Could fuel feed pump cause air in fuel line?

[Paraglider]

I've got an air in the fuel line problem and keep searching for explanations. I looked on the forum and got some good info. Here's what I've tried: (It's a 2h engine on a '82 HJ47)
1. inspecting fuel line to main tank (looks to be okay).
2. replaced fuel filter
3. replaced primer pump with a Bosch
4. bled injectors
5. bled at fuel filter nipple

I don't know if fuel is supposed to spit out when bleeding when there's no air remaining. It didn't at the injectors or at the fuel filter (came out but wasn't gushing out).

Don't know if the fuel feed pump has anything to do with it. The truck runs fine after bleeding for about 2-4 minutes with the last minute running rough from air getting in.

I have two tanks. Haven't inspected the line to the reserve tank completely but it goes to the top of the reserve tank and no way to inspect that w/o taking the tank down (too little space to see--even with a mirror I can't see close enough). Since the engine runs similarly (dies) on both tanks, I assume the problem isn't in the fuel line between the reserve tank and wherever it meets up with the main fuel line.

Don't know if the switch valve could be a point where air is getting into it. The switch is next to the gear shifter but can't really tell below it what's going on or how/where air could be getting in at the switch valve. I assume the problem is probably between the primary filter (water/sediment separator) and the injectors. Since I've bled the injectors and fuel filter and air is still getting in, I'm at a loss (and am new to the 2h engine so not very knowledegeable).

I have been advised by Gary Mudrak and Mudrak Custom Cruisers that a likely problem is a pinhole leak in the primary filter. It's really hard to see that well given its location (under the right side door bolted to the chassis.

Thanks for any help.

 

[Coastline]

Sucking air at the tubing ends ?? Rotten hoses?

 

[Solace in Solitude]

I'm not familiar with diesels... but, I had an issue that resulted in the oem mechanical fuel pump sucking mass quantities of air when the carb secondary kicked in... it turned out to be a defective fuel filter... it wasn't properly sealed, allowing air into the fuel stream. It wasn't noticeable until the secondary kicked in... e.g. under load (uphill, foot buried in the pedal)... engine would starve for fuel and die. It would restart right away, but recur every time it went under load.

You said you have a new fuel filter, so it's not likely that filter is the problem. You also said you have a switch valve... everywhere you have soft lines, you could have deterioration... possibly pin holes... you could also have pin holes in your hard lines... or, loose clamps on your lines.

How does the fuel pump work? Electric or mechanical... I assume electric.. are you definitely getting air into your fuel?

Or, do you have an oil pressure safety switch on your diesel? If so, is it possible that it's sensing < 2psi oil pressure? Maybe it needs to be replaced...


EDIT: Again, I'm not familiar with diesels... but, the easiest way of eliminating similar issues on a petrol is to simply replace all the soft lines... doesn't cost that much... with new clamps.

I also don't know how your diesel tank is configured... does it have a fuel pickup at the bottom of the tank or does the pickup enter the tank at the top? If at the top, is it possible the pickup has become separated at the top and is allowing air to be sucked from the top of the tank.

 

[Paraglider]

I'm not familiar with diesels... but, I had an issue that resulted in the oem mechanical fuel pump sucking mass quantities of air when the carb secondary kicked in... it turned out to be a defective fuel filter... it wasn't properly sealed, allowing air into the fuel stream. It wasn't noticeable until the secondary kicked in... e.g. under load (uphill, foot buried in the pedal)... engine would starve for fuel and die. It would restart right away, but recur every time it went under load.

You said you have a new fuel filter, so it's not likely that filter is the problem. You also said you have a switch valve... everywhere you have soft lines, you could have deterioration... possibly pin holes... you could also have pin holes in your hard lines... or, loose clamps on your lines.

How does the fuel pump work? Electric or mechanical... I assume electric.. are you definitely getting air into your fuel? It's mechanical, connected to the primer pump. Can't really see any way it would get air into it if all the bolts are tight.

Or, do you have an oil pressure safety switch on your diesel? If so, is it possible that it's sensing < 2psi oil pressure? Maybe it needs to be replaced... Not sure (I just acquired the rig and am becoming familiar with it slowly but surely.)


EDIT: Again, I'm not familiar with diesels... but, the easiest way of eliminating similar issues on a petrol is to simply replace all the soft lines... doesn't cost that much... with new clamps. Yeah, should just do it regardless. Some of those lines are not easy to access, but . . . .

