I have a fuel boss mechanical pump and I had an issue with some debris being stuck in the bypass valve, causing the fuel pressure to plummit. I cleaned it out and put it back together and everything seemed to be as normal around 18psi. Though, today when I went for a drive the fuel pressure jumped up to 45-50psi. Thinking the valve was stuck closed I opened it up to find all was normal. I know I've installed the valve in the correct orientation as well :/.
I'm at a loss at this point, can't figure out  why the pressure is so high! Any ideas? 
I drove for about 10 miles, how much harm could this have caused at 45psi?
Thanks 

If your pressure was fine and then spiked like that...something is blocking the overflow back to the tank or you have the check valve backwards.  I would pull the overflow line at the Tee before the check valve and blow with air hose to see if the line is clear.  Also call Richard and see what he has to say.  He will answer his phone afterhours at a decent time.  That kind of pressure could blow the top of your fuel filter canister off which is a big mess.  I would fix it before driving again.

 

To make sure you have the check valve in correctly look into both sides of it.  You will see a spring on one side and solid white on the other.  The spring is on the tank side and the white is on the engine side. 

Edited March 27, 20196 yr by Bullet

Good point, I'll check the T before the bypass valve. I know I've put the valve in the right orientation, have had to clean it out a few times now. Time for another diesel bath lol. I did notice diesel running through the hose before the bypass valve when I disconnected it. 

I thought about running it while disconnecting the valve from the tank end up to make sure fuel was going through piece by piece. 

Hard to think an obstruction would cause fuel pressure to go that high, guess I assumed the bypass valve was probably fairly closed at idle. 

 

If you are having to clean it out so many times you probably haven't got it all out yet.  I don't understand why you would have debris in the line at all.  I never had to take mine back apart from install.  I would definitely blow out the entire bypass line with compressed air to guarantee it's clean.

 

Also test your bypass valve by hand when you get it out.  Push on the white disc with a small screwdriver to make sure it is moving and depressing the spring with a little pressure. 

Edited March 27, 20196 yr by Bullet

I tested the valve before putting it back in, seemed to be ok. Polished the inside cylinder a bit with a dremel too. Perhaps was a lil more stiff than I remember. Ordered a new bypass valve just in case. Most of the debris that I'm seeing is small rubber shavings. I should have put in a strainer when I installed. 

 

It's possible to have a bad bypass valve.  You can also test that by removing the guts out of it to where it's flow straight through and then take pressure readings...or like you say get a new one and see if the problem goes away. 

 

Rubber shavings probably in there from factory when hose was made.  Either way let us know what happens next. 

I've got to ask do you have a water separator or prefilter before the pump?

I'll give an update next week, had to park the truck out of town and borrow a rig for the meantime... 

I don't have any filtration/separation pre-pump (boss pump) . I think the most allowed for the system before the fuel boss is a strainer. I do plan on upgrading to a new filtration system once it warms up here. 

Think I misread your question, yes I have the original stock fuel filter assembly. 

Edited March 27, 20196 yr by CAMG3X

I have just the opposite problem.  Over the years the fuel pressure at idle has been decreasing.  The pressure at idle was 17 psi and has now gone as low as 13 psi, when first started on a cool morning, and will settle at 14 psi.  The fuel pressure will jump to 18-19 psi when off idle.

 

This Fuel Boss system, when new, also dropped fuel pressure due to black pieces of hose rubber getting stuck in the pressure relief valve.   

I suppose the other possibility is that my Quad fuel pressure sensor has taken a dump. Though would assume it would not read at all: the pressure does fluctuate with fuel demand as expected (45psi down to 30's on mild acceleration). I do plan on testing it manually when I get to working on it. 

Ya I wonder if the bypass valve spring becomes weak over time, slowly dropping idle pressure. 

I've found all it takes is a minuscule flake of rubber to hold it up, thus dropping the pressure. I wish I blew the hoses out and added a strainer from the beginning, but I did the install in a parking lot haha. 

 

 

Big mistake most do is install the fuel pressure sensor at the VP44. This will kill it in a short order. Like mine it's got 5 foot of air brake line from the snubber to the sensor. This allows time for the pulses to fade.

57 minutes ago, Mopar1973Man said:

Big mistake most do is install the fuel pressure sensor at the VP44. This will kill it in a short order. Like mine it's got 5 foot of air brake line from the snubber to the sensor. This allows time for the pulses to fade.

Kinda like having a foxy nurse up real close while taking your blood pressure.

That’s what happen with mine. It’s slowly read higher and higher until it pegged at 100 psi and leaked fuel

Then my sensor may very well be the problem! I'll check it with the tester first and start planning a new fuel pressure system. 

Think I'm going to bypass the electric pump at some point and solely run the fuel boss. Been fine priming the system by manually spinning the pump on fuel filter changes and not sure how much the electric pump really helps with start up. 

Should I just cap the ends going from the T to the pump? Would like to keep it somewhat intact incase I need it in a bind + close the system off to not expose to elements. Plus disconnect the electric harness to the pump. Betting it will throw a code though... 

1 hour ago, CAMG3X said:

Think I'm going to bypass the electric pump at some point and solely run the fuel boss.

I run mine straight mechanical with no electric pump anywhere on the truck.  No codes were tripped when I disconnected the electric pump.  Only difference is priming the system but seems like you got that figured out already. 

Moparman

"PM box closed, use public forum"

 

OK... Cant find your address to send check.   Yes I know you wont cash till you get the chance.

 

Please post line with info

 

Thanks

 

My system is set up with the electric pump but not used but with the ECM triggering the relay.  The check engine light in this truck would come on if this was not done.  I need the light to stay off due to Calif. SMOG testing.

The relay option B was used, see below, and the 10 AMP fuse is remove to keep the fuel pump from running.  When the electric fuel pump is needed to prime the system, the fuse is reinstalled.

 

 

 

IIRC.. The code will only trip if a California truck? When I installed mine I went with the straight mechanical set up and ordered it that way, No issues with check engine light 

 

For filter changes I cheat and add a little pre filtered fuel in the canister and it doesn’t loose prime. I’m still in the market to find a prefilter strainer that’s serviceable, but searching I havnt found anything that’s even close to the 24 micron strainer, meantime I just change the strainer, but it would be nice to open it up and see what kind of crap it’s catching  and clean it.

As for the fuel pressure sensor. My sensors is a good distance from the tap point, snubber back at the tap point. As my boost and fuel pressure are mounted on the fender forward of the ABS module. 

 

This is an ABSOLUTE NO-NO... Even if there was a snubber before it still a NO-NO. NEVER install the sensor at the VP44. The pulses are still extremely strong and ruin the fuel pressure sensors. There must be at LEAST 5 foot of tubing from the tap point and snubber to the sensor. 

Edited March 29, 20196 yr by Mopar1973Man

12 hours ago, 01cummins4ever said:

The code will only trip if a California truck? 

There won't be a light on the dash but there should be a code stored in ECM for no lift pump circuit, or something like that. In California you can't have any codes or they won't pass smog. Not even sure why I'm talking about something I don't know.

By California truck do you mean one that was sold in California that something done to it or..

one that is legal to sell in California?

 

 

Is there any type of label or sticker that I could tell the two apart?