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Old 03-27-2013, 12:14 AM
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Fuel pressure monkey business, 96' Silverado

K1500 305.

Went out to start her after sitting for 2 days, and crank, crank, sputter, and die. She trys but wont start.

So I gave up till today. I put the fuel pressure gauge on it, and hit the key and it went to 24-25psi. And stayed there for a few minutes.

Hit the key again and got it up to 29psi. Hit the key again and couldnt get it any higher. So figured I have a bad pump.

I removed the fuel press gauge, and put all my tools up. And figured i'd go ahead and try to start her.
So then cranked her over and with some pedal dancin, got her running. She smoothed out after about a minute.

Kinda puzzled, I went and got the gauge again and stuck it on. Fired her up, and while its running she is at 49-50psi. Rev the engine and it wont go any higher than 55psi.

I shut the engine off and the gauge drops almost immediately till about 10-9psi.

About a yr ago, I replaced the SFI stuff with MPFI stuff (the conversion kit). All brand new.

The fuel pump I dont know how old..... it is atleast 10yrs old (never changed since ive owned the truck).

So, door #1 or door #2?

I'd hate for the fuel pressure regulator to be bad already?

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Old 03-27-2013, 03:54 AM
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I have a 96 GMC with the 305 Vortec and have had to replace the pump 4 times. If you have 10 years on yours, it may be long overdue for a change. Those pumps are small and if you don't keep the filter changed it can burn them up. Of course when mine went out, they just quit running with no pressure.
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Old 03-27-2013, 11:32 AM
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Wow, 4 times... thats no good.

Ive changed my filter over the years. But it has been a while.

I think I will attack that end of the system first I guess.
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Old 03-27-2013, 06:18 PM
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Vortecs need 55-60 psi running and 60+ to start the engine. Anything less wont cut it. Sounds like yours is slow to build pressure. It should snap right to 60 ish
Replace the pump...and the filter.
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Old 03-27-2013, 09:39 PM
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Latech, is right those vortec need min 60 psi to start, 59 psi they may start then stall.
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Old 03-27-2013, 11:27 PM
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he has the replacement MPFI system, no poppet injectors on it so it will start and run at lower pressures. but it does still need the right pressure to run right & not set codes.

with 10 years on the pump, i would consider myself lucky getting that kind of life out of it. yes its time to replace it.
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Old 03-28-2013, 12:17 AM
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Ok. Update. I had a hunch, so I tested my fuel pressure gauge, and its approx 12psi off (low). Its junk.

So I found a much higher quality gauge, and screwed it to the fuel rail.

I hit the key, and immediately, 60-61 psi.

But as soon as the pump stops, the pressure drops immediately down to 15 or so.

I tried it several times, and same result. The pressure pops to 61psi with pump on, and drops immediately to about 15psi when pump turns off.
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Old 03-28-2013, 12:37 AM
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Quote:
Originally Posted by 327amc View Post
Ok. Update. I had a hunch, so I tested my fuel pressure gauge, and its approx 12psi off (low). Its junk.

So I found a much higher quality gauge, and screwed it to the fuel rail.

I hit the key, and immediately, 60-61 psi.

But as soon as the pump stops, the pressure drops immediately down to 15 or so.

I tried it several times, and same result. The pressure pops to 61psi with pump on, and drops immediately to about 15psi when pump turns off.
Had a similar problem, it was a fuel pump. It would have enough pressure to start, but would slowly bleed off and after it got hot, it'd be useless. It is pretty common for these trucks to go through fuel pumps.

Like S10 racer my 96 Chevy with a 305 is on pump number 5 and the last pump I got on rockauto.com was pretty inexpensive and has lasted quite a while.
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Old 03-28-2013, 12:49 AM
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Alrighty. Thats what I will tear into first.

Now I guess the next question, what pump (since these appear to be a P.O.S.) do you all recommend?

I was going to go with the "Delphi" pump. Anyone have good luck with them?
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Old 03-28-2013, 12:52 AM
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Holy crap! Rock Auto is awesome!! Never used them before. Thanks!
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Old 03-28-2013, 11:07 AM
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Rock Auto has the cheapest
EP381 is a Delco unit(GM pn is 25163473) price is $64.

Be sure to order a new strainer Delco TS7 (GM number 25055461) $6.30.

Dorman p/n 57901 (GM 25124032) hold down lock ring $3.82(sometimes this is really rusty and a new 1 is needed.
All above parts are available from Roick aurto and these are Rock Auto prices.

I remove the 8 bed/frame bolts, 1 ground at the tail lamp harness another ground at the front drivers side of the bed, remove 3 screws around the fuel filler, then unclip the license plate/tail light harness.

Then grab some friend or use a chainfall and raise the bed up and rest the front of the bed on the rear tires and rear of the bed on the bumper.

Clean around the send unit of the tank, compressed air is best,
unscrew 2 brass fittings with line wrenches,
and undo vent line t
hen remove the hold down cam(lockring) by useing a flat screw driver and small hammer,
lift fuel sening unit up and out,
Insepct for signs of burning on the pump harness, replace if it looks bad.
swap out pump and strainer,
drop pump down in, replace hold down cam.
At this point I take a toilet wax ring and melt it down in a soup can, then pour the molten wax over the entire fuel sending unit where the hold down cam(lockdown ring) is. I do this to prevent corrosion, but you dont have to do it. The toilet wax is the best because it is pliable and easy to remove when you do this next time.
The reattach vent line and feed return lines.
Wire wheel teh 8 bed hold down bolts and use antisieze on them.
Reinstall and reattach ground and wiring.

Delco, Delphi are both GM suppliers and have decent pumps.

peace
Hog
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