Gt500 fuel pump voltage issue.

[Viperrmk]

Good morning everyone.

Here is the background of my car. It's a 2010 GT with a procharger P1-SC, duel gt500 fuel pumps with a upgraded power line to the fuel pump relay.

The issue I've been having is I notice on tip in of the throttle my wideband would go pretty lean (17-18) then rich (11-12) and finally stabilize at 14.8. That's when you crack the throttle. So I data logged with one of my friends and we noticed that as soon as you open the throttle a little it cut voltage going to the fuel pumps for a split second and then kicks in like normal. Under normal driving each shift the fuel pump voltage is fine.

Checked the fuel pump relay and noticed it was melting a little so I replaced it with a 40A 12V relay. Also upgraded my ground wire as well, but the problem still continues.

I'm pretty much at a lose right now. Any ideas you can throw at me? I'm going to check the whole power line from the fuse box back to the relay to make sure it's not pitched or split anywhere.

 

[Viperrmk]

Pic of relay.

 

[blownGTvert]

Has this issue always been there? Typically a lean tip in is tune related.

 

[Viperrmk]

No it hasn't, I've been running the same set up for the past 2 and a half years and it just recently started doing this 2 weeks ago.

I've also been running the same PBH tune ever since I installed the procharger and never had an issue.

 

[marsbar]

Did you check the connector on the fuel hat for corrosion and tight fit? I have herd of the pickup screen on the pumps getting debris around it could cause this problem also.
If you say it's been fine up until now something has obviously changed. Wish I could offer better advice but that's all I could think of now.

 

[Viperrmk]

Does anyone have a wiring diagram for the gt500 fuel pumps?

 

[Viperrmk]

I want to find out why the connection melted the relay. And where that wire goes. It's impossible to find any infinite this. I know I've seen one before somewhere but I can't find it again.

 

[JeremyH]

So excess heat/current can cause the voltage drop and melting relay. So, I would replace your inline filter and inspect the pump filter socks in the tank and clean them at a minimum. No one talks about those filters but they should be changed regulary as well. Also measure resistance across each pump terminal power to ground and see what you get for each pump, they should read roughly the same if one is way off from the other it could indicate a short in the pump motor causing the same over current condition.

 

[Viperrmk]

Thanks for the reply jeremyH,

I was actually coming back here to give an update. As embarrassing as it is to admit but the relay was wired up wrong. It's been wrong for 2 and a half years, granted I don't drive my stang much. So anyways I wired it correctly but I'm still having the same issue. I haven't had time to datalog it but I can see on my wideband that when I crack the throttle is goes lean 19-20 then rich 10-12 and then stabilizes.

So I thought maybe I burnt up one of the FPDM with the relay constantly providing power. So I had a spare FPDM I swapped on the the drivers side and nothing changed. I then swapped it on the the passenger side and again, nothing changed. I have battery voltage to the relay and out of it. Also I have battery voltage at the fuel pump. All of that is with key on only.

I had the relay wired wrong as followed. The small red wire was in the #30 position of the relay, then the power from the battery was in #85 and the two power wired for the FPDM were in #87.

Wiring diagram

http://www.s197forum.com/forum/attachment.php?attachmentid=51887&d=1424396380

 

[JeremyH]

Yikes! New relay and wire correctly is a good start. FPDMS rarely fail they have their own ground so having power all the time isn't a huge deal I would do the filters and check pumps next still. Do this and datalog again.

FYI pump voltage goes full at key on to prime the system then once the car turns over and is idling you should see 6-7 volts to each pump.