5lt injector pump tuning question (1 Viewer)

[advlars]

Hey all.

I fit my boost compensator, played with the timing a bit and been trying to tune fuel my 5lt injector pump and have run into some interesting problems.

When the engine is cool/cold it seems to run pretty well. But when Ive made it about a mile or two and the engine is closer to temp it coughs up some white smoke and loses power. Seems to get worse for the next half mile, and then stays about the same. Its worst in 1st, bad in 2nd and seems to get better in higher gears.

My first guess was running too retarded. And it seemed to help to advance it. But now ive advanced it incrementally back to where it was before I added the turbo (and retarded the timing) and Id like to hear everyones thoughts before I advance the timing too far.

Would retarded timing cause this effect? Could it be something else like air in my injector lines, or a misadjusted wastegate, or over/under fueling?

Thanks

 

[advlars]

Update: I advanced the timing slightly again and it seemed to help a tiny bit. Then I decided to turn up the fuel a bit and it ran terribly. Ok atfirst (when cooler), but by the time I was almost back to the house the truck would barely run by the time made it back to the house. No black smoke or excessively high egts though....

 

[AussieHJCruza]

I wonder if its sucking air somewhere?

 

[advlars]

into the fuel system? Its possible. lots of older hoses and clamps etc. is this a typical symptom of sucking air?

I still cant invision why it runs better when its cold though.... if its sucking air it should suck it at any temp right? The symptoms present themselves like clockwork depending on engine temp/ distance.

Can air get sucked in through the fuel adjustment screw? Maybe the symptoms werent effected by the amount of fuel, but rather by loosening the set screw and not setting it hard enough?

 

[AussieHJCruza]

Does the 5L have a device to advance the timing when cold? Theoretically, air in the fuel retards the timing, but that may not be it

 

[GTSSportCoupe]

Hey all.

I fit my boost compensator, played with the timing a bit and been trying to tune fuel my 5lt injector pump and have run into some interesting problems.

When the engine is cool/cold it seems to run pretty well. But when Ive made it about a mile or two and the engine is closer to temp it coughs up some white smoke and loses power. Seems to get worse for the next half mile, and then stays about the same. Its worst in 1st, bad in 2nd and seems to get better in higher gears.

My first guess was running too retarded. And it seemed to help to advance it. But now ive advanced it incrementally back to where it was before I added the turbo (and retarded the timing) and Id like to hear everyones thoughts before I advance the timing too far.

Would retarded timing cause this effect? Could it be something else like air in my injector lines, or a misadjusted wastegate, or over/under fueling?

Thanks

The injection timing is not something you should need to play around with very much at all. If it is out significantly from spec, it could be causing some of your issues. Use a proper dial gauge indicator tool that mounts to the back of the pump, and set the timing as per the factory manual for the 5L or maybe closer to the 2LT. It is a very fine adjustment. I helped a friend do it on his 1HDT and it takes patience and precision to get it right. You have to repeat the measurement a few times to make sure it is right.

Here are the specs from the manual:

At this point I'd recommend leaving the main fuel screw on the pump at the stock position. At least until you have your boost compensator settings baselined.

Tuning the boost compensator is tricky and takes a while too. There are quite a few variables. There is the cam on top, the spring rate, and pin rotation.

So basically you should be able to control your fuel starting position (using the cam), how fast the fuel ramps up (set spring rate with the star wheel), and the ramp profile (spin the pin to different rates).

Tune by EGTs, smoke, and seat of the pants. Or a dyno with AFR data if that is available to you.

The idea is to not over fuel when off boost, but also to ramp the fuel up properly with boost to maintain efficiency/power balance of AFR.

It is a bit of a learning curve. My friends HDJ81 came with some awful mismatched aftermarket performance pin. We swapped it out for a stock Mitsubishi pin laying around, and had to do a lot of tuning to get it all working right. Small adjustments can make a huge difference.

 

[GTSSportCoupe]

Here is the section from the manual on setting the timing (attached). Is this how you've been doing it?

