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dlwilson Samba Member
Joined: December 14, 2020 Posts: 99 Location: Lake Worth, FL
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Posted: Sat Jun 19, 2021 5:22 pm Post subject: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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So I have my freshly rebuilt type 4 1.7L engine with dual carbs installed in the bus, but I cannot get it to idle. If I hold my foot down I can keep it at high revs, but as soon as I let up it will die.
Before I installed it, it ran strong for 20 minutes on the bench at perhaps 2500 rpm for cam break-in, then ran out of gas, so I didn't have a chance to try it at idle on the bench. I do feel like it ran stronger on the bench, out of a gas can, than it does no.
It has dual carbs I bought from a Samba member who took them off a similar 1.7L bus engine. I have replaced almost all of the linkage from pedal to carbs, but I still don't like the feel of it.
The tank was cleaned and sealed by the previous owner. I put two gallons of fresh gas in the dry tank. The new, clear fuel filter I put below the tank looks pristine, with no crap at all in it.
It has a Chinese vacuum advance distributor. I set static timing, but am waiting on a friend who knows about such things to put a timing light on it. I have checked closely for vacuum leaks.
The mechanical fuel pump is the one that came with this engine when I bought it as a core. I didn't rebuild it. Could it be moving enough fuel when the engine is running at high RPMs, and not moving enough for idle at low RPMs? That's all I can think of.
Any other ideas? I hate to just throw a fuel pump at it.
_________________ 1977 Bus, with 1973 1.7L engine (rebuild complete, install underway) |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51144 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sat Jun 19, 2021 5:50 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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Do all 3 solenoids click? _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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dlwilson Samba Member
Joined: December 14, 2020 Posts: 99 Location: Lake Worth, FL
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Posted: Sat Jun 19, 2021 7:29 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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busdaddy wrote: |
Do all 3 solenoids click? |
What is the third solenoid? I've heard clicks from the two on the carbs, but will confirm specifically that each one is opening, but I can't think of a third one? _________________ 1977 Bus, with 1973 1.7L engine (rebuild complete, install underway) |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51144 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sat Jun 19, 2021 9:13 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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There's 2 on the LH carb, one for the idle circuit on the carb, and a second for the CIS carb that supplies the tube across under the air cleaner. The CIS carb is built into the LH unit, it's intake throat is the brass tube that sticks up and connects to the pizza slice with the elbows and bent tube. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22665 Location: NYC/Upstate/ROW
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Posted: Sun Jun 20, 2021 2:43 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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Those vacuum block offs look sub par. Get something solid in them, with a clamp. I don’t think fuel delivery is the problem but you can diagnose by inspecting fuel level in the bowl _________________ .ssS! |
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kreemoweet Samba Member
Joined: March 13, 2008 Posts: 3898 Location: Seattle, WA
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Posted: Sun Jun 20, 2021 6:55 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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The role of the fuel pump is to provide gas at a certain pressure to the carbs, and it does this
no matter what the engine rpms. How much fuel enters the carbs is dependent on the carb inlet
valves and floats, which in turn are affected by how much fuel the engine is actually consuming.
So not your fuel pump: inadequate fuel pump output would manifest at high rpms, not low ones. _________________ '67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities
Stop dead photo links! Post your photos to The Samba Gallery! |
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dlwilson Samba Member
Joined: December 14, 2020 Posts: 99 Location: Lake Worth, FL
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Posted: Thu Jun 24, 2021 7:31 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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I was able to work on it for a while tonight. These carbs only have one solenoid each, but they are operating. I found that the solenoids were screwed in loosely, and tightening them helped stabilize the idle. Then my buddy used a timing gun to set the timing to 10 degrees like Bentley says, and that made it idle reasonably well. But it won't make power.
It's really hard to get it to rev, and when it does rev, and I engage the clutch, it just dies. Like it's not making any torque. Or power.
I inspected the manifold vacuum blockoffs, and they seem well constructed.
