Will start only with a squirt of starting fluid. Runs great once started.

[7Dust]

Just spit balling here so lets start with the gages. They are wrong or you have an over pressure in the system. Most LDT's seem to be running around 30 psi idle and 60 psi high idle. Now that is the specs for minimum performance levels. Now the LDS pump has specs that are higher and over 70 psi. for high idle and idle. Yea it was said if you have some or 4-7 psi fuel pressure at the bleed screw between the fuel filters that everything should be good for pushing fuel through the head back to the tank. While the engine can run with the over pressure valve that is in the T fitting open on the secondary fuel filter wondering if this might be you problem. There are a couple of ways of checking the over pressure valve. If you gage is correct then the over pressure valve would be open well before 80 psi. I am not going to look through the TM for the open pressure of the over pressure valve but mid 70's is what I am thinking.

It’s a Harbor Freight air pressure gauge so maybe not the best tool.

The high speed pressure was me grabbing the fuel rod with the cover off. Might have been a little extra ambitious with the rev.

I have pulled the regulator I think you are talking about in the secondary filter? A spring loaded basket under the extra bolt? It looked clean but I sprayed it with some brake cleaner and acetone and re-installed.

Today I pulled the pump out again to retrace everything I have messed with since it started acting up. It WAS starting on its own (with extra throttle) before I pulled tank and filters.

I am wondering why there is seepage at the tank hanger gasket with only 10 gallons in the tank. I think the fitting at the top of the hanger (flare fitting inside tank) might be leaking / spraying the gasket making it leak and seep (also introducing air maybe).

Then it started raining on me. I might mess with it tomorrow.

 

[KN6KXR]

Well you've chased the supply to the HH pretty well. If it was leaking you should have seen it. Now maybe test the output: try cracking an injector line and see if you get a good pulse out of it while cranking.

I'm thinking you have some goo in there wreaking havoc.....

 

[Valley Rock]

Hey OP check this vid series out if you havn't already ...

https://youtube.com/playlist?list=PLp1oqEXZZEvD5MsycbwuqyTd63oYdcM9V

 

[Floridianson]

One thing for the IP is fuel flowing through the head and back to the tank so we need a good working in tank pump / inline pump to clear air after filter change.
The easy way of checking fuel flow through the head and also checking the over pressure valve would be this. The fuel line that comes off the head at the over flow valve and goes to the T fitting on the secondary filter remove it from the T fitting, Put the line in a can / jug or a way to catch the fuel. Turn on master power and see if you are getting good fuel flow and some pressure out of that line with no air. Now also the open T fitting should not be leaking or any fuel flow / pressure out of it. If it does have flow /pressure then the over pressure valve is not seating.

 

[7Dust]

One thing for the IP is fuel flowing through the head and back to the tank so we need a good working in tank pump / inline pump to clear air after filter change.
The easy way of checking fuel flow through the head and also checking the over pressure valve would be this. The fuel line that comes off the head at the over flow valve and goes to the T fitting on the secondary filter remove it from the T fitting, Put the line in a can / jug or a way to catch the fuel. Turn on master power and see if you are getting good fuel flow and some pressure out of that line with no air. Now also the open T fitting should not be leaking or any fuel flow / pressure out of it. If it does have flow /pressure then the over pressure valve is not seating.

I am seeing very fine air bubbles in the small clear-ish plastic hose that connects to the left of the hydraulic head and runs up to all the injectors - towards the HH when engine is revved.

At idle, it looks like larger bubbles might be running away from the HH and climbing the tube but it is hard to tell.

 

[7Dust]

I am seeing very fine air bubbles in the small clear-ish plastic hose that connects to the left of the hydraulic head and runs up to all the injectors - towards the HH when engine is revved.

At idle, it looks like larger bubbles might be running away from the HH and climbing the tube but it is hard to tell.

This little guy is a tiny bit bubbly.

 

[rustystud]

This little guy is a tiny bit bubbly.

You have a fuel line leak somewhere. At this point I would take off your fuel tank line and put an air chuck fitting on it. Then take off the line going into the Hydraulic Head and cap it off. Then put some shop air in the line and start looking for a leak with some soapy water (I like to use Windex spray myself) . Yes you will need to make up some fittings to attach the air chuck to it, but I've found this to be the easiest way to find a leak. Otherwise, you can go crazy trying to find it.

 

[KN6KXR]

Yep fuel line leak. It's small so when it runs the bubbles are tiny and don't affect operation (very much). When you stop all the little bubbles gather together and air bind the system. Since it's still rather small you've been able to get away with some starting fluid to bump the cranking RPM. If the leak were bigger you would have to crack the injector lines to get it running (if it would start at all). Lots of possibilities here for where it could originate. Start with basics again is what I would do. Little bubbles like that could be entrained from the high pressure pump, HH inlet, filter housings, etc, etc...

Since it's so small and apparently being hard to find I suggest getting the areas of inspection amazingly stupid clean and dry then blast with baby or talcum powder. Then run it and wait for the spots to appear. That process is a pain but it really works.

