Diesel Gurus, please help me diagnose my truck.

[SuperHatch]

I am having a number of issues that I believe may all be interrelated. I am driving an 80 series with a Mitsubishi 4D34-T diesel conversion and automatic transmission. It is on 33" tall tires and stock gears in the differentials.

I have about 400 miles on the conversion now, and have made some observations.

1 - The engine feels down on power, this is subjective, since I don't know what one of these should feel like. But suffice it to say that flooring the throttle in 3rd gear at 50MPH will require 20-30 seconds to reach 65MPH. At this point, boost is 15lbs, and EGTs are 1100-1200 degrees. There is NO black smoke pouring out of the exhaust that I can see in my side view mirror, and it is a side exit exhaust so I have a good vantage point.

2 - Just maintaining speed requires a good deal of pedal application. EGTs at cruise are routinely in the 900-1000 degree range and boost is around 5psi.

3 - The fuel economy blows. I filled the truck up for the first time and calsulated 16.5 US MPG corrected for the tire size. I am part way into my second fillup and things are looking worse, not better.

4 - There are NO check engine lights. When I put the ECU in diagnostic mode, it flashes code 1, which according to the FSM is "All Systems Go".

5 - When cruising at 45-50MPH, the engine sometimes feels like it stumbles. Like a misfire in a gasser. This is really noticeable with the converter locked up at low RPMs. If I increase speed to 60MPH, I can't even feel it anymore.



What could cause these symptoms? The engine is using no oil, no antifreeze, and generally starts up without an issue. It comes up to temp within 5 miles of leaving my home.

Possible causes:

A - Ignition timing? I never touched the IP, but the donor truck was in an accident before I pulled the motor, I wonder if it shifted?

B - Air in fuel? Could a poorly bled feed system cause the issues I am experiencing?

C - Bad injectors? How do I even diagnose this?


I appreciate all of your help and consideration, this is new to me unfortunately. I'm googling and searching all I can, but it seems like information overload at times.

 

[Jan-78FJ40]

I am having a number of issues that I believe may all be interrelated. I am driving an 80 series with a Mitsubishi 4D34-T diesel conversion and automatic transmission. It is on 33" tall tires and stock gears in the differentials.

I have about 400 miles on the conversion now, and have made some observations.

1 - The engine feels down on power, this is subjective, since I don't know what one of these should feel like. But suffice it to say that flooring the throttle in 3rd gear at 50MPH will require 20-30 seconds to reach 65MPH. At this point, boost is 15lbs, and EGTs are 1100-1200 degrees. There is NO black smoke pouring out of the exhaust that I can see in my side view mirror, and it is a side exit exhaust so I have a good vantage point.

2 - Just maintaining speed requires a good deal of pedal application. EGTs at cruise are routinely in the 900-1000 degree range and boost is around 5psi.

3 - The fuel economy blows. I filled the truck up for the first time and calsulated 16.5 US MPG corrected for the tire size. I am part way into my second fillup and things are looking worse, not better.

4 - There are NO check engine lights. When I put the ECU in diagnostic mode, it flashes code 1, which according to the FSM is "All Systems Go".

5 - When cruising at 45-50MPH, the engine sometimes feels like it stumbles. Like a misfire in a gasser. This is really noticeable with the converter locked up at low RPMs. If I increase speed to 60MPH, I can't even feel it anymore.



What could cause these symptoms? The engine is using no oil, no antifreeze, and generally starts up without an issue. It comes up to temp within 5 miles of leaving my home.

Possible causes:

A - Ignition timing? I never touched the IP, but the donor truck was in an accident before I pulled the motor, I wonder if it shifted?

B - Air in fuel? Could a poorly bled feed system cause the issues I am experiencing?

C - Bad injectors? How do I even diagnose this?


I appreciate all of your help and consideration, this is new to me unfortunately. I'm googling and searching all I can, but it seems like information overload at times.

I'll start, but I am by far not one of the best to diagnose this. Your power sounds bad-it should never take that long from 50 to 65. A 3B is faster than that

Timing could certainly be out. It will give you bad economy and bad power. How does it sound? Very diesel-ly? You should be able to get the correct timing-adjustment procedure and follow it.

Air is best diagnosed by a clear hose right before the pump. I'd expect poor running and a shaky engine though, if you get air in.

