flaky relay problem

[LONO100]

Hi all, i recently ran into a fuel pump issue and wanted some opinions. for the past few weeks, there would be some days that i would jump into my truck, turn the key, and get no turnover. then i would come back a few hours later and it would fire up no problem. i then noticed that every time my truck wouldn't turn over, i dont hear the fuel pump buzzing so i figured that it was a fuel pressure problem. the funny thing, is that i never get this failure when im driving, or anywhere else, it always happens in the morning when i first try to fire up my truck.

now, it doesn't fire up at all. i got a fuel pressure gauge, tapped into the fuel rail via the schraeder valve and turned the key to the on position and got 0 pressure. to make sure i don't replace the fuel pump needlessly, i popped the fuel pump relay and took it to work where i have a power supply. i then hooked 12 volts to it and could not get the relay to click over. i also measured no continuity and OL ohms. i figured, "yes, it's just a bad relay."

i then went to autozone and got a replacement relay, brought it back to my shop and ran the same test to make sure it was working correctly. sure enough, i was getting it to click over once i ran 12 volts, and i got proper OHM measurements. (2 mohms).

here's the weird part: i ran the same test on the old relay, and i was able to get it to click over and show continuity. my question is, has anyone ever seen this flaky of a relay before, and if so, is there something within my truck's electrical system that is causing the relay to fail? anyone ever run into this flaky of a relay?

any opinions on this would be really appreciated.

 

[bdmaash]

Yes, I agree it is the relay, with 12V on the coil it will click, unless there is a diode in it.
(diode - if the power is hooked backwards it will short across the diode. the diode is mainly there to suppress the transient from the coil, when the power is disconnected from the coil)

try and hook power to the bad relay backwards to see if it clicks also.

Relay contacts will burn (arc) over time in high current applications and may cause the relay not to work (switched power side) even if it is clicking.


and yes the connection to the coil may be intermittent, causing it to not switch sometimes.

Hi all, i recently ran into a fuel pump issue and wanted some opinions. for the past few weeks, there would be some days that i would jump into my truck, turn the key, and get no turnover. then i would come back a few hours later and it would fire up no problem. i then noticed that every time my truck wouldn't turn over, i dont hear the fuel pump buzzing so i figured that it was a fuel pressure problem. the funny thing, is that i never get this failure when im driving, or anywhere else, it always happens in the morning when i first try to fire up my truck.

now, it doesn't fire up at all. i got a fuel pressure gauge, tapped into the fuel rail via the schraeder valve and turned the key to the on position and got 0 pressure. to make sure i don't replace the fuel pump needlessly, i popped the fuel pump relay and took it to work where i have a power supply. i then hooked 12 volts to it and could not get the relay to click over. i also measured no continuity and OL ohms. i figured, "yes, it's just a bad relay."

i then went to autozone and got a replacement relay, brought it back to my shop and ran the same test to make sure it was working correctly. sure enough, i was getting it to click over once i ran 12 volts, and i got proper OHM measurements. (2 mohms).

here's the weird part: i ran the same test on the old relay, and i was able to get it to click over and show continuity. my question is, has anyone ever seen this flaky of a relay before, and if so, is there something within my truck's electrical system that is causing the relay to fail? anyone ever run into this flaky of a relay?

any opinions on this would be really appreciated.

 

[LONO100]

Thanks for your thoughts! I have been at work all day today and will report back once I get to my truck tonight and pop the new relay in.

 

[01STrunner]

My buddy had that issue with his starter relay in his F150. It would intermittently not crank. He'd try several times and normally it would finally catch. He ran through the same test and concluded it was a bad relay. He got a relay from one of the auto parts stores and ended up having the same issue. Fed up, he went to Ford and spent the $16 there for a new relay and it has worked fine since. No real explanation other than the auto parts relay was already defective.

 

[LONO100]

worst case scenario, if it turns out to be my fuel pump, does anyone have any recommendations on brand of fuel pump i should get? is it critical i go oem with it, or can i just pick one up at my local autozone?

 

[01STrunner]

Ask [MENTION=186147]koda2000[/MENTION]. He's done 5 or 6 pumps in the last year on his fleet.

 

[koda2000]

Ask [MENTION=186147]koda2000[/MENTION]. He's done 5 or 6 pumps in the last year on his fleet.

