skip Posted February 9, 2013 Share Posted February 9, 2013 Gday everyone.Ive got an 866 with an irregular miss in it. It only happens every now and then when its idling, but its really noticeable when it starts to rev. Ive just had injectors done, it starts very easily and doesnt breathe heavily. The RHS bank has new rings in it, and the heads have been overhauled. To me it sounds like a fuel pump problem, and the smoke that it blows under revs is fuel smoke. The sound is almost like a sticky engine brake but is not regular and cosistent enough. I am going to check the timing tomorrow. Has anyone got any thoughts?Thanks, Dave W Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/ Share on other sites More sharing options...
fjh Posted February 9, 2013 Share Posted February 9, 2013 These were notorious for loose valve seats and worn valve guides! listen carfully after the engine is warmed up, when shuting it down you may hear a pop pop coming from the head area!That is tipicly a valve seat. Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163118 Share on other sites More sharing options...
theakerstwo Posted February 9, 2013 Share Posted February 9, 2013 What he said. I had one at one time that was missing and pulled the pump and pump shop told me its doing what it should do. Come to find out it runs on 8 cyls when needed or certain rpm. At 1000 rpm it runs on 4 and picks up two after that till its got all 8 fueling. Pump shop said he had never seen them before but had specs for it. I replaced it with a normal pump from a junk engine. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163216 Share on other sites More sharing options...
skip Posted February 9, 2013 Author Share Posted February 9, 2013 Thanks for the input guys. I would be pretty confident that the RHS heads would be ok as they were done up. The LHS could be an unknown quantity. Would a loose valve seat cause it to blow smoke under light revs? From my experince with a loose valve guide on a 6 cylinder it made the popping sound when you backed off the revs. This V8 seems fine when you back off. This engine and pump sat around for a long time before my cousin bought the truck to restore it. And when we first started it up it flew out to full revs and I had to block the intake to stop it. The LHS rack was stuck in the pump but i managed to get it freed up without removing the pump so we dont know what the pump is like. Could it have a sticky element or maybe a worn cam to make it miss?Also, how do you go about timing this engine? Is it similar to a 6 cylinder? Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163231 Share on other sites More sharing options...
theakerstwo Posted February 10, 2013 Share Posted February 10, 2013 Reread what fjh just told you. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163261 Share on other sites More sharing options...
skip Posted February 10, 2013 Author Share Posted February 10, 2013 Reread which part Glenn? I doesnt sound like it is popping when it is turning off. And do you reckon it woud cause the engine to miss and blow smoke? Let me know what you think. Thanks mate Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163289 Share on other sites More sharing options...
e9500v8 Posted February 10, 2013 Share Posted February 10, 2013 Could be one of the dynatard relays. To find it take valve covers off and turn it on and off and see wich one isn't clicking. I have had them stuck and the truck ran like a turd. Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163304 Share on other sites More sharing options...
e9500v8 Posted February 10, 2013 Share Posted February 10, 2013 Sorry dynatard silinoid the ones on the rocker shaft Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163305 Share on other sites More sharing options...
theakerstwo Posted February 10, 2013 Share Posted February 10, 2013 Sorry dynatard silinoid the ones on the rocker shaftYes i just one month ago had one on the truck i run to have a half way miss at idle. i found it to be the selenoild bad. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163308 Share on other sites More sharing options...
theakerstwo Posted February 10, 2013 Share Posted February 10, 2013 Reread which part Glenn? I doesnt sound like it is popping when it is turning off. And do you reckon it woud cause the engine to miss and blow smoke? Let me know what you think. Thanks mateWhat fjh is talking about i alot of V8 mack engines when they were in the 865, 866 models would losen the valve seats which in most cases will get lose when hot. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163309 Share on other sites More sharing options...
skip Posted February 10, 2013 Author Share Posted February 10, 2013 Thanks again guys, I will let you know how it goes when I fire it up tomorrow.Dave Quote Link to comment https://www.bigmacktrucks.com/topic/29860-866-fuel-pump/#findComment-163316 Share on other sites More sharing options...
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