 

[Floridianson]

The line coming off #1 Injector is the injector Return lines from all injectors. It will always look like the is some air /fuel trapped in that line. While the injectors do not return fuel under pressure / flow they burp sometimes. This is not a problem and if you look at any multi fuel they will all have the little air /fuel trapped in that line. That being said that little bit of air in the injector return line never goes through the Head or injector system it just returns to the fuel tank. Since the overflow valve T has the fuel tank and injector return lines hooked together and the system when under booster pressure the injector return line have pressure pushing back on it trapping air /fuel. One thing we try and do if air is getting into the system we keep the fuel tank full to keep the rubber hose on the in tank pump covered. If that takes care of the problem then the rubber line must be replaced. Most of the time we check for air in the system by way of the bleed screw between the secondary and final filters. As for fuel air leaks anything after the IP booster that goes to 70 psi would show up as a fuel leak not take on air. As said IF there was air being sucked into the system it be in tank pump rubber or the primary fuel filter gasket. Plus you could check all the lines from tank to booster connections for being loose and the IP booster rubber line that comes from the cross over copper line. Also we do not ever need to bleed the Deuce injector.

 

[7Dust]

The line coming off #1 Injector is the injector Return lines from all injectors. It will always look like the is some air /fuel trapped in that line. While the injectors do not return fuel under pressure / flow they burp sometimes. This is not a problem and if you look at any multi fuel they will all have the little air /fuel trapped in that line. That being said that little bit of air in the injector return line never goes through the Head or injector system it just returns to the fuel tank. Since the overflow valve T has the fuel tank and injector return lines hooked together and the system when under booster pressure the injector return line have pressure pushing back on it trapping air /fuel. One thing we try and do if air is getting into the system we keep the fuel tank full to keep the rubber hose on the in tank pump covered. If that takes care of the problem then the rubber line must be replaced. Most of the time we check for air in the system by way of the bleed screw between the secondary and final filters. As for fuel air leaks anything after the IP booster that goes to 70 psi would show up as a fuel leak not take on air. As said IF there was air being sucked into the system it be in tank pump rubber or the primary fuel filter gasket. Plus you could check all the lines from tank to booster connections for being loose and the IP booster rubber line that comes from the cross over copper line. Also we do not ever need to bleed the Deuce injector.

I have double checked the rubber fuel line in the tank - even replaced it with a submersible type while I was there. I am pretty sure its not leaking but the compression fitting at the top of the pipe it connects to on the fuel hanger might have been / still is? leaking. I had all of that apart when I was cleaning the tank, hanger, and pump.

I pulled the primary fuel filter and replaced it - but I think there is a small seal on the large bolt under the alternator - I did not change it and never have in the past dozen years or so Ive had the truck.

I think I will man up and pull the alternator to change the small seal under the primary filter bolt. Maybe it is high enough not to leak fuel externally - but it lets in air?

I put a barb with a clear hose on the secondary bleed and turned on the pump. I do know that when I open the secondary bleed with just the pump running, there is lots of air at first before it clears up. If I let it sit for a minute, lots of air again.

 

[ToddJK]

I have double checked the rubber fuel line in the tank - even replaced it with a submersible type while I was there. I am pretty sure its not leaking but the compression fitting at the top of the pipe it connects to on the fuel hanger might have been / still is? leaking. I had all of that apart when I was cleaning the tank, hanger, and pump.

I pulled the primary fuel filter and replaced it - but I think there is a small seal on the large bolt under the alternator - I did not change it and never have in the past dozen years or so Ive had the truck.

I think I will man up and pull the alternator to change the small seal under the primary filter bolt. Maybe it is high enough not to leak fuel externally - but it lets in air?

I put a barb with a clear hose on the secondary bleed and turned on the pump. I do know that when I open the secondary bleed with just the pump running, there is lots of air at first before it clears up. If I let it sit for a minute, lots of air again.

Shouldn't be any air at all once the system has been bled. Have you traced all the fuel lines for leaks while running? I've found all my leaks that way as the pressures and vibrations together seemed to expose the leak. A fuel line fitting that ever so slightly has a drip coming from it will let air in. If a new seal on that bolt for the primary doesn't stop the air, check all the fittings. See if any fittings can take an 8th of a turn without much effort, then bleed the system again and wait for a while and bleed it again to see if the air pocket came back. If any of the fuel line fittings are threaded all the way in, that can also be a problem, as the ferrule is crushed to the point it no longer properly seals, I'm pretty sure there's a video about that on Tactical Repairs YT channel.
Once it's the air is bled out, there may still be air further in the lines which will get worked out as you crank the engine over, shouldn't take no more than a few five-ten second cranks and it should start under it's own power. If you use either and it attempts to start but doesn't, there's still air in there and it needs to be worked out.

 

[KN6KXR]

I put a barb with a clear hose on the secondary bleed and turned on the pump. I do know that when I open the secondary bleed with just the pump running, there is lots of air at first before it clears up. If I let it sit for a minute, lots of air again.

