Fuel Pressure Gauges

[joshs1ofakindxj]

I did some searching and got conflicting answers.

I want to install fuel gauge(s) to keep an eye on the condition of my fuel system and particularly the fuel filters because I run waste oil.

I thought I read that the pressure delivered to the injection pump was 6-8 psi, so I got a small Mr Gasket fuel gauge and plumbed it to the port where the breather is located on top of the secondary fuel filters.

The gauge was pegged, so I put on a 0-120 psi gauge and it gave me the readings I wanted I believe. I was surprised it varies with throttle. I thought I would be seeing a steady pressure from the tank pump. I'm seeing 30 psi at idle, 60 psi at normal cruise, and 80 psi when ready to shift up.

Would I find the 6-8 psi anywhere is the system?

Am I seeing the correct fuel pressure readings at the secondary filters?

Thanks!

 

[ODdave]

You definatly in the wrong spot, No way in **** that intank pump will push that much pressure. Unless somone has put the wrong one in there...

 

[gimpyrobb]

The in-tank pump puts out 5-7. You might get that at the primary. Once the fuel goes inder the radiator, it goes into the booster pump on the IP, which bumps it up to what you are seeing.

 

[joshs1ofakindxj]

I've attached a picture of a generic LDT-465 with a red arrow pointing to where I have the gauge connected.

 

[gimpyrobb]

Yup, thats after the booster pump on the IP.

 

[joshs1ofakindxj]

Gotcha. I will plum that small gauge into the line after the primary filter then.

 

[Brad Nitzke]

is there really that much psi after the booster pump? that sounds like lot.

 

[Squirt-Truck]

The booster is specified to make 30-40 psi at idle and 60-80 psi at 2800. The overflow valve on the opposite side of the HH is the bleed point. The HH needs this high pressure to fill the pump chamber fast enough to make the injection cycle. Excess is dumped by the fuel control sleeve between injections.
Not having the booster will make for a very sick operating multi. They will operate fine without the tank pump....until you get air in the line, or need to refill the filters.

 

[mikew]

I've been thinking about installing a low pressure switch that will light a dash indicator when the fuel pressure gets too low (because of clogged filters).

The Fuel density Compensator has an internal regulator set at 20 psi, so anything below that will cause the FDC to richen the mixture.

With that in mind; I'll put a 20 to 25 psi switch after the final filter, there's a boss there, just drill and tap.

While researching this I couldn't find a decent fuel system diagram. I'm sure there's one in some TM, but I gave up looking!

So... I made my own, see attached:

 

[Floridianson]

Mikew why do you just keep it simple and put a gage on the finial filters bleed port and lift your hood once and a while!!!!!!

 

[mikew]

Floridianson,

I had a clogged final filter problem the other day due to a poor batch of WMO (contaminated with a little bio-diesel sludge).

It would idle and run ok at low speed but was too restricted to run at high loads (high flow rates). I want to know the pressure at high flow rates (higher RPMs and loads)..... and no one was willing to sit on the fender to look at the gauge when I was going down the highway!

 

[joshs1ofakindxj]

I have my gauge mounted on the dash. No problemo!

 

[Floridianson]

Floridianson,

I had a clogged final filter problem the other day due to a poor batch of WMO (contaminated with a little bio-diesel sludge).

It would idle and run ok at low speed but was too restricted to run at high loads (high flow rates). I want to know the pressure at high flow rates (higher RPMs and loads)..... and no one was willing to sit on the fender to look at the gauge when I was going down the highway!

Just sit on the fender and rev it up. KISS

 

[DaneGer21]

I've attached a picture of a generic LDT-465 with a red arrow pointing to where I have the gauge connected.

I know this is an old thread, but does anyone recall what size this bleeder port is? 3/8”? 1/4”? 1/8”?

thanks

 

[frank8003]

Put the 1/8" NPT gauge into the test port where it belongs, see the TM, remember them?
Booster pump suction side as per design is 4-7 PSi of proper, not the pump diesel they sell now.
A and for sure do NOT put diesel engine crankcase drain oil in your fuel.
Wish I had new HH heads to sell, but I do Not.

 

[DaneGer21]

I would still like a gauge where I indicated for obtaining pressure after the booster pump as well, like many others have.

 

[frank8003]

I would still like a gauge where I indicated for obtaining pressure after the booster pump as well, like many others have.

Get little shut off valves and put gauges everywhere You want, can't hurt to know what is goin on