996 starting problem

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rid54
Posts: 178
Joined: Mon Oct 13, 2014 8:20 am
Location: Vallentuna, Sweden

Re: 996 starting problem

Post by rid54 » Tue Oct 02, 2018 12:20 pm

Perhaps I missed something, but is there a result from a compression test somewhere? If you are interested in your machine, I suggest you request a bit more details from your mechanic. What you said he told you is far from a proper diagnosis. What valves are worn? If there is indeed only "a wee bit" of blowback, that doesn't suggest serious compression problems to me.

Smooth starting of a cold diesel requires that the injection pump can deliver at its maximum. That requires that the feed pressure (and flow) is adequate. I still wouldn't tear down an engine until all the accessories are checked and deemed to be sound - it is simply to expensive (or too much work) to be considered the first step.

philedge
Posts: 239
Joined: Sun Dec 03, 2006 11:27 am
Location: Chester UK

Re: 996 starting problem

Post by philedge » Tue Oct 02, 2018 7:37 pm

If the engine runs 100% once started but wont start on easystart/ether, are you sure its spinning over fast? I know youve said its got a new battery but theres a host of other things that will slow cranking speed down.

Its hard to understand how an engine can run 100% but have something so badly worn that it wont fire up on ether
'66 880 Selectamatic rat.

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GeoffDEAL
Posts: 434
Joined: Tue Jan 27, 2009 8:25 am
Location: New Zealand

Re: 996 starting problem

Post by GeoffDEAL » Wed Oct 03, 2018 2:09 am

Most likely the lift pump is not working properly and maybe letting fuel back when motor is stopped, try operating manual primer on lift pump to get fuel to injector pump before trying to start and while starting, a lot leak back and then motor is hard to start, lift pump kit or new lift pump and check lift pump pushrod that operates it should be 36mm long and be sure to use the same thickness gasket- pump to engine as if old one was thick and new one thin it will put more pressure on cam and can wear out the cam lobe. Have injectors been pressure tested ? try one out of motor but conected to injector pump to see if injector pump is capeable of a good spray -Dont get in way of the spray can easily penetrate your skin ! if motor runs well when going no real oil use or excessive fumes it is Not getting Fuel to start.

ScottUSA
Posts: 64
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: 996 starting problem

Post by ScottUSA » Wed Oct 03, 2018 6:16 pm

When I first took ownership of my 885 it would not start in cold weather. It cranked at an uneven speed and if it could be coaxed into starting with ether it would miss on one cylinder for many seconds. Once warm it ran fine. Got to thinking about it and checked the valve lash... At 70f degrees there was no clearance on two exhaust valve, the other one was preloaded, that is, the valve was being held open a thousandth or two. Can only imagine how low the cranking compression was in freezing weather! Adjusting the exhaust valves to the correct .010" lash made a big difference.

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