13bt rough idle, sometimes wont start (1 Viewer)

[pradoblivious]

Hey all,

I'm a newb with a 13-bt that has developed a rough idle with a pretty extreme periodic rhythm (as if it wants to stall) (the video doesn't really do it justice)

If I kill the engine while it's doing this (and sometimes when it isn't) the truck won't start up again for a while. Instead, it just dry-cranks with a high-pitched whine

Any tips would be hella-appreciated.

-blivious

 

[stevebradford]

Most likely air getting into the system from one of manny possibilities. fuel line, water separator, injector line, primer pump, fuel filter. the one that got me was a 3 inch peice of rubber hose on the end of the injector common line that returns excess fuel to the pump. Check all of those for signs of weeping fuel. Replace any cracked hoses.

Then to bleed the air out of the system.

Bleeding the 3b injection pump.
To bleed the air out of the injection system Crack the bleeder screw (circled in yellow) then untwist the pump (circled in red) till it springs up and pump till no more air comes out. Push the pump down and twist closed before closing the bleeder screw. Try that if it's still having problems you are going to have to crack the injector line top nuts all four (circled in green). crank the motor till diesel spills out of all of them, shouldent take long.

 

[roscoFJ73]

Most likely air getting in somewhere. I guess its ok at higher rpm when you are driving it? Whats that horrid noise when you stop cranking?

 

[Hulsty]

Mine was similar replaced the primer pump fixed. Was less than 20 bucks

 

[pradoblivious]

Most likely air getting in somewhere. I guess its ok at higher rpm when you are driving it? Whats that horrid noise when you stop cranking?

The electric radiator fan apologizes for its existence haha

 

[pradoblivious]

Thanks for the helpful replies.. I read a bunch last night based on these answered, ordered a bosch hand pump JIK and will check all my lines today. You guys rock

 

[pradoblivious]

crawling around looking for line-leaks I noticed my a440 is missing some kind of little access door in the bell housing. I can see gears through it. That seems bad. Is that bad?

(no obvious signs of fuel-system leaks so far)

 

[roscoFJ73]

crawling around looking for line-leaks I noticed my a440 is missing some kind of little access door in the bell housing. I can see gears through it. That seems bad. Is that bad?

(no obvious signs of fuel-system leaks so far)

Its not too bad, as long as you stay out of mud etc till its replaced. Its called " COVER , TRANSMISSION HOUSING" part number 35119-36010. About $8.
You could probably make one yourself. It may have small hole in it to allow oil or water to drain out, the H55F gearboxes on the 3F petrol engine had a hole. I don't think my 1HZ gearbox has one, but never really checked.

Air usually gets into fuel lines without fuel leaking out till its really bad.

 

[pradoblivious]

Ok so. I'm now intimately familiar with the 13bt fuel system. I changed all the rubber in the fuel line from back to front, including the 3-inch rubber return line behind the injectors, all to no avail. I won't have the bosch primer pump in hand until Wed.

Then I read this thread: Rough running, then this morning, hard to start, then...

In it, the poster is essentially having my problem, and initially suspects a vacuum problem due to his tank not venting properly. At this point I should probably provide a detail I omitted earlier, which is my 13bt is a transplant into a 90' prado. When I read about his vacuum theory I immediately went back out and cracked my gas-cap and WOOOSH.. the truck just about pulled the cap out of my hand. Replace the cap, and run the truck for a bit -- refuses to start. Pop the cap; starts right up.

I think maybe I just need a vented gas-cap? Can anyone suggest a part #? Does my tank have a vent somewhere that's maybe clogged? Can I just drill a very small hole in my existing cap?

 

[mohawk]

I wonder if they plumbed the diesel return line too the tank breather ??.... the tank should have diesel out, diesel return , and breather i think.
Was the previous engine petrol or diesel ?

 

[roscoFJ73]

Is there a part number on your existing cap? If its a Prado cap, no sense in buying another. A pic might be useful.
But somehow I don't think the problem will be in the cap
All fuel tanks need to breathe so they can replace the fuel used by the engine with air.
As Mohawk suggested, some of the fuel/breather/return lines may be crossed.

