It was the Distributor

Look carefully at the spring sizes - they are different

IT WAS THE REBUILT DISTRIBUTOR ALL ALONG

BAD - BUS DEPOT - BAD

The last time the Terpvan ran well was with the loaner distributor from Va. Beach Fred. Since his distributor fixed the problem, I ordered a rebuilt from Bus Depot in Pennsylvania, the Christian guy.
After install, the van ran but never well. It would idle and run at wide open throttle, but would have bad hesitation off idle. If you stomped on the accelerator, it ran but it was annoying.

I looked everywhere but the distributor for about two years. Air flow meter, fuel pressure regulator, injectors, fuel pump, computer, coil, grounds, caps and rotors, plugs and wires, compression and valves. Nothing fixed the problem.

When I finally opened up the distributor and saw the two different sized springs on the centrifugal advance. It was clear. There was very little resistance so as soon as the distrubtor started to spin and the vac retard was off, it went full advance and ran poorly until the revs were up to 2K+. I compared the resistance of the VW rotor to the resistance on the Range Rover rotor and it became more obvious.

That is one of the joys of wrenching. When the harmonic convergence of all your mechanical meditations reveal the path to enlightenment, smooth running and better gas mileage right before you.

Bus Depot was no help at all. They did not even offer to send me the correct spring or even tell me where the springs come from.

I used needle nose pliers to bend the loose spring into a shorter span so that it would engage.

WOW, that problem fixed after two frustrating years.

Of course, fix one problem and others pop up but take nothing for granted and do not assume anything is working correctly.  Never say, "well it can't be the widget," I just put that in, unless you test and verify.

O2 Sensor Shielded Wire Repair

The van has been running, which is great, but it has been running rich. My mileage is very low, like 11 mpg, and the exhaust burns your eyes.

The causes of rich running can be bad Temp II sensor, bad O2 sensor, leaky injectors, throttle position switch not adjusted and perhaps other problems like poorly adjusted air flow meter, etc.

I have never been happy with the connection of the O2 sensor, so I thought I would address that as I hunt for this problem.

The O2 sensor in the 1985 1.9 engine is a single wire type. The multi-wire types are heated so that the signal begins earlier in the warm up phase. The connecting wire is green and is a shielded wire, which means the center wire runs through a tube or sleeve of braided wire which protects the voltage being carried by the center wire from being affected by electric interference. The O2 signal wire sends a very low voltage, like 0.5 to 1.2V signal to the ECU which somehow tells the ignition system to add or subtract fuel.

The test run with a multi-meter at the ECU plug determines if the center wire is grounding out which throws off the message apparently telling the engine to add fuel. You check for continuity between 5 and 7. Seven is a ground on the plug.

Although I passed that test, I was not happy with the connector I used when I put this engine in. Also, I could change the idle by twisting the connection with the engine running.

The connector was a big, clunky coaxial cable connector that I put in without soldering the signal wire to the connector male part and it was not the right size or the right connection. It was just a bad attempt at a connection.

I saw a video of how to splice shielded wire and it looked very simple and clean and frankly pretty obvious so I thought I would give it a try. Of course doing the splice in the engine compartment was a bit more difficult that the video done at an assembly table but I think it worked and here are some picture and a description so that if you choose to do this, you can do a better job. The van is still running rich.

Green shielded wire from the ECU plug

The above picture shows the shielded wire coming from the ECU plug. The copper braided center part of the wire is to the left and is just a normal wire surrounded by green insulation. The other strands of copper are on the outside of the inner insulation and are covered in another layer of green insulation. To strip this wire for the connection, you strip both layers of insulation and the shielding to expose about a half inch of the center signal wire. Then, about an inch back from the signal wire you just exposed, you have to strip the outer insulation only, leaving the braided shielding in place. The shielding is delicate and the outer insulation does not want to strip off easily. Once you have the shielding sleeve exposed, push it back over the outer insulation, away from the exposed signal wire. The inner and outer wires cannot touch. In other words, a shielded wire splice is an inner splice of the signal wire and an outer splice of the braided shielding sleeve.

