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RidinRetro1973
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Joined: April 10, 2007
Posts: 599
Location: Chicago
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 Posted: Tue Jul 04, 2017 3:13 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| skills@eurocarsplus wrote: |
| the #3 not pulling it's weight can be a result of the #4 intake stuffing the intake tract full of compression and blowing raw fuel into the intake. think of carburetor reversion, except in a "sealed" system. I have seen this where 1 misfire will set off random multiple misfires on more modern cars when the problem is in only 1 cylinder |
As best as I understood, this was Colin's explanation as well. Maybe he'll chime in to clarify.
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telford dorr
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Location: San Diego (Encinitas)
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| Posted: Tue Jul 04, 2017 8:45 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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Reasonable explanation. I would have thought that if #4 was that bad, its power output would be worse than #3. Waiting for the post-rebuild results.
While it's apart, do a full test of all five injectors to make sure they spray a nice narrow fan and don't drip.
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Amskeptic
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Joined: October 18, 2002
Posts: 8568
Location: All Across The Country
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| Posted: Wed Jul 05, 2017 7:03 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| skills@eurocarsplus wrote: |
| the #3 not pulling it's weight can be a result of the #4 intake stuffing the intake tract full of compression and blowing raw fuel into the intake. think of carburetor reversion, except in a "sealed" system. I have seen this where 1 misfire will set off random multiple misfires on more modern cars when the problem is in only 1 cylinder |
Bingo! The AFM was having a difficult time figuring out what signal to send as well. Not just raw fuel into the intake, actual combustion leaking into the intake.
Ryan deserves a rest from this painful saga.
Colin
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Amskeptic
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Joined: October 18, 2002
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| Posted: Wed Jul 05, 2017 7:07 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| telford dorr wrote: |
Reasonable explanation. I would have thought that if #4 was that bad, its power output would be worse than #3. Waiting for the post-rebuild results.
While it's apart, do a full test of all five injectors to make sure they spray a nice narrow fan and don't drip. |
Strangely enough, #4 had a decent 120 psi compression and three had 140 psi.
Seriously, I would have expected to trip across a burnt valve a whole lot sooner than this and I sure as heck would have assumed that it was #3 with the bad valve. But we can only surmise at this point that #4 intake which precedes #3 was sabotaging the charge.
Don't think there wasn't head scratching when we saw a nice spark, well timed, good compression, and verified fuel delivery coming to #3 yet it played dead.
Colin
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raygreenwood
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Joined: November 24, 2008
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Location: Oklahoma City
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| Posted: Wed Jul 05, 2017 11:29 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| Amskeptic wrote: |
| telford dorr wrote: |
Reasonable explanation. I would have thought that if #4 was that bad, its power output would be worse than #3. Waiting for the post-rebuild results.
While it's apart, do a full test of all five injectors to make sure they spray a nice narrow fan and don't drip. |
Strangely enough, #4 had a decent 120 psi compression and three had 140 psi.
Seriously, I would have expected to trip across a burnt valve a whole lot sooner than this and I sure as heck would have assumed that it was #3 with the bad valve. But we can only surmise at this point that #4 intake which precedes #3 was sabotaging the charge.
Don't think there wasn't head scratching when we saw a nice spark, well timed, good compression, and verified fuel delivery coming to #3 yet it played dead.
Colin |
You are looking at the right concept but possibly the wrong cylinders causing effect. Any of the 4 could cause what you just noted.
The firing order is 1,4, 3 2.
Looking/thinking about it in slow motion.... In a central plenum system with this firing order.....you end up with a diagonal pressure push/pull across the center of the plenum.
Intake valve one shuts first in the face of a high velocity column of air.
But unlike a carb system it does not cause reversion up to the TB. It causes reversion into the plenum.
This reversion is not normally a cause for concern....because across across the plenum you have #4 intake valve in motion absorbing some of the back pressure pulse into its runner. This is part of why a plenum and runner system.
You do have some asymmetry in the system as the next valve to absorb the reversion column is #3 on the same side....but as long as there is a valve open to absorb the reversion push....its not an issue. Its also part of the reason for the asymmetrical shape of the factory plenum.
Very well designed...and actually quite a bit better than the more symmetrical shape of the Porsche 914 2.0L plenum.
