3rd Fuel Pump in a year?

Hardtopdr2 wrote: The voltage was in millivolts on dvom.

Good call. I missed that. :oops:

I got the relay tester coming, its coming from snap-on so maybe it will be here in a week. I'll let you guys know whats new

And actually, I am just going to order the new fuel pump + filter, so I can atleast get the new pump installed and be able to run the truck and then find out where I am getting the electrical problems from. Instead of trying to find the electrical problems and fighting a dieing battery. I'll see ya guys in a week or so when it gets here.

And this is the pump I put in before.



Once I get it in, I'll just watch the fuel pressures and voltages all day and figure out where the problem is coming from thats causing the pump to burn up.

Oh and BTW the oil pressure sensor that ties into the fuel pump, I've replaced it a few years ago. I remember this thing. And my oil pressure reads normal and fine.

A thought I just had... take the relay out for fuel pump and see if you still get the same millivolt reading on that wire. Then grab a relay out of another spot and repeat your voltage check while using phone to record video of the dvom. Let us know what you find.

Dont I have to crank the engine to get the relay to switch power over to the grey wire going down to the fuel pump?

If your wondering if the relay is bad, I've tested it with a dewalt battery, I can switch it back and forth over and over.

Yes and no... when you turn key to on position this will momentarily supply power to pump to prime fuel lines for initial start up. Then when engine is running the relay is activated again to turn pump on. So in short if its not starting up depending on circuit design it may not reactivate pump/keep pump on while cranking till key is returned to on position to try again or engine is running.

but this also checks to see if your relay is bad.

Fyi these relays are not meant to take the voltage of a dewalt battery. 18 volt and 20 volt batteries are not a good way to test these. the only good way to test the relays is with a relay tester and a dvom meter to check resistance and voltage drop before and after relay. Some relays can partially fail causing voltage drop from 1 volt all the way to the point that the circuit no longer works due to the resistance in the relay starving the circuit even though the click is audible.


P.s.
I litterally just dealt with a bad relay on my mom's car that would not let the air conditioning clutch coil activate.

Yes like the others said. Check the ground.
I have found issues with that. They ground at the frame. Plus it wouldn't hurt to check the ground wire that comes from the battery to the frame as well.
I've seen them get green and ugly.

Hardtopdr2 wrote: Yes and no... when you turn key to on position this will momentarily supply power to pump to prime fuel lines for initial start up. Then when engine is running the relay is activated again to turn pump on. So in short if its not starting up depending on circuit design it may not reactivate pump/keep pump on while cranking till key is returned to on position to try again or engine is running.

but this also checks to see if your relay is bad.

Fyi these relays are not meant to take the voltage of a dewalt battery. 18 volt and 20 volt batteries are not a good way to test these. the only good way to test the relays is with a relay tester and a dvom meter to check resistance and voltage drop before and after relay. Some relays can partially fail causing voltage drop from 1 volt all the way to the point that the circuit no longer works due to the resistance in the relay starving the circuit even though the click is audible.


P.s.
I litterally just dealt with a bad relay on my mom's car that would not let the air conditioning clutch coil activate.

Cool, I got a relay tester and I'll be able to check both sides

Dtech494 wrote: Yes like the others said. Check the ground.
I have found issues with that. They ground at the frame. Plus it wouldn't hurt to check the ground wire that comes from the battery to the frame as well.
I've seen them get green and ugly.

How should I find it? Just follow the neg terminal wire?

Really loving the Scanner Danner videos, I just got a test light and power probe 4 coming in the mail, should be here next week. By that time, my new pump, filter, relay tester should be here. Stoked! Cant wait.

The negative from the battery goes to a stud on the block by the starter and a braided strap from the stud to the frame. Of course the braided cable makes a wonderful wick to absorb water, salt and dirt etc.
The fuel pump ground eyelet was usually in the LR wheel well with the bolt and eyelet on top of the frame with about an inch space between it and the box. You could re-locate it. The eyelet and bolt corrode but the frame has too much paint on it to make a connection, it uses the bolt threads for connection. Clean off the paint, clean the eyelet or crimp a new on on. You can fasten it to a more accessible location if need be.Put silicone grease on the eyelet and connection.
Or on the vans it was just in front of the tank either to the frame or the cross member.
Anyway if you hunt and trace you will discover it.
"Seek and Ye Shall Find "

I'll check the battery neg ground tomorrow.

So I just finished Day 1 and it started to rain so here's what I got so far. This was fun, I'm an electrical detective

I got the relay tester in with the relay on top.

Turning the key ON (not cranking)

The relay turns on for 2 secs (priming) then clicks off.

The fuel pump is not turning on for prime.

(This is during Key ON (not cranking)
Pin 87 - I got battery voltage exact
Pin 85 - I got battery voltage for prime, then goes to 0v after prime is finished

Inverse Polarity
Pin 86 - I got perfect battery voltage ground reading
Pin 30 - I got LESS then battery voltage ground reading. I got 10.29v when my battery is at 11.98v so that means I have 1.7v sitting on Pin 30 Circuit.

I went back to the ground for the fuel pump, this was after I cleaned it and the frame with a wire brush. I got a perfect battery voltage ground when I touch the bolt. But I didnt have access to check the eyelit. Thats when it started to rain.

So I'm thinking my next plan of attack is piercing the ground wire and seeing what reading I get.

And then piercing Wire 30 on both sides of the plugs to see if we have an issue with the plugs.

But I think its safe to say my top end (the relay and pin 85, 86, 87 are all fine)


**EDIT**

So I was going over in my head everything I did. And I see where I went wrong. You cant test Pin 30 as a ground because those are 2 separate circuits. Pin 30 goes into the motor first and another wire comes out of the motor which goes to ground so it pulls the current through the motor.

I'm excited for tomorrow, Day 2!

Alright!

So finally just got around to getting onto the computer and giving you guys an update!

Betsy is back running and running strong like always!

So I got the new fuel pump and fuel filter in. Cleaned all the grounds in the engine bay as well. Truck fired up right away after the new pump was installed. Using all my new electrical knowledge I learned from ScannerDanner Premium, here are the readings we are getting during engine running.

Pin 85 - 13.5v
Pin 86 - 14v
Pin 87 - 13.75v
Pin 30 - 13.75v

I checked the readings over and over during the next hour of the truck running to see if any voltage was fluctuating. Got nothing. Just steady numbers.

The truck is running great again. 370k miles and you would think it only had 100k on her!

The only part I dont like is, I never really found the cause of the fuel pumps burning out. Never found a bad wire, or anything.

But I think its safe to say after monitoring the voltages, whatever that was causing the problems was fixed because those are normal steady readings. And BEFORE, I used to be able to pull my fuel pump relay to KILL the pump when I wanted to change the fuel filter and drain the lines a little.

Now when I pull the relay, the truck keeps running like she should!

Thanks for the help everyone! Its been a fun learning project!

Are you getting warranty replacement on these pumps?

Umm heads up but when you pull the relay for the fuel pump the engine should die after ~15-30 seconds. If it is still running for a while or stays running you have a power wire somewhere in the harness going back to fuel pump shorting to the fuel pump power feed. Which would explain the pump burning up if it is running when car not on.

Hardtopdr2 wrote: Umm heads up but when you pull the relay for the fuel pump the engine should die after ~15-30 seconds. If it is still running for a while or stays running you have a power wire somewhere in the harness going back to fuel pump shorting to the fuel pump power feed. Which would explain the pump burning up if it is running when car not on.

Nope, power gets fed from the hydraulic oil pressure switch.