TheSamba.com :: View topic

Wed Oct 14, 2009 10:19 pm

I think this is a Vaccum/air leak issue. I am very new to this so let me know if im on the right track.

Problem:
When I start the bus and let it idle it cuts out, it starts up right away. if I feather the gas I can get it running as long as i keep it 2k-3k rpm's if I let off the gas it cuts out again. If i push the pedal to fast it will cut out most of the time as well.

Looking at the Cloth wrapped hose I noticed cracks in them at the ends, I cut out what I could from the ends and re-attached, added zip ties and hose clamps where i could. Same problem.

My plan is tomorrow to go get new hoses of the different sizes it looks like there is at leats 4 different sizes of hose in there.

Am I on on track and/or are there any other possible causes of the problem that I should be looking at as well.

The bus is a 77 FI 2.0 liter. And was sitting for about 6 months prior to my aquireing it, the previous owner had the exact same problems.

I was also told that another alternative would be to switch over to an electronic ignition and that if I did that I wouldnt have to worry about the air leak/vaccum problems.

Thanks in advance.

I am very new to this, as this is my First air colled or VW, so any pointers would be appreciated.

Thu Oct 15, 2009 1:37 am

It does sound vac related. There are a heap of hoses, so be sure you look at every one. How are the brakes? The brake booster line could have a leak somewhere; that would affect the brakes bigtime. Your bus is like mine, so it should have some by-now-defunct (and probably partially disconnected or rusted out) exhaust gas recirculation system. It is the long thin metal pipe leading from the intake air plenum (the metal box with the 4 intake pipes running to the cylinders, and which I'd bet also has cracked old hoses) to the muffler area, toward the back / driver side of the bus. Mine was leaking there something fierce, so I detached it and sealed up the hole in the plenum with a little gasket I made. Many others have done the same. Search here for "EGR leak". If you're in Cali, you have to fix it for smog, tho...

Other places it could be leaking vacuum that are harder to see/test are: fuel injector seals; cold start valve seal; intake air runners; brake booster and valve; decel valve; vac can on the distributor; Auxiliary Air Regulator (search AAR).... EGR for sure... yeah, lots of possibilities... to test some of them, you can use a piece of long plastic tubing as a stethoscope, putting it near the various components to listen for leaks. The air plenum will be whooshing normally, tho, so don't get confused....

I'd get a vac meter (cheap), test vacuum. Should be 18 inches or so.

An electronic ignition will not do anything for you if you have a vac leak; all it does is time the spark instead of having a mechanical points setup do it. Symptoms won't change a bit, and you might introduce new faults (I had a hard time with my electronic system). Get the points set up right first.

Others will give you more soon I'm sure... good luck! And don't forget that search button!

Thu Oct 15, 2009 6:36 am

Stop taking advice from whoever told you that ignition fairytale to begin with, although you should check your dwell and timing.
I agree with Travellingwriter, vacuum leaks, either at engine hoses, the brake booster or injector base seals. Also test your fuel pressure and temp sensor 2, or swap in your spare just for kicks, they're cheap.

Thu Oct 15, 2009 4:40 pm

Quote: I agree with Travellingwriter, vacuum leaks, either at engine hoses, the brake booster or injector base seals. Also test your fuel pressure and temp sensor 2, or swap in your spare just for kicks, they're cheap.

we just redid a 1977. IMHO replace all the vacuum hoses and the 4 runner boots if they are cracking. Also replace the temp sensor 2 and injector seals. Does it run once it is warmed up? Also with the stock distributor check the vacuum can to be sure it isn't leaking air. It should hold a vacuum when applied. If your bus still has an EGR valve on it and it leaks air, that can be a source of vacuum leaks.

Also - make sure the gas is fresh and not something that sat around for several years with the prior owner.

Thu Oct 15, 2009 8:47 pm

OK replaced all of the hoses except two and the 4 large diameter ones (2 on each side) The ones I didnt replace I checked with starter fluid there appears to be no leaks there. Also replaced the plugs with 4 bosch golds.

I havent changed out the fuel, but it had only been sitting for 6 months.

The bus now will fire right up and idle just fine from cold start, also can bring up the RPMs up just fine....until it warms up then it will back fire a little and cut out at idle. wait a few minutes and it starts right back up again...until its warmed up then it starts cutting out, at idle.

Any ideas?

Fri Oct 16, 2009 4:28 am

I am not sure what Bosch "gold" plugs are but if they are platinum plugs you don't want them. They do not do well in our buses.

If it were me, I would drain out the old dead gas and give it away to someone with a F150 or something and try some fresh gas in there. Change out the fuel filter also and cut open the old filter to see just how much rust is in there.

If you have about 4' for 7mm fuel injection fuel line (or 5/16" in a pinch) , hook it up to the fuel rail test port (between cylinders 3&4) and see if the pump really is putting out about 1L of fuel in 30 seconds. The 4' will allow you to see how much volume the pump puts out into a container outside of the engine bay for safety. Good clamps on the line please.

