TheSamba.com :: View topic - Tune-up Problems

Sat Sep 19, 2015 6:16 pm

So I decided that I would do something productive this weekend and do a full tune up and oil change on my FI 71 Square.

I decided to start with point gap and timing since that is pretty easy. I pulled my points out to make sure they were clean and saw they had a little bit of deposits on them, so I pulled out the set from an old 009 I had switched to electric ignition, and they were in much better condition so I installed them and set the gap.
I also checked all the contact points in the cap and the rotor. The top of the rotor had some odd burning of some sort as seen in the photo below...

I started the engine and the timing was way advanced and could only see the marks on the pulley through the generator cover. (Although it ran quite well there... if a bit high RPMs) so I set it to 0° TDC as per the brown bentley for up to '71. This ran rough and after a minute or two died and would not stay running for more than a few seconds...

Any ideas???? I'm at a loss as to why it would die at idle after adjusting gap and timing?

Sat Sep 19, 2015 6:37 pm

that rotor looks done.

Sat Sep 19, 2015 6:41 pm

Dfasty wrote: that rotor looks done.

Sure does... Question is why did it burn up so quick? I just replaced it earlier this summer. :?

Sun Sep 20, 2015 6:37 am

Something else in the high tension chain is having issues.

It could have been poor connectivity or high resistance inside the rotor between the top carbon contact and the tip.

Check......if you have resistor wires.....do you have non-resistor plugs? What is the resistance reading in your coil circuits? Condition of the cap? Voltage to coil? Condition of wires?

Just check the whole system and consult the Bentley. It shouldnt take ten minutes with a volt /ohm meter to verify what is and isnt in good condition.

Also why not just spend $5 on a new set of points to make sure there are no issues. Ray

Sun Sep 20, 2015 4:47 pm

raygreenwood wrote: Something else in the high tension chain is having issues.

It could have been poor connectivity or high resistance inside the rotor between the top carbon contact and the tip.

Check......if you have resistor wires.....do you have non-resistor plugs?
Should be normal wires and plugs.
raygreenwood wrote: What is the resistance reading in your coil circuits? Condition of the cap? Voltage to coil? Condition of wires?
11.5k ohm between 4 and 15, 11.5k ohm between 1 and 4, and 3 ohm between 1 and 15. (the bentley doesn't go into much detail about the coil other than voltage between 15 and 1 which is good) cap is clean and contacts are decent, voltage to coil is about 11.7v, wires are all good with very low resistance on all.

raygreenwood wrote: Just check the whole system and consult the Bentley. It shouldnt take ten minutes with a volt /ohm meter to verify what is and isnt in good condition.

Also why not just spend $5 on a new set of points to make sure there are no issues. Ray

Honestly I didn't even think about it, there is a new set installed now however.

Also I don't know if this would be connected or not, but unplugging #4 spark made the idle smooth out.

Sun Sep 20, 2015 8:23 pm

nogoodwithusernames wrote: raygreenwood wrote: Something else in the high tension chain is having issues.

It could have been poor connectivity or high resistance inside the rotor between the top carbon contact and the tip.

Check......if you have resistor wires.....do you have non-resistor plugs?
Should be normal wires and plugs.

Also I don't know if this would be connected or not, but unplugging #4 spark made the idle smooth out.

Plug wires swapped between 3 and 4?

Mon Sep 21, 2015 5:48 am

Bobnotch wrote: nogoodwithusernames wrote: raygreenwood wrote: Something else in the high tension chain is having issues.

It could have been poor connectivity or high resistance inside the rotor between the top carbon contact and the tip.

Check......if you have resistor wires.....do you have non-resistor plugs?
Should be normal wires and plugs.

Also I don't know if this would be connected or not, but unplugging #4 spark made the idle smooth out.

Plug wires swapped between 3 and 4?

Could be.......could also be swapped injector wires, could be a valve being held open by adjustment and getting some pressurization back in the manifold.

It could be anything that causes the vacuum signature to be odd....and that includes weak spark....or erratic spark. I would also check the resistance of the plugs.

Back to the rotor.....which looks burned. It could have been just be a defective rotor.
As for the cap being clean. ....thats not what i was asking. Inspect it with a bright light. Look for very fine hairline cracks or carbon tracks. The faintest line could be a crack which causes arcjng between poles.

Also make sure the center carbon brush has tight contact and a smooth surface. Check the resistance between each contact from the inside and where the plug wire plugs on. Ray

Tue Sep 22, 2015 6:55 pm

raygreenwood wrote: Bobnotch wrote: nogoodwithusernames wrote: raygreenwood wrote: Something else in the high tension chain is having issues.

It could have been poor connectivity or high resistance inside the rotor between the top carbon contact and the tip.

Check......if you have resistor wires.....do you have non-resistor plugs?
Should be normal wires and plugs.

Also I don't know if this would be connected or not, but unplugging #4 spark made the idle smooth out.

Plug wires swapped between 3 and 4?

Could be.......could also be swapped injector wires, could be a valve being held open by adjustment and getting some pressurization back in the manifold.

It could be anything that causes the vacuum signature to be odd....and that includes weak spark....or erratic spark. I would also check the resistance of the plugs.

