240Z WILL NOT run right

[Zed Head]

12 minutes ago, BoldUlysses said:

Is there a way to be absolutely sure the engine is exactly at TDC without pulling the head

Piston stops in the plug holes.  Rotate backward and forward and mark each spot.  TDC is halfway between.

Moght as well check the notch and groove.  Put the groove over the notch and that should be within a few degrees of TDC.  Your cam sprocket seems off in the picture.

https://www.oreillyauto.com/detail/c/comp-cams/comp-cams-piston-top-dead-center-locator-tool/com0/4795

Edited September 2 by Zed Head
nothc

[ollie]

Finally, here is the label off the o rings behind the fuel pump reed valves.  

Are you still running points?

[siteunseen]

Make sure your float bowl lids have good gaskets and are tightened down good

[BoldUlysses]

On 9/2/2024 at 3:28 PM, Zed Head said:

Might as well check the notch and groove.  Put the groove over the notch and that should be within a few degrees of TDC.  Your cam sprocket seems off in the picture.

The picture was taken right after I removed the cam cover, before I rotated the crank to TDC.  Here's the notch & groove:

18 hours ago, ollie said:

Finally, here is the label off the o rings behind the fuel pump reed valves.  

Are you still running points?

Thanks for the o-ring PN.

No, I have a Pertronix kit installed.

20 minutes ago, siteunseen said:

Make sure your float bowl lids have good gaskets and are tightened down good

They are.  I baselined the float height (21mm front, 19mm rear) just last week.  Gaskets are intact, lids snugged down.

[Zed Head]

If that's the notch it does look like you have problems.  Rotating it to get it aligned would make your damper marks even farther off the pointer.

Looks like a bad damper.  How about a picture of the face of it?  That second pulley has seen some weather.  Looks very old.  Don't be afraid to really give it a tug to try to pull it apart.  It's supposed to be very firmly bound.

[BoldUlysses]

53 minutes ago, Zed Head said:

Looks like a bad damper.  How about a picture of the face of it?  That second pulley has seen some weather.  Looks very old.  Don't be afraid to really give it a tug to try to pull it apart.  It's supposed to be very firmly bound.

Here's the face.  A pic of the back of it can be seen earlier in the thread.  95% sure it's original.

The A/C (front-most) pulley came off easily when I removed the crank bolt.  The harmonic damper itself has two belt grooves (middle one for air pump and rear one for WP & alternator) and I don't see an obvious parting line between them.

I was hoping someone with an extra (known-good) damper lying around could tell me if the timing marks are in the right ballpark relative to the keyway based on the picture of the back.

Does anyone have a source for a replacement?  The usual suspects seem to be out of them.

 

[Zed Head]

I found an ad for a "Euro" damper and it looks like yours.  Don't know how it's different from State-side.  I'll look a little more.

https://datnissparts.com/x-euro-crankshaft-damper-pulley-harmonic-balancer-240z-260z-280z-510-all-l-engines-12303-e4100/

Spun the picture in Paint 3D.

Yours

[Patcon]

It's hard to tell without a close up but it looks to have a sheared line in the rubber going around

[Zed Head]

I found another that doesn't say Euro.  It looks about the same.  Not sure what's going on here.  I'd probably take the time to verify TDC and mark it on the damper pulley.  Then use a dial-back light to set timing.

https://maseraticompound.com/products/datsun-240z-main-crank-shaft-pulley-with-extra-ac-belt-pulley

[Zed Head]

It was fun looking around at the different dampers out there on the internet.  Seems like your damper is fine.  I'd rotate the engine around twice by hand and put that bottom/left side mark on the pointer.  Then see how the cam sprocket lines up.

If you use the cam sprocket to turn the engine make sure that you turn it backward before checking your marks.  So that the slack is removed from the tight side of the chain.  That might explain some of the discrepancy in your notch and groove.

Ideally, everything is assembled and the engine is turned clockwise via the crankshaft bolt, or the fan belt, looking at it from the front, to keep the tight side of the chain tight.  Assume that the TDC/zero mark is the farthest to the left, looking from the front.

 

Edited September 4 by Zed Head

[BoldUlysses]

Yeah based on the pics you found, I think my damper is OK.  I've been using the bolt loosely threaded onto the nose of the crank to turn the engine clockwise only, not the cam sprocket.

I found my old rinky-dink fuel pump; going to put that on and see if it makes a difference with the fuel pressure issue.

I didn't replace that pump with my rebuilt OEM one because it broke, but because I like the look of the OEM one more.  So the pump above is still functional.

So, to recap, I'm chasing two issues:

1. Car dies after 15-20 minutes and won't start
2. Very poor running (hunting idle, backfiring under light load, etc)

The car ran like garbage when I installed the auxiliary tank over the weekend, but it didn't actually die on me, even after running for 20+ minutes.  So that means either 1) I've got a restriction in the fuel delivery or 2) the fuel pump output is marginal.  Maybe both.  Going to try to eliminate 2) by installing the old pump and see if it runs better.

 

[Zed Head]

I think that your cam timing might be off by a tooth.  If you're careful you can get it right without removing the front cover.  You'll need a chain holding tool.  Not sure how it would get off a tooth except for previous misassembly or radical chain wear.

Also, I think that you can get a really close estimate of TDC using the damper key keyway in the crankshaft.  The keyway should be aligned with the top of the block.  Since you have the damper off it should be doable.  Don't forget that the engine is tilted so up and down are askew.

All timing events are relative to the crankshaft and its pistons.