I would also order up a $20 fuel pressure gauge as it will be needed later in your toubleshooting process. Here is the one I like because it works and is cheap.....

http://www.summitracing.com/parts/VDO-153008/

Also confirm that your points are set correctly. The gold standard test is to hook up the dwell meter and see if you are in that sweet zone of 47º +/- 3º. If you don't own one, I like this one as it not only does the dwell and tach, but also the volt ohm meter functions that you will need later. Plus it is cheap and it works.

http://www.amazon.com/Actron-CP7677-Automotive-Tro...-2-catcorr

Always set the point to the correct dwell angle first, then set the timing. Then set the idle speed.

When you say that you did not replace the 4 big hoses are you referring to the intake runner hoses? Those would be the ones above the letter "B" here (below) on the left side. Put your finger underneath them and feel if they are leaking vacuum.

Fri Oct 16, 2009 4:41 am

bjjpdx wrote: OK replaced all of the hoses except two and the 4 large diameter ones (2 on each side) The ones I didnt replace I checked with starter fluid there appears to be no leaks there. Also replaced the plugs with 4 bosch golds.

I havent changed out the fuel, but it had only been sitting for 6 months.

The bus now will fire right up and idle just fine from cold start, also can bring up the RPMs up just fine....until it warms up then it will back fire a little and cut out at idle. wait a few minutes and it starts right back up again...until its warmed up then it starts cutting out, at idle.

Any ideas?

Just had this sort of problem on a recent road trip. Culprit? Temp II sensor. It is the little bolt-looking thing hidden waay down on the side of Cyl 3, through the tin on the left side, almost at the bottom of the engine compartment looking down. It has a single wire leading to it, so follow that. If that 10 dollar part is faulty OR LOOSE, it will lead to such symptoms, ie cold running good, but when warm, mimicking a fuel starvation because that little bugger measures engine temp, and it thinks the engine is still far colder than it is.

To test TempII, disconnect the wire. Unscrew the sensor (but first feel it with your fingers to see if it was loose like mine. If you can move it at all with fingers it is loose enough to cause all the trouble in the world... When it is cold, measure the resistance of it with a volt/ohm meter (you need one if you want to drive an FI bus, so order one today; actron makes a great automotive multitester for 30 bucks, tach dwell, etc too: http://www.amazon.com/Actron-CP7677-Automotive-TroubleShooter-Multimeter/dp/B0002LZU7K ). Cold, the resistance should be quite high, around 2000-2500 ohms. Now put the thing in the oven at 400 degrees for 20 minutes. Carefully remeasure the resistance. Hot (operating temps inside the engine hot) it should be quite LOW, around 200 ohms. This change in resistance is what you want to see more than actual figures. Keep the meter attached and wait as the TII cools in the air; you should see the resistance rocket upward toward the cool values, +2000 ohms over ten minutes or so. If it doesn't do this, it's busted, and you have to order a new one.

When screwing it back in (and/or if it was loose and you're tightening it) be extremely careful not to strip that hole, because then you'll have to remove your engine to tap it!

Like I said, this is what happened to me. Horrible hesitation/dying, thinking it was a fuel problem, turned out to be a slightly loose TT sensor, (which Randy in Maine alerted me!). Try it, you might get lucky...

Fri Oct 16, 2009 7:42 am

Yep.. Change the oil and the gas and do a tune up (new pts/condensor/cap). Change fuel filter, check fuel pressure.. Check TSII. All that should be done to rule out the simple stuff.. AND CHANGE THE FUEL LINES.. Sounds like you have changed all the vac hoses but what about them little rubber boots at spots mentioned previously? There is a 90 degree one coming off the Aux air reg (between F and G in pic) and there is a "y" shaped boot coming from the brake booster line (B in pic). Both are prone to leaking if old.. You can plug the brake booster hole on the plenum to isolate it from the vacuum system and see if it makes a difference. The 90 degree one often leaks from the bottom so its hard to see. Vac gauge is nice to have. You can also check for leaks using a piece of tubing from a small propane tank with a little flow regulator.. You just need a little propane flow, valve barely cracked, not wide open. Move the tubing around the connections stopping at each one for a few seconds and when the idle picks up, you have found a leak. Only do this outside the garage naturally and take the proper precautions. Good luck and have fun!

Fri Oct 16, 2009 7:48 am

Quote: When you say that you did not replace the 4 big hoses are you referring to the intake runner hoses? Those would be the ones above the letter "B" here (below) on the left side. Put your finger underneath them and feel if they are leaking vacuum.

Yes those are the ones I ran my finger all around them and felt nothing, also sprayed started fluid around them and nothing happened.

Quote: I am not sure what Bosch "gold" plugs are but if they are platinum plugs you don't want them. They do not do well in our buses.

