79 Bus hard start / rough running after a short rest

[St.Bus]

hmm, do you know how to adjust the AFM?
look in the type2 archives to find some info on leaning out the mixture. I would put new injector 0-rings in there also if they are the original ones.

from the type2 archive
"And last but not least, the air flow meter provides the provision for idle mixture adjustment. There is a screw in the housing of the air flow meter that is used as a valve for an air bypass channel. The air flowing through this channel is not measured by the air flow meter and so affects the fuel/air mixture. Turning the screw clockwise blocks off the channel and so richens the mixture. Turning the screw counterclockwise opens the passage and so leans the mixture, as the extra air is not measured by the air flow meter and so the computer does not compensate for it. "

[vetterdog]

I have no idea how to adjust the AFM, other than adjusting the mixture screw. I will look into it and post any results.  Today, I ran the bus for a bit, then let it sit and pulled the spark plugs to see if any were wet to indicate a leaking injector. They were all nice and dry, which is good, since I replaced all the injectors a few years ago, (so they're not the originals). I poked aroung the engine and realized that the thermostat cable wasn't adjusted properly, so the flaps connected to the cable were staying closed. I though that this might be the whole trouble, so I adjusted the cable and took the bus for a test drive. It ran really well and I noticed it was running about 50-75 degrees cooler too.  I had set the timing a tiny bit advanced to smooth out the idle, )which through this whole ordeal has been set higher and higher just to keep the darned thing idling) but after a few minutes of driving I noticed that it was idling very fast, so I stopped and turned the idle screw way down, back to about where it was originally set and it ran nice and smooth and quiet. I was sure I had it solved. I got back home and decided the timing should be reset, so I went about doing so. Now the bus was sitting after use, and as soon as I wanted to start the engine to use a strobe it reverted back to it's nasty habit of not wanting to idle. It would die instantly as soon as I took my foot off of the gas pedal. So I set the timing statically but still it wouldn't idle. It's like the problem was solved temporarily, but as soon as the bus sat still for 10 minuted or so I was back to square one.  I wasn't about to back out the idle screw 3 or 4 whole turns just to get this thing to stay running. I need to figure this out, as I have a few campouts I have promised the kids I would take them to. (Granny Grose's and Westies in the Woods, Stoke State Forest NJ) I'm getting so frustrated and desperate that I might resort to taking the thing to an actual mechanic, which for me would be the ultimate defeat.

[vetterdog]

The plot thickens. After realising that the air flaps have been closed, I figured I'd better check my valve clearances, since they're probably out of whack. Well, they were all tight, so I reset them, but now the bus won't start at all. Now I'm backing up to having to figure out why it won't start, which will mean compression check, etc. etc. and I've made some plans for camping in a week and a half. Panic isn't far off, I think.

[vetterdog]

Thanks to all who've been following this oddessy and helped along the way. Realised that my dizzy clamp had migrated southwards and wasn't letting the shaft seat all the way down into its hole, so fixed that, checked the compression (all good, right around 100) and got the bus started. It smoked a bit, heavily at first, but tweaked the idle and test drove it this morning and it runs pretty good. Smoke has stopped altogether.  As of right now it's looking good. I won't declare victory just yet, I will drive around a bit tonight and tomorrow and see how it goes. I'll be holding my breath for the next day or so.

[St.Bus]

hey it sounds like the same issues I had, I recently just redid the top FI  portion, all the hoses and boots and injector 0-rings, and when I started it up, the idle was way high!!! so I had to cut it back like 4 whole turns, also when I rechecked the timing it was at 12°BTDC, which was 7.5 with the vac leaks..so I static timed it back... I think you have some vacume leaks in there..prolly in the intakes or injector seals..Joe

[vetterdog]

Thanks for the tips, I am off from work today will look into those spots and let you know. Seems to be running a bit hot too. Getting there by degrees. (pun?)
-Dave

[vetterdog]

So far so good, but now I notice it's struggling a bit in the lower rpms when accelerating. I can feel it hesitating, at the beginning of each gear and if I cruise at the bottom of each gear's range (like 40mph in 4th gear) it bucks a little, sometimes a lot. I suspect valves need re-adjusting after all the travails of this long process, but I'm not ruling out something else. (Burned valve, or electrical) Will post any developments. Meanwhile, we will be schlepping out to Granny Grose's Friday regardless, so anyone else heading out there, be on the lookout for us on the shoulder of Rts 78 or Old 22. Look for smoke/cursing/wrench throwing.

[vetterdog]

Turns out the intake air tube was not tightened and all I needed to do was tighten it and problem was solved. Got a lot of maintenance done in the process though.

[prez]

Vacume is the key to the Air Flow Control systems, ['75-'82.]   Look for larger leaks, like these, as they were made to bediagnosed  with basic tools.   I find them to be quite relialable.

[St.Bus]

Turns out the intake air tube was not tightened and all I needed to do was tighten it and problem was solved. Got a lot of maintenance done in the process though.

LOL!
Isnt it usually the case..go to the ends of the earth and its something minor eh?
good part is, all those other items may have failed if you increased the vacuum by thightening the boot. now, you know they are out of the way and dont need replacing for sometime now...Joe