 

[advlars]

Nick,
I retarded the timing because i was worried about predetonation on an engine with higher compression ratios. I backed it off to like .4mm but it ran badly so i slowly worked it back up to about where it was originally. I measured with a dial guage per factory intructions to figure out where it was originally, what the hash mark on the block measures at and where .4mm was etc. Right now Im carefully moving it around just a hair at a time within that range trying to adjust it with the butt dyno but not opening it up and letting air in.

I havent messed with the boost compensator yet. My logic was that Im planning to run about the same boost in my 5lt as i ran in my 2lt (~8psi) so i figured it would be close while i dial in the basic fueling. Thinking more about that it makes sense that this will need to be different as im building boost way faster with the td04l and the engine is bigger. I imagine after I set the min/max height at pressure I should rotate the pin to a steeper profile with this turbo?

Also, I couldnt really leave the main fuel screw stock, as the fuel screw is on the 2lt boost comp, not on pump body. It was way underfueled in the 2lts stock setting. Any guidelines to setting this other than as much fue as possible with safe egts? Right now Im hitting about 900f preturbo if I stomp on it up a hill when the engine is still cooler. But when the engine warms up it coughs and sputters under load and doesnt do much. And i can only see smoke when it coughs.

Also, I just bought an AFR meter in the hopes i can speed up this tune. Should show up tomorrow.

 

[GTSSportCoupe]

OK, glad to hear you are using a dial gauge to set timing.

I think you are dealing with too many variables right now. Pre-ignition will only really be an issue in hot weather, high boost under heavy load. Being that its relatively cool weather right now, and you are just tuning under light load, I would think it would be just fine at stock timing for now. Once you've got the rest of the variables sorted out, then you could try pulling the timing a touch back again? What I'm saying is just set this back to stock for the time being to eliminate it as the problem.

The next item to work with would be the fuel screw. I forgot that this screw is in the boost compensator. Usually this is setup to spec by an injection shop, and it can be a tricky thing to set on vehicle. That said, we did end up playing with this screw on the HDJ81 I was talking about. It can have a huge impact on the way your engine runs/starts, and can cause the issues you mentioned above. Just a fraction of a turn can throw everything. It impacts idle speed too, so when you change the fuel screw usually you have to adjust your idle each time also. I've found that when the base fueling is just a touch on the rich side, the exhaust will be a little bit blue at idle (poorly burned diesel particles). So you could turn this screw in (compensate idle screw each time also) until you get a touch of blue at idle with a warm engine. Then back the fuel off slightly until the smoke disappears. Give the engine a couple stabs of throttle and you should see a puff of black come out with good rev response. If the response is slow, then it's lean, if the response seems too fast and smokey, it's a bit rich. Adjust as necessary and once you think it might be ok, try driving it.

Once you think you have that fairly well set, you could start playing with the boost compensator. A lot of guys pull the fuel pin and grind a angle on one side of the bottom so that it can be re-installed without hitting the follower pin. This way you can remove and reinstall it a few times with little hassle. When you pull the pin, you will see a wear mark on it where the follower touched the pin in your 2LT. Some guys put grease on the pin and install it back into the boost compensator. They use a bicycle pump to increase 'boost' pressure on the boost hose and manually exercise it to their expected boost level (with engine off of course!). They then pull the pin out and look at the grease to see how far the pin traveled. Like you say though, this should be just fine as it is the same boost your ran on your 2LT. Might just be a matter of fairly small tweaks of the fuel ramp is all that is necessary for now.

OK, so in summary, this is what I recommend: Set the timing back to stock for now. Likely the fuel screw is the main thing causing you grief, so focus on that first. Once you've got that sorted out, start tweaking the boost compensator.

Now just to cover the basics, you drove your truck for a while with the stock 5L pump setup right? You did not have any of these issues during that time? Just want to make sure you don't have any fuel supply or air issues going on here. The loss of power and coughing sputtering can definitely be a symptom of those sorts of issues. Did you replace the gasket in the lid when you did the swap? Fuel hoses and clamps all look good and are tight? How is the fuel filter? Is your tank breathing properly and not building up vacuum? Fuel return is setup right?

