Dwell Angle, Timing, and CHT sensor questions, Timing way off (well above 27 Deg) but runs...??? Options

[NJ914]

Looking for inputs from those who know...

Situation: Engine runs but timing is way off. 27 degrees is at 1800rpm[b]. 3500rpm is in the mid to upper 30's. When attempting to adjust the distributor to spec, engine dies. Only runs at higher timing angle. Not sure what the cause is.

1: Distributor gap is currently at 0.018" and dwell is 50-51 degrees through speed range.
Per the Haynes book, 1 degree of dwell can change the timing by 3 degrees.
Spec is 44 to 50 degrees.

Is this correct?

If I open the gap larger to bring the dwell down to 44 degrees, will this help bring the timing closer to spec?

2: Measured the CHT sensor cold and it was 3100 ohms. I believe it is supposed to be more in the 2000 - 2500 ohm range...?

What is the correct range for the CHT sensor cold?

It is supposed to drop below 100 ohms when up to temp. Is this correct?

Could the higher than spec resistance of the CHT sensor be contributing to the timing issue?

[StarBear]

1. Dwell Looks right on. Sure you have light on the #1 plug? AMHIK; done that. Also, I keep missing the dwell as I keep forgetting to turn the analyzer knob to the correct scale. Old school.
2. There’s a really good cht chart posted elsewhere. I’ll see if I can find it.
Otherwise, will be glad to pop on down to B’ville to fiddle with it with you.

[914sgofast2]

I suggest taking the dizzy out of the engine and disassembling and cleaning the mechanical advance weights and the points mounting plates. Sounds like things are not moving as freely as they should if the timing is getting stuck. I would first check that the screws holding down the points are not too long and are hitting the lower plate, and thereby binding up the advance mechanism. I would also check the screw holding the condenser to the dizzy to make sure it is not interfering with the movement of the plates and the arm of the vacuum advance unit as well. The CHT sensor won't affect timing at all; it only affects the fuel mixture. The point dwell you have seems close enough to spec that it should not cause the timing issues you are describing. Lastly, make sure the dizzzy is being held tightly in the engine by the clamp down bracket.

[NJ914]

1. Dwell Looks right on. Sure you have light on the #1 plug? AMHIK; done that. Also, I keep missing the dwell as I keep forgetting to turn the analyzer knob to the correct scale. Old school.
2. There’s a really good cht chart posted elsewhere. I’ll see if I can find it.
Otherwise, will be glad to pop on down to B’ville to fiddle with it with you.

Many thanks. Any chart/info would be helpful.
Would welcome your help if you feel like making the drive to B'ville.

[NJ914]

I suggest taking the dizzy out of the engine and disassembling and cleaning the mechanical advance weights and the points mounting plates. Sounds like things are not moving as freely as they should if the timing is getting stuck. I would first check that the screws holding down the points are not too long and are hitting the lower plate, and thereby binding up the advance mechanism. I would also check the screw holding the condenser to the dizzy to make sure it is not interfering with the movement of the plates and the arm of the vacuum advance unit as well. The CHT sensor won't affect timing at all; it only affects the fuel mixture. The point dwell you have seems close enough to spec that it should not cause the timing issues you are describing. Lastly, make sure the dizzzy is being held tightly in the engine by the clamp down bracket.

Thanks for the suggestions and will look into them this week!!

[StarBear]

Here is one of many threads on the CHT temp curve:
http://www.914world.com/bbs2/index.php?sho...351065&st=0
See also pic:

[NJ914]

With some help from @Starbear this past weekend, all new spark plugs, wires, and rebuilt distributor were installed to see if that solved the problem. Unfortunately, no!! (IMG:style_emoticons/default/mad.gif)

The engine will only start/run when the timing is advanced to 27 degrees at 1800rpm and will only run when cold.

Once it warms up, it dies...

Could incorrectly adjusted valves cause this issue?

Has anyone had this issue before?

I did check the MPS and it holds vacuum and both resistance readings are good.
Again temp sensor is a little high on cold resistance and will check to see what it drops to next time I run the engine. Cold start valve is open cold and closes. All vacuum hoses are new and in correct positions. New fuel injection wiring from Jeff B installed (issue was there before and after wiring replacement).

914 Gurus please help!!!

[Geezer914]

Sounds like the cam timing is off. Is this an original engine or has it been rebuilt? Is the distributor properly aligned at top dead center?

[NJ914]

Sounds like the cam timing is off. Is this an original engine or has it been rebuilt? Is the distributor properly aligned at top dead center?

Engine was rebuilt back in the late 1990's. New Cam was installed at that time. Engine ran without issue until a few years ago when it was removed to correct oil leaks. The valve cover and pushrod tube seals were replaced so I'm thinking the valves were not set correctly or were set with the pistons not 100% at TDC...?

Would setting the valve clearance with the pistons slightly off TDC cause this problem?

[914_teener]

It is not necessary to remove the engine to replace the pushrod tube seals and valve cover gaskets. Difficult to the novice but not necessary.

However...it is necessary to remove the rocker shafts to replace the push rod tubes and if not done correctly and not adjusted correctly....could screw up the valves. HOWEVER....if off by that much or if done incorrectly to affect the timing... you would defiantly know it either audibly or by inspecting and measuring the valve lash.

