3.2 rebuilt motor won't turn
 

This is my first rebuild of an 87 911 with a mechanic who did most of the engine work before I got involved. Supposedly, the motor has been rebuilt with 3.2 " Euro compression" Pistons, a Webcam re grind of the cam to "993 Super sport" specs, Clewitt PMO's/ITB with an Electromotive ECU. We reprogrammed the ECU for better run characteristics and the car behaved OK For a few days but then had intermittent starting trouble. It s even hard to physically turn the motor over as it feels "tight." As an air cooled engine newbie I am stumped.

Any thoughts/suggestions?

Doesn't sound good. But it could be something simple too.

I suggest you do two things first. Drain the oil and open up the oil filter. Remove the plug in the bottom of the case as well. Hopefully it clean oil. Trash in the oil, forget about what from, the engine needs to come apart.

Remove the spark plugs and look at the plugs for signs of detonation. This should make the engine turn over easier. You can then do a leak down and see if you have a piston/cylinder issue. Typically if you have lost side clearance, the leak down with show air escaping past the rings and out through the breather. If you have a borescope you can check the cylinder too before you do the leak down.

Good luck. Hope its something simple and not the engine.

Thank you. Very helpful. I hope to have some news this week...
Since I only have a few hundred miles on the rebuilt motor if it is something serious i will be going back to the Cali shop for $.

Keep us updated on what you find.

Feels tight... I would check how many ft/lbs are required to turn it by the flywheel to quantify just exactly how tight. Pull your plugs out and get that ft/lbs value too.


CCA battery check/starter check next.
End with cold start tuning.

Standalone tuning can be tricky for start up tuning. If you have your ignition timing set incorrectly for cranking then the engine can start sluggishly and feel like it's fighting back against the starter. For tuners, talk is cheap and it's easier to blame the hardware than look at the tune settings... Careful there, might be time for a second opinion on the timing/ECU setup.

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Will get those value today I hope. At this point all I get is a click when we try and start the motor, including when we wire the new starter directly to the battery. Confusing to a newbie like me as the motor sounded good when we had it running, no stumbling, smooth idle, pulled well through the rev band. Will pull the plugs as well and see what we find.

Feels tight when cranking? Stop. As suggested, remove the plugs and attempt to rotate the crank pulley by hand. If still "tight" (a variable opinion), perform further inspection. Something isn't right. Could be raw fuel in one or more cylinders or .....?

Take it back to the person who rebuilt the engine and ask for their assistance.

Sherwood

Seized engines don't normally go "click" when you hit the starter. They usually give you a pretty loud "THUNK!" Starters have enough power to turn over the nastiest high compression engine.

Is there any chance that it's a poor ground cable at the front trans mount? Or at the battery? Does the battery test good? Turn on the headlights and see if they dim when you hit the starter. If they go dark, it's a bad battery or bad connection somewhere.

Update
 

We found a decomposing ground cable to the trans as some of you suspected. Replaced that and she fired right up! Then a few hours later would not start again!! Ugh. BTW, motor did turn with plugs out so feeling better about that. Generally, the wiring throughout the car is a mess so pretty confident we still have an electrical/grounding issue to find. Thanks for the help.

Update #2
 

Based on tests done with new starter and “outside cables we believe the culprit is the power cable running from the batter to the starter.

http://forums.pelicanparts.com/uploa...1561491556.jpg

While the ends look fine, after 30+ years and multiple owners something is amiss between the two ends so we are planning on replacing that cable. Ugh.

With both ends unplugged, you can try a quick and easy continuity check. You should be able to touch one end (of the cable) with a meter and another to the chassis, if you get something other than 'infinity' (an open), you might have a short.

Check the B+ cable at the battery for corrosion just under the insulation right at the battery terminal. That was common. The cheap fix was to replace the battery cable terminal after cleaning off the corrosion from the cable with Coca-cola in a cup (I kid you not).

For the amount of work to R&R that cable, suggest confirming it is indeed the cable and not loose/corroded terminals. Conduct a voltage drop test to confirm. This is a good video describing the process:

https://www.youtube.com/watch?v=WMXENKujYtc

Sherwood

Nothing personal, but I bet I can test voltage drop on that battery cable faster than you can R&R it. However, if replacing good parts with new parts is already in the plans, go for it.

Already cleaned terminals everywhere, replaced all grounds. But there is no power coming from the old positive cable. Using a new positive lead the starter turns freely so process of elimination points us to replacing the old cable.

There really is no way that the starter cable can be an "open" except at the swaged on ends. It can't break somewhere, and if the insulation wore through so it was grounded you'd have a fire, or at least some sheet metal welded or cut as with a torch. So the problem pretty much has to be at the ends, and the battery end is the usual suspect. Acid or something gets in there, and corrosion forms an insulating layer between the part which attaches to the battery and the copper wires. I think the repair is to cut off the connector (saving as much cable as you can, and then try to clean the bare wire until it al is a nice copper color, including the inner strands as far in as they are discolored. Then use a clamp on connector (unless you just happen to have a swaging tool for this diameter cable).

But of course a new cable (should - there is such a thing as manufacturer's defects) will do the job.