I finally got my fuel pressure guage hooked up today. I changed the oil and fuel filter and thought it was a good time to hook it up. Well sure enough just as I suspected:

Idel:9-10
Driving 55-60mph: 7-8
WOT: 4-5

So now I need a new pump. I think I am going to buy that kit that is on the classifieds and then get a pump from summit because I have a $30 coupon from them. Im getting the Holly Blue. Anyone bought that kit on the classifieds? Just wondering if that would be the best way. After all is said and done its gonna be around $275. I dont know what to do. I can't really afford the FASS. I can't even afford the holly blue. Im going to have to wait a couple weeks until I get the money. So if anyone wants to contribute to the poorman's fuel system fund that would be great!!! Any ideas would be helpful. BTW this is a mechanical reading post filter.

Heres the kit I am talking about. Does anyone know if it replaces all the banjo bolts?

https://www.dieseltruckresource.com/...2&cat=8&page=4

 

If money is tight, why not just get a new pump from Cummins? I hear their prices are reasonable and with just the EZ, I don't think you need a high flow fuel system yet.

 

I bet it would still pass the fuel volume test. Those readings are more in the "yellow" area than the red.

 

When I first replaced just the banjo bolts, it raised my pressures 2 to 3 psi across the board. I went from almost 0 psi to 3 psi at WOT. I ended up changing the pump but there is a gain to be had. I think another bad spot is the line going from the filter to the VP-44. I'm sure if that line is opened up it will help keep the pressure up at the VP.
I would install the kit, then see if you still need the pump. I would also start useing something like "Lucas Upper Cylinder Lub and Injector Cleaner" every other tank full. It adds a lube quality to the fuel which helps the lift pump and VP. I've started useing it every tankfull.
Just my $0.02 worth

 

I would think by replacing the banjo bolts with higher flowing pieces you would actually see a drop in pressure, but an increase in volume. Maybe it's too late for me to think on this.......

 

jbody, thats what i've been trying to understand since i signed on. i work with pumps day in and day out, pd and centrifugal, if you take a small line off the discharge of a pd (positive displacement) pump and replace it with a larger ID line, in my experience anyway, it doesn't affect the pressure in the discharge line at all, given that nothing else in the loop changes. i do welcome all information as usual. thanks

 

The fuel system on a Dodge isn't quite what you're used to with your PD and centrifugal pumps. The VP44 uses a sliding vein pump to pull its fuel into an internal chamber. Overall fuel requirements at WOT are 45 GPH, however since the sliding vein pump is not pumping on every stroke, rather every second stroke, its placing a burst demand of 90 GPH - 120 GPH on the system.

Its the lift pumps job to supply this 90 GPH - 120 GPH burst demand. Since the Carter lift pump is internally regulated, while its attempting to replenish the volume grabbed by the VP44 and restore pressure (which it wants at 15), an internal bypass is opening and closing. Every single internally bypassed pump is designed to function with a certain line size. Since our fuel lines are only 1/8", and the Carter has been designed to work with 3/8" lines, as the Carter is attempting to repressurize the lines, its running into a blockage at the outlet of the pump. The pump pressurizes against the outlet, then the bypass pops open, then the pressure equalizes over the lines, and the bypass closes, ad infinitum. As such, the internal bypass valve is opening and closing far more often than it was designed to do, and wearing prematurely. And since the bypass valve is a relatively slow valve, in comparison to the rest of the system, your overall pressure drops as the valve cannot respond quick enough to changing line pressure.

Pop open the line sizes (we've actually found 3/8" to not be quite enough, but rather 1/2" to give us a couple more PSI), the internal bypass is now allowed function as it was designed to function. The pump lasts longer, and since the bypass isn't opening and closing all that often, overall line pressure stays relatively high.

Rod

 

My fuel pressure is at 13.5 at idle on a full tank and 12 at almost empty is this common? Also is fuel pressure at this level sufficient to keep the IP from going out?

 

The lift pump has less work to do when the tank is full.

If money is the issue stay stock and watch the pressure gage..

 

Pushrod: That was an interesting and very informative post about the lift pump bypass. I have always wondered just exactly why the lift pumps were failing. I didn't think it was the internal bypass valve that was actually giving up. Now the pressure change makes sense. Since pressure is just the measured resistance to flow, it makes sense that if you vastly increase the available flow, there could be a potential for a pressure increase and not a drop. However, I would have thought that going all the way up to 1/2" lines would slow down the velocity of fuel in the lines to the point where the pressure would drop. Apparently, this is incorrect? I am interested in the Max Flow fit but I thought the line size was overkill. Does going to the Max Flow kit negate the need for a lift pump with an internal bypass. Does the VP44 not have it's own bypass that returns fuel to the tank?

 

Another reason that they are failing is that the lift pump and the rest of the engine for that matter was designed for mid sized trucks. There you have like a 50 gallon tank that is bottom feed. That mess in our tanks is part of the problem I believe. With a low tank you have little pressure on the fuel to get it into the cannistor past the one way flappers and the filtering.

 

Well, a really cheapskate way to improve the fuel system on these trucks is to use 10mm rubber fuel line instead of the steel lines. First it's more diameter, therefore better flow, and it's also a damper for the pressure spikes.
The discussions about flow vs pressure are moot. The pressure we are interested in is right at the inlet of the VP44- so for a given pump reducing the restriction between the lift pump and the vp44 will reduce the pressure drop between LP and IP and therefore give higher pressures at the point we are interested in.

My experience showed me that another factor that leads to a load of problems is air in the fuel. Air doesn't lubricate and cool as diesel does. The quick connect fitting at the stock fuel tank is one of the places where air likes to get in. I replaced this whole stuff with a 10mm rubber hose to the holley blue that's mounted at the frame rail. From there it's another 10mm rubber line to the fuel filter. This long rubber line effectively increases flow over the stock system and also dampens the pressure spikes. (I've also got a wildca maxflow system from the filter to the VP44, but IMHO as long as you are close to stock it wouldn't matter)- There are cheap hose fittings for 3/8" with the holley blue and also the same fittings for the 12x1.5mm weber fittings on the filter and the VP44- available in lots of forms. Total costs of the fuel system would be about 20 US$ for rubber hose and about 10-15 for the fittings, hose clamps etc. So IMHO it's worth a try if you are on a low budget.

HTH

AlpineRAM