BJ73 3b 3.4 fuel feed problems (1 Viewer)

[DutchBJ73]

Good afternoon fellow offroaders,

I am new to the forum, and i was looking for a thread with this similar issue i am experiencing on my BJ73, unfortunately i did'nt find any. I changed the headgasket (OEM) because of a leak between the cooling system and one of the cilinders. brought the head to the shop for a crack-check, rebuild, and re-used the head.

Everything seems to operate the way it should, except for the fuel consumption. I keep getting air into the system, even though i changed all the gaskets and washers. When i bleed the air and start the car, it runs fine for about 10 minutes stationary. After 10 minutes it starts stalling and the engine shuts off. I can't find any leaks around the hoses.

has anyone experienced this issue, or maybe knows a way to fix this (or check for other problems)? I would really apreciate any info about this problem. Thanks in advance !!

(here is a pic of my fuel pump)

 

[Rigster]

This is going back a loooong time for me, but if you have a FSM, look at the fuel pump - there should be a diaphragm at the end of the pump. I would check that for starters, if it has a tear in it, that can cause issues like this. I had to replace one of those on one of my 3B's a while ago.

 

[lacalvette]

Fuel line are under vacuum from tank to feed pump (where is the hand priming pump).
Feed pump build up fuel pressure so the main fuel injection pump doesn't Cavited.

Hense any leak after the feed pump will shows fuel. Any leak before will let air in...
So flex hose connection, tank pipe, hand priming Pump, a primary fuel filter(water separator)... may start there?
Just an idea.

 

[DutchBJ73]

Hey @Rigster and @lacalvette thanks for the quick reactions! I will definitely check those hoses and connections. I just found out i didn't watch close enough at the hand priming pump. Because there was a very bad hose connected (fuel return) to the banjo bolt.

if this hose isn't the only issue i will let you know.

 

[Rigster]

Yup, that could very well do it! I should also mention that the more I think about it... the bad diaphragm allows fuel back into the tank, so hard to start... but once running seems fine, but there can also be a higher RPM idle rate. Once the tear gets bigger, the idle tends to get higher and higher....

So, if you are not also seeing those problems, then it probably isn't the diaphragm. Like I said, it was a looong time ago and it takes a little longer to pull those files up and blow the dust off of them.... lol

 

[Felde]

Yup, that could very well do it! I should also mention that the more I think about it... the bad diaphragm allows fuel back into the tank, so hard to start... but once running seems fine, but there can also be a higher RPM idle rate. Once the tear gets bigger, the idle tends to get higher and higher....

So, if you are not also seeing those problems, then it probably isn't the diaphragm. Like I said, it was a looong time ago and it takes a little longer to pull those files up and blow the dust off of them.... lol

Thanks anyway. I was always wondering what the symptoms of a teared diaphragm would be. Now I know

Good luck DutchBJ73. See you on the Buschtaxitreffen at September 10th?

 

[DutchBJ73]

Good morning guys,

The bad hose/connection seemed to be the problem.
It starts and keeps running fine now.

@Rigster
I will check the diaphragm soon, because the first startup takes a while now.

@Felde thanks for the invite, i didn't know about the buschtaxitreffen yet. I googled it and it looks awesome! Unfortunately my cruiser won't be finished that soon, so maybe next year.

 

[myusername]

Good morning guys,

The bad hose/connection seemed to be the problem.
It starts and keeps running fine now.

@Rigster
I will check the diaphragm soon, because the first startup takes a while now.

@Felde thanks for the invite, i didn't know about the buschtaxitreffen yet. I googled it and it looks awesome! Unfortunately my cruiser won't be finished that soon, so maybe next year.

The diaphragm on the end of the 3B's inline injection pump has no direct contact to fuel. It measures the pressure across the butterfly and affects the rack position to either increase or reduce fuel.

It has two lines, one to either side of the throttle butterfly. If the leather diaphragm is damaged, the 3B will tend to over-fuel resulting in dark smoke. This can result in heat/fuel issues like cracked head or dropping precups, so it's important at every service to drain any oil from the diaphragm housing and replace the diaphragm occasionally.

Generally speaking, they get ignored and most 3B's benefit from a new diaphragm. Genuine denso one I last bought was about AUD40 from memory (~USD30)

 

[Squash]

Good afternoon fellow offroaders,

I am new to the forum, and i was looking for a thread with this similar issue i am experiencing on my BJ73, unfortunately i did'nt find any. I changed the headgasket (OEM) because of a leak between the cooling system and one of the cilinders. brought the head to the shop for a crack-check, rebuild, and re-used the head.

Everything seems to operate the way it should, except for the fuel consumption. I keep getting air into the system, even though i changed all the gaskets and washers. When i bleed the air and start the car, it runs fine for about 10 minutes stationary. After 10 minutes it starts stalling and the engine shuts off. I can't find any leaks around the hoses.

has anyone experienced this issue, or maybe knows a way to fix this (or check for other problems)? I would really apreciate any info about this problem. Thanks in advance !!

(here is a pic of my fuel pump)

View attachment 2756765

You will not find leaks unless it's catastrophic.
Air is pulled in via vaccum, imagine trying to suck soda using a straw with holes. Plug the holes and the straw works, it's that simple.
Now you could try making certain that the return line is clear, open the fuel cap and/or add fuel via gravity to your IP but this does take some ingenuity.
Also make sure the pump knob is pushed down and in the locked position. This is easy if you open the bleeder to reduce pressure.

 

[Felde]

Placing a cross reference here for people with similar issues searching for advice in future:
How to bleed fuel line.
Post in thread 'remove fuel tank' remove fuel tank - https://forum.ih8mud.com/threads/remove-fuel-tank.1169566/post-14302137