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New Lift, Still Biting, Splash of Air

take the return line off and run it into a bucket running the LP and see if it will purge all the air out. are you still running the factory FFM? did you touch any of the hoses in that area or open up the filter in it?

if nothing else you can pressurize the fuel tank slightly with air, maybe 5-8 psi on it without risking rupturing it. and look around for leaks or use a spray bottle with soap to look for bubbles on the lines between the LP and the tank.

EDIT: disconnect the line from the LP going to the tank and run a hose into a jug of diesel and try it. see if that eliminates the air. if so your issue is behind the LP into the tank.
 
dbrannon79 said:
take the return line off and run it into a bucket running the LP and see if it will purge all the air out. are you still running the factory FFM? did you touch any of the hoses in that area or open up the filter in it?

if nothing else you can pressurize the fuel tank slightly with air, maybe 5-8 psi on it without risking rupturing it. and look around for leaks or use a spray bottle with soap to look for bubbles on the lines between the LP and the tank.

EDIT: disconnect the line from the LP going to the tank and run a hose into a jug of diesel and try it. see if that eliminates the air. if so your issue is behind the LP into the tank.
Click to expand...
Still running the factory FFM and touched nothing up there. This truck was running with the old Heath version of the OEM LP, even thought the LP had stopped working.

I will try the bucket test.
 
OK, disconnected the hose from the hard feed line to the tank and put it in a 1 gallon bottle of diesel I collected yesterday. This hose still goes to the pre-filter. I was able to get it to run, but still periodic bursts of bubbles and engine stutters as they pass. It is better than the full on boil of bubbles and no-start I had before.

I guess the next test is to disconnect the outlet hose at the pre-filter and drop that into the bottle of fuel.
 
OK the last test running a hose in the jug of diesel straight to the LP eliminated the bubbles and it fired immediately. Sounds like I need to delete the pre-filter.
 
That pre filter is the spin-on one you had a leak on the filter before? if so, pull the filter off and look over the filter gasket and mating surface. if anything pull the complete unit down for a thero inspection. where did you get that filter and housing from?
 
dbrannon79 said:
That pre filter is the spin-on one you had a leak on the filter before? if so, pull the filter off and look over the filter gasket and mating surface. if anything pull the complete unit down for a thero inspection. where did you get that filter and housing from?
Click to expand...
The other pre-filter with a fuel leak is on the '94, but there is no air leak. I also changed the tank and hard feed line on the '94, which cured the last of it's issues and turned it into a reliable running vehicle. That pre-filter kit also came from Leroy diesel as did the Walbro FRC 10 LP.

On the '99 it's a Leroy pre-filter kit with a Wix filter and the filter was already installed on the bracket. I did torque it down further as part of chasing the fuel leaks, but the real fuel leak issue was at the fittings.

I wrote a detailed e-mail to Leroy. At this point, I want to know if I can bypass the pre-filter and run it that way so I can get the truck down to SoCal next weekend. I ordered a new fuel tank and hard feed line, but they won't arrive until the following week, and I will be back down to SoCal in either the Suburban or the 2014 4Runner (BTW checked the transfer case I replaced the seals on and no leaks, its' spotless). My wife can haul the fuel tank and hard feed line down in her new 2023 4Runner.

I know, not your level of constraints/problems, but these are issues I deal with.
 
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@Big T I went back and looked at the photos you posted on the filter. the fittings you have threaded into the housing, are those steel made for hydraulic? fittings on the hoses are 45 deg flare and if the fittings are made for hydraulic, those will be 37 deg flare. this might be where the issue is and the two together are not getting a solid seal. I have ran into this in the past where the mating surfaces are not mating flat. brass will conform to the difference with a little finessing though. pop those brass fittings off and have a look on the surfaces to see if they are getting a full seal on the surface of the flare bevels. it could also be something as tiny as a piece of hair stuck in between like a tiny burr.
 
dbrannon79 said:
@Big T I went back and looked at the photos you posted on the filter. the fittings you have threaded into the housing, are those steel made for hydraulic? fittings on the hoses are 45 deg flare and if the fittings are made for hydraulic, those will be 37 deg flare. this might be where the issue is and the two together are not getting a solid seal. I have ran into this in the past where the mating surfaces are not mating flat. brass will conform to the difference with a little finessing though. pop those brass fittings off and have a look on the surfaces to see if they are getting a full seal on the surface of the flare bevels. it could also be something as tiny as a piece of hair stuck in between like a tiny burr.
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These fittings are from the kit Leroy sells with the Raptor LP. So I don’t know wtf the fittings are. I just buy the kit, put it together per his video and install. I don’t do hydraulics for a living; I am a banking regulator specializing in wholesale credit risk who just happens to torture himself with work on 6.5 diesels.
 