I also don't know how your diesel tank is configured... does it have a fuel pickup at the bottom of the tank or does the pickup enter the tank at the top? If at the top, is it possible the pickup has become separated at the top and is allowing air to be sucked from the top of the tank.

I'm including a photo of the pick-up from the reserve (top pick-up and w/o any clamp--but's been that way even when the rig was going 1.5 to 4. hours a stretch without dying.) I believe the main tank is also top but don't remember for sure. I'll take a look (It's currently at the mechanics so can't just step outside and look). The shop where it's at is a commercial diesel truck and RV place and my rig gets their attention when they don't have anything else going on--which is basically never--so I'm trying to trouble shoot it on my own)

I have also included a picture I took of the underside with two bolts, one brass and the other probably steel coming out of the ends of two hoses. Have no idea what that's about or the two hoses to their left that just end. Any thoughts?

Thanks!

 

[Paraglider]

I'm not familiar with diesels... but, I had an issue that resulted in the oem mechanical fuel pump sucking mass quantities of air when the carb secondary kicked in... it turned out to be a defective fuel filter... it wasn't properly sealed, allowing air into the fuel stream. It wasn't noticeable until the secondary kicked in... e.g. under load (uphill, foot buried in the pedal)... engine would starve for fuel and die. It would restart right away, but recur every time it went under load.

You said you have a new fuel filter, so it's not likely that filter is the problem. You also said you have a switch valve... everywhere you have soft lines, you could have deterioration... possibly pin holes... you could also have pin holes in your hard lines... or, loose clamps on your lines.

How does the fuel pump work? Electric or mechanical... I assume electric.. are you definitely getting air into your fuel?

Or, do you have an oil pressure safety switch on your diesel? If so, is it possible that it's sensing < 2psi oil pressure? Maybe it needs to be replaced...


EDIT: Again, I'm not familiar with diesels... but, the easiest way of eliminating similar issues on a petrol is to simply replace all the soft lines... doesn't cost that much... with new clamps.

I also don't know how your diesel tank is configured... does it have a fuel pickup at the bottom of the tank or does the pickup enter the tank at the top? If at the top, is it possible the pickup has become separated at the top and is allowing air to be sucked from the top of the tank.

Whoops. Here are the photos.

 

[Solace in Solitude]

Well, I'm sure of one thing... the bolts plugging the hoses are not oem

The pickup picture... the fact that there's no clamp makes me wonder if the hose is simply old and no longer tightly fitted to the pickup - I'd put a clamp on it... but, again, I don't know diesel.

I don't know what the bolts are helping/hurting...

Have you thought about posting this on the Diesel forum Diesel Tech / 24 volts

 

[Paraglider]

Kind of agree, those bolts aren't OEM! Never having replaced fuel lines before, when I take the clamps off and disconnect the hose, isn't fuel going to come spilling out? And if so, what's the secret to making less of a mess than necessary? All the other fuel lines have clamps on them so I assume this one in the photo should too. The fact that the bottom of the hose looks moist makes me think it should have a clamp also. Thanks for the suggestion about Diesel Tech. Mine is a 12 volt but that shouldn't matter, right?

 

[handcannon]

I'm not a diesel mechanic, but I do have a couple GM diesel pickups, so one of the first things I would do is bypass totally the complete fuel system. Get a canister of some type, gallon juice jug?, and run both main and return fuel lines (all new rubber tubing) into it directly from the injection pump. Make sure you have some kind of filtration there and a built in fuel pump in the injection pump (seems to me that most Toyota motors do), and put some clean diesel in the jug. Bleed all the air out of the lines and prove, or disprove, that the motor will run with just this system and the injection pump.

Doing this will help narrow down where your air intrusion is at. If everything runs as it should you know that the problem is further up the line towards the fuel tanks. If possible, use the same fuel jug and move your connection point closer towards the fuel tanks and check for correct running again. By doing this you can start eliminating areas that you question but are not sure about.

I know that air intrusion problems are frustrating to find as I have an old pickup, with air problems, that I use only on my property. Starting it after it has sat for overnight I will always have air in the lines. But, I have figured out a system that makes it easier to bleed the air out and start it, and once started it will always start the rest of the day until it has not been run for a few hours. I guess you could say I'm lazy because I have never gone beyond this point since I now know how to restart it (bleed air out) every morning that I use it.