One possibility is that you not only have a small leak but you also have an under performing lift pump. Assuming that you are getting a bunch of small bubbles that collect into pockets when off (sure seems like that by your description); it's possible the injector pump is just over pumping the little lift and pulling air through an otherwise pressurized line. It also might not be the lift pumps fault you could just have a really clogged line between the lift pump and the high pressure pump along with an itty bitty leak. The lift pump is low pressure but pretty high volume as you crack open the system, like the primary filter drain, you should get a really good stream out of it on the lift/tank pump alone. I'm not sure what it rated at (maybe somebody here knows?) but it's a lot.

Those lift pumps are crummy by today's standards. When mine failed it would only run when inverted. Literally I took it out plugged it in it only ran upside down. Since it's really hard to drive that way I replaced it with a nice Walbro electric on the frame rail and left the rest in place.

I actually hadn't noticed it failed for hundreds of miles. It wasn't until I did a real pre check one day and went to drain the primary that I found out. They'll run just fine without it working. Unless maybe you have a little leak and are drawing air in.....

 

[7Dust]

Shouldn't be any air at all once the system has been bled. Have you traced all the fuel lines for leaks while running? I've found all my leaks that way as the pressures and vibrations together seemed to expose the leak. A fuel line fitting that ever so slightly has a drip coming from it will let air in. If a new seal on that bolt for the primary doesn't stop the air, check all the fittings. See if any fittings can take an 8th of a turn without much effort, then bleed the system again and wait for a while and bleed it again to see if the air pocket came back. If any of the fuel line fittings are threaded all the way in, that can also be a problem, as the ferrule is crushed to the point it no longer properly seals, I'm pretty sure there's a video about that on Tactical Repairs YT channel.
Once it's the air is bled out, there may still be air further in the lines which will get worked out as you crank the engine over, shouldn't take no more than a few five-ten second cranks and it should start under it's own power. If you use either and it attempts to start but doesn't, there's still air in there and it needs to be worked out.

 

[7Dust]

One possibility is that you not only have a small leak but you also have an under performing lift pump. Assuming that you are getting a bunch of small bubbles that collect into pockets when off (sure seems like that by your description); it's possible the injector pump is just over pumping the little lift and pulling air through an otherwise pressurized line. It also might not be the lift pumps fault you could just have a really clogged line between the lift pump and the high pressure pump along with an itty bitty leak. The lift pump is low pressure but pretty high volume as you crack open the system, like the primary filter drain, you should get a really good stream out of it on the lift/tank pump alone. I'm not sure what it rated at (maybe somebody here knows?) but it's a lot.

Those lift pumps are crummy by today's standards. When mine failed it would only run when inverted. Literally I took it out plugged it in it only ran upside down. Since it's really hard to drive that way I replaced it with a nice Walbro electric on the frame rail and left the rest in place.

I actually hadn't noticed it failed for hundreds of miles. It wasn't until I did a real pre check one day and went to drain the primary that I found out. They'll run just fine without it working. Unless maybe you have a little leak and are drawing air in.....

Lift pump is pumping fine I think. 5 psi on cheap pressure gauge and maybe a quart of fuel in 5 seconds?

Wherever the air is getting in, fuel is not getting out. It’s dry dry dry no drips.

Must be a big air leak too because if I kill it and try immediate restart within a second, it just cranks until I give it a spray to fire it off.

 

[rustystud]

Don't overlook the fittings. A hair-line crack can really mess with you. Sometimes they don't open up until the fitting gets warm.

 

[7Dust]

Don't overlook the fittings. A hair-line crack can really mess with you. Sometimes they don't open up until the fitting gets warm.

I also will check the large compression fitting on top of the tank where the fuel enters the fuel line. It has leaked before and I’ve had to reflare it years back. It’s not wet - but will see.

 

[Wreckclues]

Wherever the air is getting in, fuel is not getting out. It’s dry dry dry no drips.

How about the primer pump? Just rebuilt mine, before rebuild the piston just moved freely in the tube, after cleaning and new O-rings there's a noticeable vacuum in the tube.

 

[KN6KXR]

I also will check the large compression fitting on top of the tank where the fuel enters the fuel line. It has leaked before and I’ve had to reflare it years back. It’s not wet - but will see.

It shouldn't be able to draw air in there if the tank pump is working properly.

 

[ToddJK]

Maybe an engine guru can chime in here, but if air is in the system, then how is the engine firing off using either? Shouldn't it just attempt to start but keep cranking until the air is out of the system? That's always been my experience when there was a leak in the fuel system. I still think the injectors may be dirty and have a poor spray pattern or weak pressure which is why it needs help to start but runs fine afterwards.

 

[7Dust]

The top washer on the primary filter was a rubber one that looked like hell but didn’t show signs of leaking.

I replaced it with an aluminum crush washer and also replaced the lower canister seal. Still no fluid leaks, probably no air leaks - I feel confident it’s not my problem.

I checked the compression line at the tank. It’s all in good order.

I don’t think there is a crazy amount of air in the lines at this point.

I’m thinking turn up the fuel while cranking.