3B diesel engine misfires above idle

[Awl_TEQ]

Here is the thread in the 40 section where I am documenting the engine swap as well as the tranny/ t-case and a front locker. ----> https://forum.ih8mud.com/threads/upgrades-for-the-coming-season.795621/


I also just put a new vented cap on my fuel tank. I had a temporary non-vented one on there for the last 6 months.

 

[lostmarbles]

Hi Tom, Thanks for posting. Yes, 1981 BJ42 CDN spec inline pump. Actually, come to think of it, the pump is 1983 but still inline.

I'm working from the basis that the fuel delivery system I pulled was working fine. Furthermore, the system I put in was rebuilt by a competent shop. So for now I will not worry about injectors or the IP itself. I will also leave the injector lines out of the equation because they are a) downstream of the pump b) not leaking and c) real shinny.

On the suction side I will ignore the tank and hard lines up to the rubber jumper at the steering box (LHD, I did not touch any of that during the engine swap). From that point to the inlet of the IP is where the issue lies IMO. That includes the leakage line. All of the clamps on both rubber lines are of the stock spring type clamps. These clamps are adequate from new but in light of a hard to find leak I will change them all to something more positive like what you posted above Tom.

The primer pump is new and does pressure up pretty good so my leak must be small to require 15-20 min of run time at hwy speed to develop bubbles enough to stall.

My leakage line was a junkyard find (as were the injector lines). I had them re-plated and they were acid etched as part of that process. They were nice looking lines and much better than my "mine truck" originals but it is possible the hard line of the the leakage line has a crack. This is less likely than a rubber line/clamp leak though.

As I stated above I swapped out my large lines and sealing washers on the fuel filter already.

If I can't get the rubber lines to seal and solve the problem then I will have to move on to the primer pump. Although rare, I have read a thread here on mud where a new primer pump was letting air into the system.

Since you obviously know what you're doing and this leak is tiny ... why not try pressurising your fuel tank slightly so that fuel will weep out the leak instead of air being sucked in. I used this method a few years back.

I got my son to hold an air gun against a motorcycle handbar grip that was then pushed against the fill opening like so:

Then I put wads of tissues around suspicious areas and sure enough, one of those wads became damp with fuel to reveal the location of my leak.

Here is the thread in the 40 section where I am documenting the engine swap as well as the tranny/ t-case and a front locker. ----> https://forum.ih8mud.com/threads/upgrades-for-the-coming-season.795621/


I also just put a new vented cap on my fuel tank. I had a temporary non-vented one on there for the last 6 months.

Wow. That engine sure looks nice

(I hadn't noticed that thread before.)

Are you saying your old fuel cap was completely sealing the tank?

It should definitely have a valve mechanism in it like my ex-factory cap here:

So maybe the problem wasn't air ingress at all and maybe now you've already cured your problem by replacing the cap?

 

[Awl_TEQ]

Tom, I have sourced and changed the four clamps on the the two rubber lines this morning. On a test drive I now have a new or slightly different symptom to discuss.

Still have low power across the board and more black smoke than I should. No white smoke or missing as I headed straight for the Highway. No missing as I did a 10 minute drive at my still slow top speed of 80km/h. I had noticed before that it would stall when stopped at idle. So I pulled over and set a high idle of 1000ish and sat still for a bit. Sure enough after a couple of minutes she stumbled and eventually stopped. I jumped out and bled the filter quickly and she fired right up. Then I took a longer drive to see if it would stumble at higher throttle/speeds. I went maybe 20-30 min with no missing and went straight to my driveway to time how long before she stumbled at low idle. At 55 seconds the missing started and at 1:22 she died.

So bubbles appear at idle only?

 

[Awl_TEQ]

Since you obviously know what you're doing and this leak is tiny ... why not try pressurising your fuel tank slightly so that fuel will weep out the leak instead of air being sucked in. I used this method a few years back.

I got my son to hold an air gun against a motorcycle handbar grip that was then pushed against the fill opening like so:
View attachment 880550

Then I put wads of tissues around suspicious areas and sure enough, one of those wads became damp with fuel to reveal the location of my leak.



Wow. That engine sure looks nice

(I hadn't noticed that thread before.)