My point...is that if one of the cylinders on the 1, 2 bank is weak in compression or poor in lift due to a bad lifter etc....it can cause the issue you and skills are describing just as easily.
One thing to remember.....if the reversion is getting far enough up the "food chain" to affect the AFM....its making it through the TB and that is no small feat as the turbulence plume created by the TB is roughly 3/4 length of the plenum...gets bounced off the curved wall inside the plenum and re-centered into the "air knot" or crossing in the center of the plenum.
At one time...around 1997-99...I had taken pictures of this turbulence pattern during a smoke test inside of a plenum with a strobe taken through the CSV port at about 2500 rpm. They are somewhere in my collection of 35mm black and white. Some day I will dig them out.
But the point being that yes....if one cylinder/individual runner is causing a reversion charge in excess of normal...it can screw up that knot of turbulence inside of the plenum and starve the next cylinder in line.
In the type 4 L-jet bus plenums...its HARD to create reversion that exits the TB unless you have cylinder pressure behind it (cracked/burned valve, burned seat, bent valve that is not seating all the way etc.)
But what can happen even quicker than that....is loss of positive/smooth vacuum control at the fuel pressure regulator. Just some things to think about. Ray |
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Wildthings
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| Posted: Wed Jul 05, 2017 12:43 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| Don't know if this is a California model with an O2 sensor, but if so and you have one cylinder that isn't drawing the correct amount of air for whatever reason the O2 sensor and ECU will attempt to get the mixture right and may throw the mixture off for all the cylinders as a result. |
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Hoody
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Joined: November 28, 2007
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| Posted: Thu Jul 06, 2017 7:38 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| I hope your not taking it back to the same engine builder who fucked up the build to begin with. Some times you have to cut your losses. I don't know what your budget is but the first thing you should do if you can afford it is buy a set of Ham "Stock" heads. You need a "Guru" engine builder. I know of 2 in Ohio. Both are very busy. But if they build your engine it will be a lifetime before you need a rebuild. There are waaaay too many hacks out there. I read stories every day on here about rebuilds and none of them have happy endings. Parts are getting harder and harder to find. But you can still locate them if you know where to look and are not afraid to spend the money on original German parts. PM me and I can put you in touch with my friends. |
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Amskeptic
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Joined: October 18, 2002
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Location: All Across The Country
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| Posted: Fri Jul 07, 2017 8:13 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| raygreenwood wrote: |
In the type 4 L-jet bus plenums...its HARD to create reversion that exits the TB unless you have cylinder pressure behind it (cracked/burned valve, burned seat, bent valve that is not seating all the way etc.)
Ray |
This summer I have seen three AFM flaps dance crazily during cranking and two of those three had wipers that matched my vacuum gauge needle movement.
AFMs are beautifully engineered with that little "other flap" section across the pivot from the main flap that cancels out usual manifold pressure effects on the movement of the wiper, so I think we were observing actual air flow disruption.
Colin
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RidinRetro1973
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| Posted: Mon Nov 06, 2017 8:59 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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Just a quick update!
The followers of this thread will recall that a lot of the problems with this Bus were result of half-assed-ness from a "reputable" aircooled shop. After Colin's visit, we knew the motor was fried as result of the work performed by this shop.
The engine builder and the shop are two different entities, we no longer trust the shop, but we trust the engine builder. After talking to him about what had happened, he stood behind his work and promised to make it right no matter the cost. He has since broken partnership with the shop. The problem was pulling the engine and getting it to the builder.
One of the mechanics who worked for the shop(and worked extensively on my Bus during his time there) decided to part ways with the business a few years ago and open up his own aircooled shop. He left the business because he saw the poor quality of work that was going on there and disagreed with the owners desire to cut corners. He has done a lot of great work for me on my '68 Beetle and I trust him fully. The quality of work coming from his shop is top notch, and they stand behind everything they do.
He moved into a new building in October and the Westy is their first resident. They pulled the engine within the first week and disassembled down to the block to send back to the builder for a fresh set of heads and some other bits and bobs. The season is over here, but the engine should be back in and running before Christmas. I'll be back to post an update then.
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vwwestyman
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Happyfolk
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Location: Madison, WI
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| Posted: Wed Jul 25, 2018 4:20 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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How’s the engine coming along?