 

[advlars]

Update:
I modified my leakdown tester with some npt barbs and I started to play with the boost compensator, (checking how high it rides on the ramp at 8psi) but noticed when I hooked up the air compressor I could hear a leak. after a little searching, I realized its dumping out the vaccum port beneath the boost diaphragm. I pulled the compensator apart again and realized i can basically see though the diaphragm in like 3 spots. presumably when I boost, the boost pressure is A) not actually moving the diaphram much, if at all, and B) filling my injector pump with pressurized air. Im surprised I never had these symptoms on the 2lt though. And it also seems like i should have had problems when running cold too...

Anyway. Big clue
Hopefully I can find one of these in the US and not wait 6 weeks to order from australia....

Also, in regards to the boost pin, mine doesnt seem to have any difference in ramping depending on orientation. Does the 2lte pin have different ramping and would they likely interchange?


Regarding the fuel screw, maybe I can get a measurement off the old injector cap and get a ballpark of how deep that one was.
I had the one on this pump screwed pretty far in, but never saw black smoke or crazy high egts. Maybe it was just mildly overfueled at the low end but not adding any fuel to speak of on boost. The

 

[GTSSportCoupe]

Update:
I pulled the compensator apart again and realized i can basically see though the diaphragm in like 3 spots.

Hopefully I can find one of these in the US and not wait 6 weeks to order from australia....

Good work figuring that out! Who would have thought?

Can you paint the diaphragm top side with a rubber coating or something to seal it back up for the time being?

I have a Mitsubishi 4d55t Denso injection pump I got off craigslist for $20. It has a decent diaphram I believe (I'll have to double check). Same size as the Toyota one I think. So if you are really hard up finding one I could ship that down....

 

[advlars]

Lucked out! Dealership can order me one and it should show up tuesday. Which is crazy cause my local dealership usually cant get anything for my engines. I guess if i run into fitting trouble ill spray some rubber coating on it and get back to you about the Mitsubishi parts. Thanks for the offer!

 

[advlars]

Well. My part showed up, installed it and adjusted the compensator as best I could to 9lbs of boost. Set my timing back to roughly where it started.

Took it for a test drive and the first lap was terrible. I parked for a few minutes to adjust my guages and took another lap. Lap 2 felt good! Still some light coughing under load but not terrible. But notably, the engine was still hot.

Took it out for a spin a third time, and it ran like crap...

At least the runs seemed a bit more consistent maybe...

Anyway, I guess tomorrow I will check for fuel leaks and vacuum leaks etc... I did have trouble starting and had to crack the lines and crank the engine a bunch to get fuel to the injectors. Is this normal when youve pulled the cap off the boost comp? Or maybe indicates an air leak into the fuel lines?

AFR guage is installed but giving me some trouble. Showing super lean when it works so far though.

 

[advlars]

Alright,
I replaced the fuel filter, every fuel line in the engine compartment, and ran the vacuum straight from the vacuum pump to the underside of the boost compensator (eliminating possible leaks). Engine runs great! No more coughing.

If I had to guess Id say the source of my troubles was the fuel filter. It was pretty nasty in there, and Im thinking it flowed well enough for my 2lt but not enough for my 5lt under boost. I thinking it was fuel starved under load. Love to hear what you guys think.


Btw, can anyone advise me on vacuum routing for the boost comp? does there need to be a VSV in there or should it always be under vacuum?

 

[advlars]

Ok. So now that Ive got the problems under control, im moving back on to actually trying to make it run well.

According to my afr and egt Im finding that the truck runs super lean at low revs, a bit lean under a bit of load, but runs way too rich under load. AFRS will jump to 16ish and my EGTs will skyrocket when I get on it hard. My off-idle screw is set at max already, and im afraid if i turn up my main fuel screw i will run crazy rich under load. Should I shim my aneroid pin so it cant drop as low under boost, and then turn up my main? Or can I shim my off boost cam and turn down the fuel? Not sure where to start here....