Loosing speed uphill, 8v71

[jasong71]

Compete and utter newbie here. Recently bought a 1982 MC9 w/ an 8v71 i believe (so I was told). It is an auto (not sure which, used to be a manual). I am losing power going up small hills. I have it floored and I slow right down. I was given two recommendations:

1. Change Fuel Filters
2. Check Throttle Linkage.

Figures the fuel filter part out, have not changed them yet. How do I go about checking, fixing the throttle linkage? ANy other opinions on possible causes?

Thanks,

Jason

[Gary Hatt - Publisher BCM]

Jason,

All 8v71 engines lose power going up hills.  As they get old they, just like us, they lose power for several reasons. It all depends how you define "small hills".  A hill with a 4% grade if it is long, can cause my bus with the same engine will cause me to drop down to 35 MPH. The key to it is to be sure to shift down so you keep the rev's up an keep the temp under 180.  Otherwise keep downshifting until the temp gets down below 180.

A plugged Air Filter will cause a loss of power too.  It can be cleaned and blown out but if it is really bad, it is better to install a new one.  

Or you could have a leak in your fuel line or a fitting could be sucking air, or the fuel line could be plugged.  

If the bus hasn't run for a while, it is a good idea to pour some fuel stabilizer in the fuel tank and that may break up some of the crud and water if there is any.

You can also install larger fuel injectors to put more fuel in the system, but that will also lower your fuel mileage. Some folks think the trade-off is worth it for close to $1000.

[luvrbus]

Down shift to a lower gear a 8v71 faints if it see a small hill,seriously get a run at or down shift don't wait for the transmission to shift down, do it manually.Changing the filters and being sure the governor is opening is a good start but a 8v71 is not much in the hills  

[Gary Hatt - Publisher BCM]

What are you talking about Cliff.  My 8V71 can top 85 MPH easily going down the Grapevine. 

[luvrbus]

Gary he is probably set on around 260 hp and 775 ft lbs of torque to keep the heat down for a MCI lol a 8v71 does like down hill 

[dtcerrato]

Heck, Inline 6-71 loves down hills!

[DoubleEagle]

All of the advice about the air cleaner and fuel filters is quite true, particularly the fuel filters. One bad load of fuel, or old fuel with contamination can really put a crimp on power fast in any diesel. The engine might also need a tune (running the rack). Assuming the engine is as good as it will be, you then have to not be afraid to take command of the engine and downshift when necessary and run it up to the governor limit. Then sit back and wait while watching the temperature gauge while the everybody else goes shooting by. Appreciate the sound of the 2 cycle while it is spinning its heart out for you, because it will get you to the top.

[jasong71]

I am downshifting. A small hill is a few hundred feet at a 5% grade. Flats I am doing 55 (if I am lucky) and floored.

[jasong71]

The engine might also need a tune (running the rack).

Will that include fuel filters, or is it separate?

[luvrbus]

I am downshifting. A small hill is a few hundred feet at a 5% grade. Flats I am doing 55 (if I am lucky) and floored.

It should do better than that are you getting any black smoke ? change the filter then check the shutdown cylinder on top of the governor housing and be sure it is retracting all the way and you have a small gap between the lever and cylinder rod

[DoubleEagle]

That is substandard, a 8V71 will do better than that. Change both fuel filters (they need to be filled with fuel to the top). Running the rack is done by a mechanic with skill. It is adjusting the timing of the fuel injectors and involves taking the valve covers off. You can do the filters yourself. The old ones should have numbers on them, and NAPA, at least, can get you the right ones. You might have to crank the engine for a while to re-prime the system. If you are lucky, the filters will make a big difference.

[luvrbus]

Where are you located ?

[buswarrior]

Hello, and welcome to the madness!

Please, do not touch your fuel filters unless you KNOW how to do it without losing prime.

And have the tools necessary to RE-PRIME on hand.

You have a coach that will run right now.

Lose prime, and you have a coach that will not start, and you will kill the batteries trying fruitlessly.

Do not use starting fluid as any part of this process, do it properly.

Simple check for the throttle, see if all the parts in the back on the top of the engine move their full travel when someone pushes the pedal to the floor. You can do this with engine off. Take pictures and post them here.

After that, it gets complicated.

happy coaching!
buswarrior

[jackhanow]

Shop vac primes them right up. Vinyl tubing. Jug of some sorts. Make sure it didn't have volatile liquid in it. Set it up vac to jug, jug with vinyl hose to the fuel line comming from the filter to the pump. Turn it on and wait til there is about a quart or so of fuel in the jug. Hook the line back up and start it. I've done this a lot. Works great.

[Tony LEE]

What are you talking about Cliff.  My 8V71 can top 85 MPH easily going down the Grapevine. 

Yes, no point burning those crappy old drum brakes up unnecessarily