Should not affect the gear timing unless you didn't know the car or the "New Cam" is one that doesnt' work very well with the stock FI.

"New Cam"...interesting spelling.

[VaccaRabite]

I suspect you have a configuration error.

What are the results from a compression test? (this will tell if your valves are so misadjusted that they stay open a touch) My guess is that you will have little to no compression, with gaps opening further as the engine heats up. Anyway ,its a theory. The engine needs the extra advance to get going when cold, but then the small leaks become larger leaks that more advance cant fix and the engine dies.

Have you ever adjusted your valves?

Zach

[Dave_Darling]

See if you can compare the marks on the fan to the marks on the flywheel.

--DD

[emerygt350]

Yeah, verify tdc first but I don't think you are a mile off of where you should be at almost 2k rpm. How is it running? Bad or good? Does it try to start when warm?

[GregAmy]

See if you can compare the marks on the fan to the marks on the flywheel.

Where I was going, but decided to let this horse ride.

@Superhawk996 you know wut I'm sayin'...

[Superhawk996]

See if you can compare the marks on the fan to the marks on the flywheel.

Where I was going, but decided to let this horse ride.

@Superhawk996 you know wut I'm sayin'...

(IMG:style_emoticons/default/happy11.gif)

@GregAmy

[NJ914]

I suspect you have a configuration error.

What are the results from a compression test? (this will tell if your valves are so misadjusted that they stay open a touch) My guess is that you will have little to no compression, with gaps opening further as the engine heats up. Anyway ,its a theory. The engine needs the extra advance to get going when cold, but then the small leaks become larger leaks that more advance cant fix and the engine dies.

Have you ever adjusted your valves?

Zach

Yes I have and I'm starting to think that I did it with the pistons slightly off TDC. Your theory sounds plausible. Have not done a compression test. Most likely will jump in and check the valves again and make sure I'm at TDC. Thanks for the inputs!!

[NJ914]

See if you can compare the marks on the fan to the marks on the flywheel.

--DD

Only one mark on the fan which is at 27 degrees...

[VaccaRabite]

See if you can compare the marks on the fan to the marks on the flywheel.

--DD

Only one mark on the fan which is at 27 degrees...

Put cylinder 1 at TDC. BE SURE IT'S AT TDC! Remember that a 4 stroke engine has two full revolutions of the flywheel for every 1 firing event. So you can think you are at TDC, but actually be 180* off.

Anyway, get to true TDC for CYL 1, and mark that with a paint pen through the inspection / timing hole in the doghouse.

You know you are at TDC for Cyl 1 when the piston is at the top of its stroke AND both valves are closed for that cylinder. Tht how you know and are SURE. Since you want to do the valves anyway, you will already have the covers off. I am not usually an advocate of going to TDC for valves, but this is a time when using the Krusty method isn't what you want to do.
This WILL NOT help you if your cam somehow got indexed incorrectly to the cam gear. That is the absolute worst case scenario though. Try everything else before tearing the engine down. It would be a huge bummer to pull the cam and realize that it was correct to begin with.

Zach

[GregAmy]

(IMG:style_emoticons/default/agree.gif)

Where I was going with this...you have not yet verified that the timing mark on the fan is in the actual correct position or is the correct one. You could be looking at the wrong mark, or (sorry, I can't resist) the fan hub has spun on the crankshaft.

On my 2L - what engine is yours? - I have a notch on the flyhweel at #1 TDC that's visible from an access hole at the top of the transaxle; you might have to push the sheet metal back to see it. Compare that mark to the fan marks, see if they agree.

http://www.914world.com/bbs2/index.php?showtopic=339759
http://www.914world.com/bbs2/index.php?showtopic=342133
http://www.914world.com/bbs2/uploads/post-...-1565184944.jpg

And rechecking proper valve clearance is easy enough.

http://www.914world.com/bbs2/index.php?showtopic=28758

I can't see how the cam was mis-dialed-in and yet "[e]ngine ran without issue until a few years ago when it was removed to correct oil leaks." So I think it's something simplier. - GA

[NJ914]

(IMG:style_emoticons/default/agree.gif)

Where I was going with this...you have not yet verified that the timing mark on the fan is in the actual correct position or is the correct one. You could be looking at the wrong mark, or (sorry, I can't resist) the fan hub has spun on the crankshaft.

On my 2L - what engine is yours? - I have a notch on the flyhweel at #1 TDC that's visible from an access hole at the top of the transaxle; you might have to push the sheet metal back to see it. Compare that mark to the fan marks, see if they agree.

http://www.914world.com/bbs2/index.php?showtopic=339759
http://www.914world.com/bbs2/index.php?showtopic=342133
http://www.914world.com/bbs2/uploads/post-...-1565184944.jpg

And rechecking proper valve clearance is easy enough.

http://www.914world.com/bbs2/index.php?showtopic=28758

I can't see how the cam was mis-dialed-in and yet "[e]ngine ran without issue until a few years ago when it was removed to correct oil leaks." So I think it's something simplier. - GA

Since the fan only has one mark, I was not using it for reference. I use three references.

1: The distributor rotor is pointing toward the #1 plug wire in the cap.
2: The notch in the Flywheel is at the 12 o'clock position.
3: Remove the #1 spark plug and confirm the piston is at the top.

Does this sound like I have it covered?