Rough Running w/ Dual Carbs, And now low fuel pressure too. Options

[Craigers17]

So I've been trying to track down a rough running issue with my 2056 w/ dual 40IDF's. It has not been running well for several months, and has had spells of sitting for a while. When these issues started, probably 9 months ago now, I changed out the old fuel filter and relocated the pump and filter to the front and upgraded both to the type that Tangerine sells. I also took that opportunity to install a stainless steel line and all new rubber lines. (the problem existed BEFORE I did all of this)

Recently, in the last week or so, I replaced both manifold and carb gaskets. I haven't actually opened up the carbs yet, but have cleaned all the jets. After this work, I had it running great for about a quarter mile, and then started backfiring and bogging down. I have a fuel gauge and also noticed that it is now only reading about 1.25 to 1.5. It normallly sits around 3 consistently. I suspected maybe I had a fuel line that was kinked under the tank, so I pulled it and they are fine with no leaks.

I am thinking that the fuel filter may be clogged after having sat dormant for so long, OR, I might have some clogging going on in either my fuel "T" splitting the carbs or in the "T" that contains the gauge. My only other guess is that something is going on with the floats. I know this post is a lot, but if anyone has any ideas, please feel free to chime in. Thanks!

[Shivers]

Once I had my carbs set, jetted and timed with the other carb they ran great. But now and then it would all of the sudden start to spit and run like heck. After a bit of hunting I found it was always the main jets. I made a tool that held one brissel off my wire brush that I kept in the car. Pull off the air filter, unscrew the jet stacks on top of the carb, one at a time and use that wire to clean out the jets. That was the only problem I had @Craigers17

[Osnabruck914]

As far as fuel pressure goes, I do remember that when I had a fuel pressure gauge installed in the engine compartment it was only accurate when the engine was cold just after startup. As soon as things got hot in the compartment it always read low. I would get 3 lbs cold and about 1-1/2 when hot. I'm sure I getting was a false reading from the hot gauge.

Are you confident your carbs are truly balanced?

Osnabruck914

[technicalninja]

#1 dead head fuel supply into gauge. If still 1.5 check resistance before and after pump and if none found replace pump.
Get dead head supply to 3+ before going futher.

#2 3+psi supply! pull lines from both carbs, place into 16oz bottle, test supply to both carbs (no pressure gauge) just checking flow.
8oz in each for 2 minutes run time is plenty. Usually fills up little bottles FAST, like 30 seconds.
Lots of flow. Your fuel supply works.

Connect system and check pressure system on not running. Should be same as dead head.

Always test your test equipment! Having another gauge available is preferrable.

The little cheap ass round "tuner" gauges are notoriously inaccurate!

If fuel supply is good take top off of carbs and inspect. Not nearly as hard as you think.

If you have a new gasket set available you won't need it and vice versa...

Pierce Manifold is a good source for Weber crap.

[Craigers17]

Once I had my carbs set, jetted and timed with the other carb they ran great. But now and then it would all of the sudden start to spit and run like heck. After a bit of hunting I found it was always the main jets. I made a tool that held one brissel off my wire brush that I kept in the car. Pull off the air filter, unscrew the jet stacks on top of the carb, one at a time and use that wire to clean out the jets. That was the only problem I had @Craigers17

Thanks. I'll check the main jets again, now that I have run fuel through them, but I JUST cleaned them before I ran the car.

[Craigers17]

As far as fuel pressure goes, I do remember that when I had a fuel pressure gauge installed in the engine compartment it was only accurate when the engine was cold just after startup. As soon as things got hot in the compartment it always read low. I would get 3 lbs cold and about 1-1/2 when hot. I'm sure I getting was a false reading from the hot gauge.

Are you confident your carbs are truly balanced?

Osnabruck914

Good point. You just made me remember that my gauge actually has a release valve to equalize to atmospheric pressure after it heats up. Tomorrow I will try the release and see if that changes the reading....could be a false reading.

The carbs are definitely balanced at idle. All 4 at about 5.5-6. The throats on the passenger side are a little higher than the driver’s side when the rpm’s go up.

[Craigers17]

#1 dead head fuel supply into gauge. If still 1.5 check resistance before and after pump and if none found replace pump.
Get dead head supply to 3+ before going futher.

#2 3+psi supply! pull lines from both carbs, place into 16oz bottle, test supply to both carbs (no pressure gauge) just checking flow.
8oz in each for 2 minutes run time is plenty. Usually fills up little bottles FAST, like 30 seconds.
Lots of flow. Your fuel supply works.

Connect system and check pressure system on not running. Should be same as dead head.

Always test your test equipment! Having another gauge available is preferrable.

The little cheap ass round "tuner" gauges are notoriously inaccurate!

If fuel supply is good take top off of carbs and inspect. Not nearly as hard as you think.

If you have a new gasket set available you won't need it and vice versa...

Pierce Manifold is a good source for Weber crap.

I appreciate the tips. I'll give these a shot in the next couple days. I really think that opening the carbs is going to be the solution, and possibly replacing the fuel filter. Thanks for the Pierce Manifold resource.

[technicalninja]

I've rebuilt hundreds of carbs, mostly American V8 stuff but plenty of import stuff as well.

I've never had problems with carb kits.

Until about a decade ago...

Everything is CRAP now!

For Weber carbs I want my kits to actually be from Weber if possible...

If it's not from the original manufacture, it's not a "kit" anymore in my book.

I've had to re-use needles and seats multiple times with the new junk that is available aftermarket...

[mate914]

I've rebuilt hundreds of carbs, mostly American V8 stuff but plenty of import stuff as well.

I've never had problems with carb kits.

Until about a decade ago...

Everything is CRAP now!

For Weber carbs I want my kits to actually be from Weber if possible...

