Exhaust leak, loosing boost
 

The car doesnt have power as it did before.

Rpm builds until circa 3000 (higher gears) but then it feels topped. I can rev in 2nd or 3rd tillabout 4000 but it doesnt rev too quickly.
It isnt filter or fuel delivery or pump issue.

In 5thgear (m46) at about 65-70mph my top rpm is 3000. Idk why.

Something important i noticed: turbo spools way too early compared to how it worked before. And it spools to fast too soon

The intake and exh man9folds were off, resealed w new gaskets etc.

I suspect the gasket where the exhaust pipe mounts to the engine (at turbo)
I can see a tiny blowout spot where the mating surfaces shpuld be sealed by thatgasket.

Anyone have or can get that gasket? For d24t.

Also what is the suggested timing with the so called "bigger" gtd nozzles? I feel like the car needs more juicebut idontwant toplay w the inj pump (yet). :)

Can that exh leak cause this rpm sympthom? ?
Id like to get that gasket (more than one if avail)

Thx for reading
Otherwise car runs like a champ, just had a 400mile PA trip but "limited' rpm and "reduced "power really suck.

Which gasket? The thin square one? Usually those can be carefully cleaned up and reused.

Why do you say it can't be fuel supply or IP issue?

Could you possibly have left a rag or paper towel in the intake or exhaust plumbing?

Did you open up the intake manifold extension piece that connects to the turbo outlet hose? What did you seal it with?

What story does the smoke (any?) tell? Color, amount, when?

Different nozzles are always a sexy temptation but theoretically the stock have plenty of extra capacity for overfueling before they become a limiting factor in power generation. Looks like you have the sequence wrong. Mod the IP first, then the nozzles as necessary. Or at the same time, like if you send the IP to Giles, and tell him which nozzles you plan to run, along with any other mods.

Leakage from the turbo outlet to downpipe gasket shouldn't be related to the symptoms you described. Leaks there will not affect boost or performance unless the root cause for the leak is a plugged muffler or other exhaust restriction downstream of the turbo creating excess pressure at the turbo outlet, which is extremely unlikely. There are much more common explanations that would be worth looking at before going after this.

These are textbook symptoms for a plugged fuel filter, 99% of the time this is the cause. I would start by replacing it, even if it was done fairly recently. One tank of dirty fuel is more than enough to plug a new filter and can happen anytime.

If it doesn't give you an improvement, check for other fuel restrictions. Plugged pickup in the tank? On your car, the original low pressure lift pump should run with the key on, so there should be positive pressure at the filter whenever it runs. If that pump fails it might create a restriction at the tank too. Confirm it runs and pumps fuel to the filter. One other trick that can help for diagnosing restriction upstream of the fuel filter is to install a hand primer bulb in the filter supply line and see if it collapses when the engine is running. Seeing it pull in a little bit if the car is pointed uphill or the tank is low is no big deal but if it sucks down flat then you have a problem.

If it ran properly before and now it's different, then there is a new issue and you want to find it before making changes to injectors, IP, etc. Loss of response or power at high RPM almost always means something is restricted somewhere. Fuel restriction is the usual cause, but if everything checks out perfectly there, look for intake air or exhaust blockage too.

Good news is it's probably something simple. :)

Update:

The brick runs very well since right after I installed a new fuel filter. It still runs a tiny bit like it is like dragging brakes or something....i know it is a slow car yesss....:)
But idecided to check and replace the air filter too. I feel like something is holding the car back a little bit.

But i am sure it could be a factor too that I added bigger tires to the rear, currently 215 65 r16s so im not fully sure it is related to the engine. But I eventually probably must twist on the fuel screw a tiny bit and probably retime pump 0.02mm "higher".
I feel like it is NOT getting enough fuel.

Also, thank you for everyone's response. I'll soon answer those qs for Ngoma& V8.

Glad you found the problem!

I was going to list the fuel filter as a prime suspect but you had mentioned in your OP that that couldn't be it...

A rare original fuel filter just got wasted
 

Adding a new original Volvo diesel filter worked, the described issues disappeared (immediately...but later I had to learn: they were gone only temporarily) and after the quick fix of adding a filter I was convinced that a clogged filter was the source of the problem.
Well, it wasn't.
After the new filter the car ran great on the test drive. I filled it with ATF, bled it just a bit and idled some time then ran the car on higher rpms for a short ride. Because I bled it it ran That okay.
Only a couple of miles....but already the feel of the car, acceleration and the sound of engine was so much better than it was with the previous (relatively/technically new) fuel filter. I was convinced.
I could though *still* feel something wasnt totally right and I thought something was dragging or holding car (or the engine?!?) back from being 100 happy. That was the case.

