78 Bus with startup problem

« **on:** June 23, 2006, 01:07:29 PM »

Hi,

My 78 bus is acting strangely when I start it up. I got from a 10 hour drive last weekend and all went well. Yesterday when I went to start the bus engine, there was a plop sound like when a piston misfires.

The engine revs then went a lot higher than normal, then it quit. When I give the engine some gas, the revs go way up for a few seconds, then it falls off and dies. There's no in-between. Gas = way high revs, no gas = falls off and dies after a couple of seconds of running.

Any tips as to where to start looking for the problem appreciated. This is a fuel-injected pancake engine.

Ret.Bugtech · « **Reply #1 on:** June 23, 2006, 01:48:49 PM »

How about checking ALL hoses in the engine comp. .big ones , little ones and ALL rubber boots. Check for cracks in the hoses and connections. Sometimes they look OK until you move them around. Sometimes these varments will backfire and blow boots, hoses off. So look closely. Hoses around your air-mass meter boot down to the intake pleumn(?) are famous for air leaks. Keep us posted

« **Reply #2 on:** June 23, 2006, 11:19:49 PM »

Well, that nailed it. I poked around and found a couple of hoses that were loose. One went to a canister on the right rear wall, which I think is of minor importance.

The other one was a line that runs into the firewall on the left side and entered the engine at the manifold...or at least I think it's the manifold. Maybe the airplenum. Not being all that savvy on my engine, I'm not sure how to identify it.

In any event, started right up. Thanks!

Ret.Bugtech · « **Reply #3 on:** June 24, 2006, 12:55:02 AM »

Good deal ! That hose could have been the hose to the brake booster. Did you have any problem with the brakes ? Anyway ,you are very welcome and glad it was that simple :thumbs-up:

Gobusgo · « **Reply #4 on:** June 24, 2006, 02:47:13 AM »

tlxreed Posted:

Quote

One went to a canister on the right rear wall, which I think is of minor importance.

That is most likely the evaporative canister to "filter" the gas fumes from the gas tank. It is filled with charcoal (or a charcoal like substance).

Quote

The other one was a line that runs into the firewall on the left side and entered the engine at the manifold.

Like RetBugtech said, that is most likely the hose to the brake booster. It should connect to a "Y" fitting...one part of the "Y" goes up to air plenum with an extended hard plastic hose, and the other part continues on to the air manifold. If you had been driving with it unattached, your brakes would still work, but you would have to work harder to stop the bus.

« **Reply #5 on:** June 24, 2006, 12:03:56 PM »

That's it. The hose from the firewall was loose at the Y junction. Why would that particular hose make the engine race or die off if it's connected to the brake booster? I didn't notice any brake problems while driving.

Gobusgo · « **Reply #6 on:** June 24, 2006, 01:56:36 PM »

If it is not connected, then there is a vacuum leak. These fuel injected critters will not run right if there is the slightest vacuum leak.

http://www.ratwell.com/technical/VacuumHoses.html

Go the Home page of the above link and there is a whole lot more information.

Ret.Bugtech · « **Reply #7 on:** June 24, 2006, 02:43:39 PM »

This brings up something else speaking of brakes. If you seem to have to use the same amount of effort to stop the van with hose on or off, you may have a brake booster that going South on you or the check valve on the booster is going bad. When all is right with the brakes, these vans will have brakes from hell with little effort.

VWGirl · « **Reply #8 on:** June 24, 2006, 10:37:02 PM »

Quote from: "Ret.Bugtech"

This brings up something else speaking of brakes. If you seem to have to use the same amount of effort to stop the van with hose on or off, you may have a brake booster that going South on you or the check valve on the booster is going bad. When all is right with the brakes, these vans will have brakes from hell with little effort.

is the idle change normal when you hit the brakes while parked???

Gobusgo · « **Reply #9 on:** June 24, 2006, 10:49:27 PM »

VWGirl Posted:

Quote

is the idle change normal when you hit the brakes while parked???

You know, I have noticed that with my Westy as well. It doesn't happen all the time. Also, sometimes the idle is high when sitting at the red light...sometimes not.

Ret.Bugtech · « **Reply #10 on:** June 24, 2006, 11:49:23 PM »

The idle can change if the brakes are "pumped" ,but its not suppose to remain high if the brake pedal is held down. It should return to normal idle very quickly. When I say "high" idle it may not be 50 rpm but you might notice it. The sudden demand from your booster upsets the vacumn values in the intake and is what causes this to occur. All this is pretty much normal.
I have seen boosters so bad that if you pumped your brakes ,the engine would stall or run very roughly.
Look at it this way. Every thing to do with the fuel injection or brakes are nothing but a controled air leak.

Forums

Topic: 78 Bus with startup problem (Read 3850 times)

Guest

78 Bus with startup problem

Ret.Bugtech

78 Bus with startup problem

Guest

78 Bus with startup problem

Ret.Bugtech

78 Bus with startup problem

Gobusgo

78 Bus with startup problem

Guest

78 Bus with startup problem

Gobusgo

78 Bus with startup problem

Ret.Bugtech

78 Bus with startup problem

VWGirl

78 Bus with startup problem

Gobusgo

78 Bus with startup problem

Ret.Bugtech

78 Bus with startup problem

About Us

Follow Us

Contact Us