Extra fuel pump

[rhipex]

Hi everybody, last week got me an old Navara d22 from 1999, it has a good engine, but it has an issue with a high-pressure fuel pump and the previous owner put an additional pump after the fuel filter. The pump starts when the ignition is on and helps the main pump. It works fine. My question is if I mistakenly leave the ignition on without the engine running, will the pressure build-up and brow the hoses? or there is an overflow line and the fuel will just go back to the fuel tank?

 

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pull of what you think is the return line with ignition on

 

[[email protected]]

sorry.is delivery line teed back to tank to original line at filter,(back through regulating valve. if not take the delivery hose off near injector pump and see how much pressure it builds to, when pump stops see if pump heats up test for 10 minuits some electric pumps are continous flow some are not my pump was only 8-12 lbs it would stop pulsating and wouldnt get hot when ign was left on..

 

[tweak'e]

Hi everybody, last week got me an old Navara d22 from 1999, it has a good engine, but it has an issue with a high-pressure fuel pump and the previous owner put an additional pump after the fuel filter. The pump starts when the ignition is on and helps the main pump. It works fine. My question is if I mistakenly leave the ignition on without the engine running, will the pressure build-up and brow the hoses? or there is an overflow line and the fuel will just go back to the fuel tank?

several things here.
the pump has been done poorly.
firstly its a low flow pump but might be ok (we don't get many of the TD25 engines here, i assume your in euro).
the extra tiny little petrol filter thats also fitted is a huge restriction. that needs to be replaced. i used a 100 mic 7" inline filter before the pump as a pre filter to protect the pump.
the pump should be mounted down by the tank. pumps push fuel uphill better than they suck fuel uphill.
there should be a bypass, typically a one way valve placed in parallel with the pump and pre filter. thats because the injection pump pumps more fuel than the electric pump does and the electric pumps becomes a restriction at the higher rpm. also if the electric lift pump isn't running its a restriction to fuel flow. so a bypass is required. last thing you want is to trash the injection pump because of fuel restriction. also fuel restriction ******* injection timing which has other consequences.

then there should also be a safety cutoff. this is to turn the pump off if you crash. common way is to use the engine oil pressure switch.
this also means should you leave the ignition on the lift pump won't run.

the pressure made by they pump should be low ie 4 psi and will not cause a problem to the hoses.

 

[rhipex]

several things here.
the pump has been done poorly.
firstly its a low flow pump but might be ok (we don't get many of the TD25 engines here, i assume your in euro).
the extra tiny little petrol filter thats also fitted is a huge restriction. that needs to be replaced. i used a 100 mic 7" inline filter before the pump as a pre filter to protect the pump.
the pump should be mounted down by the tank. pumps push fuel uphill better than they suck fuel uphill.
there should be a bypass, typically a one way valve placed in parallel with the pump and pre filter. thats because the injection pump pumps more fuel than the electric pump does and the electric pumps becomes a restriction at the higher rpm. also if the electric lift pump isn't running its a restriction to fuel flow. so a bypass is required. last thing you want is to trash the injection pump because of fuel restriction. also fuel restriction ******* injection timing which has other consequences.

then there should also be a safety cutoff. this is to turn the pump off if you crash. common way is to use the engine oil pressure switch.
this also means should you leave the ignition on the lift pump won't run.

the pressure made by they pump should be low ie 4 psi and will not cause a problem to the hoses.

Thank you for the reply, the thing is it was working like this for a long time, as I don't really know a lot of stuff about the engines I don't want to change anything. I will surely change the transparent filter to something better but for now, I thought of the solution. And I would really appreciate if you can take a look.


So the black left top hose is coming from the fuel tank. then it goes to fuel filter then to the small fuel filter and to the pump. What if I add a bypass with a one-way valve that will circulate the petrol if the engine is not running but the ignition is on? The pump will still work, but the fuel will just circulate without the pressure building up. Does that make any sense?

 

[tweak'e]

Thank you for the reply, the thing is it was working like this for a long time, as I don't really know a lot of stuff about the engines I don't want to change anything. I will surely change the transparent filter to something better but for now, I thought of the solution. And I would really appreciate if you can take a look.


So the black left top hose is coming from the fuel tank. then it goes to fuel filter then to the small fuel filter and to the pump. What if I add a bypass with a one-way valve that will circulate the petrol if the engine is not running but the ignition is on? The pump will still work, but the fuel will just circulate without the pressure building up. Does that make any sense?
View attachment 34342

no, make that hell no.

in this basic layout the small filter is doing nothing. think about it, the fuel has been filtered by the large filter anyway so the small one is never going to filter anything. throw the small filter away it has no business being on a diesel.

what your describing is a fuel washing/polishing system. the electric fuel pump will not do anything to help the injection pump. all it will ever do is constant pump fuel through the filter.
if that was a decent sized electric fuel pump you could fit a bypass fuel regulator which bleeds excess fuel back, instead of your proposed one way valve setup.
but you don't have that, your little pump will only do 4 psi i think it is and you still require the electrical shut off to the extra fuel pump anyway.

the one way valve just goes around the extra fuel pump. never ever bypass the main fuel filter as you will end up with crap bypassing it and destroying your injection pump. the one way valve is simply there to stop the electric fuel pump from being a restriction.

 

[rhipex]

no, make that hell no.

in this basic layout the small filter is doing nothing. think about it, the fuel has been filtered by the large filter anyway so the small one is never going to filter anything. throw the small filter away it has no business being on a diesel.

what your describing is a fuel washing/polishing system. the electric fuel pump will not do anything to help the injection pump. all it will ever do is constant pump fuel through the filter.
if that was a decent sized electric fuel pump you could fit a bypass fuel regulator which bleeds excess fuel back, instead of your proposed one way valve setup.
but you don't have that, your little pump will only do 4 psi i think it is and you still require the electrical shut off to the extra fuel pump anyway.

the one way valve just goes around the extra fuel pump. never ever bypass the main fuel filter as you will end up with crap bypassing it and destroying your injection pump. the one way valve is simply there to stop the electric fuel pump from being a restriction.

