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 Injector pump questions for 6.9 IDI
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87bluebrd
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5 Posts

Posted - 02/19/2017 :  06:43:17 AM  Show Profile  Visit 87bluebrd's Homepage  Reply with Quote
Hey everybody, I recently bought an 87 IH bluebird bus, it has the 6.9 IDI @ 180k and an at545. My plans for this bus are to convert it into an RV. I took it out for its maiden voyage/trial run about 40mi out of town. I was pretty disappointed in its performance as far as MPG's are concerned. I was averaging 6mpg's for the entire trip. Now before I go any further, I understand its a 12k lb. bus with a 6.9 IDI N/A. I understand my MPG's are not going to be the shining jewel on this bus. However.. 6mpg's was just pathetic. I need to be doing a little better to even consider taking this thing down the road full time.
Now a little about the motor. Overall, the bus and motor are in great shape, the IDI starts right up cold. I replaced the glow plugs, all the return lines, (3) fuel filters and injector O-rings. The motor does not smoke when started or idling. When I have it in neutral and get on the throttle a (small) continual cloud of white smoke comes from the tailpipe. Now Ive read, that the injector pump on an IDI should be rebuilt every 100k for optimal performance. Can anyone back that up?

Im willing to put a little time and money into this motor if it will help my engine run more efficiently. Ive spent a lot of time on school bus forums and diesel forums. But the diesel forums are (mostly) just trucks. And the Bus forums are primarily about the conversion process. There is not a lot of info on these 6.9 IDI's, which brings me here. This seemed like the most appropriate place to ask this question.

The bus needs new tires, and i'm aware of the many other factors that can increase mpg's but my main goal is to have that motor last as long as possible and run as efficiently as possible while keeping it mostly stock. Ive been quoted $270 for a full rebuild on my existing pump and maybe another 150 for new injectors all around. What do you all think? Is is worth it? The injectors have been replaced (BB), but im assuming the IP has never been touched.

Thanks for any input you might have.

International-9.0
Advanced Member

USA
459 Posts

Posted - 02/19/2017 :  09:48:26 AM  Show Profile  Reply with Quote
The 6.9s were decent engines if you took care of them. However, they were terrible when it came to pulling power, particularly when the bus was loaded up full. There were alot of hills on the route I used to ride on. I remember that the 6.9s (we had as a spare occasionally) could only pull the hills in first gear. We almost got stuck on a hill one time where the bus wouldn't even start out up the hill (nearly empty). They had a nice international V8 sound to them and weren't too noisy like the 9 liters were.

Those Stanadyne rotory pumps weren't near as good as the inline Bosch style ones. They did need work from time to time. They were not oil lubricated like the the inlines, but just fuel lubcriated. One thing with these is that they needed to be "dynamically" timed every so often (although I imagine nobody did this until the engine started running really badly). Static timing is accomplished when the pump is installed as you install the pump with the engine in a certain timing position. I'm not sure how the dynamic timing adjustments are made as I know little about these pumps. I do know that the engine did not perform right if the timing was off.

I wouldn't expect to get great mileage out of this engine, but it should be better than 6mpg on an empty load. How fast were you driving on this test drive? Did you have to stop frequently at lights or intersections? Continuous highway running at 55 or less should get better mileage than 6. If you were running 65 or more, then the mileage isn't bad.

If you really like this bus and want to keep it, then spending a little money on its well-being should be worth it. Its sound like you could improve your mileage a bit, but I wouldn't expect to get more than 7 to 8 mpg (depending on driving conditions). Particularly if you convert it and add a bunch of weight with all the things you have installed.

If you want to do some work on it, I would replace all injectors, have the pump rebuilt and timed properly (static and dynamic) and perhaps clean out the air intakes on the engine. I'm sure there is alot of carbon buildup inside the intakes. I would also get a brand new OEM thermostat (OEM style aftermarket is fine as you prob can't get IH anymore) and a new fan clutch. A bad fan clutch can kill your mileage (or cause overheating). These engines had a 192 degree stat, I think. However, you must be sure not to get a stat that is non-OEM style. This was the cause of overheating in some of the International V8s. The OEM style ones use a larger flow design than some of the generics.

Another thing you might check is your fuel pressure, particularly if you have a bit of white smoke. This engine has a small lift pump that runs off the engine cam to get the fuel to the pump. I think it only pressurizes to a few psi, basically just enough to get it up there. The end of the pump where the fuel line comes in has a rotary transfer pump that pressurizes the fuel to a higher pressure to fill the plunger chambers (I think it was around 100 psi, but not sure). Sometimes this transfer pump may not get getting the fuel to optimal pressure to fill the plunger chambers.

Also, no mention of an air filter change. Was this done with the fuel filter changes?

I might add that these older fully mechanical engines had no wiring and no emissions equipment. Although the mileage was less and they ran a bit dirtier, the reliability is superior and you almost can't kill them. Don't overheat them, change the oil every 3,000 at max, don't run out of fuel and basically the engine will never quit on you. The mileage is worse, but the maintenance cost is less and the reliability is far better. You can buy a newer engine with better mpg, but it won't necessarily save you more in the long run. It's all a matter of how you look at the whole picture.

What hp is yours? This should be on the emissions sticker on the engine. I'm not totally sure, but I think these engines had 155 and 165 versions. I think the Ford trucks might have been 170 hp.

Edited by - International-9.0 on 02/19/2017 09:55:12 AM
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87bluebrd
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5 Posts

Posted - 02/19/2017 :  10:03:00 AM  Show Profile  Visit 87bluebrd's Homepage  Reply with Quote
First I have to say thanks for your reply! During my test drive I averaged 55 on the highway, it refused to go any faster than 60 unless I was driving downhill. Unfortunately this bus has no tach, nor does it have the factory tach location (IP housing) like all the trucks with this same motor do. However I can hear an exponential increase in rpm from 55 to 60 mph. I feel that 55 is definitely the sweet spot for now. Its a 22ft 6 window by the way and that drive was done unloaded, I have it weighed unloaded at the dump @ 12,000 lbs.
I did not replace the air filter.
I do really like this bus and overall its in great shape. Im ok with low mpg's if that's what I get, that's what I get. But, I would like the motor to last as long as possible and run as efficiently as possible, if I scoop up a few mpg's here and there, that's even better. It would be worth $500 to me to get the ip rebuilt and get new injectors. either way its cheaper than regearing it...
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International-9.0
Advanced Member

USA
459 Posts

Posted - 02/19/2017 :  10:58:15 AM  Show Profile  Reply with Quote
Dang it! I got a nice long message typed and my internet stopped working when I submitted and lost the whole thing.

The engine must be geared so that it hits governing rpms at about 60 mph. I wouldn't force the bus any faster going down hills as that is likely to over-speed the engine. In general, this is not a concern as the injection pump has a built in governor. I think governing speed on this engine is around 3400-3600 on these engines. They were built as a gas engine replacement so they had a shorter stroke and higher rpm rating.

I would recommend changing your air filter. It's a cheap thing to do and gives the engine all the air possible. Naturally aspirated diesels need every last ounce of air they can get.

Aside from filter changes, I would recommend keeping the oil changed every 3,000 max. I think IH said 4,000 was the max in the service manual, but this engine is older and will have more soot get past the rings. The oil capacity on these older engines is also smaller as well as the fact that they run dirtier. So I'd keep the oil good and clean. One advantage of having the pump and injectors redone is that the fuel will atomize and burn much better which helps to keep the oil from getting contaminated as quickly.

If you take good care of this engine, it's very unlikely it will ever leave you stuck on the side of the road somewhere. These older diesels were bullet proof.

What area do you live in?
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87bluebrd
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5 Posts

Posted - 02/19/2017 :  12:20:09 PM  Show Profile  Visit 87bluebrd's Homepage  Reply with Quote
I live on the east coast of FL. But my parents live in CO. I have dreams of taking this thing up in the mountains. But after going over a few intercostal bridges, I think that's a pipe dream for now. Unless I get a different trans, re-gear, or get an OD.
I will replace the filter ASAP. Thanks for your input, any knowledge on the 6.9 bus platform is hard to find.
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International-9.0
Advanced Member

USA
459 Posts

Posted - 02/19/2017 :  12:50:15 PM  Show Profile  Reply with Quote
Where did you purchase your bus from...BGA bus sales? They are in the Hudson area over on the west coast and have a very large used bus business.

As far as mountains, I'd very much avoid those with this engine. It's not really made for that sort of thing, unfortunately. The DT466 engine is better suited for hard pulling like that. The MT643 transmission would also be better than the 545 in the mountains. 545s don't have a locking torque converter and they get really hot going up long hills. It's not that the engine and the transmission cannot do the job on occasion, but it would be more likely to bring about a failure on a high mileage engine or transmission.

