Loss of power

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chris @ shirley james
Member
Posts: 18
Our OKA, #96 has been steadly losing power over a long period of time.The motor is the original 4 cyl Perkins and is not modified in any way.Air and fuel filters are new, as is the lift pump.This week the valve settings will be done to eliminate irregular settings as a cause.Is there a fuel filter of any sort in any part of the injector pump? The motor starts easily and instantly every time so I am assuming that compression is OK. Does anybody have any suggestions as to a cause? I am running out of things to look at. Thanking all in advance for any help.Regards Chris.
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October 24, 2011 at 7:39 PM Flag Quote & Reply

Peter & Sandra James Oka 374
Member
Posts: 412
I had a similar problem on a 6.2l V8 diesel Chev engine years ago. Like your Perkins it was very slowly over a period of time getting slower and slower. Like your Perkins it always started properly and idled perfectly, just didn't want to go properly.
I changed filters, checked everything I could think of, checked compression etc etc.
It had a mechanical fuel pump like the Perkins and it also happened to be the lowest point of the fuel system and like the Perkins was before the filter. When I pulled it off I found that the chamber between the diaphragm and the pump body was acting like a sedimenter and was virtually full of crap. Cleaned it all out and as the pump seemed to work of refitted it, the difference was unbelievable, the engine went like a new one!!
While the Perkins lift pump has the sedimenter/water trap between it and the tank it could be gunked up or just tired and not providing enough fuel at wide open throttle.
From memory the engine manual gives info on fuel flow rates and how to test the lift pump.
Like many other diesels there may also be a fine gauze filter on the inlet side of either the lift pump or the injection pump. I've not pulled an Oka's fuel sytem apart so don't know.
Another point to check is if there is a filter/sock on the pickup in the fuel tank, restriction in the changeover valve if fitted with dual tanks.
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Oka 374 LT Van

October 24, 2011 at 8:15 PM Flag Quote & Reply

Dandj
Member
Posts: 367
Chris, I'm only guessing here but could dirty/blocked injectors be the problem?
Maybe someone with more knowledge can advise how injector problems show up (equivalent to worn spark plugs on a petrol engine).
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David and Janet Ribbans, Oka 148

October 25, 2011 at 8:00 AM Flag Quote & Reply

Dave and Pauline Gray
Member
Posts: 84
Chris I think it might be worth checking the wiring to the fuel solenoid if you are getting a voltage drop at the solenoid the fuel gate is not opening fully and so you will suffer a power loss due to fuel starvation. Also on the XT[mine137 had them orginally] check along your fuel lines on top of the tanks a line filter had been fitted as a primary fuel filter i was surprized any fuel was getting through them when i discovered them.
Cheers Dave
October 25, 2011 at 9:32 AM Flag Quote & Reply

joseph baz
Member
Posts: 331
Chris,just do a simple test,get a clear tube to supply fuel between the filter and the pump and see if you get a clear supply or you have minute bubbles with the flow,that will allow you to see wether you have a restriction or some air is getting into the system.hope this is of some help,let us know how you progress.
Cheers,Joe
October 25, 2011 at 10:49 PM Flag Quote & Reply

Tony Lee
Member
Posts: 539
There are small filters between the tanks and the fuel changeover valve that might be blocked
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Tony

picasaweb.google.com/114611728110254134379

October 26, 2011 at 2:01 PM Flag Quote & Reply

Hal Harvey
Site Owner
Posts: 509
Chris, if you're still suffering this, perhaps have a look at this post and see if it applies. We would be interested to hear...

www.oka4wd.com/apps/forums/topics/show/7...power-loss?page=last

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Hal

February 11, 2012 at 11:37 PM