Help; Loss of power

[Kota]

Originally Posted by tony6373

Okay, lift pump and check valve on order. Tried to leave today but M/H would not make it up the first hill (in Florida!) then suddenly it ran fine. It's just not dependable enough to drive.

Was the waste gate stuck open?

Didn't have time to read all the posts but a fuel pressure gauge is very handy to detect any issues with filters or the lift pump before they take out your high pressure pump. I doubt that any problems downstream of the high pressure pump would fix themselves. Possibly air in the system.

Sitting is the worst enemy these poor half a million mile engines have.

[tony6373]

I think I have an assignable cause! With the engine idling there were small bubbles appearing in the Racor fuel filter / separator. Bad sign. Disassembled filer and found small cracks in the plastic bowl at the bottom. So where can I get parts for a Racor 500FG filter / separator? Are parts still available? If not what would be an appropriate replacement? Surely someone else has replaced one by now. Monday I'll go looking for truck service shops and see if they can help with a replacement.

[Smartstream]

Originally Posted by tony6373

I think I have an assignable cause! With the engine idling there were small bubbles appearing in the Racor fuel filter / separator. Bad sign. Disassembled filer and found small cracks in the plastic bowl at the bottom. So where can I get parts for a Racor 500FG filter / separator? Are parts still available? If not what would be an appropriate replacement? Surely someone else has replaced one by now. Monday I'll go looking for truck service shops and see if they can help with a replacement.

Glad you found it. Diesels do not like air. Try here. Clear Bowl Kit 500, RK15405 - Racor

[tony6373]

Yesterday I sealed up the cracks in the fuel bowl with epoxy and reassembled the filer / separator. After pumping the primer for a while it started right up and idled with no bubbles or leakage. Today I will look for a new Racor 500 FT but if I can't find one I think this fix will get me back to Texas. Still waiting for the lift pump to arrive. I'm parked in a friend's side yard and don't wish to wear out my welcome.

[mayco]

Tony, glad you got it going and hopefully it will get you home. When you refer to the "lift pump" on the Isuzu, is that different from the injection pump? I dont know much about these diesels. If it is different, where is the lift pump located?

[wxbuoy]

Mayco


From my understanding the lift pump provides fuel in volume to the High pressure injection pump that provides it to the injectors. The Lift pump is between the fuel/water separator and the injection pump. The lift pump has the manual priming level on it.

[mayco]

Thanks for the info. My isuzu is running great..........for now. Hahaha! No it really is but the more information i can gather on these motors the better. Was your cummins a factory install or retrofit? Mine has the allison 4 sp. tranny which i understand was quite an expensive option with the isuzu diesel. I absolutely didnt know how lucky i was when i bought the rig from a family members estate. Lucky i hope anyway.

[shepherd57]

Mayco

Do you happen to know the rear end gear ratio on your coach. I have the same setup as you but my coach is a 32.5 with a 4.56 rear end ratio.

How is your coach for power on a long grade mine leaves a bit to be desired, I am not what is the problem as my Isuzu runs good.

[wxbuoy]

Originally Posted by mayco

Thanks for the info. My isuzu is running great..........for now. Hahaha! No it really is but the more information i can gather on these motors the better. Was your cummins a factory install or retrofit? Mine has the allison 4 sp. tranny which i understand was quite an expensive option with the isuzu diesel. I absolutely didnt know how lucky i was when i bought the rig from a family members estate. Lucky i hope anyway.

Mine is factory installed with an Allison tranny as well. Prior to the fuel issue I had all the power I needed.

[mayco]

Im not sure what rear end is in it. I just bought it last year and havent had a great deal of use yet but i did notice the same problem in a long grade situation. That was before i had done some much needed maintenance on the motor though. Im hoping that with the filters and fluids all fresh, and with my getting used to the allison shift points and such, that it will be better this coming summer. Optimist! Is your turbo registering well? Once i got my gauge working i show about 8 to 10 under load. Im at about 2800rpm at 60mph which i think is about whats expected. (Seemed a bit high on the rpm to me but after reading here on the forums i believe others register about the same)

[shepherd57]

I replaced my turbo after we bought the coach and I am seeing about the same for boost.I have the Allison 545 4 speed as well. I find that I have to just give it full fuel from a stop to get it to shift smooth I an told that is the way that trans is.

I am looking into installing a Allison 5 speed so I can have an overdrive for a better highway speed.

I am running the same RPM at 60 miles an hour same as you are.

[mayco]

Good to know.

[tony6373]

Apparently Isuzu calls this a feed pump. It is as Dave said between the fuel filer / water separator and the final fuel filter on top of the engine (which is just ahead of the injection pump). I got the new pump today and was shocked to see it looked different. Instead of a roller on its input there is just a plunger. Called Hamilton and they said that is the current style and they have been installing them for about 10 years with no problems. I have changed out the "overflow valve" which lives on top of the final filter under the double banjo fitting. New feed pump is in place but not connected and torqued down... ran out of daylight. Ordered a new Racor 500FG (water separator / fuel filter) and hope to receive it tomorrow or Wednesday. Fortunately the friend that I'm imposing on is a real motorhead and is very interested in all this.

I have the Allison AT 545 and I think a 4.56 axle. I don't drive it any faster then 60 or 62 mph and 2800 rpm sounds about right.

[mayco]

Ok, i recognize this pump, i was referring to it as a primer pump.

[shepherd57]

Tony
How is your coach for power, and fuel mileage. I am trying to figure out if I am expecting to much from my engine or if it needs more work done i.e. a valve job.

[Smartstream]

The original rated HP for the Isuzu is 135. The aftermarket turbo is low pressure because the rest of the engine is not designed for a turbo. This little engine will take you anywhere you want to go and it will take you there many times but it will not get you there real fast. Best to just sit back and enjoy the roses as you will have more time to get a good look at them.

[shepherd57]

Thanks Dan

Mine originally had a Mitchell overdrive in it and I think I have just found one to replace it with

[bkahler]

Originally Posted by shepherd57

Tony
How is your coach for power, and fuel mileage. I am trying to figure out if I am expecting to much from my engine or if it needs more work done i.e. a valve job.

John, if you're giving it "full fuel from a stop" then I wouldn't expect your fuel mileage to be all that great!

Brad

[Smartstream]

Originally Posted by shepherd57

Thanks Dan

Mine originally had a Mitchell overdrive in it and I think I have just found one to replace it with

I have a Gear vendors overdrive behind a TH 400 and it's really nice doing 65 mph at about 2500 rpm and the extra gears give you something to play with while going up hills but you still aren't going to get there and faster. I have seen 75 mph in overdrive but it's still a 30 year old truck frame and suspension and it's just more work than it's worth to be going that fast. I'm retired and I'm just not in that much of a hurry.

[shepherd57]

Brad
I am just used to the Cummins in my pickup with the tuner box I guess that's why it seems so slow.