Post Install Q's:

[Walker]

Just installed my 3990105 lift pump today and need a little help.



Q: I was told I needed the pigtail harness for this pump, but my stock harness plugged right into the new pump with no problems. Do I even need the new harness (it has the same ends as my stock one)? If so, how would the new harness connect? 1. leave the old harness on and add the new one? or 2. take off the old harness (covered in tape and loom) and add the new one seperately? Or is the new pigtail supposed to help "convert" an old style harness with the new one? I'm confused.



Q: Do the washers on the fuel lines (banjo bolts) go one on each side? They fell off when I unscrewed them, so I assumed one went on the front and one on the back as you screw them into the pump.



Q: I aslo assumed the "out" side of the pump faces to the front of the truck (going toward the fuel filter), but didn't see the writing until I got the pump off. Is this right? Just want to be sure. The pump won't run if it's backwards will it?



Other than having to be some sort of circus freak to reach the dang thing (don't know how some of you do it so easily), the install went pretty well. Had to let the filter drop to get to it all though. Fired it up and went for a test drive, seemed to be fine. But, when I first turn the key, I don't hear the pump "fire up" and cycle from inside the cab like I did in the past. Had to open the door and listen real close for the noise, but it was there. Forgot to "bump" the starter and let it cycle longer first, but she started right up. Would that be problem?



I don't have a pressure gauge, so I hope I did this thing right. It was showing symptoms of failure in the old pump (and maybe along with some paranoia on my part from reading all the posts), but I wanted to ere on the side of caution and insurance. In cab guage is next on the list.

 

[EMDDIESEL]

Sounds like you did everything fine, i just did mine last week. I got the same pump as you and it plugged right in like you were saying, no special harness required. As for the banjo washers, you need 2 per Banjo, one on each side, so you did that right too. And yes, "Out" faces the front of the truck. Congrats on your first lift pump change out, it probably wont be your last!

 

[Walker]

Gracias

Thanks for the confirmation.



Now, what set up do I use for my in cab fp gauge? I'm thinkin' electrical (don't want a fuel hose running in the cab). Exchanging my 2 pod for a 3 pod A pillar. Should I go pre or post filter (or both)? From the lift pump, filter or vp44? It's kinda confusing reading all the posts and trying to decide or know what's really best.



Any input? Anyone?

 

[Bigsaint]

Walker, the best location for the FP sender is post filter, mine's at the bottom of the fuel filter canister, some have them located at the inlet of the VP44. Either way you know what the injection pump is seeing, and you will see a lose when the fuel filter is ready for a change.



There are a few ways to add the sender post filter...



1) Ray T's modified banjo bolts with a 1/8 NPT pressure port.

2) Remove the short hardline running from the filter to the VP44 and the banjo bolts, replace with Weber adapters and run a short legnth of braided line from the filter canister to the VP44, with Aeroquip elbows and a pressure port adapter.



Another thing to consider is whether you go with a mechanical or electric gauge, you seem to be leaning towards electric. Some members with electric senders are using a 'snubber' to help to prevent damage to the sender from the pluses from the VP44 or the rattle of the Cummins from destroying same. Personally, my SPA sender is now set up without a snubber line, so far so good, but I may pay the price of a DOA sender in the long run, couldn't hurt to put one in. Bottom line, anywhere post lift pump is better than no gauge at all. Pre-filter is where I had my sender originally, better than no sender but you will be suprised at the drop of psi's going from pre-filter to post, even with a new fuel filter. Hope this helps !!!



Scott W.

 

[EMDDIESEL]

You can use a mechanical Fuel pressure gauge with an Isolator or just plumb it with braided stainless line and leaking wont be an issue, even in the rare case it did, diesel fuel will not explode and has no flammable vapors, and its only 15 psi at the most, not a problem. Braided stainless hose is good for over 1,000psi. Currently, DC's lift pumps dont get close to that number

 

[JEMOORE]

3990105

I just ordered the 3990105. The parts man told me I also needed the pigtail? I questioned this. He said the book recommended replacing it with the pump. He thought it might have something to do with electrical resistance in the wires. Also said the pumps had been upgraded a couple of times and he thought this might be part of the fix? I don't know about that, but for only around seven bucks I guess I'll go ahead and replace it also. Just going to carry the new pump as a spare for now. Maybe I'll never need it

 

[Walker]

Harness Input?

Anybody know how there could be a difference in the wiring harnesses? (stock vs. new)



I would have changed mine but the stock one is covered in tape and loom and it would be a pain to have to get back in there and swap them out.

 

[Amianthus]

I'm not completely sure

I think the pigtail is an adapter for different model years of pumps and trucks. I think it's an adapter to take the late ISB harness and make it compatable with the pump. For the older ISB's I think it just connect righ up. Or maybe I have it the other way around.

 

[Walker]

I do have one of the first 01's (built late 2000 and for example have soft lines off the waste gate not hard lines like the newer 01's), so maybe I have the "old style" harness already stock on mine and don't need the new pigtail adapter. Sure hope so.



But the crazy thing is, the new pigtail looks like it has the same fittings (male/female ends) like the stock harness (of which I can only see the female end anyway). It'd be like plugging two extension cords together just to make a longer one; not anything different at all to make a conversion/adapter. Still confused.

 

[JEMOORE]

I assumed, (and we all know what that does) that the pigtail you are talking about is the short wiring that plugs into the main harness on the top of the lift-pump and connects to the lift-pump on the bottom. I can't see how the connection is made on the bottom of the lift-pump, even with a mirror. Does it plug in or is it perminently attached? Does the new pump have this wire attached or is this the pigtail?