Good luck figuring out the problem, and like pngunme said, somebody on the diesel forum will be familiar with this particular system. They might even be able to pinpoint areas that have been found to have recurring problems on other vehicles.

Don

 

[roscoFJ73]

I also don't know how your diesel tank is configured... does it have a fuel pickup at the bottom of the tank or does the pickup enter the tank at the top? If at the top, is it possible the pickup has become separated at the top and is allowing air to be sucked from the top of the tank.

The Toyota diesels use the same tank and pick up as the petrol varieties. The only difference is that some have a fuel return to the tank and some(like the 2H) recycle the excess fuel back to the filter..

 

[roscoFJ73]

As Handcannon says, bypass the fuel system and run some fuel from a small canister to isolate the problem.
Or get some clear hose and see if the air bubbles are coming into the engine bay with the fuel.
The 2 hoses blocked off with the bolts ,where do they run to?
Are the twin tanks a factory set up?
When you finish priming ,do you screw the feed pump back into its closed position?


Try posting on the diesel forum, lots of owners there with old diesels and air in the fuel lines.

 

[Solace in Solitude]

The Toyota diesels use the same tank and pick up as the petrol varieties. The only difference is that some have a fuel return to the tank and some(like the 2H) recycle the excess fuel back to the filter..

Thanks for explaining.

So, @Paraglider has a 2H... It's possible the line he showed (with no clamp) is the return... the clamp is probably not needed.

Paraglider, you should check the setup to the main tank and come back to the aux tank after you've resolved your issues.

 

[Paraglider]

The Toyota diesels use the same tank and pick up as the petrol varieties. The only difference is that some have a fuel return to the tank and some(like the 2H) recycle the excess fuel back to the filter..

Good to know. Thanks. I checked the filter again today. There was a little bit of damp area around where the hose clamped on to the filter and a tiny glimmer (fuel) too. That was the hose that came from the tan. I took the old clamp off (one of those squeeze with pliers) and put a new clamp on it. It's dry now but didn't seem to do the trick. Truck still dies after 2-4 minutes of run time. Seems like basically, it's running off the amount of fuel that would be between the primer and the injectors. I checked the fuel line between the primer and the tank and can't see anything obvious but then I can't see that well right where it joins the tank. The lines go to the switch valve (for either tank) first. The fit seems tight at the switch valve. No evidence of any leaks. Continues to be a mystery.

 

[Paraglider]

I'm not a diesel mechanic, but I do have a couple GM diesel pickups, so one of the first things I would do is bypass totally the complete fuel system. Get a canister of some type, gallon juice jug?, and run both main and return fuel lines (all new rubber tubing) into it directly from the injection pump. Make sure you have some kind of filtration there and a built in fuel pump in the injection pump (seems to me that most Toyota motors do), and put some clean diesel in the jug. Bleed all the air out of the lines and prove, or disprove, that the motor will run with just this system and the injection pump.

Doing this will help narrow down where your air intrusion is at. If everything runs as it should you know that the problem is further up the line towards the fuel tanks. If possible, use the same fuel jug and move your connection point closer towards the fuel tanks and check for correct running again. By doing this you can start eliminating areas that you question but are not sure about.

I know that air intrusion problems are frustrating to find as I have an old pickup, with air problems, that I use only on my property. Starting it after it has sat for overnight I will always have air in the lines. But, I have figured out a system that makes it easier to bleed the air out and start it, and once started it will always start the rest of the day until it has not been run for a few hours. I guess you could say I'm lazy because I have never gone beyond this point since I now know how to restart it (bleed air out) every morning that I use it.

Good luck figuring out the problem, and like pngunme said, somebody on the diesel forum will be familiar with this particular system. They might even be able to pinpoint areas that have been found to have recurring problems on other vehicles.

Don

I'll start trying to isolate the problem. Does anyone reading these know if it would work to go directly from fuel to the injection pump without having some pressure in the line to force the fuel into the injection pump? I'm at the beginning stage of learning about the 2h engine so don't know. What could I use to filter it from a pail and is that absolutely necessary if the diesel looks clean? I'll also try posting on the diesel forum. Thanks everyone.

 

[Paraglider]

As Handcannon says, bypass the fuel system and run some fuel from a small canister to isolate the problem.
Or get some clear hose and see if the air bubbles are coming into the engine bay with the fuel.
The 2 hoses blocked off with the bolts ,where do they run to?
Are the twin tanks a factory set up?
When you finish priming ,do you screw the feed pump back into its closed position?


