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best way to bleed your fuel system

tony rodaway

tony rodaway

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Aug 28, 2016
Messages
643
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uk
got an lc90 3.0 td 98 model just wanna no the best way to get air out of the fuel system .
I changed the spring in the banjo bolt on the fuel pump return valve and must have got air in when i put it back together.
been told to prime the fuel filter and open injection valves one by one but only problem is the forth valvle seems hidden away behind the inlet manifold.

my question can it be bled with just 3 valves if the front of the car is raised
im no machanic so just want advise on best way forward.

CAR SYMTOMS
HARD TO START JUST OFF THE KEY AS NEED TO PUMP THE GAS PEDAL AND STARTS AND DRIVES OK.
 
Last edited:
If the truck can get started let is idle and run it for a few minutes and the air should be out of the system. However if you're still struggling to start it again it means air is getting back into the system. When you replaced the spring on the banjo, did you replace the copper crush washers underneath them? Check all pipe work and hoses to make sure you have no leaks. As the only thing you messed with was that banjo fitting start there.


If you want to confirm the suspicious of air in the system put a clear line on the short return piece and watch for any air bubbles.

By the way, pumping the gas pedal does not prime or do anything, other than open up the inlet butterfly. You can also manually pump the primer filter housing and see if she starts any better. Report back your findings and we'll be able to help you out better.
 
Beau said:
If the truck can get started let is idle and run it for a few minutes and the air should be out of the system. However if you're still struggling to start it again it means air is getting back into the system. When you replaced the spring on the banjo, did you replace the copper crush washers underneath them? Check all pipe work and hoses to make sure you have no leaks. As the only thing you messed with was that banjo fitting start there.


If you want to confirm the suspicious of air in the system put a clear line on the short return piece and watch for any air bubbles.

By the way, pumping the gas pedal does not prime or do anything, other than open up the inlet butterfly. You can also manually pump the primer filter housing and see if she starts any better. Report back your findings and we'll be able to help you out better.
Click to expand...


Thanks for your reply beau and been told it may still be taking air in and no never changed the copper washers but since i last got told same information i have ordered them so just waiting to be delivered.
In the mean time i covered the bolt in vasaline to see if it still does it and low and behold it still wont start.
So your saying the car bleeds its self as been told this twice so will fit new washers and let it run and see if it fixes the problem.

So this engine does not need to be bled as bleeds its self.

Beau thanks again for your input.
 
Those copper washers crush when tightened and although I've gotten away with re-using them it's always best to use new ones. Yes, the engine bleeds out any either through the injector, or coming back out via the return.
 
A garage buggered mine up once when i had it serviced while away from home , i have no idea what they did but she was hesitant to start and a few attempts by me failed to prime out the air . Eventually i cured it by pumping in anger until the primer was rock solid then starting the truck and pumping the primer again fast about 30 times .
Baffles me why it worked but it did .
 
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Shayne said:
A garage buggered mine up once when i had it serviced while away from home , i have no idea what they did but she was hesitant to start and a few attempts by me failed to prime out the air . Eventually i cured it by pumping in anger until the primer was rock solid then starting the truck and pumping the primer again fast about 30 times .
Baffles me why it worked but it did .
Click to expand...
Hi, this method worked on our Avensis after fitting a new fuel filter, it's worth a try. ( D4D motor)
 
mettisse said:
Hi, this method worked on our Avensis after fitting a new fuel filter, it's worth a try. ( D4D motor)
Click to expand...

My problem seemed to be when i put the banjo bolt back together i have some how lost a copper washer and today replaced with new ones.
Put the car back together and started with just the key and bingo it started first time so turned it off and tried again and started first time so seems problem solved but the morning time with being left overnite will see if it has solved the problem

Thanks guys for all your help and advise thats why i love this site as have fixed many problems i would normaly not attempt myself
 
I thought I had fixed my air in fuel leak because I changed the new copper washers on the banjo bolt and the car started fine every time.i left it over night got up in the morning and it started just fine so I thought problem solved but I went to work and when I got in my car to come home it again struggled to start again so just stuck now as been told it self bleeds my many people.

Q what is the metal L shape pipe on the banjo bolt pipes that faces down to the floor as just wondered what the purpose of it was in cas I had damaged it some how.
 
The classic place for air leaks is the fuel pipes (outward and/or return) on top of the fuel tank. They corrode because its a bit of a moisture/crud trap. It's usually the first place you look when reluctant starting is happening. Unless you definitely know otherwise, I would be investigating there. I haven't suffered it with the Colorado, but I certainly had exactly these symptoms with my previous 4x4 and it was the tank pipes that were to blame.

Any apparent connection to other work might be a coincidence (there is no reason why doing the spring stretch mod - if that's what you have done? - should cause an air leak afaik).
 
Thanks for your reply diggerdave and yes banjo spring was all i done but air has got in due to useing 14mm spanner but 17mm nut opened also my stupid fault andhave since replaced new copper washers but deffo air that dont wanna go.

