  Unplugged the pump wiring on the fuel side of the locking plate.  This looked good when i inspected it in the past.  This time the pump ground wire pin was black.  Inside the tiny 4 prong plug was heat discolored at the ground wire.  Cut it off both sides,  soldered in a new wire,  double insulated   the connections with heat shrink tubing.   Ran the wire through a new hole in the plate, and sealed it with black pvc.    I believe this bad dream is fixed now. 

[DeadNutz]

Great news John. I hate those intermittent problems as they will drive you nuts.

[bonneyman]

I've taken to making sure all the accessories are turned off, and then turn the key to the "on" position while listening for the pump. It hums for about 3-4 seconds then stops, and I know the pressure is up to normal. Then I crank it. Plus I carry an extra fuel pump relay to swap out under the hood just to make sure it isn't that.

[Matt_T]

I've taken to making sure all the accessories are turned off, and then turn the key to the "on" position while listening for the pump. It hums for about 3-4 seconds then stops, and I know the pressure is up to normal.

KOEO the pump is usually shut off by a timer not a pressure switch. It's a good test to confirm the pump is running but doesn't normally tell you anything about fuel pressure.

[J.A.F.E.]

Interesting I also thought the pump shut off at pressure.

[Matt_T]

Interesting I also thought the pump shut off at pressure.

Generally no, there haven't even been any fuel pressure feedback switches or sensors until fairly recently. Fuel pressure was controlled by a regulator on the rail, which dumped fuel back to the tank via a return line, whilst the pump ran continuously.

IIRC early fuel injection systems didn't shut the fuel pump off when the engine wasn't running which caused some wrecks to turn into infernos. So timers were introduced which only allowed the fuel pump to run a few seconds without the engine running. This is usually built into the ECM/PCM rather than a physical timer relay.

[J.A.F.E.]

Makes perfect sense. I was aware of the return lines and the pressure sensor would be added cost to the system - the timer is just some lines of code.

Thank you. 

[john k]

 Used to listen for the pump noise.  But my hearing loss, and any traffic or wind noise put a stop to that.  Funny how hearing loss slips away.  One of those early pumps delivered enough pressure to spray the underside of the hood, but the truck was a no start.  When i bought a fuel pressure gauge, found that punp was putting out 15 psi, spec calls for 50 -65 psi. Of course by that time the reciept had vanished.  Right now truck is running great for its 211,000 miles.  Just made a 150 mile trip pulling a car trailer.