Tree DR

I'm just about to put in the vent mod., and wondered if while I was there adding the in tank lift would hurt. My lift pump by the filter seems to be working fine. I haven't checked the pressure on the existing pump. Just wondering if the second would cause any problems?

Tree DR

What happened to all the lift pump experts?

Igor

Still waiting on the 'experts' to try things. '05/'06 trucks are different. I'm hoping that someone gives us a good example.

CRXsi

I seem to remember in one of the Walbro threads someone who had the factory in tank lift pump and had also installed a second lift pump with a second pick up in the tank. Kinda different from this situation but...

If you are refering to keeping the factory engine mounted pump and also having the in tank pump mounted at the same time...I think this would be a bad idea. It seems that there is too much resistance having a second pump up stream of another to be a huge benefit, especialy if the upstream pump fails.

If you mean should you replace the factory pump (do away with) and just put the intank unit in while you are there? Well how many mile are you at? The factory lift pump is covered under the engine warranty. A better alternative may be to look into a Walbro or FASS conversion and forget the factory pumps.

Not sure if any of this info helps but at least it may get the cogs turning.

trik396

That was me with the second pickup in the tank. I don't think it's a good idea to feed one questionable pump with another...

Igor

No, and '05/'06 don't have a engine mounted pump to begin with. Do you get any codes or any problems with running 2 pumps with second pickup?

CRXsi

Well then...good job trik396! I do remember that it was a well designed setup that seemed like it would be good.

So there you go Tree DR, know you know who to ask if you are going to try to do 2 pickups and 2 pumps.

trik396

I'm not running both pumps at the same time. What I did was add a pickup in the tank and ran the new fuel line to the frame where I mounted my Walbro pump. Then I cut the existing fuel feed line and tapped into it with the new setup. I capped the original fuel line from the tank to keep debris out of it. I removed the relay in the fuse center for the stock in tank pump. Of course I added a new relay near the firewall to trigger the Walbro.
This allows me to run the Walbro, but if by some slim chance it fails, I can re-splice the original fuel line and re-install the stock relay (about 5 minutes work) and be back on the road. Redundancy is cool...

Igor

cool, yes, this is what I need as well. Where did you tap in for the singnal for your new fuel pump relay?

Thanks.

trik396

You could just tap the cigarette ligher fuse as it is "live" only when key is on. Would work perfectly. My truck however has a turbo timer, so I had to run the relay trigger wire to that circuit to keep the pump live while the timer counted down for shutdown.
The cig lighter idea and the pickup I installed came from the Fass installation manual. You can download and print it from DPP's site, I think...

CRXsi

You could also use the existing fuel pump connector to be the trigger for the new fuel pump relay. Just use a similar connector that will tap into the power and ground for the original connector and use it as the signal for the new relay, then all you have to run is a new power wire for the pump itself and a ground from the pump to the frame.

trik396

There was some concern about doing it in that manner due to the fact the stock pump draws minimal current and the Walbro can draw close to 20amps at higher pressures... I'm not sure what the stock relay would handle or if it'd throw a code due to possible higher current draw.
That's why I went the route I did... just a thought.

CRXsi

It is true about the stock pump drawing less and that is why we are talking about using a seperate relay. You still need to run a new fused wire from the battery to the relay for fuel pump power but essentially all you are doing by running a seperate relay off the factory pump connector is powering the new relay's trigger circuit from the factory pump. The trigger circuit side of the relay only draws a few hunderd milliamps. So like 0.3A . The wire that is run from the battery to the new relay is the one that carries the higher current so that wire needs to be the appropriate size with an appropriate fuse and will not risk overloading the factory relay as the factory relay is only going to see the 0.3A approximately to operate the trigger side of the relay, once the triggered side has been actuated the relay then allows current directly from the battery to pass through to the fuel pump and is seperate from the trigger side. The same is true of the wire you ran to the cigarette lighter, if you are using this to go to a relay. The wire from the lighter to the relay is only drawing a fraction of an amp and the real work is being done by the wire going to the battery from the relay. By using the existing fuel pump connector you are eliminating having to run a wire inside.

I hope I haven't confused anyone too much yet...but yes you can power a seperate relay off the factory fuel pump connector and just run a new fused battery source to the new relay. I don't recommend running the original relay as I believe it is only rated at 10-15A and a Walbro can draw 20+A.

A good site I just found to explain how a relay works is:

How a relay works

trik396

Sorry I misread your original comment. I thought you were recommending the stock relay to power the new pump. That is what I was against.
Now running the stock relay to trigger the NEW relay, of course this is fine.
I know all about relays... I'm an electrician!

CRXsi

I guess it is pointless to explain a relay's operation to someone who can probably do an even better job of explaining it back to me!
. Too funny! anyways I guess at the very least others may have a good understanding of it now!