I had a 180 hp 9.0 liter with the 545 and it did ok. I took it up a small mountain one time and didn't have any issues, but I was careful about how I drove it. If you have a picture of your bus, attach it so we can all see. Everybody on the bus forum likes a little bus porn now and then.
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87bluebrd
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5 Posts

Posted - 02/19/2017 :  1:32:55 PM  Show Profile  Visit 87bluebrd's Homepage  Reply with Quote
Just a private sale. I've heard some guys are running additional trans coolers to run their bus's through the hills. According to them it increased their top mph even on flat land. I'm aware of the AT545's short comings but I'm afraid the 6.9 doesn't have enough hp to move that 643. We'll see, gotta get it runnin good first.
Unfortunately I don't have a picture of the bus readily available. I would love to show it off though.. I think its pretty cool ha.
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International-9.0
Advanced Member

USA
459 Posts

Posted - 02/19/2017 :  4:52:12 PM  Show Profile  Reply with Quote
Yeah, in your application, an MT would be a waste. Your engine isn't that hard on an AT but the 9 liter and higher hp t444e engines were really maxing out that particular transmission. Your engine would be the more limiting factor if you went into the hills. To me, an extra cooler is never a bad idea. Those torque converters don't like getting too hot.

If you get a picture, let us see it. Feel free to post more questions on here. There are some really good mechanics here with alot of experience. I'm not a mechanic, but I just find mechanical things and school buses really interest. So I hang around from time to time.
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Fastback
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1500 Posts

Posted - 02/20/2017 :  04:55:00 AM  Show Profile  Reply with Quote
Our first diesel bus was a 1985 6.9, our second was a 1987 DT 360. The DT 360 far outperformed the 6.9 in every way that mattered, fuel mileage, power, longevity, resale value. Wait, no, cabin heat, the 6.9 bus made more heat

Why yes, the ORIGinal CHARGER is a Fastback
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eddo
Advanced Member

USA
311 Posts

Posted - 02/20/2017 :  07:39:30 AM  Show Profile  Reply with Quote
in addition to replacing the air filter, the bottom of the air cleaner can be given a bigger hole to allow for more air. Don't go too big where you let outside air in, but the hole in bottom of the factory air cleaner was way too small. We cut ours bigger for all of our OTR trucks.

at 180,000 miles aznd 30 years, I would consider very hard replacing the INJ pump and Injectors if the haven't been done already. It may just be the fuel where I am, but inj pumps and injectors needed replaced here at about 125,000 miles. I always had more injector issues than I did o ring issues.
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International-9.0
Advanced Member

USA
459 Posts

Posted - 02/20/2017 :  4:34:41 PM  Show Profile  Reply with Quote
We had all gassers until 1984. No 1985s (cheap county!) and 1986-onward was diesel. Our 86 models were 6.9s with juice brakes. They had a really throaty rumble and an intimidating sound compared to the gas buses (and when you're 7 years old). For whatever reason, our county liked those stupid 8.2 diesels and ordered them for about 5 years. I guess until they were discontinued. I imagine they later wished they had not done that. They had a nice sound, but no guts and a very troublesome fuel system.

Fastback, I'd say the 360 was more a direct replacement for the 9.0 liter. The 7.3 was more the replacement for the 6.9, which to me, was really no improvement. But either way, the 360 was an improvement to any of those engines. The starting torque was a little laggy, but the pulling power was very decent.
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Fastback
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1500 Posts

Posted - 02/21/2017 :  05:04:24 AM  Show Profile  Reply with Quote
quote:
Originally posted by International-9.0



Fastback, I'd say the 360 was more a direct replacement for the 9.0 liter. The 7.3 was more the replacement for the 6.9, which to me, was really no improvement. But either way, the 360 was an improvement to any of those engines. The starting torque was a little laggy, but the pulling power was very decent.



You are correct that the DT360 was International's replacement for the 9.0 Liter.
The 6.9 liter was basically the low cost replacement for International's discontinued gas engines. The 6.9s crankshaft/ engine block are very similar to the discontinued 404/446 gas engine components.

Why yes, the ORIGinal CHARGER is a Fastback

Edited by - Fastback on 02/21/2017 05:14:19 AM
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eddo
Advanced Member

USA
311 Posts

Posted - 02/21/2017 :  10:20:01 AM  Show Profile  Reply with Quote
longevity wise, the 7.3's did us a lot better than the 6.9's.
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87bluebrd
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5 Posts

Posted - 02/22/2017 :  06:07:36 AM  Show Profile  Visit 87bluebrd's Homepage  Reply with Quote
Yeah I understand the 6.9 is not as desirable as some newer platforms, however as a DIY'er its everything I could ask for. Solving and fixing problems on these motors has been pretty simple so far. Honestly out of all the vehicles i've worked on its been the most accessible. Pop the fenderwell skirts of and bam! your chest height with everything! I love it.

