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Bus starts then dies

Posted: Sat Apr 09, 2011 2:56 pm
by mentalQtip
Ok. '77 2 liter fuel injected bus. Lately I had noticed that my bus had developed a stumble when starting from a stop. As it picked up rpm it would suddenly pick up power until I shifted again. Looking back I realize that overall power was down also. Yesterday it started to die on me when I left the rpm drop. Today I went out to check the timing(was about 3 degrees BTDC), adjusted to about 8, went to start it and it started ok but lasted about 5 seconds and died. Started easily again and died. Lasts about 5 seconds.
Before when I had something like this it turned out to be a vacuum hose loose but I can't find anything loose now. I'm thinking, "what could I have done while adjusting the timing?"
I'm at a loss. Any thoughts?

Re: Bus starts then dies

Posted: Sat Apr 09, 2011 3:35 pm
by bajaman72
Adjust the points first.. then set timing. Points that are off will affect timing.

Re: Bus starts then dies

Posted: Sat Apr 09, 2011 5:55 pm
by chitwnvw
bajaman72 wrote:Adjust the points first.. then set timing. Points that are off will affect timing.
2nd. It is the starting point.

Re: Bus starts then dies

Posted: Sun Apr 10, 2011 5:08 pm
by mentalQtip
ok. Checked the points at .016. Timing is 7.5 BTDC. Still starts easy and dies after about 5 seconds. The fact that it dies after running suggests to me a fuel delivery problem, right? What else could it be?
As I said in the first post, first noticed a stumble, some power loss, then started to die when I let the rpm drop, and now won't keep running at all, even when I try to give more gas.

Possible fuel delivery problem? Maybe a vacuum leak?

Re: Bus starts then dies

Posted: Mon Apr 11, 2011 3:46 am
by Randy in Maine
I am only on here for a second today, but go over here and look at what they suggest....

http://manuals.type4.org/ljet/

Re: Bus starts then dies

Posted: Mon Apr 11, 2011 9:54 am
by vwlover77
Are you sure the 90 degree rubber elbow air hose for the aux air regulator is OK? These are hard to see and if they split or break, you'll have the symptoms you describe.

Re: Bus starts then dies

Posted: Mon Apr 11, 2011 10:50 am
by chitwnvw
Have you checked with the AFM wiper to make sure that the fuel pump power is switching over successfully. You might just be getting that initial spray from the cold start valve and that is it.

Re: Bus starts then dies

Posted: Mon Apr 11, 2011 6:42 pm
by soulful66
vwlover77 wrote:Are you sure the 90 degree rubber elbow air hose for the aux air regulator is OK? These are hard to see and if they split or break, you'll have the symptoms you describe.
+1 0n this, I had the problem and this was the cause.
Regards,
john

Re: Bus starts then dies

Posted: Tue May 03, 2011 5:08 pm
by mentalQtip
Since I am very intimidated by the fuel injection part of this, I replaced the dual relay just because it was easy and I had a spare. Fired right up and idled fine. I drove it and it ran crappy so I checked the timing again (ooops) set it at 7.5 BTDC and it ran great.
Feel guilty that I didn't do any proper diagnosis.
Thanks to all for the input.

Re: Bus starts then dies

Posted: Tue May 03, 2011 5:24 pm
by chitwnvw
mentalQtip wrote:Since I am very intimidated by the fuel injection part of this, I replaced the dual relay just because it was easy and I had a spare. Fired right up and idled fine. I drove it and it ran crappy so I checked the timing again (ooops) set it at 7.5 BTDC and it ran great.
Feel guilty that I didn't do any proper diagnosis.
Thanks to all for the input.
Don't feel too bad. Part swapping was how I discovered my series resistor was bad. In theory, proper problem solving is the way, in my case it was an intermittent problem that kept leaving me SOL in the middle of busy intersections... Finally, it happened where I could run home and swap out probable bad parts, and voila problem solved.

Re: Bus starts then dies

Posted: Fri May 06, 2011 8:28 am
by Amskeptic
chitwnvw wrote:Finally, swap out probable bad parts.
Ouch, baby, ouch.
Headmaster
Itinerant Air-Cooled Academy

Re: Bus starts then dies

Posted: Wed Jul 11, 2012 10:47 am
by fractal_man
Right on the nose for me with the vacuum leak at the 90 degree fitting. Thanks to all you folks who post this valuable information.