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Van Gooo
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Joined: July 16, 2018
Posts: 44
Location: Indy
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| Posted: Thu Aug 09, 2018 8:07 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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Ryan,
I am new to VW ownership. I just read this thread front to back, and wow, you have been through the ringer with this motor. I too would like to know what is the latest with your 79. I too have FI, and this has been an education for me for sure.
Would love to know where everything stands with your bus.
Peace,
JG
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VanGooo
77 Westy
DOB 9-2-76
CA bus 2.0 FI
"It is what it is or else it would be weird." |
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Thu Aug 09, 2018 8:49 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| Van Gooo wrote: |
Ryan,
I am new to VW ownership. I just read this thread front to back, and wow, you have been through the ringer with this motor. I too would like to know what is the latest with your 79. I too have FI, and this has been an education for me for sure.
Would love to know where everything stands with your bus.
Peace,
JG |
welcome Van Gooo. 9 ft lbs only on the oil strainer nut to prevent a very costly repair. someone will post the welcome to a first time poster here.
edit :
here
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Every Type IV engine owner should know this!!!
If you over tighten the Oil Strainer bolt, you will break the engine case!
There is a Oil strainer in there.
TORQUE THE STRAINER BOLT TO NO MORE THAN 9 FT. LBS. |
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Van Gooo
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Location: Indy
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| Posted: Thu Aug 09, 2018 9:25 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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Thank you SGKent. That is critical to know about the torque on the oil strainer nut.
Thank you Tcash. This site is flat out amazing.
Will post photos of Vangooo soon!
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VanGooo
77 Westy
DOB 9-2-76
CA bus 2.0 FI
"It is what it is or else it would be weird." |
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RidinRetro1973
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Posts: 599
Location: Chicago
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| Posted: Sat Aug 11, 2018 2:43 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| Van Gooo wrote: |
Ryan,
I am new to VW ownership. I just read this thread front to back, and wow, you have been through the ringer with this motor. I too would like to know what is the latest with your 79. I too have FI, and this has been an education for me for sure.
Would love to know where everything stands with your bus.
Peace,
JG |
Hey there!
The engine got a new seat of heads as after teardown a bent valve was found. I had a IAC appointment last month, and Colin and I got the Bus running in tip top shape!
I see you're in Indy, join us next month here: http://1kathrynbowman.wixsite.com/bnnta/location
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SGKent
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| Posted: Sat Aug 11, 2018 4:25 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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awesome ending to the story. Bent valve implies a weak valve spring or sticking valve caused all this.
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Wildthings
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Posts: 50348
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| Posted: Sat Aug 11, 2018 6:15 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| SGKent wrote: |
| awesome ending to the story. Bent valve implies a weak valve spring or sticking valve caused all this. |
500 miles in three years would likely mean old rotten fuel in the tank, which could translate into the valve(s) sticking in the guides. I have become a real strong believer in dumping something like a quart of 2 cycle oil or a quart of synthetic motor oil into a full tank of gas to help lube an engine that has been sitting for a long while and is put back in service. Tight guides on a rebuilt head do not help this problem a bit. |
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Van Gooo
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Joined: July 16, 2018
Posts: 44
Location: Indy
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| Posted: Sun Aug 12, 2018 12:45 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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That is great Ryan!!
I am planning on being there Labor Day weekend!
Looking forward to me you and other air cooled buds!!
Take care!
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VanGooo
77 Westy
DOB 9-2-76
CA bus 2.0 FI
"It is what it is or else it would be weird." |
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Hoody
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Joined: November 28, 2007
Posts: 1948
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| Posted: Sun Aug 12, 2018 5:13 pm Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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| That’s great news! Glad to hear you have a mechanic and an engine builder that stands behind his work! |
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Burlyhammer
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Posts: 1693
Location: Great north woods Maine
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| Posted: Mon Aug 13, 2018 9:48 am Post subject: Re: '79 Fuel Injection Poor Performance Over 60mph |
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[/quote]
Looks like you have an Old Town Canoe
Those are made in the town beside mine in Maine. They are the best!
Here's a photo of our Westy with Old Town Kayak on the way to Buses by the Buoy in Union Maine, last year.
I have been following your thread to help with my own fuel injection issues. I am glad you got your bus going. Have fun! |
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