Trying to help out an American friend...

Technical Discussion
1

OK all you engine problem diagnosis experts. A friend of mine has a friend on the West Coast (I’m on the East) who has owned his bus for years, but has running issues which so far have not been solved by local mechanics. Have a read and see if anyone can point him in the right direction?

HERE IS THE INFORMATION I WAS GIVEN…

1979 VW Camper
2000 cc motor
either 189,000 miles or 289,000 miles
the motor was rebuilt about 25,000 miles ago and had been rebuilt at least once before.

-I have replaced the hydraulic lifters with solid lifters
-installed an electronic ignition system
-replaced the fuel injectors and intake manifold with a carburetor and intake manifold for the carburetor.

It no longer misses the way it did when we were in the mountains. Now it misses right bad during acceleration in first gear about every time I start off unless I play with the accelerator and clutch and second and third gears if the motor is not turning high rpms. At highway speed (55 mph), it runs OK, but not strong. You may remember noticing that it maintained speed going up the mountain to Wolfgap while loaded with two canoes and a lot of gear inside. It now takes a mile or more to get up to about 65 mph and sometimes that is about as high as it will go. I have urged it up to about 72 mph one time since I replaced the fuel injectors with the carburetor and it would not go any faster. before it started messing up, it would run 80+ mph with the canoes on top and all the gear inside and I could keep up with traffic on the interstate. Now I fear that it will be a nuisance on the road, especially in hill country.

The original missing came on gradually. At first, I thought it was a bit of condensation or trash in the gas. I put gas treatment in the tank and it would work fine for a month or so. Over a period of maybe six months, it gradually got worse until the miss seemed like an ‘all cylinder’ miss simultaneously. This missing would occur in all gears and at any rate of rpms. Replacing the fuel injectors with the carburetor seemed to fix this missing, but now it misses, not as abruptly as before and at lower speed and only when accelerating.

The van was in eight different garages over a period of 13 months beginning soon after we were at Wolfgap. I was told by different mechanics that it was an electrical problem and they checked all nine, as I recall, places an electrical problem could exist and everything checked out fine. Other mechanics thought it was fuel related, as did I, and they checked and even put an auxiliary fuel tank inside the van. It ran perfect for three road test, then started showing the same symptoms again. I took it to mechanics in New Bern, Greenville, Beaufort, and Wilmington, NC. Several ‘shade tree’ mechanics gave it a go too. Everyone of them admitted that they were stumped and in some oblique manner, admitted that they could not fix it and were relieved when I towed it away from their shop.

Some of these mechanics were old ‘air-cooled’ men, others were young men who had certificates from various schools that supposedly prepared them to work on any internal combustion engine. These latter ‘mechanics’ were much more reluctant to admit that they did not know whether to scratch their watch or wind their ass when it came to air-cooled.

HERE ARE THE QUESTIONS THAT I ASKED HIM…

  1. What is the Engine code? From there I can establish the fuel pump system and therefor pressures/ return hosing style etc.

  2. When an auxiliary fuel tank was used did it run fine? If so then I would assume that there is a blockage or obstruction from tank to engine, again reducing fuel pressure. Solution is to remove the tank, I think this can be done on these later buses without taking out the engine (my '69 required me to take the engine out to perform). Clean out the tank, replace all fuel line and filters at the same time with proper VW hose and clamps. Before doing this though it would be worthwhile checking to see if any pre-existing in-line fuel filters are fitted in the correctly as they are generally directional and if fitted incorrectly can restrict flow (this is easy to miss).

  3. Was the carburettor rebuilt prior to fitting. If not then again fuel delivery can be an issue. Kits can be bought to rebuild all carbs quite cheaply. If the carbs were designed to run with lower fuel pressure than the high pressure fuel injectors then again the fuel pump may require a pressure regulator as it could be flooding the carbs and bogging down the engine. When I have the engine code I can check this.