Q if you put the front of the car in the air then technicaly the air in the system should rise up to highest point is this correct with the lc90 fuel system.

Q if you have to loosen the injectors how is the best way to get to the injector under the manifold.
Is there a special tool to get to this or does everything have to be removed i,e manifold e,t,c.

Q does the the lc90 deffo bleed itself and is this 100% or can my car have an air lock that i need to remove myself if no air leak is found.
 
I don't pretend to be an expert here, but surely if the car runs fine eventually (even if it took a long time to start) then that is a sign that the air has gone; if it hadn't successfully bled the air out (through cranking) it wouldn't have started in the first place.

I remember the hassle whenever I changed the fuel filter in my old Focus TDdi - you inevitably got air in the system and could crank and crank for as long as you could but it wouldn't shift. You'd have to go through the rigmarole of cracking injectors one at a time or resorting to a good blast of EasyStart, but the point is once it had fired up and run for a minute that was it: problem solved, airlock gone.

The fact that yours runs (eventually) but is difficult to start again later is a sign that air is getting back in somehow, not that the original airlock hasn't been bled. Hence my suggestion that you look to the most notorious spot in the fuel lines for corrosion and forget about the copper washer and the banjo (if you're confident that you've put it back together right). It's certainly where I would start, but it's obviously hard to diagnose these things based on a few sentences on the internet so apologies if I've misunderstood the nature of your problem.
 
Common sense - Dave's right you have a leak in the fuel line , it may not be dripping but its sucking air personally i wouldn't waste time looking for it instead i would replace all the rubber line and hope it was cured .
 
Since you didn't have this problem prior to touching what you have, I'd say it's certainly a coincidence that the air leak has appeared anywhere else, but it is a common thing on these 90 series with age so I wouldn't knock it.

Put a clear line on the return line and look for bubbles, this will at least give you a good indicator if air is in the system. Or if you really want to isolate the tank, feed the pump from a jar of diesel.

Strange but I think I'm getting air in my system somehow as well, takes about twice as long to start, but seem to trace it.
 
Q is it possible to get the air out if i put the return pipe in a jar of diesel from the fuel pump with an added clear pipe from the return pipe going to the tank so both pipes are in the jar but one jar joins the fuel pipe together if that makes sence but will air get back in when i take the pipe out the jar so the air should stay in the jar.

Deffo air cos if i park my car in on a hill faceing down the hill car starts ok
Face the car uphill it struggles as air goes to the highest point.

Thanks for your imput diggerdave and you have just give me more options or plan B OR PLAN C.
 
The most likely place for a leak is on the return line. This is what usually causes hard starting.

The way it was explained to me was that the fuel system is like a continuous closed circuit beginning and ending at the tank. Although the leak may not be big enough to actually lose diesel, the porous return pipe is no longer vacuum-tight. When the car is parked up air slowly gets in and allows the vacuum to leak away, which allows all the fuel in the system to leak back to the fuel tank (A bit like when you suck water into a straw and can hold it there if you put your finger over the end. Once you take your finger away and break the vacuum, all the water drains out).

It's hard to start because you're repriming the system each time (I'm guessing that the car starts perfectly every time if you pump the primer first?). It's not the air leaking into the system that is the problem in itself, but the fact that it allow the diesel to leak back to the tank (obviously it's harder for this to happen when the car is parked arse-upward!). That's my understanding anyway.
 
makes sence when u explain it like that and as for the primer last two times has started ok but going to work at 05,30 hrs im not getting under no bonnet just struggle and go .will let you no how i get on this w/end as no work.

thanks again dave
 
I have had my car looked at and got all the injectors bled and got told no air in the system and since it started from me doing the banjo bolt spring went back there to see if that was the problem.
All seemed well as no damage to bolt or spring and replaced and sealed the copper washes so no air is getting in.put all the car back together and listened to the injectors with a thetascope and all injectors fireing perfect.drove car home and all seemed ok even when i started next morning started fine with -2 outside.drove to work and drove no problems even revs were sitting at just under 800rpm with no mermors so all looked got tx the machanic who fixed it saying it was fixed.

After work got in the car to come home and struggled to start again so got puzzed now so today got under my car to check the fuel pipes and to my suprise they looked in pretty good condition from start to finish with no sighns of any fuel leak on the metal pipes at least.
Got to ghe back of the car were the pipes from the tank come under the car and they look rubber as look the same pipe that go into my fuel filter but only difference was they looked damp but gonna sound strange but i could not tell weather it was diesel or water from then road.

Does any one have any pics to show how to change these small hose pipes from the tank and what size they are.

Next question if i change these hoses and it still has the problem then wots the next solution as deffo got symtoms of a air intake even down to primeing before i start works a treat but cannot find a leak as i think i would see sighns of some sort of diesel somewere.


Think it was just a coinsedence i t started after i done the banjo bolt.

Any ideas guys as useing a lot of fuel i have noticed.

 
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