Later I learned that I thought of "big things" but not the simple ones!!....

When I added the new filter, I wanted to adjust the idle too (suddenly sounded a bit low for some reason) and thought of doing something around the throttle linkage too because the pedal play never really felt right these days.

The actual repair then got postponed and only many days later I had the real time to do adjustments. Luckily. And I found it.

When I took a closer look at the ip area on another day, trying to remove the throttle linkage that connects ip to the throttle spool, I spotted a fluid leak at injector #5 and nearby. It was diesel fuel. Not much but seeping and enough to "paint" the surroundings wet/shiny.
I immediately thought it had to be the black injector return line(s) being loose, deformed, damaged, etc. But they are literally new and the proper German type also, installed correctly and gently with care.

When I pulled the hose, it would not want to come off the injector, instead it just popped out of it, the nipple part still in the little hose and a now a "hole" in the injector:)

I said wow but I didnt lose my mind... This has happened before...my fault! When the injectors were put in, gtd new 170bar ones btw, i havent had the proper tool so i used a SnapOn 27mm that felt right but it wasnt the best. It bent and pushed in (down!) several of the injector nipples.
It touched and bent most of all injector nipples on almost all injectors.
I fixed the injectors soon after, left #5 untouched because that time that was a dry one.
Now, months later, I found that leak and did the same little project:
Removed the return hoses from the injector, chemically dried it, let it sit safely so dirt could't get in, touch up the nipple w extremely smooth sand paper and clean it all over again, dry it, then
JB Weld nipples back, by adding just a touch of glue and push it in then create a nice ridge at the bottom of the injector nipple so it holds and looks alright. Then wait a day, have it all covered/protected from *any dirt that might get in.

A day later, I reconnected the black injector return lines, using a new piece, of course, bled the system again at the filter (idk why) and up at the injector hard pipe on the top too.
Car is equipped with the in-tank fuel pump that the gasoline Volvos use in there. It helps the pump and it helps a lot (or some) when/if there is any air intrusion anywhere.

In the past, I often saw air in the transparent fuel line in the mornings...the line that connects ip and filter but i never paid much attention bc car always gets it through with a single touch of the key (before even starting).

Only later I explored that when/if return line on #5 is touched (car not running) , air between ip and filter reappears. So I sealed inj #5 and calling it a day.

The brick runs AWESOME, the turbo used to spool too early and way too high but no real acceleration happened and the car was unresponsive and rpms topped at 2700-3200 in 5th gear (m46)...(problem gone!!!), engine now sounds smoother, balanced, high speed low rpms are gone, i can rev it anytime and turbo responds and sounds totally differently, no leak at the injector. Super peppy and the linkage was adjusted too so the pedal play isnt that sick anymore. I would like a quarter of a turn on the pump now. Just to see what it does. Or I will check and readjust timing first (add 0.02 probably)

#5 had one nipple jbwelded earlier so it took this much time for me to spot the problem (i first thought i did all 12nipples back then... but only did 4injectors= 4x2, plus one of the 2 of injector#5...#6 didnt need them fixed.... i learned the hard way now lmao)

I really like how it runs. Back to life...amazing. Air in fuel limited everything and as we know it: the tiniest amounts count!

Get those ugly dry rotted return lines off asap, dont let air create running issues...trustme it sucks to drive a d24t and think that it is how it supposed to run :))))) "it is an old car...diesel...etc...it is warm/cold out" etc :) lol..not true! Runs like a real champ now. Always ran good but now it runs great again. Plenty of power and a real joy to handle. Small adjustments are coming.

The thing is, they run so simple and are so oldshool and also they do tolerate several issues for such a long time (including worn rings for example, high oil consumption, etc, they even run ok with low compression, for years, misadjusted pumps, all sorts of leaks, extremely high miles etc) ...nice engines, really. :)))

Cliff's Notes
 

Cliff's Notes: Small, almost imperceptible leaks at the injector return lines can and do cause performance and starting problems.

