Bus won't break 35 mph

[kiltgy]

Took my 74 (dual carbs) on an 1800 mile trek around oregon. No problem.

Colin came by the next week. We went through the bus. No major problems.

The following weekend I drove to Seattle (180 miles) no problem.

On the way home, about 100 miles in, the bus died. Se acted like she was running out of gas.

Eventually got her started agin by monkeying with the fuel mixture and idle. Limped it home.

Went through everything. Replaced the fuel filter. Blew out the fuel line. There was a little bit of junk in the line.

Got it all cleaned out.

Put everything back together.

Took the bus to the coast (90 miles). On the way out I could not get the bus above 50 mph. On the way home i was down to 35. Climbing hills I was down to about 12 mph (regardless of grade). The bus starts great and runs fine all the way to 35 mph. Then it is like a giant hand just grabs it and pulls it back.

I have replaced the fuel filter attached the the fuel pump. The fuel pump works. The fuel line is clear and flowing well. The fuel pressure regulator is clean. We checked and re-synched the carbs.

I am STUMPED.

Ideas?

[Amskeptic]

(90 miles). On the way out I could not get the bus above 50 mph.
On the way home i was down to 35. Climbing hills I was down to about 12 mph (regardless of grade).
Ideas?

I must warn you not to push a VW when it is not feeling well. Let's say you have a fuel starvation issue, your foot-to-the-floor at 50 mph is going to be a lean blow torch on the valves.

Start your diagnostics with a plug pull. Let me know if they are scorched white, and if there is a noticeable variation between 3/4 and 1/2.

Check fuel hose for a dumb kink or pinch. If you are absolutely sure that all solenoids are functional (a good idle ) then please go buy a spare fuel pump (you need one anyway) and do a swap. Check timing and let us know if you get 28* at 3,400 rpm.

Do not dump a totally stumped here. You need to give us some primary effort at diagnosing. Hey! I am a teacher too, no grumbling.
Colin

[satchmo]

(90 miles). On the way out I could not get the bus above 50 mph.
On the way home i was down to 35. Climbing hills I was down to about 12 mph (regardless of grade).
Ideas?

I must warn you not to push a VW when it is not feeling well. Let's say you have a fuel starvation issue, your foot-to-the-floor at 50 mph is going to be a lean blow torch on the valves.

Start your diagnostics with a plug pull. Let me know if they are scorched white, and if there is a noticeable variation between 3/4 and 1/2.

Check fuel hose for a dumb kink or pinch. If you are absolutely sure that all solenoids are functional (a good idle ) then please go buy a spare fuel pump (you need one anyway) and do a swap. Check timing and let us know if you get 28* at 3,400 rpm.

Do not dump a totally stumped here. You need to give us some primary effort at diagnosing. Hey! I am a teacher too, no grumbling.
Colin

If you don't get 28-30 degrees at 3400 rpm, check your distributor vacuum can, advance (cone shaped) side, for leakage.

Tim

[Kubelwagen]

"A little bit of junk in the line."

I suggest looking a little closer at this too. I had similar symptoms and found that my tank was full of very fine rust. It had gummed up the fuel pump quite a bit. Taking the pump off and tapping it on the deck produced globs of rust/gas gel. It wasn't all that apparent from looking at the filter or fuel line though.

[Amskeptic]

If you don't get 28-30 degrees at 3400 rpm, check your distributor vacuum can, advance (cone shaped) side, for leakage.
Tim

That specification is centrifugal advance no vacuum hose.
With the vacuum hose, he should get a 40* BTDC at a throttle blip.
Since he is (I think . . .) pretty much flooring it, the vacuum advance signal is no longer in the mix.
ItzaWeirdOne
Colin

[Amskeptic]

"A little bit of junk in the line."

I suggest looking a little closer at this too. I had similar symptoms and found that my tank was full of very fine rust. It had gummed up the fuel pump quite a bit. Taking the pump off and tapping it on the deck produced globs of rust/gas gel. It wasn't all that apparent from looking at the filter or fuel line though.

Thank-you, good point.
Colin

[RSorak 71Westy]

you definitely have a fuel supply restriction. When its not running well is it only running on 2 cylinders on 1 side, or all 4 poorly?

[Amskeptic]

you definitely have a fuel supply restriction. When its not running well is it only running on 2 cylinders on 1 side, or all 4 poorly?

Another good point!
Colin

[kiltgy]

Ok, back. Sorry it has taken me so long to get on this. The rest of my life has kicked in to high gear :(

Replaced the fuel pump. No change.

Pulled each plug wire. Response on all four cylinders.

Engine immediately dies when throttle is opened.

Pulled the solenoid wires on the driver's side. No response. Pulled all the solenoid wires at the coil and the engine died. (Granted, the engine has been doing a lot of dying).

So, current thought is solenoids? yes?

[RSorak 71Westy]

Ok so it runs poorly on all 4. We need to figure out if this is a fuel supply or ignition problem. I suspect fuel supply. Did gas flow freely out of the hose from the fuel tank when it was disconnected from the pump while you were changing it? If not figure out why, because this your problem.

[Amskeptic]

Pulled the solenoid wires on the driver's side. No response.
Pulled all the solenoid wires at the coil and the engine died.
current thought is solenoids? yes?

No, you slip past specificity, leaving us maddeningly lost yet.

You pulled WHICH solenoid wire on driver's side? You have the
central big one or left-carb-only little one.

No response you mean there was no change in idle, right? So that is the problem child, whichever one you select, central or left side only.
Let's say that the central is OK and the left side is the one playing dead. Switch the solenoid with the right side one. Did the problem switch sides too? Then the solenoid itself is a problem.
Did the problem stay on the left? Likely dirt in the carb passages
(or needle valve is sticking closed IF the central idling circuit is ALSO playing dead).
Colin