D24T.com  

Go Back   D24T.com > Technical Discussion Area > Diesel Engine and Drivetrain

Reply
 
Thread Tools Display Modes
  #1  
Old 06-25-2018, 09:23 PM
RedArrow RedArrow is offline
Senior Member
 
Join Date: Jan 2013
Location: NY
Vehicle: 740
Posts: 783
Default 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.

Last edited by RedArrow; 06-25-2018 at 09:29 PM.
Reply With Quote
  #2  
Old 06-25-2018, 09:54 PM
ngoma ngoma is offline
Supporting Member
 
Join Date: Nov 2009
Posts: 990
Default

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.
__________________
1985 744 gle d24t
1985 745 gle d24t
Reply With Quote
  #3  
Old 06-26-2018, 12:24 PM
v8volvo v8volvo is offline
Supporting Member
 
Join Date: Jun 2009
Location: Livingston, MT
Vehicle: '86 745, '83 764
Posts: 1,348
Default

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.
__________________
86 745 D24T/ZF 345k lifted 2.5"
83 764 D24T/M46 155k
Reply With Quote
  #4  
Old 07-16-2018, 05:57 PM
RedArrow RedArrow is offline
Senior Member
 
Join Date: Jan 2013
Location: NY
Vehicle: 740
Posts: 783
Default

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.

Last edited by RedArrow; 07-16-2018 at 06:00 PM.
Reply With Quote
  #5  
Old 07-16-2018, 10:12 PM
ngoma ngoma is offline
Supporting Member
 
Join Date: Nov 2009
Posts: 990
Default

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...

Quote:
Originally Posted by RedArrow View Post
It isnt filter or fuel delivery or pump issue.
__________________
1985 744 gle d24t
1985 745 gle d24t
Reply With Quote
  #6  
Old 07-28-2018, 05:28 PM
RedArrow RedArrow is offline
Senior Member
 
Join Date: Jan 2013
Location: NY
Vehicle: 740
Posts: 783
Default 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. ))
Reply With Quote
  #7  
Old 07-29-2018, 10:42 PM
ngoma ngoma is offline
Supporting Member
 
Join Date: Nov 2009
Posts: 990
Default Cliff's Notes

Cliff's Notes: Small, almost imperceptible leaks at the injector return lines can and do cause performance and starting problems.
__________________
1985 744 gle d24t
1985 745 gle d24t
Reply With Quote
  #8  
Old 05-18-2020, 10:48 PM
RedArrow RedArrow is offline
Senior Member
 
Join Date: Jan 2013
Location: NY
Vehicle: 740
Posts: 783
Default 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.
Reply With Quote
  #9  
Old 08-10-2020, 09:42 PM
RedArrow RedArrow is offline
Senior Member
 
Join Date: Jan 2013
Location: NY
Vehicle: 740
Posts: 783
Default 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
?

Last edited by RedArrow; 08-10-2020 at 09:46 PM.
Reply With Quote
  #10  
Old 08-11-2020, 10:58 AM
ngoma ngoma is offline
Supporting Member
 
Join Date: Nov 2009
Posts: 990
Default

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

Quote:
Originally Posted by RedArrow View Post
...had an issue with the fuel adjuster that i had to turn left right left right quite a lot until it `unclogged`.
What is this "fuel adjuster" that you are turning left and right? You lost me there.

Quote:
Originally Posted by RedArrow View Post
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?
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.
__________________
1985 744 gle d24t
1985 745 gle d24t
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -8. The time now is 02:49 AM.


Powered by vBulletin® Version 3.8.10
Copyright ©2000 - 2021, vBulletin Solutions, Inc.