3B diesel engine misfires above idle (1 Viewer)

[Jeff Hastie]

Hi everybody,

I hope someone can give me some advice on the issues I'm having with my Landcruiser. The vehicle in question is a 1981 24 volt BJ42, with about 310,000 km on it, and a 3B diesel engine {no turbo}. I have searched this forum and the internet in general with no luck.

Here is the problem: The engine starts great {instantly, even now in winter}, and runs good at the lowest idle rpm, after glow plugging it for a minute. However, the engine will misfire {shake, run really rough, white smoke, etc...} after the rpm is raised any amount above low idle. As the engine gets a little warmer, it is able to run at a little higher rpm without missing. At high end operating temps it can be rev'd all the way without missing.

Here is what I have done to try and fix this problem, which has gotten worse over the course of about 2 years: Replaced all 4 injectors with rebuilds, and bled fuel lines {did nothing}, replaced glow plugs several times {nothing}, replaced fuel and air filters, and tested with no air filter {nothing}, drained fuel-water separator {nothing}, added fuel conditioner {nothing}, tried Seafoam engine treatment in the cylinders {nothing}, replaced thermostat {nothing} adjusted valves {nothing}, and replaced injector pump diaphragm. This last "fix" lowered my idle down to where it needed to be, and stopped the misfiring at idle... but only because the rpm is now lower at idle. Rev it up, and it still misfires.

One other weird thing about the misfiring is that it does not seem to be coming from any one cylinder. I have cracked open the nut at each injector to shut off the fuel... when rev'd up in this state, the engine still runs rough with white smoke. I plan on checking the injection timing in the near future, and that is really my only remaining idea, besides checking the compression... although I don't have a gauge. I'm hoping that there is some simple fix that I'm overlooking for this problem, and hopefully you guys have some suggestions. This truck is my daily driver, and works well enough if you let it warm up for 20 min or so, and I'd rather not have to tear the engine apart.

Lastly, on a side note, I also own a BJ60 with 630,000 km and body issues, same engine model as that mentioned above... runs great, and can rev up right off the bat without a miss. In fact, it misses a little at idle when cold, and giving it throttle smooths it out... like you would expect, and the opposite of my troubled BJ42. Thank you in advance for any suggestions you may have on this issue.

 

[yotahed]

try running the truck off a small pop bottle of fuel straight to the lift pump. then youll know if its pump or engine related and not fuel lines or fuel tank.

Start it from cold as you normally would to re-create the issue, if it runs fine, you have an issue in you lines or fuel tank pick up, or an air leak.

If it still runs like s***, it would be possibly a bad lift pump/seal, crack in the injector leakage pipe, bad seal on one on the pump/filter feed lines.....

run it off a bottle and see what it does. that will narrow down your search anyhow.

cheers

 

[slowandsteady BJ]

Seen this lots in higher mileage 3b's. In fact I have only seen one that didn't do that and it had 140,000kms and perfect compression. I always figured it was a misfire in one pot due to low(er) compression. Just wait for the old girl to warm up a bit she's probably a bit cranky in the morning.


However, If you do find a cure post it up!

 

[yotahed]

Yea, mine does it every once in awhile, like every six months, warm or cold outside and letting it idle for 10 mins after starting...kind of like a couple small bubbles in the lines. Only does it for a few seconds and then not again for a long time..

 

[Bandit_guy]

Beg, buy, borrow or steel a compression gauge and check it. White smoke means too cold and too cold is either low compression or not enough preheat. I'd check it cold and warm. You will see lower numbers cold then warm but if you're in the 400 psi range at warm temps then you're good. You say when she's at normal operating temp everything is fine, then you may not have much left to do but get her hot.

 

[cruiser_guy]

Compression should be your first test.

Cold with the numbers for each cylinder
Hot with the numbers for each cylinder
Finally, hot with a squirt of oil in each cylinder, again with the numbers
Post this up and then we'll go from there.

I've not had issues like this with any of my 3B's over the years.

I hope you saved all the glow plugs, they are expensive to toss if there is nothing wrong with them.

Beg, buy, borrow or steel a compression gauge and check it. White smoke means too cold and too cold is either low compression or not enough preheat. I'd check it cold and warm. You will see lower numbers cold then warm but if you're in the 400 psi range at warm temps then you're good. You say when she's at normal operating temp everything is fine, then you may not have much left to do but get her hot.

 

[Jeff Hastie]

Thanks for the feedback guys, I will look into your suggestions when I can. The issue of air in the fuel seemed to be a common reply... wouldn't this also cause rough running at idle, and hard starting? That was my assumption, anyway, so I never really went to any great lengths to find out if there was a tiny air leak somewhere. This motor starts great! I forgot to mention, as well, that I did replace a leaky fuel pump primer to no effect. Also, it really doesn't seem to be an issue of just needing to warm up... with my other, older 3B, giving it a little throttle smooths out the engine when its cold. What would cause sudden and constant misfires when doing this? And wouldn't low compression cause problems when starting, and at low idle? That's my hope, anyway... really don't want to rebuild. As for throwing out glow plugs, I just meant that I have gone though a few sets and discarded them as they burned out. They are expensive!

 

[RufusTheDufus]

If you can find some Diesel Purge it would be worth a test. The Mercedes diesel guys love that stuff. Much better than Seafoam. Fill your fuel filter with the stuff and also run it from a jar/can into the injection pump.

Have you tried a a fuel tank treatment to kill bacteria?

 

[peteinjp]

My 81 2b starts and runs fine for about 20 seconds- then it misses badly. I have manual glow i.e. glow resistor. I have to glow 2 times - 3 in winter- to get it to run without missing when I first start it. I had a compression check and cyls 1&4 were very low. 2&3 were great.

