Fuel line getting filled by air during hot days (1 Viewer)

[Emil Schmid]

Hello, My FJ60/1982/477'000mi gets more and more a fuel problem if the thermometer rises above 100° as the fuel line gets air in and the Aisan carburetor starts studdering and finally stops and misfires due to lack of fuel. The fuel line is new, three parallel electric 12V pumps Facet-Purolater-Solid-State #40108 (4.5-6.0 psi) are new, fuel filter is new, and all the concerned electric parts are new. After emptying the fuel tube, the engine runs again for a few miles, but as soon I have to accelerate the air is back again. Might the pumps be too weak, or should they be serial (one after the other)? Thanks for any advice or hint!! (www.weltrekordreise.ch)

 

[Seth S]

Does your carb cooling fan work?

Do you have all the heat shields on the exhaust manifold
What was wrong with the stock mechanical pump?

Have you tried insulating the fuel line?

 

[3_puppies]

WAG is the metal lines or rubber hose or the fuel pickup in the tank is your issue.
X2 on the stock pump?
why 3 electric fuel pumps and where are they located?

 

[tmxmotorsports]

No way you need 3 fuel pumps. Rubber lines might be collapsing from suction I would drop the tank and have a looksee for rust clogging the pick up in the tank.

 

[KWalkerM]

Its not collapsing. Your fuel pump(s) are causing cavitation in the fuel line.

Do you have a return line to the tank to bleed off excess pressure?
What size fuel line are you running?
How hot are your fuel pumps getting?
Does your frame mounted fuel line run near the floor heaters?
How far is your pump set up from the fuel tank?

 

[OSS]

Get rid of the electric pumps & install the Toyota mechanical pump.

 

[Seth S]

When I bought my truck I noticed a clicking sound everytime I turned on the ignition. Eventually I found someone had installed a small electric pump inline with the fuel hose. Because the carb cooling fan wasn’t working the PO probably took the truck somewhere for hard hot starting. That somewhere figured it was a fuel vapor lock situation and installed the pump. Which didn’t fix anything . I removed the pump and the truck actually runs better now that it’s back to the stock fuel filter and pump.

 

[Emil Schmid]

Thank you all for your replies and sorry for any delay! - we are currently traveling in Argentina where internet out of town isn't always available.

It's now very hot (up to 110°, but in the early morning it's fine to drive for 2-300 miles), although the phenomenon of bubbles while accelerating started the other day already at 80°. Here's what exactly happens (from a non-mechanic):
The engine starts jolting more and more, mostly when accelerating. Sometimes, if I take the throttle back the engine returns to normal, but mostly it will stop finally. Then the 3 pumps are running dry while being pretty noisy, hence the whole fuel line must be dry. Screwing off the fuel line at the carburetor shows that there's no fuel. Switching on the ignition - not the starter - reruns the fuel pumps and after some seconds a mixture of fuel and air arrives. After having collected about half a quart, it's time again to screw in the fuel line at the carburetor. From then on the engine runs sometimes without problems for hundreds of miles if the air temperature is not too hot, otherwise it might stop again after a few hundred yards and the procedure restarts. I tried to cool the carburetor down with wet rigs what helped occasionally.
Now to the different questions:

2+7) Seth S:
A fan is blowing directly at the carburetor.
The original mechanical pump had the same "illness", thus it was replaced 1982 by Toyota Switzerland under warranty by two (now unknown) electric pumps, which weren't later anymore manufactured, hence replaced by 3 Facet pumps (see above).
The fuel line isn't insulated but relocated completely away from the engine.
The hood was lifted in the back about ¾” to allow the hot air leaving easier the engine bay.

3) 3_puppies:
The 3 fuel pumps are located just besides the modified fuel 55 gal. tank in the back, i.e. there is first a 2¾ ft. metal and rubber connection to the 3 pumps sitting on the frame and from there about 17¾ ft. long fuel line consisting also of metal (original) and rubber to the carburetor with a filter halfway.

4) tmxmotorsports:
The tank was completely cleaned about 300 miles ago and didn't show rust.
The rubber line doesn't look that it would collapse, contract or implode.

5) KWalkerM:
The explanation about cavitations makes somehow sense to me, but what can be done to stop it - stronger pumps? As mentioned, the current 3 pumps work with 4.5-6.0 psi on a parallel operation; there is a stronger pump of the same brand available with 6.0-8.0 psi, but is one enough (price $169 ea.)?
There's a return line to the tank.
Size of fuel rubber line: 5/16" (7.9mm).
The pumps are not particularly hot, they are still touchable.
The fuel line along the frame doesn't run close to a heater.
The distance between the outgoing metal line from the modified 55 gal. tank to the pumps sitting on the frame is about 2¾ ft.; from the pumps to the carburetor about 17¾ ft. = totally 20½ ft. Halfway sits a fuel filter.