Again thanks for getting back to me. So the small filter needs to go, will do that shortly. But I didn't understand of where should I place a bypass. I don't think I can remount the pump closer to the tank. Is there any chance I can place a bypass on the system like it is (without the small filter)?

 

[tweak'e]

the bypass goes in parallel to the electric pump. its job is to allow the injection pump to suck fuel through when the electric pump cannot keep up.
ie fit a T connection either side of the electrical fuel pump. one way valve allows fuel in the same direction as the electric fuel pump.

the electric pump really needs to go before the main filter. that pressurises the filter, keeps any air leaks out and is real handy for priming the filter after a filter change. (i have a button i can press to run the pump which fills the filter, makes filter changes a breeze).

with the pump after the filter, any broken bits from the pump will go directly into the injection pump and damage it $$$$.

 

[rhipex]

the bypass goes in parallel to the electric pump. its job is to allow the injection pump to suck fuel through when the electric pump cannot keep up.
ie fit a T connection either side of the electrical fuel pump. one way valve allows fuel in the same direction as the electric fuel pump.

the electric pump really needs to go before the main filter. that pressurises the filter, keeps any air leaks out and is real handy for priming the filter after a filter change. (i have a button i can press to run the pump which fills the filter, makes filter changes a breeze).

with the pump after the filter, any broken bits from the pump will go directly into the injection pump and damage it $$$$.

SO like this?

 

[tweak'e]

SO like this?
View attachment 34350

yes thats its.
ideally have a pre filter to protect the pump, but those pumps are pretty cheap anyway and 100 mic pre filters can be costly.
if you can mount the pump and bypass down at the tank, there usually room. they always work better pushing fuel rather than sucking.
and of course the electrics triggered of an oil pressure switch (with a primer switch) for safety.

 

[rhipex]

yes thats its.
ideally have a pre filter to protect the pump, but those pumps are pretty cheap anyway and 100 mic pre filters can be costly.
if you can mount the pump and bypass down at the tank, there usually room. they always work better pushing fuel rather than sucking.
and of course the electrics triggered of an oil pressure switch (with a primer switch) for safety.

Thank you again ), I just moved the tubing so the pump is before the filter, now I need to get a bypass. Also I think the reason that it if up under tge hood is because there is somewhere the system is sucking air between the pump an the fuel tank. But my original question persists, is there anything I can do to “foolproof” this system? I mean to make sure nothing bad happens even if the ignition is on and the engine doesn’t run. Maybe there is a fuse I can tap in with add a circuit that works only with engine running?

 

[grumpy too]

As Tweek suggested have the pump triggered by an oil pressure switch, not sure what he meant by (with a primer switch), will be doing this myself soon as putting in an auxiliary tank and want to make sure the extra piping etc has a bit of help.

 

[tweak'e]

Also I think the reason that it if up under tge hood is because there is somewhere the system is sucking air between the pump an the fuel tank.

one of the reasons for having the pump down by the tank is that you reduce risk of it sucking air in and any leaks are noticeable when it leaks fuel out. you only have to worry about the connection between tank and pump sucking air in.

Maybe there is a fuse I can tap in with add a circuit that works only with engine running?

not that i'm aware of which is why many use a oil pressure switch.

not sure what he meant by (with a primer switch),

its just a switch so you can turn the fuel pump on anytime you want. main reason for this is for priming the fuel filter after a filter change.

if you want to go fancy, i have mine rigged to the glow plug circuit so the pump runs when the glows turn on (primary glow). not perfect as the pump turns off when the glow finishes before you start the engine (glow timer). you could get a separate timer or possibly even run some sort of latching relay setup (so ignition turns pump on, oil pressure switch turns it off.).

 

[grumpy too]

Thought that might have been what you meant, actually did that on the Isuzu with dual tanks but never had the oil pressure switch in circuit.
On the subject of fuel/tank etc can anyone tell me if any of the d22's have a low fuel light, I took the tank out of a 2008 and it only has two wires for the gauge but the plug has 4 wires to it, the Pollack c/o valve and switch is double pole so can do both.

 

[redkite]

My D22 (a 2004 model) has a low fuel light. I think only the petrol versions had a fuel pump (and thus four wires) in the tank, the diesel engines don't seem to have a pump,

The low fuel light and the fuel gauge on the dashboard are both controlled by the same sensor in the tank.

 

[grumpy too]

Might have to let the fuel run down to see if I get a low fuel light on the 2011 I am driving, it has been down pretty low but will carry some fuel and try it a bit lower.
If it does can drop the tank and change them over as it has a leak when filled too much.

 

[bods]

My 2010 had a low fuel light. Supposed to come on with around 13l or something left in the tank according to the manual. I saw it a few times, but didn't like waiting for it once I fitted the long range tank as it didn't have any sort of corral for the fuel pickup to sit in like the factory tank does. Not so bad on flat road, but not great on hills when the fuel has a lot of area to move around.

 

[grumpy too]

Probably need to drop the tank on the 2011 to see where the leak is so be easy to check the sensor and swap it for one out of a 2008 that only has two wires, re the swirl tank have taken the one out of the damaged tank and was thinking of trying to install it in the tank I am going to build where the spare tyre is, would prefer a long range tank in place of original but can get 200l by adding the extra tank and the original, not quite enough but better than jerrycans.
Might see what the circuit diagrams say.