I was mistaken they are Bosch super plus plugs

Fri Oct 16, 2009 7:57 am

bjjpdx wrote: Quote: When you say that you did not replace the 4 big hoses are you referring to the intake runner hoses? Those would be the ones above the letter "B" here (below) on the left side. Put your finger underneath them and feel if they are leaking vacuum.

Yes those are the ones I ran my finger all around them and felt nothing, also sprayed started fluid around them and nothing happened.

Don't get too paranoid about those until you check that TempII. My air runner hoses are loose enough that I can turn them by hand when the engine is cold/off (yeah, yeah, I've been meaning to change them). I still drove 7000 miles the last 5 months without a vac problem (18 inches of vac). I did, however, get nailed by a tempII problem...

Fri Oct 16, 2009 11:32 am

You are doing well because those hoses had to be replaced anyway and you have now eliminated them as contributory.

Check the temp II. They are cheap and available.

When you start cold: At the back of the air plenum there is a gold colored injector. It sprays extra fuel when the engine is cold and first starts. There is also an aux air valve that opens to let the idle speed come up when it is cold. As the engine warms up the extra injector (CSV or cold start valve) and the aux air valve turn off, forcing the engine to use its base mixture and idle.

The temp II sensors are a common failure. I would just buy 2 and replace it, keeping a spare. If that doesn't solve it, I would replace the gas because I had a boat in San Diego that had over-winter gas do this to me once and it was the gas gone bad that kept causing it to die. If that doesn't get it, consider adjusting the idle speed screw outwards (speed up idle) on the throttle body or the air bypass screw on the AFM inwards (richens idle AND low speed mixture). Don't adjust them yet until you try the temp II and consider new gas. Unless you have an air fuel mixture gauge you may not be able to get the AFM back to where it needs to be, and it may be treating symptoms rather than the problem.

Last - I don't remember seeing if you - plugged the brake booster line temporarially and checked the vacuum advance to see if either were leaking vacuum?

Fri Oct 16, 2009 6:08 pm

Ok I just replaced the Temp II sensor. before I start it up I want to replace the 4 large Diameter hoses on the intake manifold. Do I have to remove the manifold to get those hoses on, or is there a work around?? there doesnt seem to be enough room in the gap to get the hoses on.

Please help I am out in the garage staring at it right now :o

Thanks in advance!!

Fri Oct 16, 2009 6:19 pm

I believe that I was able to slip them all the way onto the runners (runners may have been off but I think they were on) and once they cleared pull them back with my fingers onto the plenum. I used a small hook type tool to work any folded areas. If you are unable to slide them try some silicone spray or talc on them.

Fri Oct 16, 2009 9:57 pm

Didnt end up replacing the 4 hoses. I got the temp 2 in and added new points. Re-connected all of the hoses and now she purrs like a kitten. Took her on a drive through the neighborhood and it has alot of power. Runs real well. Im very happy. Going to Swap out the fuel filter tomorrow and start working on some of the cosmetics.

Super stoked!!

Fri Oct 16, 2009 10:21 pm

Congrats! Those 4 hoses are super tight to put on even when you do it right; ie removing at least half of the runners on one side and unbolting the plenum from the case. Needs to be done for sure, but like I said, if everything else is buttoned down tight vac-wise, you'll be able to run your bus fine for a long time....those things end up looking worse than they are sometimes, i think..

Fri Oct 16, 2009 10:49 pm

Now i just need to get it through smog (DEQ) so I can get my tags. Thats my next goal.

Sat Oct 17, 2009 3:50 am

If you feel the intake runner hoses are sort of loose, you may be able to tighten them up using hose clamps that fit from the local auto parts store until you can replace those the easy way (with the engine out and the FI system all removed).

Always have a new TS II in your parts stash sitting right next to a new set of points. It will save you someday.

Sat Oct 17, 2009 9:17 am

will do for sure. I just cinched some zip ties around those 4 hoses. It runs insanely good. Best $1,500 buck I ever spent. Going to put in a new fuel filter and work on a few cosmetic stuff. Oh and find out if I can adjust the E brake, looks like it adjusts some where near the rear passenger side tire.

Sat Oct 17, 2009 9:26 am

bjjpdx wrote: will do for sure. I just cinched some zip ties around those 4 hoses. It runs insanely good. Best $1,500 buck I ever spent. Going to put in a new fuel filter and work on a few cosmetic stuff. Oh and find out if I can adjust the E brake, looks like it adjusts some where near the rear passenger side tire.

are you talking about the hand brake? correct me if I'm wrong, but doesn't that adjust in the center and forward of the rear wheels, at the spreader bar (the little thing that equalizes the pressure of the single cable from up front and distributes it to the back brakes...)

Sat Oct 17, 2009 10:35 am

The best place to start adjusting the e-brake is to start at the rear brakes and make sure they are adjusted up correctly.

Those star wheels get rusty and need to be cleaned up on the wire brush side of the bench grinder. Lubricate with a 50/50 mix of wheel bearing grease and anti-sieze.