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Solid State Relay for ECM-Controlled Lift Pumps?


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It's been my observation that since I put my lift pump on an ECM-triggered relay that the pump (none of three tried) doesn't do its normal startup routine.  I hypothesize it's because the pulse-width-modulation signal from the ECM isn't reliably making my normal relay close.  In a semi-unrelated internet search this popped up.  It's a solid-state relay that fits the normal mechanical relay base.

Hella part number: H41773001 http://hellahd.com/index.php/default/electrics/relays/mini-iso-relays/12v-spst/h41773001-931773987/

https://www.lingenfelter.com/PDFdownloads/HELLA41773001.pdf

Thoughts?  I expect most will be 'that's a solution to a problem that doesn't exist' :) 
EDIT:  I see that the duty cycle is only 90%, but I don't know if that's at the max ambient of +125 degrees Celsius.  Surely a lower ambient could boost that to 100% duty cycle. This is incorrect, I believe.  The 'rated amperage' at 85C (185 degrees F) is 20 Amps.  I guess the 'maximum ambient' of 125C is for when it's just sitting around on a shelf.

Further edit, I read the 'base' is different than a "normal" relay, so some wiring switcharoo in the relay base would be needed.  Easy to do, just something to remember.

 

After all these edits, this may be a terrible idea!
I've used these in my homebrew setup for a while with great results, but that's obviously not in an underhood environment:
https://www.amazon.com/TWTADE-SSR-40-3-32V-5-60V-Solid/dp/B079BGGVYX/ref=pd_sbs_5?pd_rd_w=nfADM&pf_rd_p=ed1e2146-ecfe-435e-b3b5-d79fa072fd58&pf_rd_r=5QE4JEKCV24F2YA3MVS8&pd_rd_r=d231ae23-7cb1-4c3f-853d-c0c6ac98488c&pd_rd_wg=NqsDN&pd_rd_i=B079BGGVYX&psc=1

Edited by LorenS
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I use the micro relay type that you find in the PDC for my Airtexs backup lift pump.  There is no problem with it cycling with the key bump.  Check out the relay in option B the article below. 

 

Installing Protective Lift Pump Relay - Fuel - Mopar1973Man's Dodge Cummins Forum 

 

 

 

 

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If I bump the starter it runs, but it doesn't run reliably when the key is turned to "on". It's supposed to run for a few seconds, according to my manual. It did that before I installed the relay. I do not remember if that key "on" is the lower duty cycle like it is while cranking engine.

Edited by LorenS
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On 12/19/2020 at 7:45 AM, LorenS said:

If I bump the starter it runs, but it doesn't run reliably when the key is turned to "on". It's supposed to run for a few seconds, according to my manual. It did that before I installed the relay. I do not remember if that key "on" is the lower duty cycle like it is while cranking engine.

I'm assuming you have the air dog ddrp?  I just put one of them on after my fass ddrp went south. It seems that the air dog reacts slower than the fass as I noticed what you mentioned. The fass reacts faster for some reason

 

Later

D

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On 12/19/2020 at 4:45 AM, LorenS said:

It's supposed to run for a few seconds, according to my manual.

 

From the FSM for my '02 truck...

 

The transfer pump is self-priming: When the key is
first turned on (without cranking engine), the pump
will operate for approximately 1/4 second and then
shut off. The pump will also operate for up to 25 seconds
after the starter is engaged,

 

- John

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I have the FASS pump.  It also did this with the stock-style pump when put on the relay, and the stock-style replacement I put on because I thought the original was going bad when it wouldn't run the "two seconds" as stated in the FSM.  I just checked a few minutes ago, and the FSM does not say if that 2 seconds is at 25% or 100% so I have to assume it's at 100% - the 25% seems to ONLY be while cranking.

However, I just realized the relay isn't the only thing that changed, I also moved the lift pump to the frame and thus extended the wiring harness.  Can't image that has anything to do with it, but perhaps.  I do not believe I ever ran the stock pump off of the ECM without the relay, and I KNOW for an absolute fact that I never ran the FASS off of the ECM without the relay.  I say that because that could have stressed the ECM circuit in some way (got hot and ruined a soldered connection, etc.)

7 minutes ago, Tractorman said:

for approximately 1/4 second

For the 2001s it says 2 seconds.  I just checked it a bit ago.  And, it USED to be 2 seconds!  Only changed when I added the relay, extended harness, and relocated the pump.  Same pump. And another brand new Carter I carried for a spare.  I installed the FASS DDRP later.  I haven't had my truck to a dealer, so shouldn't have been 'flashed' or whatever.

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32 minutes ago, LorenS said:

However, I just realized the relay isn't the only thing that changed, I also moved the lift pump to the frame and thus extended the wiring harness.  Can't image that has anything to do with it, but perhaps.

 

I don't think moving the lift pump to the frame should make a difference, either.  In fact, I installed a used frame-mounted FASS lift pump a few years ago.  It is run by the fuel pump relay that a Dealer installed in 2005 along with my VP44 replacement and in-tank lift pump conversion that was done under warranty at that time.

 

I use a fuel pressure switch with an LED indicator lamp in the dash for my low fuel pressure warning system.  Even with only a 1/4 second bump my fuel pressure warning lamp goes out briefly when I turn the ignition switch to "run".

 

I know I am not much help here, I just wanted you to have something similar to compare to.

 

- John

 

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Most of us that run a mechanical fuel pump either have the electric fuel pump disconnected, like I do, or don't have one installed at all so we never see nor need that ¼-2 seconds of initial fuel pressure.   

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Key on pressure is nothing... That little burp of pump is the ECM booting up and the lift pump runs for a brief second pulse then off again. Lift pump doesn't get any signal till the crank sense. Now while cranking it reduces the fuel pressure with 50% duty cycle on and off. Once started the pump runs 100% duty cycle constant on.

 

I tend to prefer the electric pumps being you have your prime cycle and pressure reduction during cranking. With a mechanical pump if you lose prime for any reason you will not get it started again most likely. Like my current customer he HAD a mechanic pump but the regulator failed starve the VP44 out of course ruin the VP44. Now He's got a FASS 150 and it failed in 100 miles too wiping out the VP44. (P0216 and P1689) Again, like I keep telling people the pump is mounted in the "damage path" and the got hosed with all the water and snow from the rear tires. Both failed VP44 and FASS 150. Now doing the warranty work for this customer. 

 

I had a nice long chat with FASS tech team on trying to get this resolved. 

Edited by Mopar1973Man
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