Fuel starve

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Manu

Manu

Manu
Joined
Aug 23, 2015
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France
Hi
My Car is a 68 barracuda powered by a 340ci
I replaced the fuel pump And have a rebuilt carb but still face the problem of not getting fuel when engine runs at idle speed once hot ( typicaly ok when starting cold but then Starving when hot )
No issue when engine runs above 1200rpm

other Point is that i also get the carb dry when car is stopped For 30mn after running and engine is at running temp

could it be due to some issue on my fuel line ? Other ?

thanks for your support
 
Check the fuel inlet in the tank. An inlet restriction is 10X worse than an outlet restriction.
 
Manu said:
Hi
My Car is a 68 barracuda powered by a 340ci
I replaced the fuel pump And have a rebuilt carb but still face the problem of not getting fuel when engine runs at idle speed once hot ( typicaly ok when starting cold but then Starving when hot )
No issue when engine runs above 1200rpm

other Point is that i also get the carb dry when car is stopped For 30mn after running and engine is at running temp

could it be due to some issue on my fuel line ? Other ?

thanks for your support
Click to expand...


If you're running a dual plane intake with a 4 bbl, this gasket is thick to help keep fuel from boiling....

Edelbrock Heat Insulator Gasket
 
Modern fuel is terrible for boiling. Before I "went EFI" the best thing I did was to build a return system, use a thick carb insulator, and ran a rear mount electric pump. There is some evidence that Carter/ Ed carbs are worse than Holley, as the fuel bowls are "right down on the deck" and transfer heat from the intake, into the carb bowls.

At the time I even considered building something like a plywood spacer, 1/2" or so.
 
Check the jumper from the sender to the mainline, if your pump sucks air, this is the prime place for it to happen. if using gear clamps here, you need two per side and clamps staggered 180*. If that's not it, try it with the gas cap cracked, you could be having a vent issue.
 
Manu said:
Hi
My Car is a 68 barracuda powered by a 340ci
I replaced the fuel pump And have a rebuilt carb but still face the problem of not getting fuel when engine runs at idle speed once hot ( typicaly ok when starting cold but then Starving when hot )
No issue when engine runs above 1200rpm

other Point is that i also get the carb dry when car is stopped For 30mn after running and engine is at running temp

could it be due to some issue on my fuel line ? Other ?

thanks for your support
Click to expand...

You want your fuel filter and gas line to carburetor set up like in this picture, keeping the gas line and filter away from the hot cylinder head.

And do not want the fuel filter horizontal up on the intake manifold area either.

Screenshot_20200730-073349_Gallery.jpg
 
Manu how about some more info about what you have going on. What carb? What intake? Electric pump? Manual pump? Stock 340? Or 500hp 340? Maybe a few pictures will help someone with a keen eye identify something. All the suggestions so far are a guess at best without knowing more info.
 
Go electric pusher. no dry carbs. No start up woes. hidden switch=Theft deterrent. JMHO
 
Manu said:
Hi
My Car is a 68 barracuda powered by a 340ci
I replaced the fuel pump And have a rebuilt carb but still face the problem of not getting fuel when engine runs at idle speed once hot ( typicaly ok when starting cold but then Starving when hot )
No issue when engine runs above 1200rpm

other Point is that i also get the carb dry when car is stopped For 30mn after running and engine is at running temp

could it be due to some issue on my fuel line ? Other ?

thanks for your support
Click to expand...
Also if you can eleborate on how you determined the engine is not getting fuel, that will help.
The fuel level in the carb's bowl is the key point to seperate whether there is a delivery problem or not.
A restriction in the delivery system will effect high flows more than low flows.
And the fuel bowls need to refill more quickly (engine uses more fuel) driving at higher rpm and more throttle.
So restrictions cause the fuel level to become worse under more throttle.
Therefore, based on your post, the problem may not be a fuel delivery problem.
 