EGR now removed and it counts. BC it leaked
 

The EGR mushroom now is removed and I made blockoff plates that seal the intake pipe and the exhaust manifold hole too.
A significant increase, drives a little better than earlier bc there was a leak between the exhaust manifold and the turbo area.

The turbo spools as it should and is more audible than earlier when exhaust manifold leaked. It is smoother and engages better and stronger. My RPMs still have a little pause at or slightly above 3000rpm but most of the annoyance is gone.
It does feel like an exhaust blockage but i simply can not believe that in my case bc I drive it on long trips and there should be none of the soot in there. Unless the exhaust pipes or the mufflers self deteriorated and partially clogged themselves which I also doubt.

As i`m typing here I have a feeling my injectors suck. I`ll investigate further lol.

o-ring in 740 td intake manifold, front...plus rpms `limited` at 3000
 

I`m adding a new fuel filter again although I doubt my rpm limiting is due to the filter clogged. as i rev the engine the rpms hesitate and hold a little, at about 2800--3000. once it passes 3000 area, it goes up peppier. also..... higher speed revs arent happening unless you really push the car for it. only if floored and even not always then. no weird smokes, no sounds, just it wont rev as it should. runs very beautifully otherwise.
it`s been some time for her doing this. also at a standstill she does that but if you rev it hard (only when WARM) it does reach higher rpms in the end. but it isnt smooth and isnt too quick for her to `skip` the 3000 level. I know i turned the fuel down but that itself shouldnt be the cause of weird rev ranges. esp not a hang issue at around 3000 rpm. I`ll try to adjust a few things tomorrow and check the filter too. i doubt it is related to my filter!

the other engine i saved, the green one that sat for years, had an issue with the fuel adjuster that i had to turn left right left right quite a lot until it `unclogged`. i did that today for the red wagon and will see if it changes tmorrow. it helped the green d24t to be able to rev peppy and return to idle well and also not hang at any rpm range. it used to hang a little and get sticky up there around 2700-3200rms. solved now but idk if red wagon will be cured by just that. I will see the timing too bc belt may have stretched minimally(???) and timing may be a little off. car isnt too fast:) but that should not limit revs , at all. timing was .93 last time i checked....idk. will see.



In the 700 td intake manifold, somewhere at the front of it, is there an o-ring that can go bad or age and cause a pressure leak?

also, how to adjust properly the boost valve and what is the suggested method to do it right?


where to send injectors for a reliable pro rebuild with proper nozzles, preferrably stock setup not the high kPa versions. also not the crappy nozzles
?

Are you seeing any bubbles in the clear fuel line into the IP?

What is this "fuel adjuster" that you are turning left and right? :confused: You lost me there. :o

Is there a Bosch accredited shop that services semi truck fuel injection systems in your area? They usually have the proper equipment, access to parts, and (importantly) service 100s of systems per week for professionals that depend on their rigs and would not put up with shoddy work.

Sounds a little to me like a sticky governor or worn pump plunger, though as mentioned above air ingress could be a factor too, since air will play havoc with everything about how the pump operates including dynamic advance, internal pressure, governor behavior, etc.

I did see something one time that was unusual on an old 1.6L diesel VW injection pump, with a great many miles on it, where over time a low spot had been worn in the main plunger. The result of this was that the control collar wanted to hang in one position, right on that low spot, and the engine revs would stick there (I think this was around 1500 rpm, depending on engine temp) until you disturbed it by dragging the engine back down to idle with the clutch or by making a large control input with the accelerator. So internal IP wear is a theoretical possible cause for a hanging issue or other non-linear response issue like this.

But before considering that, ruling out all the common and easy variables is definitely the first step: air leakage in, fuel pressure leakage out, fuel supply restriction, fuel return restriction, fuel quality. You could also run some diesel purge if you want, which usually doesn't make a difference but sometimes does.

And one other thing to not forget about is the internal pressure relief valve, screwed into the pump at the drive end from the top. If this is out of adjustment or has fallen apart, it makes the engine run weird since it throws the internal pressure curve off which controls dynamic advance, etc. It is a rare issue but the one thing that can help cause it is operating with a plugged fuel filter -- which I think you did experience one time not too long ago if memory serves? Running with the fuel restriction sucks the pieces of that valve apart and then the retainer can fall out and the valve spills its guts into the bore. No big deal to fix it, you just carefully rescue all the pieces from the hole and reassemble the valve (being careful to let no dirt inside!) and reinstall. If the basic checks don't give you any progress I would check this next.

