I think My truck has a lift pump in tank and one on the Block, Looking for some Guidance.

[Joey.G]

Hi, So my son recently got a 1998.5 24 V, While changing the battery terminals tonight I noticed a relay near the battery, Two Wires run towards lift pump and I think get spliced in with one connector with 2 wires plugging into the DDRP on the block and the other connector plugging in near the block, One wire which is orange runs down and connects to a green wire under truck kinda near the fender where I think it runs towards tank. the last wire from relay goes to battery power.

Is it possible I have an in tank lift pump and a Block mounted one?
How can I verify?

Is it bad running both?

Truck runs great , I plan to hook up a fuel pressure gauge in the near future.
Thanks

 

[SAndreasen]

My one truck had the pump in the tank and one on the block for a lot of years finally the one in the tank quit working now just the one on the block works . Bump the key and listen if you can here a pump running in the tank

 

[Joey.G]

Okay, I'll check that, I have to bump the key not just turn it to on correct? I m pretty sure the its wired for an in tank, Just not sure if it is still in there or not.

 

[SAndreasen]

Okay, I'll check that, I have to bump the key not just turn it to on correct? I m pretty sure the its wired for an in tank, Just not sure if it is still in there or not.

It is supposed to run for just a second with the key just turned on but it doesn’t always . If you bump it it runs for 20 or 30 seconds

 

[Joey.G]

So I bumped the key and the tank buzzes as does the Block mount so I am running 2 pumps, It has a new DDRP Fass block mount. But in order to get the pump out of the tank I'll need a non intake pump sump set up which I am seeing for over $400, I might as well upgrade everything for that price. It's working as is so I am going to get a pressure gauge set up and start there.

 

[BigPapa]

I’ll say this one more time, the in-tank pump is hands down the best option. If you’re going there anyway, replace it if it needs it.

If both are running, why do you need to replace anything?

 

[Joey.G]

Big Papa I believe this is the first time I have heard you say that, I am trying to do figure out if running two pumps is bad, not alot of information out there and what is out there is mixed. I am not against running bintank pump, and I would usea Fleece intake if that was a better option. Some people said it's bad for ECM to power two pumps.

 

[Topzide]

@Joey.G, He wasn't referring to this thread. One the many other threads about lift pumps, the conciseness is the in tank pump far exceeds the other setups with less issues in the long run. Sure, anything electrical can have a premature failure and then you have those that are on a particular bandwagon for "brand name" following. Yes on the ECM not liking the 2 pumps. If your truck was wired correctly with a relay to provide power when ECM "tripped" the relay, the ECM is probably okay. Correct wiring makes a huge difference on anything electrical on our trucks. Fuses and relays are our best friend when adding things to our trucks. The web site; https://www.the12volt.com/ , has a lot of good info for wiring. Search and read other threads about lift pumps on TDR, plenty of guys have been down that road and have shared what has worked the best! Just ask the questions, TDR members will provide the info!

 

[BigPapa]

Big Papa I believe this is the first time I have heard you say that

Yes, referencing other threads, but it was stated in your thread here.

https://www.turbodieselregister.com...relocation-kit-questions.274511/#post-2726568

 

[Joey.G]

Gotcha I was even thinking about that thread, I just discovered the two lift pump set up , I posted this to try and figure out if it is safe or not and if I need to change something right away, conflicting information about running 2. I am not against the one in the tank or on the block. Just want it set up right. All the wiring appears correct with a relay. They tapped into harness with another connector for the block pump. I found this while redoing battery cables and was wondering what the one wire was powering.

 

[SAndreasen]

Gotcha I was even thinking about that thread, I just discovered the two lift pump set up , I posted this to try and figure out if it is safe or not and if I need to change something right away, conflicting information about running 2. I am not against the one in the tank or on the block. Just want it set up right. All the wiring appears correct with a relay. They tapped into harness with another connector for the block pump. I found this while redoing battery cables and was wondering what the one wire was powering.