Thanks to all for your feed backs. Very useful !
I will check those points next week end if possible . Here below also a few answers :

-engine is stock ( rebuilt with oversize bore as it was completely blocked when i got the car )
- X head ( original )
- Carburetor is a rebuilt carter avs ( uremco )
- mechanical fuel pump ( replaced by a new oen from Crown )
- filter : horizontal located as per stock mounting
- new gas tank and sending unit set
- TTI exhaust line and schumacher headers

I will post a few pics

regarding now how i analysed The issue :
- no problems when driving Above 30mph
- problems start when engine si hot and i am in a traffic jam or when Manoubering to park : low rpm , engine will stop
- the plastic filter will show to Be low level insude and i will need to run The starter for like 20 sec prior to get fuel back in the filter And to get teh engien running again
- But the filter si never totally empty , which open teh door to the fuel possibility
- in fact this does not happen when i have the engine cold And i leave the car
52EAB3ED-9BFA-49F4-AAB4-DC0D3D103BA6.jpeg
1079408F-95A2-4456-BF07-0926627F129F.jpeg
B2AA96C2-2D7C-4377-A74E-5846CC264BAE.jpeg
B6F07838-83DF-4FBA-8067-BB4F7DA75C0C.jpeg

A5C0B0FA-F7B3-4BF4-8720-DA7DE9E7BBB8.jpeg
A5C0B0FA-F7B3-4BF4-8720-DA7DE9E7BBB8.jpeg
A3A64818-A6EB-44DF-803D-1B0CC0CEE474.jpeg
 
This car si one of The few that were assembled in the Simca factory in the netherlands ( to avoid high taxation issue in europ for import of fully assembled cars that applied in the end fo the 60s )
She is a matching number with only 74000km (50000 miles ) and was driven from 68 To 74 Then stored in a sort of scrapp yard ( indoor by luck )
She has speedometer In km/h / windshield and side glasses made in Belgium to pass european markings .
But all other stuff si similar to US versions
I did a full resto : engine and trasn rebuilt / front brakes rebuilt keeping original calipers / full inside And outside paint work / all gauges working except water temp that is burned

thanks again for your support
Manu
 
Yes that's helpful.

Manu said:
regarding now how i analysed The issue :
- no problems when driving Above 30mph
- problems start when engine si hot and i am in a traffic jam or when Manoubering to park : low rpm , engine will stop
- the plastic filter will show to Be low level insude and i will need to run The starter for like 20 sec prior to get fuel back in the filter And to get the engine running again
- But the filter si never totally empty , which open teh door to the fuel possibility
- in fact this does not happen when i have the engine cold And i leave the car
Click to expand...

Seeing more vapor in the fuel filter when the engine is hot is normal. On the other hand if the vapor keeps increasing until it takes up most of the filter, that does suggest a problem. (In the US and Canada we use different fuel in the winter which has a larger portion of low temperature vaporizing componenets)

Differences between number 1 & 2 is rpm, load, and vehicle speed.
idle for '68 should be around 650 rpm and 30 mph in 3rd gear maybe 1250 rpm ?
Load at idle is the transmission and friction. Load at 30 mph is only fractionally more.
Speed obviously increases airflow in the engine compartment and underneath. So this can help cool the lines.

Usually when a carb is only getting vapor, or nothing, it can still idle on the fumes. But when load is increased and fuel demands go up there's not enough fuel.
I know this is a pain, but if you can recreate the problem at or near your garage, then stop the engine and take off the top of the carburetor to see the fuel level.
There may even be a wet level spec in the shop manual, but if fuel is well above the entrance to the rods and jets, then vaporization is not reason the engine is dying hot.
If it is empty - then we can chase the fuel delivery.
If its not empty, then suspect its carb setup and possibly timing. Remove a spark plug and see if its showing excessive richness or leaness. Excessive rich builds up carbon so if its too rich under a particular condition it will remain on the plug.

Manu said:
- filter : horizontal located as per stock mounting
Click to expand...
Should be slightly tilted - which it looks like it is in the photo.
see this page in 1963 Chrysler master Tech booklet >Carburetion and Performance Diagnosis (Session 188) from the Master Technician's Service Conference
(At the time, the main concern was not vapor lock, but a high pressure vapor bubble after the pump pushing excess fuel into the carb bowls)

Manu said:
- mechanical fuel pump ( replaced by a new oen from Crown )
Click to expand...
I have not found Crown to carry particularly high quality parts. I've had to use there stuff on my jeep, but fortunately not on my Barracuda.