You need to give us the full information on the Prado, is it a 90 series or a 1990 model. Petrol ,diesel?? Which engine originally, 1KZ 2L 1VZ 22R?

 

[pradoblivious]

I'm just on my way out to bleed the injectors. I have both a main line and return line to the tank, I'll see if I can tell what the return line is plumbed to (they both had gas in them when I replaced the hoses).

The truck is a 1990 lj78 prado, formerly possessing the infamous 2lte engine. We threw evans waterless coolent in it and drove it across the US four times and all up into the mountains -- our eyes glued to the EGT meter -- before finally giving up on that engine. It was just too anemic. The truck is no stranger to these forums, it's the same truck detailed in this thread: 1990 LJ78 in Montana

We went out of our way to have the engine/tranny swap done by a vendor who has a fantastic reputation in these forums, so I want to say I'd be surprised if the plumbing were amiss, although I admit, I feel like I'm not having a great experience with the vendor. The swap was quite expensive, and took over a year to complete, and one week later here I am troubleshooting fuel problems, but we do what we must for love I suppose ¯\_(ツ)_/¯.

Other than some Japanese lettering, my cap is identical to the cap pictured here:

If yall think my tank vents are clogged, that's no-doubt what it is. The cap is original to the truck. I was just thinking maybe by virtue of the 13-bt's needs, I might need to switch from the stock cap to a vented version.

I assume the gas tank vent ports are on top of the tank and I'll have to drop it out of there to get at them?

 

[pradoblivious]

So bleeding the air out of the injectors made it purr like a kitten, but it still didn't start after being run around the block. Removing the gas cap didn't help it start this time sigh. I'm going to take it out on the highway and see if there's still a leak letting air in somewhere. I really hope I have whatever leak that allowed air into the injectors plugged.

In the meantime, I took a look at the plumbing, and the return line seems to be plumbed into the same input in the injector pump that the injector return line is plumbed into. It's hard to describe so I modified this diagram. It looks like so..

 

[pradoblivious]

I took some pics of the return lines so you can see it IRL:

the new looking rubber line with the screw clamp is the return line to the tank. The metal line coming over the top of the pump is what the 3" rubber hose connected to the injector common line connects to. You can also see the larger input line from the tank running down into that port thingy that the hand-pump is mounted into .

Here's a closeup of the side of the returns port (does it look like it might be leaking to yall?) ..

 

[stevebradford]

The excess fuel should not go to that port on the pump. That might be your issue right there your getting air into that line from the tank return. The return fuel should tie into the same banjo bolt the new fuel does on the primer pump. At least that’s how it is on the 42 and 60 series.

Excuse the rust it’s my yard 42. Excess fuel from the injectors goes here.

That port your returning the fuel to does...?

It might be sucking air into that part of the pump from your return line to the tank. This system doesn’t need a return to the tank.

 

[pradoblivious]

Thanks. Your photo and diagram don't quite match, but I assume your photo is authoritative. The fuel line and return line both terminate at the "inlet hose" side of this part

Is your tank line coming in from the bottom and the return line from the top? What do yall think I should do with my tank return line? just cap it off? Is the pump port my lines are connected to now active in some way? or is just connecting those two hoses together?

 

[stevebradford]

Close but it should go here.

Yes pinch off your tank return line and take it for a drive.

This is where a 40 and 60 series return the excess fuel to.

 

[roscoFJ73]

This system doesn’t need a return to the tank.

This is what I thought. I think its mainly the rotary pumps that return the fuel to the tank and I think its because this helps to cool the fuel.

 

[pradoblivious]

Awesome thanks, I ran out of "personal time" today, but I'll see what I can do tomorrow. I have a feeling the banjo bolt down below only has one port on it though. Maybe I can swap the two-ported-bolt up top with the 1-port bolt that's currently down on the inlet thing?

Can I get some clarification on bleeding the injectors? Some threads say to crack all four and crank the engine until gas comes out all of them. Other threads say run the engine with one port cracked until it stops foaming. Are both methods safe/valid? I read horror stories of injector heads doing awful things to the cylinder internals when they don't spray right..

 

[pradoblivious]

For what it's worth, the 13bt in this thread is plumbed identically to mine.