Are you saying your old fuel cap was completely sealing the tank?

It should definitely have a valve mechanism in it like my ex-factory cap here:

View attachment 880552
View attachment 880553

So maybe the problem wasn't air ingress at all and maybe now you've already cured your problem by replacing the cap?

Smart problem solving there Tom.

Yes, the old cap was creating a vacuum that the other engine seemed to be able to overcome. I have a similar cap to yours now. Since it was new I planted my lips on it and was able to get it to pass air with very little suction.

 

[arnott1t]

kev, we had issues once with the injector washers sealing. A small knick caused exactly them same scenario you've described though I'm not sure it ran well down the highway. We were able to hear a sucking noise while priming and thats how we found the leak. Another option i was just thinking about was clamping your supply line to the primer upstream and pumping the primer to make a vacuum and maybe here the suck? Anyways these leaks are frustrating so best of luck!

 

[lostmarbles]

Tom, I have sourced and changed the four clamps on the the two rubber lines this morning. On a test drive I now have a new or slightly different symptom to discuss. ....Still have low power across the board and more black smoke than I should. No white smoke or missing as I headed straight for the Highway. No missing as I did a 10 minute drive at my still slow top speed of 80km/h. I had noticed before that it would stall when stopped at idle. So I pulled over and set a high idle of 1000ish and sat still for a bit. Sure enough after a couple of minutes she stumbled and eventually stopped. I jumped out and bled the filter quickly and she fired right up. Then I took a longer drive to see if it would stumble at higher throttle/speeds. I went maybe 20-30 min with no missing and went straight to my driveway to time how long before she stumbled at low idle. At 55 seconds the missing started and at 1:22 she died.
So bubbles appear at idle only?

I think our engines have the ability to spit some air out through the injectors when the revvs are up so I think this is the reason it dies at idle only.

In other words, I think a small amount of air is still entering all the time, not only at idle.

It sounds like we have had an impact when working on that little section of hose in the bleed line though. So I wonder if more work is needed there.

I note that you're running 1/4"/6mm hose there whereas I'm running 5.5mm. Sure it is only half a mill difference but with these small diameters that's over 8%. Did you find it at all loose?

I don't particularly like that fabric-coated hose I was sold by a local diesel injection shop here because it seems to be unreinforced (apart from the fabric). But at least it was a push-fit on the spigots rather than a sloppy fit.

And I think the black smoke (and low power to some extent too) is a different issue ... Perhaps your timing is too far advanced?

Edit (later)... Perhaps the thing that really had the impact was changing the fuel cap... Less vacuum in the tank will equate to a lower rate of air infiltration of course... So on that basis ... I guess I'm back to suggesting the "tank pressure + tissues" line of attack...

Smart problem solving there Tom.

Yes, the old cap was creating a vacuum that the other engine seemed to be able to overcome. I have a similar cap to yours now. Since it was new I planted my lips on it and was able to get it to pass air with very little suction.

I can still get a decent w-h-o-o-s-h noise when I take my cap off during a long trip.

kev, we had issues once with the injector washers sealing. A small knick caused exactly them same scenario you've described though I'm not sure it ran well down the highway. We were able to hear a sucking noise while priming and thats how we found the leak. Another option i was just thinking about was clamping your supply line to the primer upstream and pumping the primer to make a vacuum and maybe here the suck? Anyways these leaks are frustrating so best of luck!

I suspect Kev's leak is too small to make any sound .... but then again I shouldn't judge because I'm pretty deaf..

 

[Awl_TEQ]

Tom, I ended up not using that 1/4" hose I bought for that very reason... too loose. I used the tube that was on there with the new clamps. The clamps are pretty much bottomed out though so I'd like to find smaller ones. The hose is snug though.

I think I will bring the timing back a little now that the white smoke has lessened. And then take a trip down to the retail area and see if I can find a smaller clamp.

 

[Awl_TEQ]

I didn't get any clamps. I retarded the timing a smidge which put me about where we started and had the expected result of masses of white smoke. So I advanced it a smidge and tightened it all up.