Even if I had know about the other options for todays bus motors.. 444 460 etc, I got this bus running and driving for 1500! So it was a little hard to pass up. Either way thanks for all the feedback. Ill post a pic as soon as I get one.
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Donguy
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7 Posts

Posted - 03/16/2017 :  8:42:08 PM  Show Profile  Visit Donguy's Homepage  Reply with Quote
Maybe you have resolved the problem with your bus butI would like to give any advice I have. I used to overhaul these injection pumps when I worked in a injection shop way back when.
These are very good pumps with a couple of trouble spots. Once they are taken care of they work for years. The biggest problem they had was with a hydraulic advance piston getting stuck inside the housing. A dead giveaway to that is an easy check. While in neutral, put the accelerator to the floor quite quickly and run it for a few seconds. If the piston is stuck or beginning to get that way, you'll get lots of blue smoke and the engine will run rough and act as if it's sucking air in the fuel.
The second problem was with the torque fuel screw. A spring inside would get very weak after it was in use.
To get this fixed requires the pump be taken off and sent to a fuel shop. It's an easy repair and when it's recalibrated you'd think you put in a new engine.
Regarding the static timing, this pump turns clockwise when you're looking at it from the grill. If you look on the top of the mounting flange you will see two lines. One on the pump and one on the engine block. When everything is proper you want the pump line to be on the passenger side of the block line by the thickness of a couple of lines or so. Going against rotation is advancing it which is what you want.You can turn it by loosening the three nuts with a modified 9/16" wrench and moving it by hand. Whatever you do, never never never do this with the engine running. You run a huge risk of seizing up the pump and then you can kiss more money away and have to buy a new one.
Hope this helps.
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International-9.0
Advanced Member

USA
459 Posts

Posted - 03/17/2017 :  5:00:29 PM  Show Profile  Reply with Quote
Don,

That's some very interesting feedback on the injection pump. It's really cool to know that you used to work on injection pumps.

I have a manual (in storage) that talks about these pumps. I remember that there were 2 pistons that squeezed together to pressurize the fuel. They were squeezed together with a cam ring. This ring would rotate back and forth to keep the injection timing right. The metering valve would allow a specific amount of fuel into the chamber. The more fuel, the more the pistons would be pushed away from each other (and towards the inside of the cam ring). Since the position of the pistons varied with the fueling rate, the timing for the start of injection would always change, if it were not for the dynamic timing compensation.

I assume the hydraulic piston you reference was in charge of varying this timing? Or am I confusing this with something else?

What was the function of the spring you were talking about? What was it connected to?

Did you ever work on any of the inline Bosch pumps?
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Donguy
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7 Posts

Posted - 03/20/2017 :  7:45:21 PM  Show Profile  Visit Donguy's Homepage  Reply with Quote
Yup, you nailed it. The piston I'm referring to in technical gobbily gook is called a hydraulic advance piston. It moves the cam ring in relation to engine rpm to advance or retard the beginning of injection.
The spring I refer to is inside the governor spring assembly thats in the top end of the pump. It's job is to give torque fuel at specific speeds and add a little more strength to the main governor spring.
I have worked on Bosch inlines and their version of rotary pumps, Cummins, all the Japanese versions of inlines and pretty much everything else out there.
It's a trade on the way out, has been for quite some time. Their not making these anymore so basically its repair whats in the field and once that dries up, hasta lavista.
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International-9.0
Advanced Member

USA
459 Posts

Posted - 03/22/2017 :  6:15:55 PM  Show Profile  Reply with Quote
Correct me if I'm wrong, but didn't the 6.9 pump governor work on a min/max principle instead of an "all speed" style? Basically, you directly controlled the metering valve with the throttle and the governor only interfered when minimum or maximum rpms came into play (or with a "droop/slip" range of the min or max). I think the 8.2s were this way to, although they used unit injection.

The inline pumps usually seemed to use the "all speed" style governor. A throttle position more or less corresponded to a specific rpm. The fuel could go anywhere from none to max depending on how far above or below you went from the target (my own term) rpm.

What was interesting about the pumps on the 9.0 International engines is that they would actually over-fuel at lower rpms. You were actually supposed to press the throttle when cranking (just momentarily) as it would over-fuel and start the engine really quickly, with lots of black smoke. I loved the response on that engine. No turbo lag, lots of torque and very quick revving due to the short stroke.
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