hit a bump - engine starting rough

[Whaanga]

Today I took the bus for its annual inspection. ('73 bus with 914 type 4 engine).

Of late, it has been running rough and was able to pinpoint the trouble to a bad set of points. I posted my question here here and had lots of help (Thank you).

https://www.thesamba.com/vw/forum/viewtopic.php?t=721067&highlight=

Since replacing these items (along with a new set of plugs), the engine has been running flawlessly.

HOWEVER, today - as I drove into the parking lot of the inspection place, I went over a bump in their driveway and right away the engine started running poorly and loss power. It got through the inspection and the mechanic put it the lot. I checked the connections at the dizzy and spark plugs and all seemed well. I climbed underneath to check the fuel filter and it seems a little dirty. I shook it around a little and checked all the fuel lines. All seemed well.

I got in the bus, started the engine and it ran GREAT again. BUT - on the way home it suddenly showed the same symptoms and I lost power. But then it ran great for a mile and then it started having troubles again. It even backfired a couple of times. I got home OK and letting it cool so I can take a closer look at the fuel lines.


It's also very hot here today and I wonder if I experienced vapor lock?

I'm wondering how it went from running so smoothly to a loss of power and backfiring all because of a bump.

I always appreciate a chance to learn from all the great help here.

Thanks,

Jeff
_________________
Late 1973 Bay w/a transplanted 914 Engine

[xyzzy]

Replace fuel filter since its cheap, and check/clean the groundstrap while you're down there.
_________________
-----
1973 VW Westfalia 2L hydraulic, dual Solex PDSIT
1987 VW Vanagon Westfalia

[Daverham]

The only time hitting a bump has caused my bus to run poorly was when it jarred loose a wire on the fuel pump relay. I removed, cleaned, pinched them a bit tighter with pliers and re-installed all the connectors on the relay and never had that problem again.

[Jeff Geisen]

Did ya change the condenser?
_________________
I Corinthians 4: 1 thru 5

‘63 ragtop - ‘68 single cab

[Whaanga]

Yes, I changed the condenser when I changed the points - a few days ago - but not since I hit the bump today.

Are you suggesting I change it now?

Thanks
_________________
Late 1973 Bay w/a transplanted 914 Engine

[Whaanga]

Ok Samba-land,

Here's an update. I changed out the filter and this is what I removed:

Also - about a year ago I removed the tank and had it professionally boiled. But I never changed the filter. So I don't think I have any rust or gunk in the tank but the filter looks a little messy. And today when I changed the filter, I let some fuel run out and it was free flowing and void of any debris.

I checked all of the electronic connections and then took a drive. I'm glad to report that the bus drove wonderfully!

Heading toward home I turned right onto my street and was going a little fast, as soon as I rounded the corner, the engine started to sputter, lose power, and even backfired. I kept going, but slowed down and then had an idea. I removed the gas cap and the engine smoothed right out and the bus drove beautifully.

Thinking back, I recall that today when I turned into the inspection shop, I also made a rather quick right hand turn. And then I recall that on the way home today (before the engine ran poorly again), I made another right turn.

My take is about 1/3 full right now so I'm wondering if I had a more full take, would this issue disappear?

And why does a quick right had turn cause this issue? Or is there something else that I'm missing?

Thanks,
Jeff
_________________
Late 1973 Bay w/a transplanted 914 Engine

[TomWesty]

What carb/carbs are you running?
_________________
If you haven't bled on them, you haven't worked on them.
Visit: www.tomcoryell.com and check out my music!

[Whaanga]

I have a dreaded single Weber progressive carb. The issue with this carb is that it runs rich and I cannot lean out the mixture.
_________________
Late 1973 Bay w/a transplanted 914 Engine

[Amskeptic]

[Whaanga]

Thanks All for your input. Colin - I now have two sets of Solex dual carbs and will organize one good, fully functional set. In the mean time, am still dealing with an intermittent fuel delivery issue.

It will take some time to prep for the dual carb install and I still want to enjoy driving the bus. Is it worth the effort to address the issue in my single carb - and what exactly makes a carb flood? Is this a case where I can replace the jets?

Also, since my engine is from a 914, I have to use an electric fuel pump. The one that came with the bus is a Faucet and chirps all the time. I finally installed a fuel pressure regulator but wonder if the pump is an issue. How does one evaluate the health of a fuel pump.

And, since I have not had a fuel pressure regulator, could I have comrpomised the components of the single carb with way more than 3 psi being dumped into the Weber single carb?

Thanks
_________________
Late 1973 Bay w/a transplanted 914 Engine

[mikedjames]

Float chamber fuel metering valve needle wears, and then it leaks at low flow rates. At low speed it floods the engine. At higher speed the engine draws enough fuel to cause the float to drop and the leak ceases to be delivering too much fuel.

High fuel pressure could cause such a leak also, requiring the float to be impossibly high to shut the valve against the pressure.

Shutting off the bus to count all four wheels present will fix the fault as effectively as fiddling with the fuel cap as the spare gas boils off and it runs again
_________________
Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[SGKent]

it could be flooding but it could also be a little water in the gasoline. Run a can of iso-heet or something like that - a fuel drier. 91% isopropyl works too. 70% already has too much water in it to use.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Abscate]

[Whaanga]

Thanks for the comments -

I just watched a couple of great videos from a guy at Pierce Manifold in California who does an excellent job explaining how the Weber progressive carb works. I may have an issue with a lose float pin that is allowing the float to have lateral movement causing the rich/flooding situation.

Abscate - let me know the next time you're passing through - it's all left turns to my house so you should make it just fine.
_________________
Late 1973 Bay w/a transplanted 914 Engine

[SGKent]

twice in my life I have gotten a little water in the fuel. Once in the 1971 bus and once in the CJ7. When it happens it sits around the bottom of the tank and sloshes when going around a corner or bump. The engine will stumble, misfire, even die for a couple seconds, etc., and if any gets into the bottom of the carb bowl it takes a while to get all of it out. Newer fuels that have alcohol in them are prone to getting water in them. While it might be something else like a float problem, maybe the float is sinking etc, but it would be smart to run a can of fuel drier in the tank for $2 before diving in any deeper mechanically. Might not solve it but having been there a couple times myself, water in the fuel will absolutely cause the issue you have. That would be the first place I would start. Especially because of all the moisture that has been in the air this year in many parts of the USA.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin