New Fuel Pump Problems, or not?

[schotzky]

Okay, so my 1997 Ram 1500 5.9 was failing to start. I had a hunch it was my fuel pump, it would start up after tapping the tank a couple times with a hammer. One day it failed to start so I ordered a Delphi pump and replaced it. In the snow.

So the truck starts up just fine when I get it all back together. Great, except the fuel gauge doesn't work. I go to the gas station and fill it up, boom the gauge goes to full. Except now the truck wont start. Tap on tank with hammer, boom, truck starts.

Get it home. Mess with it more and notice when i start the truck, it revs, almost dies, then evens out.
When I rev RPMs and let off, the truck almost dies, or dies. Then has trouble starting again.

I briefly looked at the wiring and connectors when I had the tank out, 99% positive I got it all connected properly. I also cleaned the tank out with soap and water and dried it pretty well. The pump was an exact match, except it had that stupid 4 Pin connector adapter. Also tried swapping relays around to see if that was bad. Fuses all look good.

Im no expert, but I think it might be electrical and not pump related, perhaps voltage or a bad ground killing the pump? I have a tester, where and what should I look for?

 

[schotzky]

A little update and a bump, now the truck wont even start.

 

[Ghostman]

If you haven't already, I would definitely replace the fuel filter. Just to eliminate that possibility, especially after being replacing pump and cleaning tank.
Definitely check all connections and voltage, to the tank.
Sounds like it is an intermittent issue, like a connection, wiring.
If you have a pressure gauge, be sure to check pressure.
Just going through a process of elimination.
Is it EFI? Fuel injected

 

[schotzky]

The filter is combined with the pump, all one unit.

I dont have a valve to check fuel pressure, not sure how else to do that.

Its fuel injected.

It's cold and dark, I'll mess with it another day. Gonna check spark and get in there with a test light. I need to drain and drop the tank again.

 

[Ghostman]

You could also have air in the line as well. How long did it run, after initial start up from changing pump?
There should be a pressure valve near the fuel rail to release pressure/air, bleed the line.

 

[schotzky]

It ran for about a day. I started it, let it run got 10 mins. Shut if off. Went to the gas station to fill it up and it wouldnt start at the station. Tapped the tank with a hammer, like I had done prior, and it started right up.

Now it wont start at all. I was looking for a valve to test the pressure earlier but couldnt fine one .

 

[schotzky]

Let it run FOR10*

I'm phone posting. Damn auto correct.

 

[dapepper9]

97 is like the only year that didn't have a schrader valve on the fuel rail. Unfortunately guys with 97s need to either swap rails or put the gauge in-line.

When you turn the key on does the pump prime every time?

 

[schotzky]

I've tried to listen for the pump but I can't hear it and I dont have a helper to turn the key while I listen at the tank.

 

[Ghostman]

I'll have to pull out my old manual if I can find it.
Do you have a Haynes/Chilton manual?
There are also some posts here to download some of the manuals. I'll try to find a link for you.
Definitely try to find someone who can give you a hand, make sure the pump is coming on. If you don't hear the pump coming on, then not getting power to it. And if it is intermittent, a connection, short in the wiring, or ground.

 

[schotzky]

I dont have a manual. I'll update you guys tomorrow or the day after, i've gotta work all weekend.

 

[dapepper9]

Right here in the diy section is the factory service manual. It's for a 2001 but these trucks changed so little through the years mechanically that 98% of what's in there will match

 

[schotzky]

Right here in the diy section is the factory service manual. It's for a 2001 but these trucks changed so little through the years mechanically that 98% of what's in there will match

Thanks I'll check it out

 

[schotzky]

Hey. I didnt abandon this. My internets been down for days, I dont get 4G at my house, and it's been sub zero temps.

I havent done anything, again appreciate your responses.

I've been thinking, and it started after I cha fed my fuel pump. But then it's doing the exact same thing the old fuel pump did. So maybe it was related to me disconnecting the battery for a couple days.. idk.

Theres a few things I want to check but it's been so damn cold. I'll update I find out more

 

[schotzky]

Ok, I got the tank dropped. The relay bed is readin 12 volts, relay is good, and I'm only getting 6 volts to the fuel pump, it drops to 2 volts when cranking.
I'm looking for bad grounds and a bad wire but havent found anything. Is 6 volts to fuel pump normal?

 

[Yeret]

Sounds pretty low to me. I'm doubting the fuel pump would even operate at just two volts.

I do believe that most electric fuel pumps require a minimum of eight volts to operate effectively and that's just enough to get an engine running. It would probably run quite rough until the charging system manages to supply twelve volts, which would restore peak fuel pressure.

As far as verifying voltage through the wires is concerned, that's an area that I'm quite weak in. I'm fortunate that every electrical problem that I've encountered in my truck was the result of failure with the sensor/module itself. Well, except for my intermittent low beams, which was caused by a loose hot wire at the multi-function switch.

How healthy is your battery? Believe me, I've tested old batteries time and time again that read twelve volts with a multimeter but completely failed to do much of anything when actually hooked up. Lack of capacitance will ruin your day.

 

[schotzky]

Battery is healthy. I think my problem might be inside the relay box even though my relay reads 12v. I think it's where the wire go into the box.

The wire looks healthy all the way up, is low voltage all the way back to the junction box. Got dark so I'm gonna mess with it more tomorrow.

I've been checking grounds as i find them.

 

[EvilSpirit]

Continuity test between the fuel pump output term in the power box and the term at the pump should tell you if you have a wire issue causing the voltage drop.