71' GTV 1750 spark plug wire order - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 15 (permalink) Old 07-13-2019, 06:40 PM Thread Starter
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71' GTV 1750 spark plug wire order

I know there are plenty of threads on this already but the answers are not as clear as I'd hoped and to someone who is fairly new at working on older cars I was hoping for a more detailed step by step.

So I was checking spark plug wires for resistance as I'm refreshing the ignition system on my 71 gtv and I'm not clear on the order of what plugs from the distributor to what cylinders on the engine. If I understand correctly, cyl 1 to 4 is from radiator to windshield #1 being closest to the rad. The distributor cap is has raised numbers molded into the plastic 1,3,4,2 clockwise with when looking at it from over the passenger side fender.

Firing order is 1,3,4,2 so I need to connect plug wires:
cyl 1 (front near rad) to #1 on the dizzy
cyl 2 wire to #3 on dizzy
cyl 3 to #4 on dizzy
cyl 4 (closest to firewall / windshield) to #2 on dizzy.

Is this correct. I read its possible for the assembly to be 180 degrees around so if thats the case what does the plug wire set up become from cylinder to distributor? I tried what I thought was 1,3,4,2 but it cranked for a bit then popped a loud backfire, I knew something had to be off.

Thanks.
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post #2 of 15 (permalink) Old 07-13-2019, 07:01 PM
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You're overthinking this, 1 to cyl 1, 2 to cyl 2, 3 to cyl 3 4 to 4

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post #3 of 15 (permalink) Old 07-13-2019, 07:06 PM Thread Starter
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Blue is towards firewall / windshield

Red is towards radiator

Photo is taken as level horizontally as possible looking over the passenger side fender.

Not sure if this helps at all to determine if things are installed 180 deg off. Cap has a slot in it so that only goes on one way and rotor is a flat round disk marelli rotor that has 1 square peg and one round peg so that also only goes on 1 way.
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post #4 of 15 (permalink) Old 07-13-2019, 07:09 PM Thread Starter
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Originally Posted by VabeneGTV View Post
You're overthinking this, 1 to cyl 1, 2 to cyl 2, 3 to cyl 3 4 to 4
I also tried that and it starts but is hesitant to rev and sounds as if its running on 3 of 4 cylinders. My initial toughts not knowing distributors was exactly as you said 1 to 1, 2 to 2 etc but then a search of "firing order alfabb" and it seems that the plug wires don't just got in simple order of 1,2,3,4. That's why I felt I needed to ask my own thread because I was getting a little confused and wanted to be sure.
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post #5 of 15 (permalink) Old 07-13-2019, 09:21 PM
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Originally Posted by AlexBassila View Post
If I understand correctly, cyl 1 to 4 is from radiator to windshield #1 being closest to the rad.
Yes, that's correct

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The distributor cap is has raised numbers molded into the plastic 1,3,4,2 clockwise with when looking at it from over the passenger side fender.
Yes, and that's the firing order (1, 3, 4, 2).

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it starts but is hesitant to rev and sounds as if its running on 3 of 4 cylinders.
One thing you haven't told us: Has the distributor been disturbed since you removed the wires?

- If it has been removed or rotated relative to the timing cover, you'll need to use a timing light to adjust it back to the correct orientation.

- If it hasn't been removed/rotated, you may have a situation where the distributor is off from the original orientation. Remove the cap and note where the rotor is pointing when the timing mark on the crankshaft pulley is at the "F" position AND both #1 valves are closed. You'll need to pull the #1 sparkplug and peer down into the combustion chamber to verify that both valves are closed. If #1 intake valve is open, then ignore the numbers on the distributor cap, hook the wire to #4 sparkplug to the distributor terminal where the rotor is pointing, and connect the other wires to the distributor terminals to preserve the 1-3-4-2 order as the rotor rotates clockwise. (and yes, this is confusing)

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'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

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post #6 of 15 (permalink) Old 07-14-2019, 09:54 AM Thread Starter
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Originally Posted by Alfajay View Post
One thing you haven't told us: Has the distributor been disturbed since you removed the wires?

