uroboric

...talking about me. first time removing intake manifold on my 86 951 - purpose was to replace cycling valve, which was busted. got everything off ok without stripping any bolts (well i did but not one that mattered), changed the CV and some vacuum lines (the ones connecting to it mainly). reassembled everything without issue, or so i thought. got fuel rail back on and verified firing order for wires - went to start engine. just cranked, so i verified plugs one more time, noticing that i didnt have contact on cylinder 2. made sure all plugs were seated properly, and went to try to start again. this time it sputtered and died. tried to start again. this time i heard an absolutely terrible clunking sound, and the engine abruptly shut off. has the engine seized?

Voith

Hard to tell from that description. Pull the plugs out and slowly turn the crank.

ehall

Did you mess with any belts? Otherwise, it doesn't sound like something that would seize an engine, but Voith is right. We need a LOT more info.

ehall

Also are you suurrre you got the firing order right?

travisgreen

Were you missing any nuts or bolts to finish? Sounds like you may have dropped something I the head

Paulyy

this could be the case.

unlikely the belts are out of place. unless they're really out of place valves will bend enough so the engine can turn over with 0 compression

uroboric

yes i followed the firing order from clarks garage. verified several times ... i dropped one bolt - when i was bolting the IM back on i used the wrong bolts originally in the rear (where the two 5mm hex bolts go), so when backing out to replace i dropped a 10mm bolt down into the depths somewhere, wasnt able to find it. i dont see how it could have gone into the head though as everything else was already bolted back together. unless there is some intake or some port exposed down there that im not aware of...btw no belts were touched.

uroboric

just found this thread - im screwed. same area I was working on when the bolt fell. except I didn't take the head off..

https://rennlist.com/forums/924-931-...ining-nut.html

Eric_Oz_S2

Do you think the bolt dropped into the bellhousing and jammed the flywheel?

uroboric

i don't know man..i don't know how to start diagnosing this really. haven't touched the car since this happened -

Paulyy

Follow these steps.

1. Pull the spark plugs out
2. put a socket on the crank pulley and turn it clock wises.
if it jams up. stop. Then turn it anti clockwise.

you may feel it's the piston if you've gotten a bolt in the cylinder. or you'll hear the bolt if it's in the fly wheel.

black944 turbo

You may want to pull the starter and see if you dropped it in the whole where the speed and ref sensors are.

NM'87 951

I used to have a starting problem that sounded like a sick 'thunk' and turning over just stopped. We haven't fixed everything yet, but when we did our vac lines and got our injectors and rail cleaned and rebuilt we seem to have the problem much much less.

I have a thread on here somewhere i posted a video of the sound for diagnosis help. May be you can find it and it might help answer.

The check of the flywheel would be good too, I just don't think that is as likely.

ehall

You would have to be MEGA unlucky to have that bolt fall into the bell housing hole, unless you were working RIGHT over that area. Could it have, yes, but I bet against it. Do what Paulyy suggested first. My guess is some other reassembly oops. Check fuel lines/damper/FPR. Check the vac lines to those components. Usually, it's something really simple. Check the IC couplings as well. My guess is that you have something loose, rather than a bolt in a hole. Hopefully, anyway.

mahoney944

Extendo magnet time. I recommend a flex one for the head.