Roll of heat shrink tubing

Some heat shrink tubing will be helpful to seal up the splices and keep the inner, signal wire from touching the outer shielding sleeve.  The same diameter heat shrink will not work on both. So if you have it, use one heat shrink that will work on medium gauge wire and get a larger size that would work on say a TV cable. Remember to slide the heat shrink tube on before you join any of the wires together. You also need to slide on the shielding braided sleeve before you join anything together. 

Here is where the shielding braid comes from.

The source for the shielding braided sleeve

I used some coaxial cable from TV installation as the source of the braided shielding sleeve. The picture above shows outer insulation stripped away and the process of cutting the braided sleeve. Going at it with cable cutters will make an even messier braid.

Shielding from a piece of coaxial cable to be used to shield over the splice

It is worth saying twice. You need to remember to slide the sleeve of braided shielding onto the wire before connecting the wires. The shielding sleeve is going to cover the inner splice of the signal wires.

Back to prepping the sleeve. To cut it free you strip the outer insulation and then push the sleeve up to make a bulge around where it comes out of the remaining outer insulation. Then you snip the bulge with small clippers. Once it is cut, you can pull the sleeve off. Cutting the sleeve with wire cutters deforms the braid. As you can see with this picture, cutting it with snips also mashes it up a bit.

Green shielded wire inner spliced to new signal wire

The same double, stepped stripping is done to the wire that you are splicing so that you have two exposed inner wires separated from the outer shielding braids and the outer insulation so the inner wires can be kept from connecting with the shielding. I used a crimp connector with heat-shrink as the connector and then another piece of heat shrink to slide over the inner wires. You have to remember to put the heat shrink tube on before connecting the wires.

After the signal wires are crimped together and the connector and the heat shrink are sealed up to insulate the center wires from the shielding sleeve, the shielding sleeve is slid over the splice overlapping with the shielding that was exposed with the stepped stripping. I used small zip ties to hold the sleeve in place before pulling the heat shrink tube over the shielding. Otherwise the heat shrink would have caught on the braids and not passed over the entire splice area. This was the part of the project that was difficult in the engine compartment. I used a heat gun to melt the heat shrink and placed a block of wood behind the splice area to protect other wires in the area from the heat. There is a "C" shaped nozzle that goes on the heat gun which makes a little chamber, like the tube of a breaking wave, to heat the single wire, but I do not have one of those. 

Although this did not correct the rich running, this splice is an improvement over what was there before. I am sure that the signal wire is connected from the O2 sensor to the ECU plug and I am sure that the signal wire is not grounding out. I also know that there is some small voltage being generated by the O2 sensor. I only tested with a 10 volt range on an analog meter that I keep in the van and that is not low enough to show the 0.5 to 1.0 voltage ranges and fluctuations that I should be seeing.

I have read that the default message if the O2 sensor is disconnected tells the engine to run on the rich side. So hopefully I am getting a voltage up on the high end which could point me to another cause, like leaky injectors, for the rich running.

I may have solved the puzzle of my running problems. More than two years ago, a great person from the Full Moon Bus Club lent me a distributor to help diagnose a problem. The van ran well with the loaner so I ordered a rebuilt from the guy in Pennsylvania. Needless to say, I did not have the same results with the rebuilt distributor and figured it must be vacuum leaks or throttle position switch or air flow meter or fuel pressure and on and on.

Symptoms were that van would start and idle but as soon as I cracked the throttle it would hesitate and bog and miss. It would run OK at wide open throttle.

Turns out that the re-builder used two different sized springs on the centrifugal advance counter weights. The effect was that there was no resistance at all from one spring. As soon as the RPM's started up, the distributor went full advance.

I had a ridiculous and completely unsatisfactory response from the company I bought the distributor from. If you look carefully at the top spring in the picture, you can see where the bail of the spring on the right side does not touch the shaft. Also, compared to the bottom spring, the top spring smaller gauge wire. I bent the bail to shorten it and problems went away. Sort of.

When I reassembled the distributor, which had no shims and might not have had the key-way pin that locks the trigger wheel into place. Whatever I used as a substitute key-way pin fell out or got chewed up. I redid that with a pin cut from a nail that fit fairly snugly in the slot and so far so good.