'77 bus hard starting and poor idling.

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mentalQtip
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'77 bus hard starting and poor idling.

Post by mentalQtip » Tue May 24, 2016 1:58 pm

This bus is fuel injected, has hydraulic lifters, and runs pretty well. Getting it started can be frustrating and usually involves frequent cranking and waiting. While cranking usually there is no firing at all and then after waiting seconds to minutes it often will fire right up. Sometimes it will start firing slowly and increase to the point where the gas pedal helps it and it is running.
Idling doesn't usually work until the bus has been warmed up for maybe ten minutes or so and even then may die at a light. After really warmed up it idles pretty reliably.
We've sprayed all around the engine bay looking for any vacuum leaks and found nothing.
Again, it runs really well when driving and feels strong.

Thanks

Joseph

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asiab3
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Re: '77 bus hard starting and poor idling.

Post by asiab3 » Tue May 24, 2016 2:15 pm

Hi Joseph,

The fact that your engine runs well at operating temperature tells us that the warm up system is more than likely at fault. However, before we proceed, there are a few questions:

Has the engine always performed this way? Or is this a new thing? Did it slowly get worse, or did it happen suddenly? Does a basic valves/dwell/timing tuneup help at all?

Do you know what camshaft is in your engine? If you don't, can you contact the builder and confirm a stock-style camshaft?

On a scale of "what's an air filter," to "L-Jet Wizard," how would you rate your fuel injection familiarity?

I have my suspicions, but I'll leave them out until we know more details,
Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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dingo
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Re: '77 bus hard starting and poor idling.

Post by dingo » Tue May 24, 2016 6:45 pm

possibly AAR (aux air regulator) is stuck closed ?
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mentalQtip
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Re: '77 bus hard starting and poor idling.

Post by mentalQtip » Tue May 24, 2016 11:53 pm

Hi asiab3. The engine is a picknpull engine sitting in the garage for some years. No history. It started as poorly running and slowly with attention getting better. Finding that the marks on the flywheel were vastly not where TDC were helped a lot. Is now running electronic ignition. My knowledge of fuel injection is marginal, at best, tho getting better slowly. The engine came with no fuel system so fuel injection was added when the engine was pulled into service and installed. The engine ran badly until the electronic ignition was installed with finding that TDC was about 24 degrees retarded from the 7.5 BTDC mark. Ran alot better then. Also moving the large wheel in AFM 7 spaces ccw. made a huge improvement in the engine power and smoothness. But all along the engine still won't idle or start easily.

Joseph

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tristessa
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Re: '77 bus hard starting and poor idling.

Post by tristessa » Wed May 25, 2016 11:58 am

mentalQtip wrote:finding that TDC was about 24 degrees retarded from the 7.5 BTDC mark. Ran alot better then. Also moving the large wheel in AFM 7 spaces ccw. made a huge improvement in the engine power and smoothness.
The factory pulley mark was at ~17BTDC when we verified the engine was actually at TDC using the "Pull out the #1 spark plug and watch the piston" technique, which is why it would idle nicely at what appeared to be 24-25BTDC using the factory mark. Once we found that the mark was wrong, everything made a lot more sense. :cyclopsani:

Having ~8V at the coil while cranking wasn't helping things. We've got a relayed power feed to the coil for now, pulling 12V straight from the batttery (fused) and using the factory wire to activate the relay. Yes, I know it's not "correct" to do it this way -- we're in troubleshooting/problem-solving mode.

Electrically, the AAR system is functioning correctly. Joseph swapped in a different AAR and said things seemed a little better, but we need to check/clean/verify AAR functionality and also make sure the CSV system is working right and not constantly dripping/dumping gas into the plenum. He's got the old AAR and another spare at his place, I've also got a spare in my garage we can try. Might have him bring the Bus over this evening if he's available.

Yes, the AFM is currently 7 notches CCW on the large cog from where we started, done using the "nudge the AFM wiper CW/CCW and see what the engine likes" method. I'm hesitant to go any farther CCW without putting an air/fuel sniffer on it. Tried calling Westy78 the other day and didn't get an answer, have been too busy to try bugging him again .. or bugging Gypsie. Both have LM-1 meters...
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asiab3
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Re: '77 bus hard starting and poor idling.