Bad injectors will give bad power and fuel economy. Often you get smoke though. The best way would be to pull them and have them tested by a good diesel shop. Or just swap in rebuilt ones.

cheers,
J

 

[blis]

sounds odd, if i googled right that engine is rated for 165hp@3200rpm which should give better performance...

egt sounds bit on the high side for cruise but nothing too serious considering you aint getting black smoke and otherwise it starts ok and such...

About the injectors, one way to test them is let to let engine idle and loosen/remove one injector pipe at time and listen if the engine sounds/runs different, if there is no chance with injector pipe removed then that injector is faulty/broken/out-of-spec... Definately not the most scientific way to do it but helps to rule out injector failure...

About the injection timing, definately a possible reason but requires a bit of time to check out...

Could always a tranny issue thou?

 

[prado t]

Since the motor is not infront of me; Stumbling under low rev high load, no smoke, bad fuel economy and low on power I would say INJECTION TIMING RETARDED


If you were stumbling under high rev hi load and blowing blueish white smoke with the occasional popping noise I would say fuel system is getting plugged ie fuel filter


The ECU part scares me

 

[SuperHatch]

First off, I appreciate everyone's input.

I'll start, but I am by far not one of the best to diagnose this. Your power sounds bad-it should never take that long from 50 to 65. A 3B is faster than that

Timing could certainly be out. It will give you bad economy and bad power. How does it sound? Very diesel-ly? You should be able to get the correct timing-adjustment procedure and follow it.

Air is best diagnosed by a clear hose right before the pump. I'd expect poor running and a shaky engine though, if you get air in.

Bad injectors will give bad power and fuel economy. Often you get smoke though. The best way would be to pull them and have them tested by a good diesel shop. Or just swap in rebuilt ones.

cheers,
J

Yes, it sounds very diesel-y, and is quite rough at idle, but I can't really comment on the roughness for sure since I'm using the gasser engine mounts.

I am thinking timing right now... but not sure.

sounds odd, if i googled right that engine is rated for 165hp@3200rpm which should give better performance...

egt sounds bit on the high side for cruise but nothing too serious considering you aint getting black smoke and otherwise it starts ok and such...

About the injectors, one way to test them is let to let engine idle and loosen/remove one injector pipe at time and listen if the engine sounds/runs different, if there is no chance with injector pipe removed then that injector is faulty/broken/out-of-spec... Definately not the most scientific way to do it but helps to rule out injector failure...

About the injection timing, definately a possible reason but requires a bit of time to check out...

Could always a tranny issue thou?

I agree, the rated power output should have no problem moving this truck. Not to mention I have a full 3" exhaust, boost turned up a bit, and an electric fan vice mechanical, which should all add power.

I was thinking tranny issue, but besides the abnormally low shift points, it shifts just fine. Engine braking isn't exagerated, and the brakes don't seem to be dragging. The converter locks up, not really sure what could be wrong in there as it is actually quite simple inside.

Since the motor is not infront of me; Stumbling under low rev high load, no smoke, bad fuel economy and low on power I would say INJECTION TIMING RETARDED


If you were stumbling under high rev hi load and blowing blueish white smoke with the occasional popping noise I would say fuel system is getting plugged ie fuel filter


The ECU part scares me

I am thinking retarded timing as well, just not sure as to why it would be out since I haven't touched anything on the IP.

The prestroke actuator could also be messed up, but according to the FSM that would throw a code.

 

[canucksafari]

If it isn't the timing, I remember something similar to this in a post either here or on Patrol4x4. It turned out to be a defective TPS. But Like Prado T says, it is very hard to diagnose this without being there.

 

[Fromage]

Mine has not gotten the greatest fuel mileage, but it is better than 16. I am getting about 18-20, but that is lots of 75-80 mph and driving in town. In comparison, I was lucky to get 12 mpg before the swap doing the same type of driving. On one highway run towing my flatbed trailer (2500 lbs) empty I got approx. 18 at 60 mph on the dot, with lots of hills.

It took a long time to get the mileage figured out as I was always changing things and it seems to vary a lot depending on what I have changed, but I did get a solid 5 tanks in the last month where I was sub 20.

Mine will accelerate faster than that, for sure. Once I get it back together I will take some video so we can compare, but my zero to 60 time is around 25 seconds on 295 tires with all stock fueling but more boost.