  4. Has the timing been set correctly by someone who knows the engine specs?

  5. What colour are the spark plug tips when removed? Grey, brown or dirty black? Are the correct spark plugs fitted?

HERE IS HIS REPLY…

I have started to answer your friends questions three times only to have the VW do something different the next time I drove it. It just seems to have a ‘revolving problem selector’ in it somewhere. When I adjusted the carburetor in accordance with the instructions, I only got about 7 MPG and sometimes it seemed to miss and sometimes, when accelerating, it seemed to be trying to just die from too little gas, but would pick up and go. I changed the adjustment to a point where the MPG is much better and sometimes it seems to be trying to die like before. Sometimes it runs just fine. I think that one day soon, I will drive it a while and then start all over and write to your friend and just describe the symptoms for that one trip.

I took it to a mechanic who told me that the motor did not have a code. I don’t know.

Below is a draft I started from a few days ago.

Thanks for getting information from someone who seems to know what he is talking about when he is talking about an air-cooled VW.

Responses by the number of the question:

  1. I have no idea about the engine code, but I will take it to a mechanic tomorrow and see if I can find out.
  2. The motor ran fine after the auxiliary tank was put on line. It ran good until the third, and what was to be the final, road test. On this test drive, it started missing just like it had been before the tank was placed in the van.
    *Note: The motor misses now sometimes during accelerating in the first three gears. In 4th gear now, it runs smooth. It does not miss after it gets hot. When the fuel injectors were installed, it did not miss until it got hot and then it missed in all gears sporadically.
  3. The carburetor is a new Weber, I believe it is. Additionally, at every check, the fuel pressure was always good.
  4. The timing was set by the most reputable VW mechanic in this part of eastern North Carolina.
  5. I have not seen the plugs when removed, but I will have them checked tomorrow.

ALL SUGGESTION POLITELY CONSIDERED.

Cheers,

Bob

2

1st thing I would do is try another ignition module. Does it have a rev counter fitted? I had a similar problem on a stock car and it turned out to be a fault in the rev counter unit. Sometimes the car would run OK then start misfiring took us ages to find the fault.

3

Hiya

Im guessing it’s a CV engine its the US version of a CU.

The number can be found as below might be covered in gunk.

If it is a CU / CV then the webber should be 34 DAT carb.

They are known for being a nightmare to set up, being thirsty and for very poor cold running.

Most swap for std Solex 34-32 or peirburgh 2e3.

Kev

4

Thanks Guys,

I’ll pass the suggestions on.

Bob

5

I’d suggest the following Bob…

Get the tank & fuel lines checked for flow,
Renew the fuel lines & filter anyway,
Try a new fuel pump or an electric one,
Change ignition module - or at least try a check with new points,
New spark plugs and HT leads,
New gaskets for carbs & manifolds,
Replacement aftermarket carbs like Webers, Dells or Empi/Kadrons.

If that don’t sort it, he’d probably be as well to get a new engine built!
Best of luck… :thumb:

6

If the problem is there with both carbs and fuel injection on the vehicle and has been checked with another fuel supply and makes consistant good fuel pressure I’d pretty much certainly say it’s an electrical problem (unless there’s a problem with the bores sealing/valve timing/etc which I’m assuming a mechanic would’ve discovered with a leakdown test). Unless there’s a load of crud swirling round in the tank and blocking hte jets in the carbs. I’d eliminate this by giving the carbs a clean and then running it off a fuel line into a jerry can.

I’d then go through the electrical system checking all the power wires and earths. I’d also be looking for any sign of damage to insulation and any sign of movement in things like fuses. Are the HT leads new/have others been tried? If you find nothing try a new (or blagged of a mate) module for the sparks. If this makes no difference then I’d get a meter on the power feed for the ignition and check it’s not suddenly dropping off from a small short/poor connection caused by heat or vibration.

I had a customer a few years back with a similar problem sometimes his car’d run great, sometimes it’d just start running crap. It was a race car so had no MOT/tax/insurance so couldn’t test it on the roads to try trace it. I spent ages looking at it (he’d already been through it several times with and without help to try trace the prob) I eventually traced it to an inline fuse on a live feed to a fan switch for the radiator. It was a blade type, the ones with a tiny part of the connection sticking up at the top, this was intermitantly touching onto a hose clip which was touching the block. As it was only a tiny connection it didn’t cause any heat damage to the wire but, drew enough current to upset the voltage his DTA engine management was getting making it freak out.

Hope he gets it sorted soon!!!