BJ-40 Rough Idle

[Max Wilder]

Hello again,

Long Story:

In the last week:
I replaced the front motor mounts with aftermarket (the only) ones from SOR.

I noticed that the hand primer-pump on the injector pump was broken and leaking fuel a little bit, but didn't get around to fixing it (and didn't notice any issues at all) until one day it died on me.

I replaced it with the aftermarket Bosch pump, pumped it, bled air from the bleeder on top of the fuel filter, and it worked fine again.

A while later I had the oil changed (I CAN'T do it here at my apartment) and when I got in it to drive it away I noticed that it was idling rough.

Now at idle it's vibrating/shaking too much. The engine doesn't sound noticeably rougher, but the vehicle is rattling and vibrating significantly more than it did. though it still runs smooth as long as the rpms are up.

I can't think of any connection to having the oil changed, greased, and fluids checked.

I suspected an air leak and the new hand pump seemed to be seeping some fuel so I replaced it again and bled the air again, but it made no difference.

I can't think of what could be causing it. I would suspect the motor mounts but I noticed no change after replacing them until days later when I had the oil changed.

Short Story:
Rough Idle?

 

[crankycruiser]

Sounds pretty well exactly the same as what my HDJ80 is doing. If u work it out let me know!!!

Ive changed injectors and checked fuel lines for leaks (maybe not well enough) and im still having issues!

 

[roscoFJ73]

Ive been using aftermarket mounts and never had a problem,maybe the rear mount needs looking at .
How fast is it idling?
Diesels (especially old ones)will rattle themselves to pieces if the idle is too low

Of course this doesnt explain why it changed after it come back from where the oil was changed.

 

[b3stock]

Rosco has it there, my 3b rattles like a old steamer and once I adjusted my idling it was great even warm it'd just shake and vibrate at the lights! Realistically it should sit at a grand at idle, our 2h and my 3b are the same, do you have a taco on yours?? Try that and I don't think it's hard for the accelerator cable to slip, stretch or just age really. Good luck with it! And engine mounts Should improve the overall ride of you girl too.
Cheers
Kellee

nothing like a lungful of diesel in the morning, hj47 bj40... alllll mine!!!!

 

[magnus_heydoc]

If you have a little air in the injector lines you could crack each one, one at a time, while it's running and bleed out any trapped air. Pull your hand throttle a bit so it's less likely to stall.

1k idle is too high IMHO, but 850-900 is where one of my 3B's resonates at idle. 650 is what the manual says but that's pretty darned low. There's a screw to turn on you IP to adjust idle speed.

 

[lostmarbles]

I can't think of a likely/reasonable connection to the oil change work either.

But clutching at straws, I similarly start thinking of "idle speed" as the only thing that could possibly have been somehow "knocked out of adjustment".

Here's a pic of where the adjustment is (in support of what Magnus_heydoc has written):


Mine's set around the FSM recommendation (625-675rpm) and it's still pretty smooth.

(Too fast and it may make it harder to shift from neutral into 1st.)



PS. I haven't noticed mine idling rough no matter how fast or slow I have it set. However I've certainly seen some engines that don't continue to run smoothly below certain rpm figures.

PPS. I checked my RPM by using this old Smiths Tachometer on my alternator and doing some mathematics with the results:

 

[Moe R]

It's possible that when u changed the primer pump that air made it's way into ur IP. Try bleeding that first then the filter bleeder.
If u get bubbles from the IP might be the problem. Personally I would not adjust the idle above 650 but thats just me. If u have to adjust to keep the engine running it is only evidence of a larger problen hopefully a small one.
In the pic it's the yellow arrow, forget the red circle (not my engine)

 

[lostmarbles]

... Personally I would not adjust the idle above 650 but thats just me. If u have to adjust to keep the engine running it is only evidence of a larger problen ....

I agree.

I was hoping that perhaps GoboFongo's idle speed was below 650 and that this extra-low idle speed was causing the engine-shaking.

 

[lostmarbles]

Another thought here.

I bought some aftermarket mounts myself and found that the dimension arrowed was too large:



This meant that when you tightened the securing bolt from below, the shock-absorbing-mount wasn't gripping the chassis-mount.

I solved the problem either with a washer or by grinding ... I can't remember which.

But if your mounts have the same dimension error GoboFongo then they could be rattling from normal engine vibration making your engine idling appear noisy and rough.

 

[Max Wilder]

Thank you so much for all the input.

I found that same thing with my mounts, and will try adding a washer there.

It runs smooth at higher RPMs, but I think it would be much too fast for just an idle adjustment.

I will try and bleed the injector lines, I didn't do that yet, only the fuel filter bleeder. I kind of doubt that it's an air leak though because it starts easy and runs fine except at idle.

I'll let you know how it goes, thanks again.

 

[roscoFJ73]

Did you check the gearbox mount?

 

[FF LC FREAK]

I found that same thing with my mounts, and will try adding a washer there.

I'm glad I'm not the only one. These mounts were from SOR. You can see the shiny washer that I added. That sure helped with my shaking when I added the washer. I didn't notice it at first. It wasn't until I started driving that I realized how much shaking was going on.

 

[lostmarbles]

I'm glad I'm not the only one. These mounts were from SOR. ...

Mine were from Roodogs in Australia.

I suspect they all get them from the same supplier.

.....I found that same thing with my mounts, and will try adding a washer there.

I've tried to show here how the washers need to be to get the mount properly clamped up:

...It runs smooth at higher RPMs, but I think it would be much too fast for just an idle adjustment.
I will try and bleed the injector lines, I didn't do that yet, only the fuel filter bleeder. I kind of doubt that it's an air leak though because it starts easy and runs fine except at idle.
I'll let you know how it goes, thanks again.

I doubt there's an air leak too because when you don't have a fuel-return line to your fuel tank (as we don't with our BJ40s), I've found that any air ingress tends to have the more-dramatic effect of stalling your engine and stopping it from restarting (rather than just making it idle roughly).

And it sounds like your idle is already fast enough because the factory setting of around 650rpm is noticeably slow. (So slow that I tend to use the accelerator pedal to increase it a bit when I'm trying to warm it up after a cold start.)

So I'm stuck for other ideas.

That's one reason I like to do ALL work on my cruiser myself. You have the peace-of-mind of knowing nothing has been tampered with that shouldn't have been and that no-one's gone for a secret joyride in it.

In my view, to make a 1B BJ40 diesel miss at idle (which would be the normal cause of "a rough idle") would normally take "uneven compression" - but then how could an oil change suddenly cause that? (With clean fuel, the IP is normally too reliable to be suspected ... but a "sudden injector-fault" is of course another possibility to consider.)

 

[Max Wilder]

Tonight I'll at least be able to eliminate some possibilities and let you all know.

I appreciate your input immensely.

[rant]
I'm pretty discouraged about this; I bought the BJ and doubled the miles on it (50k miles at present) in two years without a single issue beyond having to replace the IP diaphragm when I got it home. Now I got married and moved (back) to college, have no money, and in the last 6 months I've had to rebuild the clutch, the alternator, replace brake cylinders, replace clutch and brake master cylinders, deal with one air leak, and now this. All without access to a shop beyond my garage and limited access to Harbour Freight.
[/rant]

I'm thinking about locking it in a storage unit and buying a cheap honda until one day when I have extra money.

 

[Moe R]

Yeah, I'd probablly feel the same way too except, a fellow cruiser happened along ( he left a note on my rig) and uttered some simple words of encouragment. Good luck man!