- If it has been removed or rotated relative to the timing cover, you'll need to use a timing light to adjust it back to the correct orientation.

- If it hasn't been removed/rotated, you may have a situation where the distributor is off from the original orientation. Remove the cap and note where the rotor is pointing when the timing mark on the crankshaft pulley is at the "F" position AND both #1 valves are closed. You'll need to pull the #1 sparkplug and peer down into the combustion chamber to verify that both valves are closed. If #1 intake valve is open, then ignore the numbers on the distributor cap, hook the wire to #4 sparkplug to the distributor terminal where the rotor is pointing, and connect the other wires to the distributor terminals to preserve the 1-3-4-2 order as the rotor rotates clockwise. (and yes, this is confusing)
Nothing on the distributor has been removed or put back in a different orientation. I removed the cap and the rotor to inspect and put them back as they were. The car ran last year although I should have payed more attention to which plus went where before removing and testing them.

Do you agree with the above post of connecting 1 to 1, 2 to 2, 3 to 3, 4 to 4(cyl to distributor) Or should the wires go like this:

cyl 1 (front near rad) to #1 on the dizzy
cyl 2 wire to #3 on dizzy
cyl 3 to #4 on dizzy
cyl 4 (closest to firewall / windshield) to #2 on dizzy.
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post #7 of 15 (permalink) Old 07-14-2019, 11:46 AM
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The numbers on the cap go in this order, 1-3-4-2, the distributor turns clockwise, the rotor hits number 1 post, moves on to number 3 post, then number 4 post on the cap, finally number 2, which is the firing order. That's why 1 goes to 1, 3 to 3, 4 to 4 and 2 to 2. By connecting the leads the way you are doing you are firing cylinder 2, when you need to be firing number 3, again you are over thinking this, the numbers are there for a reason.

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post #8 of 15 (permalink) Old 07-14-2019, 11:50 AM Thread Starter
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Originally Posted by VabeneGTV View Post
The numbers on the cap go in this order, 1-3-4-2, the distributor turns clockwise, the rotor hits number 1 post, moves on to number 3 post, then number 4 post on the cap, finally number 2, which is the firing order. That's why 1 goes to 1, 3 to 3, 4 to 4 and 2 to 2. By connecting the leads the way you are doing you are firing cylinder 2, when you need to be firing number 3, again you are over thinking this, the numbers are there for a reason.
Ok, thanks, I will try again.
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post #9 of 15 (permalink) Old 07-14-2019, 02:59 PM
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Do you agree with the above post of connecting 1 to 1, 2 to 2, 3 to 3, 4 to 4(cyl to distributor)
Sorry, but it just isn't that simple. Spark plug #1 needs to go to the distributor terminal that the rotor is pointing toward when cylinder #1 is at TDC on the firing stroke (I explain how to verify this in post #5).

In an ideal world, yes, the numbers on the distributor cap will correspond to the spark plug / cylinder numbers. So if your wires aren't that way now, hook them up that way, and see if it runs OK. If so, you're done. If not, you won't have hurt anything.

But if it doesn't run OK with 1 to 1, 2 to 2, etc., then someone has installed the distributor 180 off, or the oil pump ??? off, and you'll need to figure out where the rotor points at #1 TDC.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

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post #10 of 15 (permalink) Old 07-14-2019, 06:13 PM Thread Starter
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Originally Posted by Alfajay View Post
Sorry, but it just isn't that simple. Spark plug #1 needs to go to the distributor terminal that the rotor is pointing toward when cylinder #1 is at TDC on the firing stroke (I explain how to verify this in post #5).

In an ideal world, yes, the numbers on the distributor cap will correspond to the spark plug / cylinder numbers. So if your wires aren't that way now, hook them up that way, and see if it runs OK. If so, you're done. If not, you won't have hurt anything.