Do not buy an AirTex fuel pump. They're junk. I highly recommend the Bosch 69128 fuel pump. I'm waiting on my latest purchase to arrive in the mail. Paid $58.12 with free shipping.

Here's what you get. You will not need the large O-rings.
http://www.ebay.com/itm/Electric-Fu...ash=item43cd775259:g:dtEAAOSwDNdVrpDK&vxp=mtr

You'll also need a new strainer (Aixtex FS199 or equivalent) and a new fuel filter. You'll have to determine if your ST has the 2 or 3 port fuel filter. Mine had the 3-port, but some have the 2-port.

I also recommend you replace the hose from the in-tank fuel pressure regulator to the fuel line nipple. The Bosch kit comes with enough new hose to do this.

Irregardless of what the compatibility charts may say, the Bosch 69128 pump will work. I've checked this out with Bosch Tech Support. I've installed this pump in two 2000 Mountaineers, an '01 Sport Track and an '01 Explorer, one replacing an AirTex fuel pump that didn't last 2 years. All the Bosch pumps are performing perfectly.

 

[LONO100]

thanks for the info koda! i happened to be searching the inventory of my local pick n pull and for the first time ever, i found a 2004 sport trac in their yard. i drove over there during my lunch hour yesterday to check it out, and i pulled an OEM fuel pump off of it for 30 bucks. i took it back to my work where i have a shop, and power supply and ran leads to it and fed it 12 volts and the thing ran perfectly.

i havent had the time to mess around with my truck since my last post, but i should have some time this afternoon, or friday to sort out whether it's just the relay or the pump itself. if it's just the relay, im still glad i was able to pull this fuel pump for 30 bucks as a back up for when the fuel pump eventually fails.

ill report back with results by the weekend. thanks everyone!

 

[LONO100]

Well, the relay was popped, and with the new relay I bought, I confirmed that the fuel pump is also dead. I pulled the fuel tank down and the pump I got from the salvage yard doesn't fit, I pulled the used pump from an 02, my trac is an 03, and I guess they have different shaped tanks.

So that leaves me with having to fork over some major dough for a new pump. I'll continue to report my progress on this thread. Thanks everyone for all the tips and info.

 

[LONO100]

Update: So this turned into a big mess. The pump I got from the salvage yard didn't work, so I ended up going to AutoZone for a brand new one. They said it would take a day to come in. So in the meantime I tried to return the pump I first got from the salvage yard but I was only able to get salvage yard credit so that sucked. Then when I finally got the new pump from AutoZone, it ended up being the wrong pump so I had to return that pump for the proper one.

They gave me a pump for a sport, not the sport trac, and so the correct pump once again had to be ordered. So two days in and the correct pump finally shows up. They tell me the new pump doesn't come with the strainer in the kit so they sell me one for 20 bucks. I get home and the new pump gas a strainer so now I had to return the strainer they sold me.

Finally after almost three days, my truck finally got its new pump and is back on the road doing work. I was going to do a write up, but if you google search there is a pretty good one on mysporttrac website.

The things I would add are to take the time to clean out your tank, its a ***** getting that thing out by yourself so you might as well get your moneys worth. Also, I saw on many videos and write UPS that guys can't figure out how to remove the fuel line connections without breaking them.

Its pretty simple, just get a flat head, and press down on the rim of the connector, then separate. Once you see the rim of each connector it will become obvious, but don't pull or pry, just press down on the tab on the rim of each connector.

Try to take all of the fuel out of the tank before you try to pull down the tank, its awkward enough just trying to move that tank around. I just used a floor jack to support the tank while I unfastened the straps. Then once I got both straps off, I just slowly lowered the tank.

Anyway, hope this thread helps someone, just remember, if you think your fuel pump is toasted, go through this progression: Check to confirm you are still getting spark/air, then check the fuel pump fuse and relay. Turn the key in the on position and listen for the pump to buzz. If your fuse and relay are good, and you don't hear the pump buzzing, then get a fuel pressure gauge and connect to the fuel rail. If you turn your key to the on position and get 0 pressure, or anything under 50 psi, your pump is dead. Then move forward to removing the tank.

Once you get the pump out, you can confirm that its dead by running 12 volts to the harness. This cam be done with an power supply power supply. Or use a multimeter and test resistance to see if the pump is shorted.

Thanks again everyone for all the tips and info.