Engine/Transmission (1994 - 1998) Pusher pump on 12v

[nfox]

Can a person run a 5psi pusher pump in line before the the factory lift pump on a 12v motor?

 

[Joe G.]

Why?

 

[krs]

Sure, but... . why?

 

[Jim Fulmer]

Nfox, you can see what I run as an aux system, up to say around 450 HP the stock system is fine, after that you would benefit from an aux helper system.



Jim

 

[BTanzini]

nfox If you are trying to increase fuel pressure why not put the pump between the fuel filter and injection pump, any over pressure will go out the overflow valve, will it not, yet you can boost pressure to the injection pump.



What type of 5psi pump are you looking at installing?

 

[Joe G.]

I think if you put a 5 PSI electric pump in the system the stock piston type pump used with the P7100 pump would wreck it with pressure spikes.

 

[nfox]

Fuel Pump

When i was at diesel extravaganza friday and saturday, i talked to a few people about the volume of fuel going to the injection pump and they said that the stock setup is barely enough to feed the p-7100? Do i need to upgrade to a better fuel system or not? There is to many opinions out there, any advice would be very helpful.

 

[Joe G.]

If you were not getting enough fuel your fuel pressure would drop. How do you know that the "few people" knew what they are talking abour? Ask Joe Donnelly if he is using the stock pump and if so, is he haveing any problems supplying his P7100 with fuel. As far as I know he is making more HP with straight diesel than anyone else.

 

[Jim Fulmer]

Remember one thing, Joe is only supplying fuel for the dyno... . Joe don't flame me... please. It just depends on the fuel system and what the pump needs, put a guage on it and do some high speeds passes and see were it goes then report back.



Jim

 

[Roger rodbolt]

Originally posted by Jim Fulmer

Remember one thing, Joe is only supplying fuel for the dyno... . Joe don't flame me... please. It just depends on the fuel system and what the pump needs, put a guage on it and do some high speeds passes and see were it goes then report back.



Jim

:-laf :-laf :-laf

 

[illflem]

I did the math one time and figured that at the rated output of the lift pump you would have to be getting less than 1/2 mile per gallon of fuel at 60 mph to use all the fuel the lift pump puts out. Even if you figure half the fuel is going out the return it gets you up to a whopping 1 mpg.



Not sure if 5 psi will be enough pressure to cause a problem but folks who have installed higher psi pusher pumps on 12 valves have had to remove their fuel heater. It's designed to be on the suction side and will leak with too much pressure.

 

[Joe G.]

I suspect that the stock lift pump would be sucking fuel through a 5 PSI pump so hard that it would just overpower the little pump. If it survived that I don't think there would be any increase of fuel delivery. This lift pump is not a wimpy pump like used with the rotary injection pumps.

 

[Strick-9]

On my personal truck, I first found the problem with inadequate fuel volume about two years ago.



The fuel system would supply 35 psi at high idle, yet under load in 'express mode' it would drop to 3 psi.



I started by changing the overflow valve. Then swapped lift pumps. No changes. The fuel system passed the normal idle @ 25 psi /high idle @ 35 psi tests that are described in the service manual.



But very rarely does anyone test under load @ max fueling rates. About a year after I installed my auxillary system, J. R. Adkins calls me to discuss it because he's having the same problem. Then Jim Fulmer goes down the same road. Several months ago, I found out Haisley machine sells a kit just for this problem.



It is a problem with trucks with high fueling levels.



In this case, an inline pump would not solve the problem because you need more volume rather than pressure. Pressure is dictated by the flow rate through the overflow valve. With increased volume, you will get an increase in pressure.



A good system includes a new pickup tube in the tank, has it's own filter and feeds directly into the banjo at the pump. This way you can keep the fuel heater and reliability of the stock lift pump, and just have the extra fuel available at the flip of a switch.



Jim makes a great point. Put a gauge on your truck and go drive it. Race it or sled pull it, whatever you enjoy. And monitor what the fuel pressure is doing during the event. Then you'll know for sure whether this applies to your truck.



-Chris