Engine/Transmission (1994 - 1998) Overflow valve location?

[icexprt]

Why does it look like my overflow valve is located at the supply side of the P7100 and not the return line? My return line has what looks like a typical banjo bolt, and my supply line at the pump has what looks like the overflow valve??? I just installed a guage to read fuel pressure and have about 1 to 2 psi at idle and a max of 12 psi at speed. So, I was going to test the overflow valve operation next and noticed it seems to be in a different location than it should be? Seems to me if it snubbed off excess pressure at the pump inlet, I would probably see really high pressures at my guage port location at the filter outlet?.... unless it was stuck wide open and flowing fully through the P7100 and back to the tank?

I have a 95 2500 with 410,000 miles with an automatic trans and is bone stock.

 

[LandShark]

Here's what an overflow looks like from a 1995.

 

[icexprt]

I know what it looks like from all of the pics available on the internet. I'm wondering why mine is located on the fuel inlet side of the pump and it seems that every one pictured on the internet is located at the fuel outlet? When I replace it, should I leave it where I found it or move it to the return side of the pump? It also seems to me that if it was designed to be on the inlet side, it is probably a different design overflow valve? I'm not sure you could it on either side and it function properly? I'm still trying to figure that one out!

 

[bdenson]

where is it located on your p7100.if looking at pump from drivers side it is on top left backside of pump.

 

[icexprt]

No, that is where the return line banjo fitting is with a standard banjo bolt.... my overflow valve is on the side of the pump facing the fender where the fuel supply line banjo fitting attaches to the pump.... the short steel line from the filter outlet to the P7100. I have pictures of both if I can figure out how to get them from my phone and posted up here.

 

[icexprt]

Here is the pic of the retun line on pump (engine side of pump)

 

[icexprt]

Looks like I finally figured out how to post a pic! Here is the pic of the fuel supply line connection of pump (side facing fender).

 

[bdenson]

i do not see how that works.

 

[bdenson]

i would put it back like should be.

 

[icexprt]

Runs good! Starts quick! Yea, I don't get it either? I'm quite sure nobody has ever had reason to mess with these connections on this truck. My company has owned it since new, and I don't recall any work ever being done on that portion of the fuel system where someone would have had reason to remove these and perhaps re-install them incorrectly. I'm 99.9% sure it came from the factory set up like this.

 

[icexprt]

Below is some info from Geno's... read the next to the last "note". This makes me think they have seen this before? I'm pretty sure I came across similar info from another source also.... although they have been repeating what they read from this same TSB? I'm gonna try and find it now.


TSB 14-07-96

Low Pressure Fuel System Diagnostic Procedures

Visit Geno's Garage
for Truck accessories.
Date: Aug. 2, 1996

Models: 1994 - 1996 (BR) Ram Truck (also applies through 1998 12V models)

NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH THE 6.9L CUMMINS DIESEL ENGINE.

Symptom/Condition:

The Bosch P7100 inline fuel injection pump may be affected by fuel supply pressure variation. If the fuel supply pressure is low or pulsates excessively, the following symptoms can occur:

Low rpm miss/instability
White smoke
Hard starting
Low power
Diagnosis:

This bulletin contains diagnostic information supplemental to 1994, 1995, and 1996 Ram Truck Service Manuals and should assist in the diagnosis and correction of the above Symptoms/Conditions.

1. Verify that the fuel shutdown solenoid linkage is properly adjusted. Improper adjustment could affect fuel delivery in the injection pump. Refer to the 1996 Ram Truck Service Manual (Publication No. 81-370-6108), page 14-106, regarding fuel shutdown solenoid shaft adjustment.

2. Verify that the fuel transfer/lift pump supply pressure to the injection pump is within specifications. Normal fuel transfer/lift pump pressure specifications are 17 - 22 psi at idle and of 25 - 35 psi at 2500 rpm (no load).

3. Place a drain pan below injection pump.

4. Remove banjo bolt and gaskets from fuel inlet line fitting at side of injection pump (Figure 1).

5. Install Special Tool 6976 (SPX Miller) and tool gaskets from tool kit 6977 (SPX Miller) in place of the banjo bolt (Figure 2). Tighten tool into injection pump.



6. Install a 0-60 or 0-100 psi fuel pressure gauge to adapter tool 6976 (Figure 2).

7. Start and warm engine and record fuel pressure. Pressure should be 117-152 kPa (17-22 psi) at idle speed. A minimum of 172 kPa (25 psi) should be indicated after raising engine speed to its rated rpm (2,500 rpm) with no load.

8. If supply pressure is less than 17 psi at idle or 25 psi at 2500 rpm (no load), restrict the fuel return hose by pinching the hose (Figure 3). If pressure returns to normal or above, replace the overflow valve with a new valve (P/N 04883838AA). The overflow valve is located on the side of the injection pump (Figure 4).