Manu said:
- TTI exhaust line and schumacher headers
Click to expand...
Those can put out extra heat near the fuel line. On various setups I've had exhaust related heat issues along the frame rail and also going over the rear axle.
 
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I had the same issue with my 67 273 and ethanol fuel a long time ago. I could watch the horizontal filter fill and empty in cycles after engine warmed. I finally decided that more pressure was building in the bowl than could escape the bowl vent. When the float opened the needle gate, fuel vapor came back into the filter. A thicker base gasket under the stock 2 brl. and fuel line routing (vertical filter) and pump from 73 up model cured it. Then later on real ethanol free fuel/real gas came available all around me so thats what I buy for every carborated engine I own. Mowers, weed eater, all work better. I haven't had to replace those little plastic fuel lines on the weed eater again since.
 
Manu, with that style of carburetor and fuel line routing etc, I would focus my attention on making sure the float levels on the carb are dead nuts accurate and get the idle mix squared away. Next I would set initial timing a little higher than what the factory called for, making sure not to have too much total (you’ll have to limit this inside the distributor) as retarded timing can cause some heat issues. Then set idle mix again after setting timing. If that doesn’t help I would look in to isolating the heat from the carb with a thick fiber gasket, (edlebrock makes a nice one). Also I might look in to wrapping the fuel lines. It sounds like vapor lock may be your problem. How is the outside temp where you are?
 
Just read the initial post again. A loose fuel pump eccentric or a pump arm that is bent could also cause low fuel pump output at idle. Just a thought.
 
Yes
That would be bad news as it would mean quite some mechanical work ...how could i check that without major opening ?
 
make a spacer out of marine grade plywood or particle board..Available everywhere. Had a 340 with an AVS on it and that was a bear starting back up after it was hot. Had to pump that carb about 10 times.for it to start. Vapor lock or boiled out fuel. I had a electric pump so i believe it was vapor lock.
 
Manu said:
Yes
That would be bad news as it would mean quite some mechanical work ...how could i check that without major opening ?
Click to expand...
I'd first check if fuel level in the bowl is the problem.
And since it only happens hot, whereas cold the choke is closed using more fuel, but also at fast idle (1600 rpm?).
The thing to do is look in the bowl and see what's there. Then decide on next step.
 
67Dart273 said:
Modern fuel is terrible for boiling. Before I "went EFI" the best thing I did was to build a return system, use a thick carb insulator, and ran a rear mount electric pump. There is some evidence that Carter/ Ed carbs are worse than Holley, as the fuel bowls are "right down on the deck" and transfer heat from the intake, into the carb bowls.

At the time I even considered building something like a plywood spacer, 1/2" or so.
Click to expand...
Would youi please provide more info on electric pump with a return system.
I have been wanted to add an electric pump with return to the tank.
How do you add a return fitting to a stock fuel tank?
 
Like this if you are going external electric fuel pump with a carburetor:

Screenshot_20200901-074604_Chrome.jpg


If you are switching over to TBI / EFI that is a whole other can of worms.
 
If I was having this problem, I would be doing a fuel volume test.
I have had pumps with a weak lever return spring, that would just not pump sufficient fuel at idle.
If the volume is not there, do not condemn the pump yet; it may be a restricted delivery line.
If you see bubbles in the delivery, it could point to sucking air, or it could point to something in or near the entrance to the pump that is dissociating the fuel.
 
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512Stroker said:
Would youi please provide more info on electric pump with a return system.
I have been wanted to add an electric pump with return to the tank.
How do you add a return fitting to a stock fuel tank?
Click to expand...
There are many ways to do it. Plumb it in to the fuel filler tube, drill a hole in the stock sending unit and solder in a fitting, use a bulkhead fitting in the sending unit, or the top of the fuel tank. Pick your poison. Once you have a “port” all you have to do is use a return style regulator and plumb the return port on it to the new port you just added.
 
AJ/FormS said:
If I was having this problem, I would be doing a fuel volume test.
I have had pumps with a weak lever return spring, that would just not pump sufficient fuel at idle.
If the volume is not there, do not condemn the pump yet; it may be a restricted delivery line.
If you see bubbles in the delivery, it could point to sucking air, or it could point to something in or near the entrance to the pump that is dissociating the fuel.
Click to expand...
Thanks
 
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