Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Helen in Dillon -- 2 problems, 2nd opinion

Re: Helen in Dillon, CO (1978 VW bus)

Helen had 2 problems, and I doubt the Car Guys did much to help either one.

a. Her momentary loss of power on hills and while accelerating sounds like a partially plugged fuel filter. When the mechanical fuel pump can’t get the required amount of fuel to the carburetor float chamber the engine will lose power. Within a few seconds, if some fuel is still getting thru, the pump catches up with demand, fills the float chamber and the engine runs OK for a while. The same thing happens if the carburetor itself is defective – float gets stuck in closed position. So my diagnosis: clogged up fuel filter or defective carburetor. Suggestion: replace the fuel filter(s) first; if that doesn’t solve the problem, rebuild the carburetor(s).

b. Helen has installed an auxilliary battery to run propane heater during the night, set up with relay to charge when engine is running. Fine, but I suspect her auxilliary is a normal car battery or maybe a “deep cycle” marine/RV battery, but not adequate in aH (amp-hour) capacity to do what she needs. Normal car batteries are not designed for slow drain, deep discharge (<12v. at rest) and doing so will destroy them by sulfation. Her present battery is most likely badly sufated already and can’t accept or deliver nearly the amp-hours she needs. Keep in mind also that at low temperature, a battery’s aH capacity is greatly diminished, so when it’s cold out, the battery is least able to do its job.

What capacity deep cycle battery would work? Measure the current required by the propane heater running on full 12 v. input. Let’s say it’s 5 amps. Multiply this by 20 – even though you may only run heater 7 hours/night, capacity will be impaired by low temperature AND you only want to draw battery down to 50% of capacity before recharging. To get 100 aH capacity (even more would be better) you need a really substantial battery – at least one, maybe 2 big “golf-cart, fork-lift” deep cycle batts in parallel. Helen needs to study in depth about lead acid batteries, and get a hydrometer. Voltage is not an adequate indicator of charge state.

Didn’t hear the call, but I had a '79 VW bus and a '71 VW camper bus. The motor in the '71 was a basic VW bug motor. In the '79 it was a more powerful Porshe motor (same as 914 I believe) which is what Helen has in her '78. There are aftermarket carbs and manifolds for these motors which worked better than the OEM set ups, so at this point who knows what the carb(s) are in Helen’s bus. Most of these old buses have been modified over the years. Helen needs to find a good mechanic that knows these old VW motors. Not so easy these days as young mechanics have no clue about these motors. Find a VW mechanic that is 60+ years old and she’ll be OK.

I didn’t hear the show but it’s not likely a carburetor problem. A '78 Bus should have AFC fuel injection on it. A hesitation could be caused by a clogged fuel filter, weak pump, or a problem with the airflow meter, etc.

That’s all assuming the engine is not getting weak. I’ve been to Dillon a few times and that’s quite a bit of altitude to be shoving an old bus through even when things are right.

I agree about the battery/heater question; starting batteries, which is what she probably has one of running the heater fan, are not made to be deep-cycled, and she needs to replace the heater fan battery with a real deep-cycle battery, such as one made by Trojan or one from West Marine- but it needs to be a real deep-cycle battery which won’t get sulfated and ruined by repeat deep discharges. That will fix THAT problem.

As to the hesitation when she goes uphill under load, I think T&R may be right on the coil. What she’s talking about sounds like an engine stumbling under load- either a fuel suoply issue (not likely) or an ignition system that’s not equal to the task. It would be worth checking the plug wires and all the ignition parts- also the points etc. I think a car that old still has points.

These vans also had contact point distributors. It’s possible the points could be closing up due to the distributor cam not being lubricated now and then or retarded ignition timing. Lubing the dist. cam is often overlooked and it’s pretty easy to foul up the ignition timing, all depending.

The 78 VW Bus in stock form should be using L-Jetronic fuel injection (very good system).AFC was used much earlier.AFC (Air Flow Control) was used on many of the Type 3 VW’s.It could be said to be one of the very first massed produced electronic fuel injection systems. AFC injection was such a nightmare I would run when they came in.L-Jetronic made my work so much easier.

In regards to the OP’s situation,I would be testing the air flow meter.The air flow meter has a vane inside it and it can get bound up or just plain fail in certain positions.Fuel pressure is a good basic figure to have on hand.

As we see from my second post,the Bus came standard with electronic ignition but I have seen these distributors replaced with breaker point units.Replacing a AFC’s system with breaker points would be trickier as those distributors had what is refered to as “trigger points”.

As far as I know, the L system is the AFC system unless there’s a terminology difference.

The old VW factory Type 2 manuals I used to have (and sold on eBay due to non-use) referred to it as AFC; meaning it was controlled by the flap in the airmeter.

Until 5 years ago, we had a '77 VW Westy for many years. (We now have an '87 Westy.) Our engine would, on many occasions, randomly quit running for a moment or two and then resume running. It once quit running completely and did not start until the following morning after it had be towed to a VW/Porsche specialty shop. It started for them immediately. They said they just turned the key and it started. They had no explanation. It kept on momentarily “cutting-out” and we kept checking things (ignition, replaced fuel pump, etc.) for many more months. Except for the one time, it never just totally quit so that we could pin down the problem.

We heard somehow of someone else that had had the same problem and had replaced their double relay to solve the problem. We finally replaced the double relay. (If memory serves it sits on the left side of the firewall above the engine. With the ignition powered-up the 2nd part of this relay powers the fuel pump.) It ran smooth as silk for years from that day on.

