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Failure on Initial Engine Start After Rebuild

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Re: trouble on 1st start

Gadwhite said:
OK pulled valve cover and set to TDC, here is a picture of the valve position for #1 Cyl, both valves closed
View attachment 53023

And the engine with timing markView attachment 53024. I also rotated 180 and here is the valve position at that setting.View attachment 53025
Click to expand...

OK, the second TDC picture looks about right as well. The intake valve should start to open a bit before TDC, and I think that's probably what it's doing. Have you checked that the valve stem to rocker arm clearances aren't too tight?

Also, there have been a lot of discussions in the past about certain electronic ignition modules failing if the 12VDC power is left on them for too long without starting and running the engine. If you have a set of points and a condenser, it might be be worthwhile to fit them for the initial starting, and then re-install the electronic ignition once the engine is running and sorted a bit.

You mentioned using a timing light. It's been my experience - and that of many others - that many of the newer lights (eg Harbor Freight), are very poorly shielded, and the noisy ignition systems on these old cars may cause them to flash erratically so you can't determine what the timing actually is. This is why I suggested setting up the engine by using the Static Timing Method (Google it), which uses a 12v lamp to set the initial distributor position. I don't know if this will work with an electronic ignition system - I've never tried it.

The valve timing is probably OK from what I can see in the pictures. If the valve clearances are OK, set up the ignition system. Ignore the fuel system, and try a puff of starting fluid to see if it will try to start. If that is successful, then move on to the carbs. Good luck. Jim
 
Re: trouble on 1st start

Static timing should be good enough to get it to fire and run even if its rough.
Have you confirmed the firing order ?
Dissconnect and tape off the white wire going to the battery isolation switch .
If you are using points do you have the plastic isolater washer in the correct place , is the distributor grounding out internally ?
 
Re: trouble on 1st start

An easy way to check if you have sufficient spark: Disconnect the high voltage wire from the coil at the distributor. Crank the engine while holding the end of the wire near a ground (like the block or head). Remember, the high voltage is ~ 30,000 volts, so use something to insulate it from you. If the spark will jump at least 3/16", you're good. That checks the coil and primary circuit, but not the timing, rotor, cap or plugs.
 
Re: trouble on 1st start

John Turney said:
An easy way to check if you have sufficient spark: Disconnect the high voltage wire from the coil at the distributor. Crank the engine while holding the end of the wire near a ground (like the block or head). Remember, the high voltage is ~ 30,000 volts, so use something to insulate it from you. If the spark will jump at least 3/16", you're good. That checks the coil and primary circuit, but not the timing, rotor, cap or plugs.
Click to expand...
John thanks will try this tonight
 
Re: trouble on 1st start

John Turney said:
An easy way to check if you have sufficient spark: Disconnect the high voltage wire from the coil at the distributor. Crank the engine while holding the end of the wire near a ground (like the block or head). Remember, the high voltage is ~ 30,000 volts, so use something to insulate it from you. If the spark will jump at least 3/16", you're good. That checks the coil and primary circuit, but not the timing, rotor, cap or plugs.
Click to expand...

Gadwhite said:
John thanks will try this tonight
Click to expand...
Received the email with this link in it today; timely...

https://www.underhoodservice.com/how-not-to-test-a-spark-plug/?eid=284850671&bid=2050472
 
Re: trouble on 1st start

"Also, there have been a lot of discussions in the past about certain electronic ignition modules failing if the 12VDC power is left on them for too long without starting and running the engine."
Trying to sort out my own first start and gave up for a couple of days to let the frustration subside. Left the ignition switch in the on position for two days. Came back and checked the spark timing again and Nothing.
New module arriving in a couple days.
 
Re: trouble on 1st start

Mike Tobin said:
"Also, there have been a lot of discussions in the past about certain electronic ignition modules failing if the 12VDC power is left on them for too long without starting and running the engine."
Trying to sort out my own first start and gave up for a couple of days to let the frustration subside. Left the ignition switch in the on position for two days. Came back and checked the spark timing again and Nothing.
New module arriving in a couple days.
Click to expand...

Dad built a Cobra replica with an MSD ignition. After he passed away, it was several months before I got back down there to start going through stuff. My mom couldn't drive it (and didn't want to, it is a bit of a handful!), so the car had just been sitting under its cover.