Back to the rotor.....which looks burned. It could have been just be a defective rotor.
As for the cap being clean. ....thats not what i was asking. Inspect it with a bright light. Look for very fine hairline cracks or carbon tracks. The faintest line could be a crack which causes arcjng between poles.

Also make sure the center carbon brush has tight contact and a smooth surface. Check the resistance between each contact from the inside and where the plug wire plugs on. Ray

Plug wires are correct 1 4 3 2, not 100% on the injector wires but due to the set they have taken over time and how it runs when I switch them I feel like they are correct.

Tomorrow I should have a fair amount of time to go over stuff, so I will check all the valves. Which points should I be checking on the spark plugs? I assume the terminal to the center electrode?

Ah, I see what you mean about the cap, I will check that tomorrow as well.

I am thinking there is something causing a vacuum leak or similar with cylinder 4 since it is the only one that affects how the engine runs. I will try to reseal the manifold to the head and spray some WD40 around the joints.

Tue Sep 22, 2015 8:13 pm

nogoodwithusernames wrote: Which points should I be checking on the spark plugs?

Check the wires from end to end. You're looking for about 1,000 ohms.
As for the plugs, check the gap, and toss up a pic of them, so we can see how they look.

Wed Sep 23, 2015 2:24 pm

Here is a quick photo of the contact inside the cap, they all only had a couple Ohm resistance.

Bobnotch wrote: nogoodwithusernames wrote: Which points should I be checking on the spark plugs?

Check the wires from end to end. You're looking for about 1,000 ohms.
As for the plugs, check the gap, and toss up a pic of them, so we can see how they look.

Here is a photo of the plugs, it looks like 2 & 3 are still fouling. Should I disassemble and clean the distributor and make sure the points for the injectors are working and set right? What measurements do I need to check and what do I need to lubricate? The bentley shows the exploded diagram but doesn't have much info that I saw.

Plug wires were all under 1.5 Ohms

Wed Sep 23, 2015 4:37 pm

Since you have the sleeves on the wire ends of your plugs, I am guessing you have non-stock wires/connectors.

The originals had a spring inside the bakelite connector that engaged the raw threads of the plugs (inside your sleeves).

Often the aftermarket wires are carbon core, which can break internally and have high resistance, sometimes just while driving under vibration and the high voltages (much higher than your VOM uses).

Original wires are stranded wire, and the resistance is in the SP end connectors.

Check your wires especially for resistance when bent slightly. Don't bend them too far or you may break the carbon core.

Thu Sep 24, 2015 8:08 am

I think Phil and Ray are onto it. You may have an issue with your plug wires. Can you show us what you're running?

Thu Sep 24, 2015 8:43 am

They are aftermarket wires, although they are copper core not carbon.
I have this set from ACN http://vwparts.aircooled.net/Megavolt-Plug-Wire-Se...p;CartID=0

I can check the resistance while I bend them around and see what happens later today. When I measured them yesterday they were all between 1 and 1.5 ohms.

Mon Sep 28, 2015 10:20 am

nogoodwithusernames wrote: I can check the resistance while I bend them around and see what happens later today. When I measured them yesterday they were all between 1 and 1.5 ohms.

Ok so I didn't get a chance to check Thursday, and was up in Fort Bragg for a 3 day weekend. I will try to get some time around work the next few days to check the wires at different bends.

Mon Sep 28, 2015 6:42 pm

Look at the wires in the dark while the engine is running. Any suspect spots will show up as a blue glow. That's how I found out my Bosch wires were bad. They can ohm out OK but still be bad under high tension.

Mon Sep 28, 2015 8:02 pm

Buy a compression tester & check them because your spark plugs look pretty bad. You might need new pistons & cylinders and/or a valve job.?

Mon Sep 28, 2015 8:38 pm

Have a look at the injector points in the distributor, also. 2&3 inject together, as do 1&4. Your 2&3 plugs look fouled, maybe indicating an injection issue on those cylinders.

Tue Sep 29, 2015 2:56 pm

Thanks for the suggestions, I will go through all of that when I get a chance.

I am also picking up a used T3 engine this weekend. I plan on rebuilding it and running it so that I can pull the existing engine and FI out. This way I can take my time to go through the engine and FI components without needing to worry about getting to work after the weekend is done.
I don't know if I want to just build it as a temporary stock engine or step it up and build the "mileage master" on ACN for some extra power and better economy. If I did that I would run it more long term rather than just until the FI motor is gone through. Any suggestions or opinions (either negative or positive) are welcome regarding the two options! (And yes if tram reads this it would involve driving a car with carbs on it :twisted: )

Also is it possible to run the FI engine on a stand like you can with carbs or would that be to complicated to setup?

Tue Sep 29, 2015 8:43 pm

nogoodwithusernames wrote: Thanks for the suggestions, I will go through all of that when I get a chance.

Also is it possible to run the FI engine on a stand like you can with carbs or would that be to complicated to setup?

I think you could. You'd need to set up the FI relays to power up the ECU, and fuel pump, but that shouldn't be that difficult.

Thu Oct 01, 2015 8:41 pm

Ok well I had a chance to pull the distributor and check on the injector points. One of them was a bit stiff so I cleaned them up and put some oil on the bearing bit. This helped a lot so it's running fairly decent!