I would start with injector testing, then check the coolant temperature sensors, and check the mechanical timing as per the manual. If you need a copy of the procedure I can send it to you.

I hate to say it but I am a bit dissappointed so far by the fuel economy of the swap but since everything is not 100% I am not losing faith just yet. I have never gotten advertized mileage out of anything, so driver habits has a lot to do with it I am sure. I also think that a lot of the mileage claims on here for 80 series trucks are inflated. It would be nice to get an auto 80 series HDT to compare, but I think that I would be getting sub 20s with that too...

 

[SuperHatch]

If it isn't the timing, I remember something similar to this in a post either here or on Patrol4x4. It turned out to be a defective TPS. But Like Prado T says, it is very hard to diagnose this without being there.

Well, I just went outside on my lunch break with a multimeter and check the primary and secondary TPS output voltages per the FSM, all is within spec... good thought though!

Mine has not gotten the greatest fuel mileage, but it is better than 16. I am getting about 18-20, but that is lots of 75-80 mph and driving in town. In comparison, I was lucky to get 12 mpg before the swap doing the same type of driving. On one highway run towing my flatbed trailer (2500 lbs) empty I got approx. 18 at 60 mph on the dot, with lots of hills.

It took a long time to get the mileage figured out as I was always changing things and it seems to vary a lot depending on what I have changed, but I did get a solid 5 tanks in the last month where I was sub 20.

Mine will accelerate faster than that, for sure. Once I get it back together I will take some video so we can compare, but my zero to 60 time is around 25 seconds on 295 tires with all stock fueling but more boost.

I would start with injector testing, then check the coolant temperature sensors, and check the mechanical timing as per the manual. If you need a copy of the procedure I can send it to you.

I hate to say it but I am a bit dissappointed so far by the fuel economy of the swap but since everything is not 100% I am not losing faith just yet. I have never gotten advertized mileage out of anything, so driver habits has a lot to do with it I am sure. I also think that a lot of the mileage claims on here for 80 series trucks are inflated. It would be nice to get an auto 80 series HDT to compare, but I think that I would be getting sub 20s with that too...

Thanks for the advice, I'll check the sensors per the FSM. I also talked to me local Fuso dealer and they're willing to let me stop by and plug their MUT-II in to verify some stuff that simply can't be done at home.

I thought your mileage was much much better than that. I remember you quoting numbers in the 27-29MPG range, which is why I was so confused. Are you calculating in Imperial gallons? If so, 20MPG imperial is close to 16MPG US.


I was really really hoping for 20MPG US with the truck... we'll see if it happens, but this tank looks worse than the last, not better.

 

[Jan-78FJ40]

Well, I just went outside on my lunch break with a multimeter and check the primary and secondary TPS output voltages per the FSM, all is within spec... good thought though!



Thanks for the advice, I'll check the sensors per the FSM. I also talked to me local Fuso dealer and they're willing to let me stop by and plug their MUT-II in to verify some stuff that simply can't be done at home.

I thought your mileage was much much better than that. I remember you quoting numbers in the 27-29MPG range, which is why I was so confused. Are you calculating in Imperial gallons? If so, 20MPG imperial is close to 16MPG US.


I was really really hoping for 20MPG US with the truck... we'll see if it happens, but this tank looks worse than the last, not better.

You should get close to 20mpg (US), that is what the HD-Ts get. I have a brand-newly rebuilt 1HD-T in my 80 and get 19.5 when driving in the city and bait on the highway with 70mph plus. Driving it with 60 mph makes a huge difference and gets it up to 23mpgs. You should be seeing the same.

I think you should have your injectors tested(cracking the fuel line, as bliss suggested, will only tell you whether they are totally clogged) and then look into the timing. Some engines are extremely sensitive to that. The 13BT for example will lose most of its power and return 13mpgs when timed incorrectly. don't be stuck on not having touched the timing-maybe it was out to start with, maybe the collision changed things...
cheers,
J

 

[Dougal]

Take the injectors off your list. Direct injection injectors don't result in power loss when worn, they just smoke a little when the engine is cold and stop it sounding as good at idle.

 

[jamie_scotland]

Mine will accelerate faster than that, for sure. Once I get it back together I will take some video so we can compare, but my zero to 60 time is around 25 seconds on 295 tires with all stock fueling but more boost.

