WHAT is a "Pusher Pump", and why use one?

[Gary - K7GLD]

Of necessity, one of the single largest issues of importance for the 24 valve Cummins trucks, is the absolute need to carefully monitor fuel pressure as supplied to the VP-44 injection pump.

That pump has proved to be somewhat sensitive to fuel lubricity, pressure and flow. It is both cooled and lubricated by the flow of fuel thru it - a fact further complicated by the steady decline of diesel lubricity as steady efforts to reduce sulphur content has also adversely affected the lubrication characteristics of our fuel.

A fuel pressure gauge is an absolute MUST for a knowledgeable 24 valve owner concerned about the health of his expensive VP-44. Next in importance, are steps available to enhance the fuel supply to the VP-44 - and one of the best and most used methods, is installation of some form of aftermarket fuel pump - either a substitute pump felt to be better than the OEM fuel pump (lift pump) - or a supplemental (pusher) pump to reinforce and enhance the ability of the OEM pump to do it's job.

Aftermarket pumps such as the FASS, RASP, and the currently popular Walbro are being used, as well as one of several available Carter types that are nearly identical to the stock OEM lift pump also manufactured by Carter.

The focus of this thread, is the use of a Carter 4600 "Pusher pump" as I have installed on my own ‘02 truck. Here's a shot of mine in original form, installed as most feel works best, down on the frame rail as close to the fuel tank as possible:



Mine has gone thru several evolutions to further enhance reliability and operation - those will be covered later. The added pusher pump needs power to operate - and most users prefer to pick off a small amount of current from the existing LP power circuit to power a relay that in turn provides contacts to take voltage direct from the battery to power the added pusher, and not draw added excessive power from the computer controlled primary LP circuit - here's a shot of the common Radio Shack relay with 20 amp contacts that I use:



Some users trying to simply power the added pusher pump directly off an available keyed circuit, quickly discovered that if fuel PSI above about 7PSI is applied to the VP-44 before and during attempts to start the engine, it won't start - due to an over-pressure sensor in the VP-44 that prevents engine starting.

The OEM setup, and the computer controlled circuit that control power to the OEM LP actually only powers the LP for a split second at key-on to prime the VP-44, then shuts down to allow the engine to start - then, once the engine fires, again powers the LP for normal engine operation. That's why the added relay, controlled by the same lead that powers the OEM LP is used, to key the added pusher in tandem with the OEM LP.

NOW, as to some suggested additions to the pusher pump as seen up above. One potential disadvantage of the added pusher is, if it should fail or stop for any reason, it's possible for it to block fuel flow and starve both the OEM LP and the VP-44 - a potentially serious event!

For that reason, I have devised a homebrew flip-flop valve that functions purely off fuel flow and pressure at the pusher pump - it is closed by system fuel pressure in normal operation, but will open if the pusher fails, and permit fuel flow AROUND the pump if that happens - it looks like this disassembled:



And as assembled on the pusher, ready to mount back on the truck:



It has been tested, and functions perfectly with no need for operator intervention - I built my own, but places like Jegs offer them for about $24 or so.

End result with my setup, is about 23 PSI fuel pressure at idle, and about 16 PSI at cruise, either empty or RV towing:



Full load up steep grades usually show about 12 PSI - totally adequate for proper VP-44 operation.

To those who might be critical of the rather wide range of PSI, I might mention my use of a Frantz sub-micron fuel filter in my systen that adds about a 4 PSI drop in full-load pressure due to the added restriction of that filter - I can live with that, since I still have plenty of pressure for my needs - and greatly value the vastly superior purity of fuel supplied to my VP-44.

My pusher setup has been on my truck since new, and has performed flawlessly for about 4 years and 40K miles - there are other good aftermarket setups available as kits - but at just under $100 in total cost at time of original installation, I'm fully satisfied with mine.

(THERE Chad - satisfied?) LOL!

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White '02 Quad cab, NV5600, GAUGES! Comp, Walbro, DTT SS intake, Rip's 4 in. exhaust, Don M's 1.6's, DSS, Frantz oil bypass & fuel filters, Amsoil air filter, MOBILE Ham Radio-IC-706, 600 watt amp, '88 Kit 24 ft. 5er, 418 HP/978 Tq., 24 ft KIT 5er.

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Last edited by Gary - K7GLD : 11-16-2006 at 03:07 PM.

Sweet Write Up Gary...... TOP NOTCH AGAIN !

Thanks

DM

[Dr. Evil]

Originally Posted by

Sweet Write Up Gary...... TOP NOTCH AGAIN !

No doubt...Gary definitely deserves his "Tech Specialist" title. Nice work indeed.

[BSouth]

A guy can learn a lot from this site. Thanks for that write up seems like u know ur stuff!

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05 3500 Yellow 6 speed, Mega cab dually fenders, Rumble Bee Scoop, Edge Juice w/ A2, Striker 2, Valair 3600 DD, 5" Silverline exhaust, Icebox with torque tube, Rokkteck, Quad Rail Gauge, Brite Box w/ Fogzilla

[mrmajestic]

Gary, you seem way more knowledgeable than me on this subject. I will let you or someone else explain how flow also plays in to the equation. Hence the Vulcan and similar kits.

