Hi guys today I was driving the bus around my moble home park and there is alot of speed bumps and at almost every speed bump my bus would die and it would also die when ever I would press the brakes while driving. It wasent a bad die like the engine just cut off but when I would press on the bracks the engine would slowly die. It wasent doing it yesterday so I dont know whats wrong. In my driveway it it was idleing really low but I fixed that and it idles really good The bus wont die at all when im driving it or when its parked. It only dies when I press on the brakes. It doesent have that much gas in it so I thought maybe when I press the brakes the gas would go to the front of the tank and the engine would stall. It sounds dumb but thats the only thing that I could think of Does anyone know whats wrong?
greetings, it sounds like a vacuum leak, at least it is easier to check simple things first , check all rubber hoses you can find. then i would get 4 or 5 gallons o gas . do u have a good fuel filter ? are your batery connections clean & tight ? check your fuses ?
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one sees great things from the valley, only small things from the peak.
I dont know if its a vacum leak or not but it might be cause the vacum lines look pritty old. I went and put about 1 and a half gallons in earlyer and if felt fine driving around like nothing was wrong at all but then I took it back home and turned it off and a little later I turned it back on again and tried to drive it and the same thing started to happen but not as bad as earler in the morning. I just got a brand new fuel filter when I got my fuel pump witch happend on tuesday but I was thinking that maybe it was having truble getting fuel. When I started it a cuple of times it sounded like it was cutting out on me so I think I might need to flush my gas tank I dont know if you read my last post but my gas tank was clogged and I unclogged it but I think it might still be clogging up the lines maybe. My battery is very tight and it is a new battery and my fuses are good also so I think its somthing to do with the fuel on this one My sending unit is bad also so I think its just giving me signs to take the tank out and fix it up a little
I really dont want to cause im lazy but I guess I must
Ask yourself ... "how old are my vaccuum hoses, vent hoses and fuel lines?" If you don't know the question, replace them all. Use good german VW style hose in the right size. Particularly replace your fuel lines ... all of them from the gas tank forward. a 77 should have fuel injection, unless someone took it out and put in carbs, so you also need to look for a fuel line from the fuel pressure regulator back to the gas tank. Its messy, but it could save your bus. Ever notice busses at the wrecker with burned bums? Ever wonder why? Old fuel lines bursting under pressure and spraying gas on hot engine. Boom! Very nasty.
Replace all the lines if you haven't already, they could be over 20 years old!
The FI system requires all your hoses to be in good shape to work properly, as it take readings on the air pressure, and your distributor is vaccuum advance. the hoses crack and the end, so have a look, if they come off easy, or are crackled when you roll the end between thumb and finger, they should be changed over. Its a good preventative measure, even if it doesn't solve your present problem.
The prior post suggests a vaccuum problem because it happens when you put on the breaks. Your breaks are vaccum assist, and there is a 1/2 diameter hose coming either through the back engine tin, or next to it, on the driver's side which connects to a fitting on your plenum, driver's side, towards the back of the engine (closer to you looking in -- remember, you are at the back looking forward, so the back is closer, front is farther away). The hose goes into a T or Y shaped black rubber doo-dad, with 3 outlets, one for the hose to the vaccuum unit up front, at the other end, to the plenum, and the one at the top, connects to another hose that goes to this metal vaccuum diaphram mounted on the firewall, about the size of a hockey puck.
All those hoses and fittings should be in good shape, or replaced.
But, having said I that, I don't think that's your problem. I'll bet you are introducing air into your plenum when you put on the breaks, making the air mixture into your cylinders too lean. Since it happens when you break, you may also want to check the vaccuum assist servo under the van. I'll be that something in the break system is leaking air, when its supposed to only borrow the vaccuum created by all the air rushing into your engine.
It might be possible to diagnose the problem by having someone apply the brakes while you are under the van, and listen for air leaks from the break system backwards.
Replace the hoses if they are old or of "unkown" vintage. But, I think your problem is likely going to be with your brake servo upfront.
Anytime you step on your brakes and the engine idle changes there is a vacuum leak, the booster pulls alot and is a easy indication there are some bad lines.
Thank you guys very much for all the help I am going to get under it today and check out the air hoses and see whats up Hopfuly I will find the problum right away
The bus wont die at all when im driving it or when its parked. It only dies when I press on the brakes. It doesent have that much gas in it so I thought maybe when I press the brakes the gas would go to the front of the tank and the engine would stall. It sounds dumb but thats the only thing that I could think of 
I dont know if you read my last post but my gas tank was clogged and I unclogged it but I think it might still be clogging up the lines maybe. My battery is very tight and it is a new battery and my fuses are good also so I think its somthing to do with the fuel on this one 