I'll have to go under and check where those two hoses blocked off with the bolts go.
I would guess the reserve is not factory installed but don't know. Unfortunately, I bought it from someone who turned it over right away and did little to investigate or know the history from the previous owner and says he has no way of contacting the previous owner now. I replaced the old, original primer pump with a Bosch that doesn't need screwing.

 

[roscoFJ73]

I looked in the parts diagrams and couldn't see an auxiliary tank. Actually they did have an auxiliary tank as they call it ,but it was really a jerry can.

 

[roscoFJ73]

I have also included a picture I took of the underside with two bolts, one brass and the other probably steel coming out of the ends of two hoses. Have no idea what that's about or the two hoses to their left that just end. Any thoughts?

Thanks!

Its obvious those 2 loose lines would plug into the 2 that are blocked off. They have just added a bit of fule line on so they could jam the bolts in.

 

[roscoFJ73]

I'll start trying to isolate the problem. Does anyone reading these know if it would work to go directly from fuel to the injection pump without having some pressure in the line to force the fuel into the injection pump? I'm at the beginning stage of learning about the 2h engine so don't know. What could I use to filter it from a pail and is that absolutely necessary if the diesel looks clean? I'll also try posting on the diesel forum. Thanks everyone.

Toyota diesels DO NOT have lift pumps in the fuel tank or in any part of the fuel line ,so no pressure. The injection pump has its own built in feed/lift pump that runs mechanically from the injection pump. If anything , the fuel lines have vacuum in them ,about 2psi I think.
The feed pump can draw up to as 4 times the amount that the engine needs. That's around 54 litres an hour but that would be at high rpm.
The rotary pumps recycle it back to the tank(it cools the fuel which cools the pump), the inline pumps (2H 3B)recycle it through the fuel filter.

No need to filter clean looking diesel for short runs. Use a small mower fuel can with a rag jammed in the top. Position it with zip ties so its roughly the same height as the fuel tank,but its not too important. The hand primer will suck it up and the feed pump will feed the injection pump when its running.

You can also isolate the source of the air leak by using a short piece of plastic hose. You could join it where the fuel line enters the engine bay and connect it to the filter.

 

[handcannon]

Toyota diesels DO NOT have lift pumps in the fuel tank or in any part of the fuel line ,so no pressure. The injection pump has its own built in feed/lift pump that runs mechanically from the injection pump. If anything , the fuel lines have vacuum in them ,about 2psi I think.
The feed pump can draw up to as 4 times the amount that the engine needs. That's around 54 litres an hour but that would be at high rpm.
The rotary pumps recycle it back to the tank(it cools the fuel which cools the pump), the inline pumps (2H 3B)recycle it through the fuel filter.

No need to filter clean looking diesel for short runs. Use a small mower fuel can with a rag jammed in the top. Position it with zip ties so its roughly the same height as the fuel tank,but its not too important. The hand primer will suck it up and the feed pump will feed the injection pump when its running.

You can also isolate the source of the air leak by using a short piece of plastic hose. You could join it where the fuel line enters the engine bay and connect it to the filter.

This is some good info for me, and others like me who are not very familiar with Toyota diesel motors. I am semi-familiar with the Nissan SD-22 and their in-line IP, and it does have a fuel pump built into the IP. GM 6.2 and 6.5 use a rotary IP, and although they can suck up some fuel to the IP it is very hard on them to do which is why they have an electric fuel pump back next to the fuel tank.

I had forgot about using clear plastic line while looking for air in fuel. My 83 GM 6.2 pickup has the air problem and I use clear line on the return out of the IP. Since it has been almost a year since being run (transmission problems) I had forgot about the clear line. I use the clear line (and the electric fuel pump) to be able to tell when I have enough air out of the system to be able to run it. Once all the air, that has accumulated while the motor sat without being run, has been purged I can start and run it all I want, until it has been left sitting for several hours and accumulated more air. At which time I need to start all over again with purging the air out.

Don

 

[roscoFJ73]

Isnt it easier to just fix the leaks once and for all? My HZJ75 had an overnight air leak and it drove me nuts.

 

[Paraglider]

Thanks for the info, RoscoFJ73, about how the fuel pump system works and how to set it up to test it. That makes it easier. By the way, I assume that when everyone says to connect directly to the IP, they mean to the primer pump, where the first flexible fuel line starts. Correct me if I'm wrong on that.