Is that 25 seconds a typo?! A diesel with 165 bhp should move even a heavy 80 to 60 a lot quicker than that!

My 1HD-T puts out roughly the same power and is quite a lot faster to accelerate. I reckon about 14s would be a good estimate but I'll time it next time I go out.

 

[Dougal]

Is that 25 seconds a typo?! A diesel with 165 bhp should move even a heavy 80 to 60 a lot quicker than that!

My 1HD-T puts out roughly the same power and is quite a lot faster to accelerate. I reckon about 14s would be a good estimate but I'll time it next time I go out.

The 200hp 100 series takes over 14 seconds. My RRC with estimated 170hp is 17 seconds. It would be faster with a good auto, slower with a bad auto.

20+ seconds is more common that most people realise.

 

[jamie_scotland]

The official 0-60 mph book time of a UK diesel 100 series is 12.7. And the factory Range Rover classic with the 111bhp diesel Tdi is 16.8 and I can't think of any reasonably modern 4x4 that would be any slower!

25 seconds just seems incredibly slow! I'll time my 80 tomorrow just for interest.

 

[Dougal]

The official 0-60 mph book time of a UK diesel 100 series is 12.7. And the factory Range Rover classic with the 111bhp diesel Tdi is 16.8 and I can't think of any reasonably modern 4x4 that would be any slower!

25 seconds just seems incredibly slow! I'll time my 80 tomorrow just for interest.

I've always found official times to be a little optimistic, maybe I'm not thrashing the vehicles enough. I Couldn't do better than 14 in the 100 series here and haven't found a 200 or 300tdi rangie/disco/defender that can keep up with my 17 second RRC either.
Current defender (2.4 commonrail) is allegedly 17 seconds and it's got a far fatter torque curve than the 200/300 tdi's ever did.

Here's my 0-100 phone dyno plot. Ignore the HP column, vehicle weight wasn't set. I was running 2 phone dyno programs at the same time, the aDyno one agreed but the plot isn't as clear.

Anyone timed a B series cruiser?

 

[Fromage]

Take the injectors off your list. Direct injection injectors don't result in power loss when worn, they just smoke a little when the engine is cold and stop it sounding as good at idle.

So an injector that has a seized needle or poor spray won't affect power? Really?

 

[Dougal]

So an injector that has a seized needle or poor spray won't affect power? Really?

It won't affect power in the amounts you are looking for. I had my Isuzu injectors rebuilt about 5 years back. All new tips, rebuilder reckons old ones were shockingly bad etc etc.
No difference in fuel economy and no noticable difference in power. But idle was cleaner.

If you dyno'd it you might find 5%, but Hatch isn't looking for 5%, he's looking for 50%.

 

[SuperHatch]

Well, I timed the truck 0-60.

In fully auto mode with OD off... 22-23ish seconds.

Shifting manually... 18-19 seconds.

By the way, this is with the pop-off valve blocked and the boost turned up to 18-19lbs.

I guess my butt dyno blows for guestimating power, seems right in line with Fromage's truck.

 

[crushers]

you cranks the air but never touched the fuel, what did you expect to happen?

LJ78 28 sec from 0-100
PZJ70 18 sec from 0-100
BJ42 23 sec from 0-100
PZJ75 +T+PI 13.8 sec 0-100

but you are saying it takes 20 - 30 sec to go from a rolling 50 mph to 65 mph, that is surprisingly slow.

 

[SuperHatch]

you cranks the air but never touched the fuel, what did you expect to happen?

I expected the EGTs to cool off, which they did. I've been driving the truck for a week, I haven't gotten to messing with the fuel yet... all in due time.

LJ78 28 sec from 0-100
PZJ70 18 sec from 0-100
BJ42 23 sec from 0-100
PZJ75 +T+PI 13.8 sec 0-100

but you are saying it takes 20 - 30 sec to go from a rolling 50 mph to 65 mph, that is surprisingly slow.

Thank you for the comparison points, helps me keep things in perspective. I need to retime the 50-65 acceleration...

I have to be honest though, the more I drive the truck the more responsive it feels. I don't know if those new clutches in the trans needed time to bed-in or not, but the shifts are getting crisper and the truck is feeling more responsive overall.

 

[crushers]

give it a couple / few tanks to settle in.

what were the EGTs before increasing the boost?