The car started right up and ran well, and over the next few days I drove it several times since I had to take it out to get it a new inspection, etc - ANY excuse to drive it, really. During some engine tweaking, I left the key in the "on" position for a couple of minutes. That's all it took to fry the MSD's brain. When we contacted MSD, their reply was basically, "yeah, that will happen sometimes to that model, there's no way to fix it, and here's the P/N of the new, redesigned module that you can buy to replace it". Jim
 
Re: trouble on 1st start

John Turney said:
The test, with 3/16" go/no go number, comes from the Bentley manual [B.3(5)].
Click to expand...
I do seem to have a good spark with it jumping about an inch. The spark does pulse on and off. Is that normal? The color appears to be blue to white spark2.jpgspark1.jpg
 
Re: trouble on 1st start

You have what appears to be a healthy coil, judging by the picture. The fact that it is pulsing probably indicates that the the distributor is triggering it. I assume that's the coil wire in your picture. If it is, plug it back in to the cap and repeat the test with each of the plug wires, and plugs. Are the plugs gapped correctly?
 
Re: trouble on 1st start

OTOH, if you leave the key in the 'run' position in a points-based ignition system--and the points happen to be closed--you can fry a coil. So, in a way, you can think of an Ignitor (I) as a fuse to protect your coil. Probably best just to make sure you turn the key off.
 
Re: trouble on 1st start

Bob_Spidell said:
OTOH, if you leave the key in the 'run' position in a points-based ignition system--and the points happen to be closed--you can fry a coil. So, in a way, you can think of an Ignitor (I) as a fuse to protect your coil. Probably best just to make sure you turn the key off.
Click to expand...

+1! I knew that, BUT, there are lots of shiny objects on engines, and I am easily distracted...:eek:
 
Re: trouble on 1st start

Jim 58 BN6 said:
You have what appears to be a healthy coil, judging by the picture. The fact that it is pulsing probably indicates that the the distributor is triggering it. I assume that's the coil wire in your picture. If it is, plug it back in to the cap and repeat the test with each of the plug wires, and plugs. Are the plugs gapped correctly?
Click to expand...
Plugs are gapped correctly at .025, I actually pulled and checked them, last night to check compression (94,95,93, 90,90,90). I do get a blue spark at each plug.
 
Re: trouble on 1st start

Ah, those compression numbers, "(94,95,93, 90,90,90)", indicate a problem. If this is a freshly rebuilt engine I would expect 130's unless you're at altitude. Typically rings, valves or head gasket.
 
Re: trouble on 1st start

Jim 58 BN6 said:
Did you have the throttles open when you checked the compression?
Click to expand...
, Yep throttles open, and yes this is fresh rebuild. one note Exhaust for cylinders 1-3 has a large hole just after headers. I can try some oil in the cylinders to eliminate the rings.
 
Re: trouble on 1st start

Since the engine hasn't been run, the rings won't be seated and compression will be lower until they do. Cam grind and timing will also affect compression.

If the spark is jumping about an inch, that's good. Getting spark at the plugs is also good. Next, take off the cap, put the end of the coil wire near the center of the rotor and turn the engine over. Make sure the spark isn't jumping to something inside the distributor. I had that happen on mine.
 
Re: trouble on 1st start

I'd go with Vette's suggestion. Put the points back in and static time it. Seems like you've got spark, fuel and compression but everything's not arriving at the right time for it to fire off. Some of the timing lights, particularly the dial backs, don't play well with electronic ignition, that's why I'm suggesting a static time. It's easy and will get you running if you are in the ballpark. I'd take out the electronic ignition just because you've tried everything else and nothing else has worked. They do fail and why not eliminate it for now as a fail point" Otherwise:

Picture3.jpg
 
Re: trouble on 1st start

Gadwhite,

John is right about ring seating, plus a lot of builders deliberately assemble the pistons/rings 'dry' for better ring seating on start-up.
He is also right that the cam grind will affect compression readings - a radical cam with long overlaps will generate a lot less cranking compression than a 'stock' cam grind.
​
​
The compression will get better after running but
those numbers are low and may be taking us back to the question of valve timing.
​
May be it's time to talk to the builder? Did he/she degree the cam or just count chain links?

Or, borrow a degree wheel from the builder and do some utube searching and degree the cam yourself.
Unfortunately you will need to raise the front of the engine to get the damper off, but it can be done in situ.

I like Jon Robbins credo - "do it all yourself, you will be glad you did".
My own mantra is "the only way to guarantee failure is to not try."​

Dave
​
 
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