But if it doesn't run OK with 1 to 1, 2 to 2, etc., then someone has installed the distributor 180 off, or the oil pump ??? off, and you'll need to figure out where the rotor points at #1 TDC.
OK so something is certainly not correct. Just to list what was done recently:

-changed oil and oil filter
-NKG iridum plugs
-cleaned rotor and cap contacts with deoxit
-put plug wires back on in order 1to1, 2to2 etc

car will not start and just backfires out the exhaust. I've never messed with the ignition system other than pulling the plug wires to test resistance and clean the contacts in the cap. Can I get to tdc by jacking up the rear end and rotating one of the rear tires (car is currently in a garage not much space to roll forward or back in 5th). If I forgot to mention in my main post the car has a bosch blue coil and marelli distributor, webber 40dcoe's. I don't have another known good coil to swap in as my other spider has a marelli plex system and last time I started it prior to pulling the plug wires and oil change, it started but needed many throttle blips to get it started and sounded like it was not running on all cylinders (almost boxer engine unequal length headers type of sound).

Thanks

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post #11 of 15 (permalink) Old 07-14-2019, 07:50 PM Thread Starter
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So I have an update. I just did the TDC procedure and removed the distributor cap. It is infact swapped 180 degrees because tdc for cyl#1 has the rotor pointing at #4 on the distributor cap. Given this info Alfajay you said that this should now be marked as #1 and then based off that continue with the firing order clockwise.
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post #12 of 15 (permalink) Old 07-14-2019, 08:17 PM
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Given this info Alfajay you said that this should now be marked as #1 and then based off that continue with the firing order clockwise.
Yup.

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the car has a bosch blue coil and marelli distributor, webber 40dcoe's. I don't have another known good coil to swap in
It's not the coil. If it ran OK before you removed the wires, and won't start now, it would be an incredible coincidence if the coil just decided to become flakey at the same time. Get the distributor connected correctly and you'll be back on the road.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 07-14-2019 at 08:25 PM.
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post #13 of 15 (permalink) Old 07-14-2019, 08:38 PM Thread Starter
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Originally Posted by Alfajay View Post
It's not the coil. If it ran OK before you removed the wires, and won't start now, it would be an incredible coincidence if the coil just decided to become flakey at the same time. Get the distributor connected correctly and you'll be back on the road.
Yeah didn't think so just figured I'd give some more info in case it helped. When I pulled the plugs 2 were wet and 2 were completely brand new (I just put them in 2 days ago) so it confirms my theory that it was not running on all cylinders. Thanks again for the help Alfajay. Ill reconnect the plug wire in the correct sequence tomorrow and get her fired up!
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post #14 of 15 (permalink) Old 07-15-2019, 05:11 PM Thread Starter
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Originally Posted by Alfajay View Post
Yup.



It's not the coil. If it ran OK before you removed the wires, and won't start now, it would be an incredible coincidence if the coil just decided to become flakey at the same time. Get the distributor connected correctly and you'll be back on the road.
Got the distributor marked where #1 actually is and hooked up the wire and the car runs again! Just curious would you have any pointers / tips to diagnose an almost stall at around 2k rpms? as you slowly apply throttle it will almost stall out the engine and you can hear the cabs freaking out like a stronger sucking noise and the if the throttle is held or more throttle applied it will almost certainly stall out. once you jab the throttle and get it past 2k rpms she revs till redline no problem, its just that initial bit of throttle that wants to choke it out. The new spark plugs don't seem to have helped that much. The carbs have been looked at and "tuned" by our local alfa club mechanic but the 2k bogging remains. I had had opened the top cover and used an entire can of carb cleaner to hose out the main jets the idle jets and every hole I could in the carb itself and also sprayed a bunch of cleaner in the bowl / float area and let it sit overnight, no improvement from that either.
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post #15 of 15 (permalink) Old 07-15-2019, 05:14 PM
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Glad you got the ignition wire problem solved.

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pointers / tips to diagnose an almost stall at around 2k rpms? as you slowly apply throttle
Search the BB for topics like: "Weber transition idle jets to main jets". That isn't an uncommon problem; you'll need to play with Weber jets and air correctors to eliminate it. Paying a Weber specialist - not your local alfa club mechanic - might be worthwhile.

Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L
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