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Eureka! [sort of...]

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tosoutherncars

tosoutherncars

Jedi Knight
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OK, so I've been chasing down a heavy miss / stumble. For those who haven't been following along up until now, the car is:

1500
9:1 compression (approx.)
electric fan
Weber DGV / Carter elec. fuel pump
Pertronix optical / Crane XR700

Recent 'light' rebuild - valve stem seals, lapped valves, mild porting, head gasket, rings & rod bearings.

Now, since I put everything back together, I've had a bad stumble. At first I thought it was the dreaded DGV dead spot, but it was missing throughout the rev range and in all conditions.

I had (have?) no idea what the cause could be, but some of my main suspects were / are...

- coil, wires, rotor, cap
- Fireball XR700
- bad cam lobe
- stuck valve
- bad juju, no mojo

Have replaced the coil as a matter of course, since it was an old one I scavenged off my old VW.

Now this morning, after messing with timing, mixture, all sorts of other unrelated things... I put a spark plug test light inline with one of the wires.

flash flash flash flash _____ flash flash _____ flash flash flash _____ flash flash _____ flash _____

<span style="font-weight: bold">Ah - HAH!!</span>

Checked, and the miss is across all cylinders.

<span style="font-weight: bold">Now, how do I start hunting this down? </span> I popped the cap, and the optical trigger still looks like it's set up correctly.

What's next?
 
Oh... and I do have a brand new dizzy (w. points) from the previous owner. If I want to swap that back in, to confirm it's the pickup / XR700, what do I need to connect? Just the plugs, coil and... what's the little wire on the side, HT lead? My memory is going...
 
Change the Rotor.

Change the Dizzy cap.

Change the condencer.

One at a time please and report. LOL
 
- I don't have a condenser do I, with the points system gone?

- I don't have a spare rotor, so that will be next.

- Distributor cap to follow.
 
Okies, my bad, no condencer. Worth a try, in worse case you will have a couple of cheep spares in your box.

Keep us posted, we will overcome.
 
First, try a replacement coil HT wire. Then mebbe th' rotor.
 
Aye, can only be HT wire, roter, cap, or coil unless the electronics for the dizzy are bad. Nice call doc.
 
Coil HT wire? The coil has... two wires going to the XR700, one for the tach, two leading to the ballast.

https://www.cranecams.com/pdf/90002000a.pdf

Pic attached... So no HT lead, right? Leaving coil (checked) cap or rotor, or XR700?
 

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ummm... Duncan, th' "HT" wire is th' BIG FAT one to th' centre of th' cap, lad. "High Tension"
 
Aaaaaaaah. As in, comes with spark plug wires? Gotcha. I have three, and I believe the stutter is present with all three. Will double-check tho.
 
Doc, seems like it just may be one of those bad roters that folks been talking about?
 
That was #2 on my "WAG" list.
 
Which wire do you have running to the coil (+) terminal? There are several to choose from on a 1500 retrofit. One is a white wire with a green stripe. This wire connects to a loooooong wire that is buried in the harness. The long wire acts as a built in ballast for the coil. So if you had the white/green wire running into an external ballast and then into your coil, you could be starving your sparky box for juice.

Just one a them wild guess things.

Here's another... is your fuel pump still running off of the ignition circuit? That could be creating some "noise" or draw down in the line that is making Mr. Sparky unhappy.
 
Morris said:
Which wire do you have running to the coil (+) terminal? There are several to choose from on a 1500 retrofit. One is a white wire with a green stripe. This wire connects to a loooooong wire that is buried in the harness. The long wire acts as a built in ballast for the coil. So if you had the white/green wire running into an external ballast and then into your coil, you could be starving your sparky box for juice.
Click to expand...

I believe the two wires feeding into the ballast are white and white / grn. I'll check in the light of day.

Morris said:
Here's another... is your fuel pump still running off of the ignition circuit? That could be creating some "noise" or draw down in the line that is making Mr. Sparky unhappy.
Click to expand...

Guilty as charged... I'll jump the pump power straight from the main (+) block, and see if that makes any difference.

Order of operations, then...

- make sure stutter is present using all HT leads, aka cap to coil spark plug wire-lookin' thing.

- call around, find cap & rotor.

- move fuel pump power to better location

- check ballast wiring
 
Thoughts...

I think, in troubleshooting, I *may* have swapped in a known faulty cap. Don't ask me why I kept it, I don't know. Have already swapped newer cap back in, will see what that yields in the morning.

Found a new set of Bosch wires. If cap alone does not fix stumble, will swap those out, and hunt down a new rotor.



BUT... Drove home in the pouring rain today, and the car started to run as though on only three cylinders. (Maybe two!) The RED light in the dash came on, stayed on (even when the car was shut down) and the car is now deader than a dodo.

Truth be told, the red light has been very, very faintly glowing for some time.

Am I right in remembering a) that it's the Alt / charging light, and that b) the new fan and fuel pump have succeeded in cooking the old Lucas? Time for me to explore the Delco swap?

And... (pure fantasy time) if the system was running down, any chance that's what's causing a miss?

Wet & dark out there now. Will investigate further in the morning.
 
If ya have a "glowing" light, the alternator is HIGHLY suspect.
 
Groovy... well, looks like this weekend is AC Delco alternator swap, cap / rotor, re-wire, re-time, re-set mixture and see if the danged thing will work!

Brother's wedding in two weeks, don't know if they're using the Midget for their 'Just Married' departure... but I'd like it to be ready just in case!
 
I would not go buying parts until you get the charging situ fixed. Could be all thats wrong . Voltage got low enough to to be at the threshold of the crane system thus the miss and now no spark. Try charging the batt with the cables disconnected, check that the volts are up close to 12 and then reconnect and see if it starts. If it does somthing a miss in the charging. Not the ignition, regulator maybe? Bad post connection to battery, fuse panel power ground cable ahh yes endless opertunitys.
 
Chris,

I'm normally not a big fan of just throwing parts at a problem, either. With the addition of an electric rad fan and an electric fuel pump, I'm sure I've overreached the capacity of the poor old alternator (30A?) which looks like the original! The battery is new, so I can rule that out as a cause.

So yes, the battery is off & charging as we speak. I'll upgrade the alt. and go from there!
 
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