Post by asiab3 » Thu May 26, 2016 4:08 pm

tristessa, do I understand that you're working with mentalQtip in person? That's awesome! Let us know if there's anything we can do to help.

Is the pulley mark itself wrong? Or is the scale different from what it should be? I thought the T4 fan/pulley system couldn't be installed wrong due to bolt offset, but I guess if the fan was disassembled (A BIG NO-NO) then anything could be possible…

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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tristessa
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Re: '77 bus hard starting and poor idling.

Post by tristessa » Thu May 26, 2016 4:53 pm

Yeah, we've been rassling with this thing for a while.

He brought the Westy over last night and we tested three spare" AAR's, including his old one. All close up within the specified amount of time, though "my" spare off the shelf closed faster and got more "closed" than the other two. Told him to swap it in and see if that helped.

It's a factory plastic scale in reasonably good condition, the pulley mark itself was wrong. if someone disassembled the fan/pulley and put it together wrong, the mark would be 90*deg off (4 bolts). If the assembly had been put on the hub wrong (assuming missing locating dowel), it would be 120*deg off (3 bolts). No matter how I work the numbers, I can't find anything in that scenario that would make the marking 17*deg off. Next thing to check get to the bottom of the problem would be to pull the hub off the crank and check the woodruff key and the keyway, but for right now we're on the "making it start and idle correctly" path and will come back to that part of things later.

As soon as he sends me his address (because I haven't been to his new place yet), we'll be borrowing Westy78's LM-1 to check the mixture more .. maybe tomorrow afternoonish, maybe Sunday evening. I'm booked Saturday with taking my wife to see The Cure...
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tristessa
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Re: '77 bus hard starting and poor idling.

Post by tristessa » Fri May 27, 2016 9:49 am

Joseph swapped the AAR for "my" spare and it seems to idle pretty well. Rattle from the throwout bearing that goes away when the pedal is engaged, rattle from the shifter that says "worn shift rod bushings" to me. Test drive continues...
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sgkent
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Re: '77 bus hard starting and poor idling.

Post by sgkent » Sun May 29, 2016 9:50 am

If the AAR did not solve the issue, which I suspect it will not because holding the throttle open a little as the engine warms accomplishes the same thing as to testing purposes, Looking at the TSII, ignition switch, fuel pump, FPR, and CSV will probably be the most productive. The AAR should really be called a "Cold Idle Throttle Bypass Valve" because that is what it does. It effectively holds the throttle open by bypassing air around it. The CSV, FPR, TSII, and fuel pump all determine how much fuel is delivered when the engine is cold. A cold engine needs more fuel


Fuel Pump fails to start or its relay fails - no fuel pressure in run position or at all
CSV - no enrichment when cold starting
FPR - wrong fuel pressure can cause lots of issues
TSII - temperature enrichment circuit fails
Ignition switch - as they age the plastic part with the contacts cracks. This can cause changes in distance between contacts so that it fails to connect all the circuits when cold, or the opposite - it can make the connections when cold then open up when warm.
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asiab3
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Re: '77 bus hard starting and poor idling.

Post by asiab3 » Mon May 30, 2016 12:13 am

Steve, while I think your points are good for troubleshooting, I would not discount the differences in throttle and AAR air so quickly; the position of the AAR hose is always next to the CSV on L-Jet systems, at least as far as Volkswagens go. Nissan borrowed L-Jet and did the same thing: CSV and AAR are plumbed as close as possible within the confines of engine compartment real estate. Same with the 82-89 Spiders, no? (I'm not sure on that last one. Never peeked under the hood, only internet readings…) The airstream complimenting the CSV fuel squirt can help atomize the fuel more efficiently, maybe enough to even make a noticeable difference. Westfabulous went through this exact issue a few years ago…

Since the throttle cracking also gives more vacuum advance, I think the test of bypassing the AAR with a hose is substantially different enough to warrant a few minutes of time, especially if money is tight and new parts aren't handy to swap in.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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