It has a Chinese vacuum advance distributor, and we can see it advancing. We tried taking off the vacuum hose (and plugging it) and that didn't help. It backfires out of the driver side carburetor sometimes. It's not driveable.
I've never been a strong carb guy, and haven't touched one for many years. I do have the single Weber and intake that came with this engine, and I did soda blast it and put in a rebuild kit before I bought these carbs. I'm thinking about putting that on, just to rule out these carburetors.
Anybody have suggestions? _________________ 1977 Bus, with 1973 1.7L engine (rebuild complete, install underway) |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16970 Location: San Diego, California
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Posted: Thu Jun 24, 2021 7:48 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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Good luck, you need it. I hate those carbs _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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orwell84 Samba Member
Joined: May 14, 2007 Posts: 2537 Location: Plattsburgh, New York
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Posted: Thu Jun 24, 2021 7:58 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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Do you have all the hoses hooked up? I think the short metal hose from the brass tube on top of the carb has to be hooked up to the pizza slice as BD mentioned.
Not sure about the missing solenoid. There is a big one that I don’t see in your photos. Years ago mine stripped it bore and immediately the bus fell on its face. Same thing happens when one of those elbows splits or any of the gazillion hose connectors.
I hated them too when I had them. I recently had them rebuilt and going to try them again. We’ll see. |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51144 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Thu Jun 24, 2021 8:57 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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dlwilson wrote: |
........used a timing gun to set the timing to 10 degrees like Bentley says, and that made it idle reasonably well. But it won't make power |
Is that 10 BTDC, or ATDC? (I'll bet Bentley says after). That only works with the original DVDA distributor and the matched carb(s), try setting it to 7.5 BTDC and once it's running set it to 28 BTDC @ ~3500 RPM with the hose(s) off.
Odd there's no third solenoid, is there a regular idle jet screwed into the hole? _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Alan Brase Samba Member
Joined: March 28, 2004 Posts: 4532 Location: Cedar Falls, Iowa
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Posted: Thu Jun 24, 2021 10:07 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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aeromech wrote: |
Good luck, you need it. I hate those carbs |
Haha. I know what you mean. But it had to be done to make a clean running engine that passed US EPA in 1972-74.
BUT they were SO GOOD, that VW used them on the air cooled 2 liter engines sold ROW until last air cooled T3's in 1983.
They are easily the most complicated to set up correctly, sensitive to air leaks at about 6 places, throttle shaft wear, AND they work best set up with the DVDA dizzy.
Having said this. the OP appears to have TYPE 3 carb installed on the left side. The photos seem to show a stud to hold the the air cleaners in place, which is not used on the bus.
My old school observation: German carbs never feared doing things the difficult way. Solex and Zenith were always way more complicated than Webers or American carbs. When new, they worked VERY well. _________________ Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16970 Location: San Diego, California
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Posted: Thu Jun 24, 2021 11:35 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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Okay, take what you just said and add in 48 years and replacement Chinese made parts. _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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Alan Brase Samba Member
Joined: March 28, 2004 Posts: 4532 Location: Cedar Falls, Iowa
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Posted: Fri Jun 25, 2021 12:01 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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aeromech wrote: |
Okay, take what you just said and add in 48 years and replacement Chinese made parts. |
But why do we need Chinese parts? I can buy genuine Solex parts from a vendor in Italy. And Brazilian Solex from the USA.
I don't need very many parts actually.
I'm thinking I might put these on my 1980 Westy. I'll pay good money to get the genuine VW Vanagon (Mann) air cleaner and warm air ducting.