Hi,

I don`t see any bubbles in the clear line between the fuel filter and IP. Not in the morning, not at idle and not at slow or high rpms.
Although it could maybe be possible for the system to introduce air somewhere under the clamp where the hose reaches the IP. IDK. I`ll check that just in case.
Also I could use a similarly clear line for the return side and inspect. That may be a good idea, I think.. not sure.
I personally don`t think it is air-related. How annoying that it seems like a clogged filter limiting but it isnt. Last time it helped but did not solve my issue fully.
But I also had an air bleeder bolt there with stripped threads. Since then I swapped on another housing from another d24.

I used to drive a 240 diesel car for years where you`d see air in fuel hose every morning. It got air in at multiple spots and took time to find them all. Car was used for fishing&hunting most of which on really bad, sometimes rocky unpaved forest roads or literally through fields... used as a sleigh :) That car always found the way to get air in the fuel system :) so I know how it sounds and feels when a sudden oversize bubble makes it in. :) same for the brakes :)

I had a chance to experiment on my engine stand d24t too when the clear hose bet filter and ip was not attached correctly, also it was split at some point but not seen (underneath area). It hardened and the clamp cut into it but it only got air in at certain RPMS, weird.




IDK what other names the `fuel adjuster` has but isnt it called smoke screw too? idk. :) Basically it is the first thing dieselers touch when they bought the car. :))))
circled in green, pict #5



Just so you all know, the ip has recently been flushed using atf from a jar and left sitting... and should be relatively clear inside.



Here`s a fresh video, taken with a fully warmed up engine, to illustrate the RPMs and the range I`m talking about. Notice how it stops in both directions at about 3000rpm. Doesnt stop but sticks, kind of.
I suggest watching the video SLOWED DOWN. Youtube has that option. Set it to 0.25 or 0.5 speed to see it best.

Look at this video and lmk, can this be caused by injectors? Nozzle failure or whatever? I doubt, but what do you guys think? Worst case scenario i`ll just get the pump off and install the other one but I don`t feel like messing with it.

It might be the case that I have to for many reasons :0)

A few days ago one of the fuel hard lines, cyl#4, started leaking drops of fuel and it stinks. Not much but at least I know why. The end at the IP side got too tight or it simply aged. I think the end deformed just a tiny bit, maybe. Is there a way to touch those up and fix it?

Sorry one more thing, two of the threaded parts where these hard lines screw `up` on the ip, were loose yest. I removed the entire fuel line assembly and took a look. I took care and was aware of the rubber vibration dampeners etc.
Havent seen damage... The 2000 grit sandpaper helped the end of the leaky line but it didnt fully cure it. Can I fix it better? maybe modify it back to more of a cone shape at the tip? then it flattens anyway when you tighten it. I know it is a very sensitively small torque.

I grabbed a nonturbo assembly and used the cyl #4 part of it and will swap that one piece into my turbodiesel assembly.

I think that even if those two were loose it would not affect my ip bc it is not the side where air would go inbound. Anyways. Looks like I`m around the Ip this time.
Today it gets the pipe from the nonturbo in then I`ll see if it leaks or not. The IP side nipple looked intact (the part that is part of the pump).

also this: :)
The front head of the IP always seemed to look `wet` by fuel so Im sure there was always something going on there. It is high time to reseal this entire IP btw.

I think it leaks near the wax arm too, on the side, and although i have a full reseal kit idk yet if I should touch such a million-piece item (=INJ PUMP)

It prob leaks at the rear seal too or idk... although in that case the air-rpm limit would be explained at least, right? :)

I dont think it is my fuel shutoff valve that wets the front head but I could look at that too. I just hate messing with Ip in-car. backbreaking exercise to reach in


here`s that rpm video. slow the playback down to 0.25 speed or 0.5
https://youtu.be/TwqBGBq7tlM

Thank you for the earlier responses too! I`ll follow v8`s advice on the order of diagnosys/fix.

I attached a picture and circled in purple the nipple where the hard line developed a leak. Can these be touched up? Shall I swap in another nipple from another pump? Or is it always the hard line itself that creates the `leak`? I guess so.

Also , what is the hole for? two, circled in yellow. THX

Forgive me, I'm easily confused. To my perception, you're asking a lot of questions here, and jumping all over the place. Can you please:

1. PRIORITIZE your issues, in order of importance.
2. NUMBER your questions, keeping them aligned with each issue.
3. REFRAIN FROM adding superfluous information that does not pertain to your prioritized issue.

