3b high idle questions

[brisveganbj42]

hi guys,

i went wheeling on the weekend and when I stopped to book into the 4wd park i discovered my 3b was idling at about 1600rpm.

The road in was very rough and bumpy and i had also noticed the engine was hotter than usual on the drive there (although it was a hot day).

I had recently replaced the governer diaphram about 6-8months ago so although im aware the high idle is a result of this failing im not so sure.

Before going away for the weekend I noticed that it was taking longer for the RPM's to drop to idle speed when i had taken my foot off the clutch.

I also noticed on the weekend that you could apply some load (via the clutch) and it would bring the revs back down breifly.

I only got back yesterday so haven't had a chance to do much diagnostics.

Things on my list are:
- check vacuum to diaphram
- check for vacuum leaks around the intake manifold (spray some ether and listen for the pickup).
- check accellerator cabling (pretty sure this is ok).

I guess i'm just after some feedback to make sure i'm on the right track with the things to check and test. So any comments would be appreciated.

Thanks,

Andrew

some pix from the weekend

[KOOTENAY KRUZER]

Sounds to me like your on the right track, the less difference in pressure across the butterfly, the higher the RPM. Easiest thing to check though - when it is idling fast is the throttle lever resting on the idle stop?
I have had similar problems that turned out to be the rubber floor mat getting under the pedal and resisting its return to idle position.

[brisveganbj42]

Things on my list are:
- check vacuum to diaphram
- check for vacuum leaks around the intake manifold (spray some ether and listen for the pickup).
- check accellerator cabling (pretty sure this is ok).

Checked for vacuum leaks around the intake manifold.. nothing came up
- checked accellorator cabling and that also appears to be ok.. noticed that if the cable gets caught under the airbox it then increases the idle.

drove the 40 into work today.. it was ok.. but i still think its idling too high probly about 750-800rpm instead of the 650 it should be.. but at least its not 1600rpm..

i'll keep an eye on it and see how we go.. interesting that the high idle isnt consistent (like something was busted)..

[roscoFJ73]

Have you checked the spring on the accelerator pedal(Im assuming they have one). On the 60 and 70 series the spring gets old and causes erratic high idles.

[MrMoMo]

Uh, not to state the obvious, but did you perhaps bump a hand throttle?

[brisveganbj42]

I can confirm hand throttle was/is pushed in
I can also confirm the accelerator pedal is in its rest position fully.

no problem with the obvious questions I could of overlooked something simple.

If the engine appears to take longer than usual to drop to idle speed after coming off the clutch, would this point to something??

like instead of 3secs for the rpms to drop to idle it takes about 7-8secs?

[brisveganbj42]

i noticed on the way home from work that the revs seemed normal when cold but after heating up they increased 150-200rpm.. didnt notice any black smoke.. also didnt get a chance to test the intake manifold for leaks while it was warm.

not sure if it means anything but thought id add it.

[KOOTENAY KRUZER]

My '79 (with a 3B) idles at 500 RPM cold and 650 RPM warm. I set the idle for when the engine is warm, if I want it to idle higher when cold I use the hand throttle.

I don't have a tach in my '83 but there seems to be about the same difference between cold and warm with that engine (3B) as well as I can tell by ear (and vibration).

As far as I can recall when I had the B engine in the '79 it behaved the same way, I think it is just the nature of the beast.

[brisveganbj42]

if i haven't changed the idle settings would i need to change them to fix this issue?

I have noticed that it appears that I have no engine braking at all..

could this be a compression related issue? I've done a few bits to figure out what the problem is but I havent been able to find anything.

I really want my p.o.s. sorted cos i dont like driving with a high idle.. so i might take it to a professional to sort out..

[KOOTENAY KRUZER]

The symptoms are similar to a small leak in the diaphragm. I know you replaced it recently, so try to think if there is any other way you can be having less pressure difference across the diaphragm or butterfly valve than you should have.

[brisveganbj42]

vacuum test was ok

compression test came back with:
psi 200/ 220 /220 /200

mechanic thinks its worn pistons/rings..

might have to start looking for a replacement 3b..

:(

[watrob]

Originally Posted by brisveganbj42

vacuum test was ok

compression test came back with:
psi 200/ 220 /220 /200

mechanic thinks its worn pistons/rings..

might have to start looking for a replacement 3b..