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I’ve ran both pump for about 7 years before the one quit . The ddrp is a fine pump and it’s good for 300 horsepower I’ve ran it with 400 horsepower and no problem at all and no catastrophic injection pump failure either .

 

[Joey.G]

How did you know one quit? Did you check to see if they were running bonce in a while? Pressure change? Did you remove the one pump when it went bad? Thank you

 

[SAndreasen]

Hi, So my son recently got a 1998.5 24 V, While changing the battery terminals tonight I noticed a relay near the battery, Two Wires run towards lift pump and I think get spliced in with one connector with 2 wires plugging into the DDRP on the block and the other connector plugging in near the block, One wire which is orange runs down and connects to a green wire under truck kinda near the fender where I think it runs towards tank. the last wire from relay goes to battery power.

Is it possible I have an in tank lift pump and a Block mounted one?
How can I verify?

Is it bad running both?

Truck runs great , I plan to hook up a fuel pressure gauge in the near future.
Thanks

https://www.bluechipdiesel.com/diagnosing-a-lift-pump-issue

 

[SAndreasen]

How did you know one quit? Did you check to see if they were running bonce in a while? Pressure change? Did you remove the one pump when it went bad? Thank you

it quit running that’s how I know it quit

 

[Joey.G]

Gotcha, some say it'll run on one pump and others say it can't pull though the pump.

 

[BigPapa]

You could test flow and pressure with each pump off and also bypassing the DDRP. Other than that, I have no ideas.

 

[petersonj]

@Joey.G , personally, I would pick one or the other. Which ever one you pick, eliminate the other and clean up the plumbing.

There is no value in using two lift pumps. All you need to know is that you have a positive pressure at the inlet of the VP44 injection pump when the engine is under its most demanding load. The actual value is not important. Also, it has been proven back in April of 2001 (right here on the TDR) that higher lift pump pressure does NOT increase fuel return flow from the VP44. The positive displacement vane pump (that the lift pump feeds) inside the VP44 determines fuel return flow via the 14 psi overflow valve.

Maintaining a two-lift pump system is more expensive and when a problem arises it will be more difficult to diagnose. If one pump fails, the other pump must push or pull through the failed pump. The failed pump becomes a restriction.

It seems that the least expensive solution would be to use the in-tank lift pump and bypass the engine mounted pump.

- John

 

[Joey.G]

I have a digital gauge that goes between the filter and the VP, it's part of the quadzilla tuneronce I get that all hooked up I think I may try to pull power from one lift pump at a time and get pressure. If one pump is bad or for any reason pressure drops really blow at idle would this harm the VP just for a shirt test? I am curious I guess what each pump would do. My ultimate plan would be to eliminate one lift pump. I am trying to find the plate/ Block that went in place of the lift pump on the block to let fuel pass. If I can't find one then I guess I'd have to run new lines. Petersonj I feel the same way. I appreciate you guys helping me out and giving me your thoughts and ideas.

 

[SAndreasen]

Gotcha, some say it'll run on one pump and others say it can't pull though the pump.

I’ve actually got two dead in tank pumps the has been dead for several years and works fine

 

[petersonj]

I have a digital gauge that goes between the filter and the VP, it's part of the quadzilla tuneronce I get that all hooked up I think I may try to pull power from one lift pump at a time and get pressure. If one pump is bad or for any reason pressure drops really blow at idle would this harm the VP just for a shirt test? I am curious I guess what each pump would do.

This test will serve no purpose. You are going to base your test results on fuel pressure only, with no regard to fuel flow. If you disable one of the lift pumps, you have no idea of the internal flow resistance that will be present in the disabled pump which could adversely affect the flow and pressure of the operating pump.

If you operate two equal displacement pumps in series with the same pressure regulator setting on each pump, the pressure will be doubled at the outlet on the downstream pump, but the flow will be the same through both pumps and through the line after the downstream pump. This will be the case in your application.

If you operate two equal displacement pumps in parallel with the same pressure regulator setting on each pump, the pressure will be the same at each pump outlet, but the flow will be doubled after the common connection downstream of the pumps.

Sometimes, keeping things simple is the best solution.

- John