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1999 2500 Quad Cab, 5spd, 4X4, 3.55 LSD, 152K miles, Buckstop w/9K winch, Torque King M/S, K&N FI Perf Kit, 275HP Inj., TST PM3/Smarty stack, PDR boots, Wabro/Areomotive and 1/2" line, PAC Brake w/SWAC, Summit Turbo back 4" pipe, EZ drain, silencer ring MIA, pyro/boost/FP gauges, SBC Con OFE w/HD Adj Hyd, Brite Box, DSS, Centramatics, BFG LT285/75R16/E

[Dr. Evil]

Originally Posted by mrmajestic

Gary, you seem way more knowledgeable than me on this subject. I will let you or someone else explain how flow also plays in to the equation. Hence the Vulcan and similar kits.

This is fairly obvious but, more flow = cooler and happier VP-44. Is that what you are asking? Or am I missing the point of the question?

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Last edited by Dr. Evil : 04-24-2006 at 09:58 PM.

[mrmajestic]

I think that increased flow may be as important as pressure. I run 22 lbs. at idle but can easily drop to 5 lb. at WOT with 38 lbs. of boost. Maybe I was just reminding myself to install a line kit.

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1999 2500 Quad Cab, 5spd, 4X4, 3.55 LSD, 152K miles, Buckstop w/9K winch, Torque King M/S, K&N FI Perf Kit, 275HP Inj., TST PM3/Smarty stack, PDR boots, Wabro/Areomotive and 1/2" line, PAC Brake w/SWAC, Summit Turbo back 4" pipe, EZ drain, silencer ring MIA, pyro/boost/FP gauges, SBC Con OFE w/HD Adj Hyd, Brite Box, DSS, Centramatics, BFG LT285/75R16/E

[Dr. Evil]

I believe that the reason that DC went from testing fuel pressure to testing flow was so they could pass a huge number of failing lift pumps that would not pass the pressure test. As far as Im concerned, DC did this to save big $ - not to help their customers.

Originally Posted by Dr. Evil

I believe that the reason that DC went from testing fuel pressure to testing flow was so they could pass a huge number of failing lift pumps that would not pass the pressure test. As far as Im concerned, DC did this to save big $ - not to help their customers.

I agree...........I had one OEM l/p that would produce 12 psi at idle and at a slite I mean slite touch of the throttle and the psi went to zero........this pump prolly would have passed their flow test but not mine.......not for a second

OEM l/p flat scare the hell outa me

[Gary - K7GLD]

*IF* I could maintain a steady 5 PSI right at the VP-44 inlet under ALL engine operating conditions, I'd be happy as a clam!

As long as adequate fuel flow is available right at the VP-44, even at single digit PSI, that's really all that's necessary - the job of the DC supplied LP is only to SUPPLY FUEL to the VP-44, NOT to in any way pressurize the VP - that's the job of the larger and better engineered VP-44 internal vane pump that feeds and pressurizes the individual fuel injection plungers.

It has been pretty well demonstrated and proved that applying vast volumes and pressures of fuel to the VP-44 does NOTHING to improve it's performance, cool it or improve internal lubrication.

All external fuel supplied to the VP-44 IMMEDIATELY faces that internal vane pump, which has positive engagement spring-loaded vanes - we ain't gonna force ANYTHING past that pump - and it rotates in time with the rest of the internals of the VP-44, so only just so much fuel is going to circulate thru the VP, regardless of HOW much you might spend on efforts to crowd more thru it. In fact, excessive pressures might even damage some of the more sensitive seals and control diaphrams...

All the above comments come directly from the Bosch injection pump manual as used by Bosch certified pump rebuilders...

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White '02 Quad cab, NV5600, GAUGES! Comp, Walbro, DTT SS intake, Rip's 4 in. exhaust, Don M's 1.6's, DSS, Frantz oil bypass & fuel filters, Amsoil air filter, MOBILE Ham Radio-IC-706, 600 watt amp, '88 Kit 24 ft. 5er, 418 HP/978 Tq., 24 ft KIT 5er.

[TrueValue Truck]

Originally Posted by Whitmore

OEM l/p flat scare the hell outa me

Thats why the 7psi max on my 3rd gen concerned me when I put my gauges on. Running stock , it never drops below 5psi.With the performance setting on the BD pup , it will drop to 4psi when I tromp on it.

Any 3rd gen guys that had simmilar fuel psi reading with the stock lp and have upgraded to an aftermarket , Id love to know what kind of readings your getting.

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Caldwellfire.com

06 3500 SRW MC ,Smarty REVO,X2 Race stack, Commander,CFM, Monster Air COI,AFE Torque tube,FASS 150 HPFP LP,Muffler delete,Tipple disc Converter and VB ,ProComp 2" leveling kit,Timbren's,Reese Class V Tow Beast

[eflynn1959]

Gary, where do you get that flip-flop valve part # at jegs