NEVER IN MY LIFE have I ever put carbs on an original FI car, but I just might on this one. Pretty sure CB sells bigger vents 28mm? _________________ Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home |
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aeromech Samba Member
Joined: January 24, 2006 Posts: 16970 Location: San Diego, California
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Posted: Fri Jun 25, 2021 12:34 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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A vendor in Italy? When I was installing these carbs on a bus a couple years back the solenoids that were available domestically were hit or miss. Sure, I guess great quality parts exist somewhere but I don’t know where. Seems much easier to install some brand new Webers. I guess if you want an original bus and have the time, money, and determination you can do it _________________ Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound |
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Alan Brase Samba Member
Joined: March 28, 2004 Posts: 4532 Location: Cedar Falls, Iowa
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Posted: Fri Jun 25, 2021 1:12 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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Well the Webers don't even USE idle jet solenoids. You could just replace them with fixed idle jets and still be where the Webers are at. Totally do not need complete idle shut off unless perhaps with automatic to stop run on.
I don't see how putting Webers on is gonna be easier in the short term. I do have a brand new set laying here , but never considered using, I was so wowed by the big vents that CB sells.
I guess I got big VENT envy? I made a 912e conversion to an old SWB 911 once, used these carbs. took the vents out and bored them to about 29.5, I think. The owner loved it. I got the 911 engine. All good. _________________ Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home |
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dlwilson Samba Member
Joined: December 14, 2020 Posts: 99 Location: Lake Worth, FL
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Posted: Fri Jun 25, 2021 5:45 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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I checked the emails I exchanged with the seller, and the carburetors are:
Solex H 32/34 PDSI 2 and 3 Carburetor set
Whatever that is. They have the upper balance tube, but not the lower. The upper tube can be connected to the brake booster, but for now I have it blocked off to rule out booster leaks.
For now, I'm thinking I'll try the single Weber, just to be sure the issue is these carbs.
[edited: but first I'll try busdaddy's suggestion of 7.5 BTDC] _________________ 1977 Bus, with 1973 1.7L engine (rebuild complete, install underway) |
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dlwilson Samba Member
Joined: December 14, 2020 Posts: 99 Location: Lake Worth, FL
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Posted: Sun Jun 27, 2021 9:35 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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busdaddy is the man. 28 btdc has the bus driving out of my garage and driving down the street. yay. after a couple minutes it sputters and dies, but then it restarts after a couple tries. I think maybe I’m running the carb bowls out of fuel? _________________ 1977 Bus, with 1973 1.7L engine (rebuild complete, install underway) |
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dlwilson Samba Member
Joined: December 14, 2020 Posts: 99 Location: Lake Worth, FL
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Posted: Sun Jun 27, 2021 9:58 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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busdaddy is the man. 28 btdc has the bus driving out of my garage and driving down the street. yay. after a couple minutes it sputters and dies, but then it restarts after a couple tries. I think maybe I’m running the carb bowls out of fuel? _________________ 1977 Bus, with 1973 1.7L engine (rebuild complete, install underway) |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51144 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Sun Jun 27, 2021 10:17 am Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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You could rig a temporary tank to sit on the rear shelf (outboard motor tank?) and gravity feed it, if it quits quitting you found the problem.
That 28 BTDC is revved until it stops advancing (hoses off) at 28 regardless of how much higher you rev, right? _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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Alan Brase Samba Member
Joined: March 28, 2004 Posts: 4532 Location: Cedar Falls, Iowa
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Posted: Sun Jun 27, 2021 3:32 pm Post subject: Re: new 1.7L type 4 dual carb engine won't idle, is it fuel pump? |
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busdaddy wrote: |
You could rig a temporary tank to sit on the rear shelf (outboard motor tank?) and gravity feed it, if it quits quitting you found the problem.
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Some lawn mower engine tanks work okay for this. I have a plastic Lawn boy tank with built in lever shutoff.
Definitely sounds like tank screen plugged with debris. Ugly job if there is any fuel left in tank. Nobody likes a gas bath and it can turn deadly.
I'm a great fan of removing the screen and just putting a fuel filter right under the tank. That is easily change with a clamp on the inlet line.
And you WILL NEED to change it. A few times. OR back flush the filter. If it is plugging the screen, there is a LOT MORE varnish/ rust debris inside the tank. _________________ Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home |
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