If it's not from the original manufacture, it's not a "kit" anymore in my book.

I've had to re-use needles and seats multiple times with the new junk that is available aftermarket...

So true and sad. Its almost like they are trying to make carbureted engines obsolete.

Matt

[BENBRO02]

Mine was running poorly with dual carbs (backfiring) and it turned out to be a leaky float in the carb. It runs great after replacing the float.

[Craigers17]

Mine was running poorly with dual carbs (backfiring) and it turned out to be a leaky float in the carb. It runs great after replacing the float.

Good to know. This is actually my biggest suspicion, ...I ordered Tomlinson's Weber Tech Manual, so I plan to try to gain more insight into carbs very soon. My carbs are actuallly Empi, but have worked well in the past.

[Superhawk996]

Once I had my carbs set, jetted and timed with the other carb they ran great. But now and then it would all of the sudden start to spit and run like heck. After a bit of hunting I found it was always the main jets. I made a tool that held one brissel off my wire brush that I kept in the car. Pull off the air filter, unscrew the jet stacks on top of the carb, one at a time and use that wire to clean out the jets. That was the only problem I had @Craigers17

Thanks. I'll check the main jets again, now that I have run fuel through them, but I JUST cleaned them before I ran the car.

Not at all uncommon to get debris the bottoms of the bowls and to continually pick up garbage into the jets until the bowl is cleaned out, and the on-carb strainers cleaned.

[technicalninja]

Once I had my carbs set, jetted and timed with the other carb they ran great. But now and then it would all of the sudden start to spit and run like heck. After a bit of hunting I found it was always the main jets. I made a tool that held one brissel off my wire brush that I kept in the car. Pull off the air filter, unscrew the jet stacks on top of the carb, one at a time and use that wire to clean out the jets. That was the only problem I had @Craigers17

Thanks. I'll check the main jets again, now that I have run fuel through them, but I JUST cleaned them before I ran the car.

Not at all uncommon to get debris the bottoms of the bowls and to continually pick up garbage into the jets until the bowl is cleaned out, and the on-carb strainers cleaned.

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)

And, you don't have to take them off of the manifolds to do this (or change a popped float).
Ripping the tops off is GRAVY...
A little air, B12, rags and the bowls are clean.
I'd use a big "dog" towel to catch the resulting spray.

Pull tops, clean bowls, adjust change floats/needle and jet, clean jets.
A "poor boy" carb rebuild would take me less than 1 hour for both...

[930cabman]

Have you checked the fuel flow? Disconnect the fuel line before the split for the carbs and run your pump. It should flow a good amount

[Craigers17]

So last time I posted, I had a suspicion that my fuel pump or filter were not working correctly, as my pressure was dropping and the car was bogging down. I SHOULD HAVE stuck to my gut and started troubleshooting the pump first. That said, I wanted to maintenance the inside of these carbs because I had never opened them.

I took them both off today, dissembled most of the important parts, cleaned out the all the jets and circuits as best as possible and added new gaskets. I did find some junk in both bowls and I've tried to include some pics. Also, I have never adjusted the floats, so I adjusted them "closed" at roughly 12mm and "open" at between 23 & 25. The floats themselves looked great, but they were probably at around 6-8mm at the closed setting. Not sure how much difference that makes or if anybody has different numbers to shoot for?

Anyways, put it all back together and car won't start at all now. I didn't have time to troubleshoot much after that, but it doesn't look like it's getting much, if any fuel....leading me back to my original suspicion. That said, I feel better about the carbs having been cleaned and floats adjusted.

In the next day or so I'll check the flow to the "t" and get some voltage measurements to the pump. I do hear the pump kick on, but it doesn't sound as loud as normal.

[technicalninja]

You did have some nastiness.

Looks like a goober in the top of the chamber in the first picture.

Some crustiness on the main well tubes in another.

I'd have put a few ounces of fuel in the bowls to test/flush out the accelerator pump circuits.

The carb bodies look NICE, however.

They needed to be "poor boy" rebuilt now.

Is the picture of the floats with your new adjustment?

Something I've noticed over the years is when the floats are right the parallel lines/surfaces are also parallel to the top plate. This is on almost everything, not just Webers.

It looks like the outer float is a little bit bent downwards (high level) but picture angle may be playing a part.

If "12" is pictured, then 6-8 would have been a significantly higher fuel level in the bowl.
Tuning/jets might change
Did it run rich?
Too high a fuel level in the bowl tends to make things rich.

Get an 8oz container with a squirt top and dump 2 oz of fuel into each carb through the bowl vent. It should run then.

I'd run a bunch of fuel through the pump/lines looking for trash in it.

[Jack Standz]

Just set the float level on IDF carbs. 12mm was too much and caused the fuel to leak out the carb top/vent. 10mm seems to be the "goldilocks" amount, just right.

So, suggest you check the floats for straightness/twist... Should be even/level for both front to back and side to side. If not, the float might catch on the inside of the carb or not "float" at the correct level.

[Jack Standz]

As far as fuel pressure goes, I do remember that when I had a fuel pressure gauge installed in the engine compartment it was only accurate when the engine was cold just after startup. As soon as things got hot in the compartment it always read low. I would get 3 lbs cold and about 1-1/2 when hot. I'm sure I getting was a false reading from the hot gauge.

Are you confident your carbs are truly balanced?

Osnabruck914

Thanks and also to the Ninja for pointing this out. We've had that problem of inaccurate fuel pressure gauges or ones that change when the motor gets hot. It'll drive you in circles.

[Jack Standz]

The little cheap ass round "tuner" gauges are notoriously inaccurate!

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/smile.gif)

[930cabman]

The little cheap ass round "tuner" gauges are notoriously inaccurate!

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/smile.gif)

Agreed, where is a good source for us CSOB's?