BTW, if you ever smell gas from time to time and cannot find the leak, check out the short section of flexible fuel line where it passes through the firewall into the lower left corner of the engine compartment.

Hope this helps.

No AFC was the early system used in Type 3’s that was primairly based off of manifold vacuum.AFC was the system that everyone said could be affected by CB radios.Before 1975 Type II Buses had dual carbs. There may have been one or two years that AFC made it over to the Bus,but it would have been way early.I have taken many of those dual carbed buses and installed a webber conversion kit.Not worth the money if you ask me.The early carb buses would develope vacuum leaks at the throttle shaft housings

I am finding other sources refering to L-jetronic as AFC and the Type 3 as D-Jetronic. I always called the system on the Bus with the air flow control meter as L-Jet and more commonly the Type 3 as D-Jet.It is more likely the AFC terminology refers to the L-Jet system, rather than the D-Jet system being called AFC.My bad

My guess is that Helen’s problem is a faulty or plugged fuel pump, or plugged fuel filter, or, what I’d check first, a faulty fuel pump relay or burnt out wiring where the fuel pump relay plugs in into the relay panel. This later problem was common in late 70’s CIS fuel injection VW Rabbits at least.

Still, there’s a few of things I don’t understand about Helen’s problem.

First, is the propane heater to keep the engine compartment warm overnight, so it’s easy to start the next morning? Or is it to heat the passenger compartment, like if they are sleeping in it overnight? I’m assuming it is for heating the engine. But I’ve never heard of using propane for this application. It seems like it would be dangerous to have an open flame inside the engine compartment.

Second, whaterver the propane heater is used for, why does it need it’s own battery? The heat is coming from the propane, not the battery current. It might need a battery for turning itself on and off to maintain the set temperature, but I don’t see any need for a second battery just for this. Turning itself on and off a few times during the night should take very little current.

Third, why is the ignition coil involved in the two batteries? I don’t see any reason for this at all, unless the ingition coil is used to fire a spark plug on the propane heater to turn the flame on. But wouldn’t the propane heater have this anyway?

Retarded ignition timing could also cause a hesitation, loss of power, etc. I forget the year it started but the Type 2 bus was outfitted with a magnetic timing plug. Timing could be set with a light or with the VW electronic service tool.

That service tool (at least in my experience) turned out to be a bit flawed when it provided erroneous timing information. In other words, the tool may have showed the timing as correct when it actuality it was off by a mile.
In one case, a bus engine was fried because of that tool when it caused the timing to be advanced way too much. Corporate VW was involved and the factory rep insisted it was a mechanic screwup. Knowing the mechanic who did the work I didn’t buy that for one second and as it turned out, the rep had to eat some crow when the tool was proved to be faulty right in front of him. After that, no one would touch that tool and used the light.

George, the heater is vented outside and uses a heat exchanger so it needs a fan. Fans draw lots of energy.

Helen: Your missing problem is probably the CYLINDER HEAD TEMPERATURE SENSOR.

I have a 79 bus and these seem to go out every 5-10 years. When they start to go out they have these momentary shorts that tell the engine it is cold, so the fuel injection system dumps a bunch of extra fuel into the engine. The engine stalls for as long as the sensor is erroneously grounded, often only a fraction of a second. The reason it seems speed sensitive, or engine speed sensitive is that some internal sensor part is breaking down and causing the sensor to ground out.

You can buy the sensor from a dealer or order it from a good parts store, but get a Bosch part. It’s a bit tough to reach the sensor for removal and installation, but you should be able to do it yourself. Also, make sure your new sensor is connected solidly to the existing wire harness, the plastic around the terminal connection makes it hard to see if there is a solid connection. I once had this entire problem occur simply because the sensor was not plugged solidly into the wire harness.

I also have an auxiliary battery for my forced air propane furnace, and it seems like the comments above deal with the problem correctly. You need to charge it more. Keeping it warm helps, too. I have mine (a gel-cell so it doesn’t off-gas explosive hydrogen gas) inside the van in the spare tire spot near the furnace. But still, I need to charge it if I’m not driving 10 hours a day. Keep a small trickle charger handy and plug in whenever you can.

Good Luck!

Thanks @TwinTurbo for the info. We rarely need engine heaters in San Jose! Years ago I lived at 6500 feet in Colorada mountains tho, and some people used electric heaters there. But propane seems like a good alternative, and the only alternative if you don’t have access to a plug, like if you are camping out. It’s good someone makes these things since they’re properly vented and use a heat exchanger. Yes, the fan would need its own battery.

I still don’t understand why Helen’s ignition coil in involved though.

And a note to Helen about her VW loosing power.

I had a similar problem with a late 1970’s Rabbit. Some days I’d step on the gas, and the car would just go “uggggg” and hardly accelerate at all. This car had the early VW fuel injection system that had a big round disc as the airflow sensor, hinged to a gadget that allowed the proper amount of fuel into the injectors through a complicated gadget they called the fuel distributor. Everytime my VW Rabbit lost power like that, I could fix it by taking that part of it all apart, cleaning out the fuel distributor/plunger, etc, and replacing the fuel filter with a new one. Apparently I was getting bad gas filled with clay or sand like stuff, which somehow was getting past the fuel filter.

Anyway, maybe it’s worth a try for Helen too, if she has the same kind of FI system in the bus.