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Fittings at the 7:05 mark in the video:

https://leroydiesel.com/products/raptor-100-bcd-kit/

"This is a simple kit to install when you buy the BCD kit. We machine the fitting to connect directly to the FSU & attach right to 1/2″ hose. You will run 1/2″ hose to the pre filter then up to the Raptor pump witch mounts to the frame with supplied bracket. Then from the pump you will connect to the original hard line (that was the original outlet of the stock LP) with another machined FSUx1/2″ fitting. Note: if you are buying the optional HO final filtration kit also you will only get one FSUx1/2″ fitting"
 
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War wagons issue ended up being a flap on the inside of the fuel hose at the ip inlet-
One of my examples as to why metal T at the ip is needed for fuel pressure gauge.

@Big T pressurize the tank, look for the leak.
Everything else is a slow progress at best.
 
I’m just going to bypass the pre-filter tomorrow and do some test runs. i think the Leroy pre-filter is good for stock fuel flows, but is overwhelmed by the Raptor lift pump.

I now know what’s causing the slow leak on the ‘94 with the Leroy pre-filter kit in front of rhe Walbro FRC-10.
 
OK bypassed the pre-filter with a direct connect to the hard feed line from the tank and I am boiling fuel:


New tank and hard feed line have been ordered, but they will not arrive during my stay here this trip.
 
My Assessment:

For a while now I have had a leak from the top of the fuel tank if I brimmed the tank to the top of the fuel fill. This disappears as the fuel is drawn down. I'm thinking I got a leak in the seal of the fitting to the fuel sender unit (FSU) at the tank. This did not show as bad as it is now because the OEM lift pump does not draw as much fuel, but the Raptor lift pump draws a lot more fuel which accentuates the leak at the FSU and draws in air.

I had to replace the tank and both the feeder and return lines to the FSU on the '94. The seal in the feed line was essentially gone and the seal in the return line was broken. I do not have air in the clear line on the '94, but I do have the same slight leak at the prefilter, evidenced by a fuel dip off the filter cannister. I can fix that fuel leak by wrapping the fittings and plugs in teflon tape. Also different pump with the original Walbro installed in the '94, which probably draws less fuel, but it's not drawing in air. The difference being the new feeder and return lines and new tank.
 
If you're interested in bypassing the stock FSU, I installed this draw straw kit on my truck. Have yet to use it as the IP died shortly thereafter and truck has been parallel parked ever since, but I was personally excited to get away from the stock setup

airdogliftpumps.com

AirDog | 901-01-0351-QC | Suction Tube Kit (Draw Straw)

Find the Suction Tube Kit (901-01-0351-QC) and other AirDog Replacement Parts and Accessories at ADLP - Free Ground Shipping over $55.00.
airdogliftpumps.com airdogliftpumps.com

I drilled a hole for the rubber grommet behind the tank FSU and made my own 1/2" fuel line using NPT and -AN fittings instead of the supplied quick connect ones as I just don't trust them.

Bonus of this setup is you can use the original feed line as another return port if you ever install a fuel pressure regulator that needs a return line

I know you're not in salt country but I can't stand how the factory fittings always freeze up on the steel lines and how it's a stupid uncommon fitting. I know Leroy sells fittings to adapt to barbs but at the end of the day you're still sucking fuel from the tank from a 3/8" fitting and then into a 1/2" line. How much of a restriction this creates leading to sucking in air elsewhere I don't know, but the draw straw kit linked above seemed like the easiest route in terms of fab skills (drill a hole, cut a plastic tube to length) and time (took a few minutes when I swapped tanks last fall)

1693846289435.jpeg

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