Right now, all these things are swimming around in my thoughts and don't know what to do with them:
fishing
sandpaper
backroads
cracked line
hardlines
wax arm
reseal kit
wet head
vibration dampers
cyl #4
rear seal
million-piece item
nozzle failure
fuel adjuster
yellow holes
bleeder bolt
brakes
fuel shutoff

Don't worry about me, I'll get better :o

Moved side discussion to its own topic to avoid hijacking this thread.

Discussion: Injection Pump Pressure Control Valve and Varying Amounts of Electronic Control

Thanks for moving those posts.

Back to the original question of a slight hang at ~3000 rpm:

I think the most important question is: is this a NEW issue that recently started, or has it done this all along? And can you feel it when you are driving, like it's a driveability problem? Or is it just something you can notice if you are carefully watching for it with the engine revving with no load, but makes no difference in the way the car drives?

Also, are you sure this is happening in the engine itself, not just in the tachometer? The old tachs in these cars often move with a bit of a jerky motion. What happens if you raise the revs more gradually than you did in that video? Does it still hit a sticky spot at 3k?

IMHO: as long as it doesn't present a problem in how the car drives, or represent a sudden new issue that is rapidly getting worse, then this might be one of those problems that's not worth putting too much worry into. The internal governor in the IP is a complex mechanism and there are lots of different ways it needs to respond to RPM, load, temperature/pressure, etc. What you are seeing might just be a fairly normal part of its operation, or close enough at least.

If there's no visible air in the fuel either entering or leaving the pump, and it has a good fuel filter on it, and the car's performance is still good and not detrimentally affected by this phenomenon, then I would probably just keep running it and see if the problem changes.

Could it run a little better/smoother/more evenly with a freshly rebuilt IP? Maybe yes. But it sounds to me like this issue is subtle enough to not be worth all that work and expense, at least not right now, as long as the IP is working fine otherwise (starts good, quiet, clean running etc) and not leaking.

The leaks from delivery valves (what you described as the nipple) at the pump head are common, since those valves often want to unscrew themselves when you take the fuel pipe off. Tightening them to their required torque in the IP head (can't recall but you can look it up), then the fuel delivery pipe to the valve with its required torque, should fix. The fuel pipes do crack every now and then. If you discover that's the reason for the leak, let me know, I have a box full of spare fuel delivery pipes and will send you one.

I read your earlier post again a little closer. A couple more things:

1. Injector nozzles probably are not the issue here, they don't really have any control over engine speed. I would not worry about them at all, at least not for this issue (I know you have had some other issues with them though). Failed nozzle will cause smoke, knocking, misfire, etc, but not changes in RPM control.

2. Static timing setting probably isn't related either. If the timing is close enough for it to start cleanly, then it should be close enough to rev through the full range.

3. I think I am understanding that you turned down the "smoke screw" / quantity screw / fuel adjuster, as we are referring to it here. Just as an experiment, what happens if you turn it back in a little bit, like a quarter turn? Does that improve response and get rid of the dead spot you are noticing? It might create a little smoke too but let's just try it for the sake of knowledge. That screw has a large effect on the motion of the governor parts and it could be that it's the reason the engine is not as snappy as you would like.

I will report back how it went,
thank you for the parts offer and your valuable response.

Thanks for the responses, and i`m sorry for not returning to this thread with some results. I`ll write an update once I have some extra time.


In the meantime, I`d like to know where to find the dome-shaped metal gasket that is in the turbo wastegate area under that cover that is held up by four nuts. I think I will also need a new cover and probably all studs will break at removal. UGH...
I think, old Mercedes cars used that very same gasket btw, I would need more than one, at least two, if anyone could locate it pls let us know.

I can see signs of an exhaust blow-out (grey stains) below the unit, between the two lower nuts. The cover also rusted away pretty badly, i`m not sure I can reuse it. As far as I remember, that cover is just a flat plate, right? THX.

Probably there is a complete kit with every part necessary for a full turbo rebuild project (gaskets, studs, dome gasket, other gaskets and nuts etc, bolts for the turbo and its housing etc)? I`ll search ``Garrett T3 rebuild kit``.

gasket is this: 409262-0000 Actuator Gasket
Post #8 here: http://www.peachparts.com/shopforum/...te-gasket.html