:(

How are going mate, have not spoken to you in awhile, there is 2B with gearbox on ebay.au for $500, it would keep you going for awhile.

Anyway how have things been?

I bought a damn good 2H out of a 1987 75 series, low klms for $800 the other day as backup if my 2H gives up the ghost, have you thought of dropping a 2H into the old girl?

[brisveganbj42]

Originally Posted by watrob

How are going mate, have not spoken to you in awhile, there is 2B with gearbox on ebay.au for $500, it would keep you going for awhile.

Anyway how have things been?

I bought a damn good 2H out of a 1987 75 series, low klms for $800 the other day as backup if my 2H gives up the ghost, have you thought of dropping a 2H into the old girl?

Hey man,

I have considered it but would like to keep it 4cyl if i can.. putting a 3b in there should be a no brainer. not too sure id want the lower powered 2b.. i have a 5spd so just need the donk.

I have a few feelers out at the moment so we'll see how they go..

thanks for the heads up tho.

Cheers,

Andrew

[eleblanc]

Originally Posted by brisveganbj42

vacuum test was ok

compression test came back with:
psi 200/ 220 /220 /200

mechanic thinks its worn pistons/rings..

might have to start looking for a replacement 3b..

:(

How can worn piston/ring cause high idle?

I just came back a tripp and my truck is now idling 1000 instead of 700.

[amaurer]

Originally Posted by brisveganbj42

vacuum test was ok

compression test came back with:
psi 200/ 220 /220 /200

mechanic thinks its worn pistons/rings..

might have to start looking for a replacement 3b..

:(

Your 3b would never run with those numbers. You should consider the possibility that your mechanic is retarded.

That aside, low compression wouldn't cause high idle.

[brisveganbj42]

Originally Posted by amaurer

Your 3b would never run with those numbers. You should consider the possibility that your mechanic is retarded.

That aside, low compression wouldn't cause high idle.

Hmm.. i'm confused.. While I trust my mechanics judgement I'm keen for a second opinion...

She starts fine and blows a bit too much black smoke.. but apart from the high idle it seems ok.. When I purchased the bj42 it was advertised as being recently rebuilt.

Any assistance is appreciated before i spend big bucks (big bucks to me!!) on something when I dont need to..

thanks.

[brisveganbj42]

Originally Posted by eleblanc

How can worn piston/ring cause high idle?

I just came back a tripp and my truck is now idling 1000 instead of 700.

Did you fix this problem yet? if so what was it?

[eleblanc]

Originally Posted by brisveganbj42

Did you fix this problem yet? if so what was it?

No, i did not. I will have to change the diaphragm, i guess.

Did you fix yours?

[brisveganbj42]

Originally Posted by eleblanc

No, i did not. I will have to change the diaphragm, i guess.

Did you fix yours?

kinda.. bought another 3b to slot in..

but no.. same high idle..

only happens when its warmed up

still takes a while for idle to drop to a higher than normal level

its been driving ok but have noticed a drop in power over the last week or so of driving.. I have been taking the clutch out with the brake on at lights to drop the idle speed down from 1500rpm lately.

[KOOTENAY KRUZER]

Originally Posted by brisveganbj42

its been driving ok but have noticed a drop in power over the last week or so of driving.. I have been taking the clutch out with the brake on at lights to drop the idle speed down from 1500rpm lately.

Not sure about your apparent loss in power, but the rest of it sure sounds like the governor diaphragm has ruptured again. I know you just replaced it recently, but I wonder how old the replacement was?

[brisveganbj42]

Originally Posted by KOOTENAY KRUZER

Not sure about your apparent loss in power, but the rest of it sure sounds like the governor diaphragm has ruptured again. I know you just replaced it recently, but I wonder how old the replacement was?

it would also explain the noticeable increase in black smoke too.. anyway.. I'm going to swap engines with one with a better compression readings and I'll replace BOTH diaphragms when they are out of the vehicles..

That should tell for sure but its an expensive exercise..

[brisveganbj42]

damn i hate it when you guys are right!!

decided to take out the diaphragm while it was easy to get to and check it out.. found 3 big rips in it..

[eleblanc]

You can ship the engine you are replacing at;

56 Boul Industrial,
chateauguay, QC, Canada

[brisveganbj42]

heheh.. i'll compression test it once its out and if its any good i might just do that..

i wonder how many "i told you so"s id get?