can fast Fuel pump cause damage to P-pump?

[Justinb]

need some more advice,

Just recently installed a Fass Fuel pump and I have had many problems with it and I think I finally fixed the problems but my truck still won't start. Started looking at the injection pump on my 97 12 valve and could the Fass Fuel lift pump actually cause damage to the injection pump?

The injection pump is not working anymore. I checked and I'm getting fuel to the injection pump, checked the fuel shut off synoloid, that works, checked the overflow valve, thats fine, made sure the return fuel line is not plugged with debris, thats good, the gear is not loose and the nut is tight on the pump shaft, and i cracked the high pressure lines and no fuel at the pump or injectors.

The injection pump has failed and like my precious statement could the Fass Pump have actually caused internal damage to the injection pump? my truck ran fine until i installed the Fass pump. really getting sick of one problem after another since installing the lift pump on my truck. any thoughts?

 

[BigPapa]

No, the FASS pump can’t damage your p-pump. How do you know you’re getting fuel to the IP? Where are you checking it?

The p-pump is all mechanical, nothing inside that can be damaged by a lift pump.

 

[GAmes]

I'm guessing the FASS doesn't delivery the quantity or the pressure that a p-pump requires. I suggest you scrap it and go back to the inexpensive, reliable mechanical pump.

 

[Justinb]

I took off the fuel supply line to the injection pump, put into a gas can, turned the ignition on to start the lift pump and verified I'm getting fuel. It filled up a 2.5 gallon can in a matter of seconds. plenty of fuel. i don't have a pressure gauge so that the only way to verify I'm getting fuel to the injection pump.

 

[GAmes]

A gauge verifies pressure, but you could crack the banjo bolt at the pump to verify flow. The overflow valve is what creates the pressure. The question is the pump strong enough to open the OFV.

 

[Justinb]

I did that too. There was no flow until I started cranking the engine. Don’t know if that’s what the injection pump is supposed to do. I also removed the overflow valve and installed it and tried it both ways. Had fuel flow when I cranked the engine over with the valve removed and no flow when it was installed. So, obviously not enough pressure to crack the ball valve in the return valve.

 

[GAmes]

Don’t know if that’s what the injection pump is supposed to do.

This is from the factory service manual.. I suggest you get one. I was not able to cut/paste the illustrations.

FUEL INJECTION PUMP
The fuel injection pump is a Bosch P7100 series inline
type (Fig. 9). The injection pump is driven by the
engine camshaft. A gear on the end of the pump shaft
meshes with the camshaft gear. The pump is timed
to the engine. Fuel injection occurs near the end of
the compression stroke for each cylinder.
The RQV-K governor (Fig. 9) has a pump timing
feature. This will allow the pump shaft to be oriented
in a position corresponding to top dead center (TDC)
for the compression stroke of cylinder number one.
Indexing the governor flyweight assembly to the
shaft during assembly establishes pump timing.
. As engine speed increases, the internal pump pressure
increases. An air-fuel control (AFC) (Fig. 10) on
the governor ensures that regulated fuel delivery is
matched to intake manifold pressure (turbocharger
boost) for emission control.
The mechanical fuel transfer pump delivers fuel
under a low- pressure of approximately 172 Kpa (25
psi) to the injection pump through the fuel filter/water
separator. The injection pump then supplies highpressure
fuel of approximately 120,000 kPa (17,400
psi) to each injector in precise metered amounts at
the correct time.
Excess fuel is returned to the fuel tank by an overflow
valve (Fig. 7) on the injection pump. This vent
opens at approximately 152 kPa (22 psi) and returns
fuel to the fuel tank through the fuel return line.
Diesel fuel and engine oil are used to cool the fuel
injection pump. A separate oil feed line from the
engine supplies engine oil to the pump. The oil
returns to the engine through an opening at the front
of pump.
A KSB (cold start) solenoid is not used.

 

[BigPapa]

Now, when you say you "removed the overflow valve and installed it and tried it both ways", did you remove the ball and spring from the OFV and reinstall just the body in order to test it "both ways"? I've primed and bled many a p-pump system and have never had to turn the engine to get fuel flow through the OFV.

It's possible that your pump is not set up for use on your '97. As Gary posted, pressure to the IP needs to be at least in the mid-20's. Most pumps sold by FASS are set up to push @10-12psi and have to be modified to run the higher pressures. It's nothing major, just changing out a ball and spring if I remember correctly. I've found this to be the reason most 12-valve owners that buy a used pump have so many problems with them. Most of the time a used FASS was originally used in a 24-valve apllication.

Higher HP engines require even more pressure at the pump. On the UTR pulling truck, the Bandit, we ran two FASS pumps in order to get 60-65psi during a pull at full throttle. At that time it was @ 1200HP.

 

[Justinb]

I physically removed the over flow valve and turned the lift pump on (not turning over the engine) and no fuel flow through the injection pump. Then turned the engine over with the over flow valve removed and fuel sprayed everywhere. Made a huge mess. Then installed the over flow valve again and turned the engine over and no fuel flow. Assuming the fuel pressure is not high enough to crack the valve. So according to your comment something is possibly blocked in the internals of the injection pump?

The lift pump I bought from fass says it runs at 45 psi and 150 gph. That is what they recommended for a 12 valve engine that is within a 0 to 700 hp range. I do not have a pressure gauge to validate that.

I bought this 97 dodge Cummins early this year and the guy I bought it from said he took really good care of it but I think that meant cosmetically not mechanically. It’s a beautiful truck but I have had to replace almost everything on it so far. It keeps falling apart.

By the way thanks for your info it’s helping

 

[GAmes]

Then installed the over flow valve again and turned the engine over and no fuel flow. Assuming the fuel pressure is not high enough to crack the valve. So according to your comment something is possibly blocked in the internals of the injection pump?

No fuel flow to where? The OFV sends fuel back to the tank when it opens. Have you cracked any of the injector line fittings at the top of the IP or at the injectors, then cranked the engine over? There is nothing to block in the internals of the IP.

 

[BigPapa]

Sounds like you’ve got the right pump. I’m wondering if you have it plumbed properly. If you give us the part number from your invoice we can double check for you.

We’re trying to help, not trying to infer that you don’t know what you’re doing or that you’ve done something wrong. Gary is spot on with everything he’s told you and he’s one of the most experienced members here when it comes to the 2nd Gen 12-valves.

As far as your truck “falling apart”, what have you had to replace? Engine parts, driveline, or suspension?