Since I was into it I figured I would inspect the injector lines, sealing washers and crosstube for the leakage line. I pulled everything off and destroyed one of the washers in doing so. I also took all the lines off of the other motor to compare witness marks on the sealing surface of the lines. They are all similar. I thought maybe they were over tightened or something. I have three 3B's in the garage as well as a spare set of injectors from the junkard so I found four decent washers and carefully re-assembled.

No change to symptoms whatsoever. I went for a nice long drive and then stalled in the driveway after less than a minute of idling.

 

[RufusTheDufus]

With the spare 3Bs around do you have a primer pump you can try to swap to address the air issue?

BTW, what gears and tires are you running?

 

[RufusTheDufus]

When you swapped the EDIC from the donor engine did you verify the pump arm angles/rod length adjustment per the FSM?

 

[arnott1t]

Ok couple more ideas

1. Try running truck from a Jerry can. Run a hose into can from lift pump and see if it will idle. The result will tell you where the leak is.

2. If leak is down stream of lift pump run truck from Jerry can by supplying the injection pump directly and cutting lift pump filter and bleeder out of the picture. Shouldn't need much supply for idle and the injection pump would likely pull the fuel enough. Or... Place can on roof and get a siphon feed going to injection. Ever 3' is about 1psi I believe.

 

[Awl_TEQ]

With the spare 3Bs around do you have a primer pump you can try to swap to address the air issue?

BTW, what gears and tires are you running?

Yes. Tomorrow I will swap a different primer in.

I have 33" KM2's, H55f and 4:1 gears in the t-case. The 4:1 gears have the added effect of 10% underdrive in high range. When the 33" tires and the 10% underdrive high range are combined I have, in effect, stock final gearing.

When you swapped the EDIC from the donor engine did you verify the pump arm angles/rod length adjustment per the FSM?

Nope. Just slapped it on. But I'm over fuelling at speed with constant black smoke but no power.

Ok couple more ideas

1. Try running truck from a Jerry can. Run a hose into can from lift pump and see if it will idle. The result will tell you where the leak is.

2. If leak is down stream of lift pump run truck from Jerry can by supplying the injection pump directly and cutting lift pump filter and bleeder out of the picture. Shouldn't need much supply for idle and the injection pump would likely pull the fuel enough. Or... Place can on roof and get a siphon feed going to injection. Ever 3' is about 1psi I believe.

I'll try the direct feed tomorrow when I start changing hard parts.

 

[lostmarbles]

It just occurred to me that there is a simpler way to put pressure inside your fuel lines to help locate this tiny leak.

This BJ42 is mobile right?

So why not fill the tank right up close to the top of the filler neck and then park it nose-down on the steepest bit of ground you can find?

Then leave it overnight (preferably above a surface where drips of diesel will become immediately apparent .. such as above sheets of cardboard packaging) and see what there is to see in the morning.

At the very least, with your tank full right up to the neck and your fuel pump having very little (ie - almost none at all) sucking to do ........... your stalling-at-idle should almost disappear - even on level ground. So it should be an easy way to confirm we're on the right track (before you even get to the point of parking it nose-down overnight).



Edit.. I don't know anything about how this engine has been overhauled so I just want to concentrate on the air-ingress issue alone...

 

[RufusTheDufus]

I used a pressurization technique to prime the fuel system on a 13B-T this past weekend. The engine sat for a few years and the hand primer pump wouldn't move any fuel. It took me far too long to figure this out. I happened to have a cheap 4 psi electric inline pump laying around from a previous project. It's the type that turns on at less than 4 psi and off at 6 to 8 psi. I'd expect this would work as well to diagnose a pre-injector pump leak.

 

[Awl_TEQ]

Primer pump. It was leaking and when replaced there was no more air ingress.

Still under powered though.

 

[arnott1t]

nice work!
do you have gauges and what not for underpowered trouble shooting?

 

[lostmarbles]

Well done!

Did you go for the Bosch primer?

So now it's on to the low power and black smoke..

At least with black smoke I think we can rule out underfueling.

I wonder if there's any way valve timing could have been messed up?

Or perhaps this engine got one of these heads I've read about that runs smaller valves?

Is there a thread that documents the build of this engine?

 

[diogenese]

black smoke has to be a lack of airflow. blocked intake , valve timing or excessive clearances or blocked exhaust.