How long does it take after you get it started to run without missing?

Pete

 

[cruiser_guy]

Thanks for the feedback guys, I will look into your suggestions when I can. The issue of air in the fuel seemed to be a common reply... wouldn't this also cause rough running at idle, and hard starting? That was my assumption, anyway, so I never really went to any great lengths to find out if there was a tiny air leak somewhere.

Air in the line can make starting difficult and it can result in random shutdowns/low power for no apparent reason once the concentration of air is too high for the engine to deal with.

This motor starts great! I forgot to mention, as well, that I did replace a leaky fuel pump primer to no effect. Also, it really doesn't seem to be an issue of just needing to warm up... with my other, older 3B, giving it a little throttle smooths out the engine when its cold. What would cause sudden and constant misfires when doing this? And wouldn't low compression cause problems when starting, and at low idle? That's my hope, anyway... really don't want to rebuild.

Warming up the engine changes the shape of pistons and blocks very slightly due to differences in thermal expansion, thus the recommendation to do a compression test when the engine is at operating temperature. If the compression is poor at startup and improves once at operating temperature you can either live with it or rebuild, there are not a lot of other options.

Those are my opinions anyways.

 

[Jeff Hastie]

After starting the engine in winter, with the block heater plugged in, I generally have to manually glow plug it for about 1 minute average after the auto glow timer shuts off {another 20 seconds}. I installed a manual glow circuit to the vehicle because the auto glow time was just not cutting it for winter temps. With the heater not plugged in, glow times are triple. Then it idles great... just don't touch the accelerator! Also, I have not tried a treatment for fuel tank bacteria, or that diesel purge stuff... something to look into. I would love to check the compression, but gauges and mechanics are expensive, and I don't know anyone around who has one to borrow. My hope is that the issue is something else that I have not thought of, that could cause misfiring at higher rpm, and smooth running at idle.

 

[RufusTheDufus]

Check ebay for a diesel compression tester. I think you can find them for about $50-ish.

 

[peteinjp]

Might it be possible that fuel delivery is not metered correctly? Easy things to check and do are the diaphragm as well as new hoses to the throttle body.

A question to the more knowledgable ones.... Is the idle fuel metering dove in relation to the vacuum at the throttle body or is it simply a setting on the pump?

At any rate you should check compression and if possible leak down test. If your looking at the possibility of a full rebuild then a compression test is a minimal expense.

Pete

 

[yotahed]

Idle fuel is set at a specified vacuum and specified rack travel. But you can adjust the idle rpm at the throttle body.

The way they explain it the manual is complete nonsense and is meant to confuse the hell out of people.

Starting fuel is usually more than full load fuel, and as soon as rpms rise to idle, the governor cuts it back.

 

[brownbear]

Check compression.

It's not air. Air doesn't go away when warm. It stays in the loop till you crack the b nut on the nozzles which you did already. I bleed mine all the time.

Try plugging in with a block heater. See if that helps as the heads and cylinders will be pre-warm.

But the #1 suspect seems to be compression.

My 3B needs occasional extra glows when starting. I never raise the idle till it is solid. If I raise my idle it does what you say. Coughs and smokes. But if I leave the idle low and occasionally hit the manual glow everytime it coughs I get a smooth idle in a min or two.

 

[Jeff Hastie]

I just bought a compression gauge, and will post the results this weekend.

 

[BEE-JAY42]

Sounds like text book retarded timing, mark where your pump sits then advance the timing on it to see if it makes any difference. If it doesn't you can then return your pump to it's original position no harm done. It's the first thing I'd do and won't cost you anything.

 

[Jeff Hastie]

Here are the compression test results, with front cylinder being #1:
Cold test {-5 degrees Celsius ambient temp, with block heater plugged in}. Engine definitely cranked a little slower than during hot test.
#1 cylinder: 430 psi
#2 cylinder: 320 psi
#3 cylinder: 370 psi
#4 cylinder: 390 psi
Hot test {took it for a drive down the road}
#1 cylinder: 440 psi
#2 cylinder: 380 psi
#3 cylinder: 420 psi
#4 cylinder: 425 psi

After testing hot engine compression, I added a little engine oil to #2 cylinder, and got a reading of 470 psi. This seems to indicate that the rings in this cylinder are worn; however, a compression of 380 psi wouldn't cause constant misfires, would it? Even with the engine fairly hot, right before the test, it was still missing when rev'd to about 2500 rpm {no tach, so that's a guess}. Also, it still misfires when rev'd with #2 and #3 injectors "shut off". Also, my service manual says the minimum acceptable compression is 284 psi. Tomorrow I will try and play with the timing, as BEE-JAY42 suggested. Thanks again for your help, and I look forward to your responses.

 

[peteinjp]

My compression showed 1&3 at the minimum and 2&4 close to the maximum and my truck runs just fine once its warmed up for a few minutes.....


Pete

 

[lostmarbles]

The average of 440, 380, 420 and 425 is 416. And 10% of that is 41.6. So your figures should range from 374 to 458 to comply with "no more than 10% variation. - And they do.

So I don't think compression is to blame..

You haven't mentioned smoke.

Normally when my cruiser "misses a beat", this event is accompanied by a short puff of white smoke from the exhaust depicting unburnt fuel. So I'd expect your "sustained missing at higher revvs" to give you lots of white smoke. Is this the case?



PS.

Just some further thoughts..

Does the EDIC arm stay put while this "missing" occurs (or is it wandering back and forth)?

And could there be some sort of air restriction that starves the engine of air at higher rpms (like a collapsed air intake hose)?