NOTE: High pressure at idle indicates that there is a restriction. Make sure that the overflow valve is located at the pump outlet, not the pump inlet (Figure 4).

a. To install the new overflow valve, remove the overflow valve from the pump. A clean lint free rag should be placed beneath the valve to catch excess fuel. Install the new valve and torque the valve to 24 Nm (18 ft. lbs).

NOTE: ALWAYS USE NEW RUBBER COATED SEALING WASHERS (PIN 4761245) WHEN REPLACING THE OVERFLOW VALVE.

 

[icexprt]

Found the other one... I guess I'm sort of answering my own question... I guess I should just order a new valve and install it at the return line. Just can't figure out why it would have come from the factory this way, or why it has never been a problem if it is wrong?


Ram Diesel Injector Pump Problems

Injector Pump Overflow Valve Diagnosis

See TSB 14-07-96 for additioanl fuel pressure and overflow valve tests.

The most common problem related to the injection pump is the Overflow valve, located at the return line connection. Look for this connection at the front of the injection pump on the engine side of the pump.
Subject: Re: Low fuel pressure
From: "Fest3er" <murphyn@mc.net>

> I've had a couple responses on the question of low fuel pressure, but
> still not the answer I need. Can someone tell me the process of
> analyzing whether the problem is the valve or the lift pump? I am
> taking the pressure reading on the output side of the fuel filter.
> Where exactly is the pressure valve?

According to my '98 manual, the overflow valve is on the left side of the fuel injection pump, near the front. It says the valve opens at about 22 PSI; the transfer (list) pump supplies fuel to the injection pump at about 25 PSI.

Skipping to the Diagnosis and Testing section (paraphrasing)....

For symptoms:

low RPM miss/instability
white smoke
hard starting
engine dies at idle
low power
fuel filter cracking
Inspections:
check fuel shutoff solenoid adjustment. If it's not right, fuel pressure could be low
check supply and return lines for kinks, etc., that could restrict fuel flow
check fuel filter/screen (which you say are OK)
check lift pump pressures. S/b about 22 PSI at idle and 25-30 PSI at 2500 RPM. Install Spec. Adap. Hose Tool 6539 in the return line, then pinch the adapter's rubber hose and see if there's any change; book suggests a smooth-jaw vise-grip.
If there's change, first ensure the overflow valve is installed at the OUTLET of the injection pump, *not* the inlet; if that's OK, the overflow valve most likely needs replacing. However, the valve is matched to the injector pump during (re-)manufacturing.
If no change in power is noted, then the lift pump needs replacing or the cam lobe is worn. Note: *don't* pinch the regular return line; outside may be rubber, but the inside is not.
That's it in a nutshell: three pages condensed to a half page. Given the medium complexity of the diagnosis process, it would be wise to have a copy of the service manual handy (I *did* leave out a lot of detail, wanting to relate the ... high points of the procedures).
Good lock,
Fest3er


Replacement overflow valves are available from Piers Diesel Research Inc.
18940 -94th Avenue, Surrey, B.C.

Phone 604 888 4159


Use a 3/4" wrench to unscrew the valve. Make sure that you do not lose the
sealing washers on each side of the fuel return line fitting.

 

[MLee]

Isn't there a pressure tap that looks like that Banjo?
If it were me I'd pull it and see if it is a OV. Check the guts inside, spring and check ball. If it is check spring length, should be .055" long a smidgeon over 1/2 ". and then put it where it belongs, That on top is just a banjo bolt.

 

[icexprt]

Yea, that's my plan for the moment... when I get a minute I'm gonna remove it and disassemble and figure out exactly what it is and how it works. For the record, last weekend when I went to install the fuel gauge, I removed the outer hex bolt piece thinking it was just a standard banjo bolt and noticed it was not.... it is tapered to a point on the inside. I didn't have any spring or check ball flying out upon removal. If there is a spring it stayed up inside the fitting. I just put it back together and decided to tap the fitting on top of the fuel filter for the gauge installation. I'll post pictures of what I find later.

 

[icexprt]

So here it is disassembled. No sprimg or check ball. Just what you see here. I'm thinking bleeder valve maybe?

 

[bdenson]

no spring or ball,i have not seen this.i would put the right stuff back where it should be from factory.

 

[icexprt]

A part of me agrees I should order an overflow valve and install it on the return side of the pump... and another part of me thinks I should leave it as it came from the factory? At least I'm pretty sure it came from the factory like this.... I don't recall anyone ever messing with any part of the fuel system besides the lift pump. Most likely I'll put an OV on it, and see how things go from there. Assuming my truck came like this from the factory, I would think there would be others out there set up like mine? Has no one here ever seen a 12 valve with no OV?