 

[Seth S]

Do your electric pumps run continuously or do they cycle on and off as the fuel bowl fills and drains?

 

[3_puppies]

where does the return line to the tank come from? where the original pump would have been or by the carb?

 

[KWalkerM]

Thank you all for your replies and sorry for any delay! - we are currently traveling in Argentina where internet out of town isn't always available.

It's now very hot (up to 110°, but in the early morning it's fine to drive for 2-300 miles), although the phenomenon of bubbles while accelerating started the other day already at 80°. Here's what exactly happens (from a non-mechanic):
The engine starts jolting more and more, mostly when accelerating. Sometimes, if I take the throttle back the engine returns to normal, but mostly it will stop finally. Then the 3 pumps are running dry while being pretty noisy, hence the whole fuel line must be dry. Screwing off the fuel line at the carburetor shows that there's no fuel. Switching on the ignition - not the starter - reruns the fuel pumps and after some seconds a mixture of fuel and air arrives. After having collected about half a quart, it's time again to screw in the fuel line at the carburetor. From then on the engine runs sometimes without problems for hundreds of miles if the air temperature is not too hot, otherwise it might stop again after a few hundred yards and the procedure restarts. I tried to cool the carburetor down with wet rigs what helped occasionally.
Now to the different questions:

2+7) Seth S:
A fan is blowing directly at the carburetor.
The original mechanical pump had the same "illness", thus it was replaced 1982 by Toyota Switzerland under warranty by two (now unknown) electric pumps, which weren't later anymore manufactured, hence replaced by 3 Facet pumps (see above).
The fuel line isn't insulated but relocated completely away from the engine.
The hood was lifted in the back about ¾” to allow the hot air leaving easier the engine bay.

3) 3_puppies:
The 3 fuel pumps are located just besides the modified fuel 55 gal. tank in the back, i.e. there is first a 2¾ ft. metal and rubber connection to the 3 pumps sitting on the frame and from there about 17¾ ft. long fuel line consisting also of metal (original) and rubber to the carburetor with a filter halfway.

4) tmxmotorsports:
The tank was completely cleaned about 300 miles ago and didn't show rust.
The rubber line doesn't look that it would collapse, contract or implode.

5) KWalkerM:
The explanation about cavitations makes somehow sense to me, but what can be done to stop it - stronger pumps? As mentioned, the current 3 pumps work with 4.5-6.0 psi on a parallel operation; there is a stronger pump of the same brand available with 6.0-8.0 psi, but is one enough (price $169 ea.)?
There's a return line to the tank.
Size of fuel rubber line: 5/16" (7.9mm).
The pumps are not particularly hot, they are still touchable.
The fuel line along the frame doesn't run close to a heater.
The distance between the outgoing metal line from the modified 55 gal. tank to the pumps sitting on the frame is about 2¾ ft.; from the pumps to the carburetor about 17¾ ft. = totally 20½ ft. Halfway sits a fuel filter.

Here is the quick and dirty answer followed with in depth tech breakdown.

Move your fuel pump as close to the aftermarket tank as possible while being at the lowest point on the frame, upgrade your inlet line from tank to pump to 3/8s and get rid of any filter or reducer fittings between tank and pump. Verify your fuel pressure regulator (FPR) isnt close to the rear foot heater lines and heating it up.


Its your fuel pumps getting hot trying to pull fuel from too far away from your long range tank, getting hot and cavitation on the outlet of the pump. I can almost guarantee that is your biggest issue because its a common issue with identical symptoms to people like myself running external fuel pumps for V8 swaps. After chasing an identical problem I made several easy and cheap fixes. Your fuel pump should not be more than lukewarm to the touch. I am running a huge 30-100psi fuel pump at 65PSI for a fuel injection system and after fixing it, its usually cold to the touch at all times. Your pump should not be noticeably hot to the touch at all. should have no problems at the low PSI you are running to keep your pump cold to the touch.

Its probably a couple of other issues compounding it too that ill run through.

Let me guess, you are running parallel pumps because you ran into fuel delivery issues on the swap to the long range tank?

First, in tank pumps will always be easier on a fuel pump because the fuel acts to cool the pump and its way less likely to cause cavitation. I dont run an in tank pump because its prohibitively expensive and time consuming for me to do. There are work arounds to this though with external frame rail pumps.

Most fuel pumps do not like pulling fuel, they only like pushing fuel. Move your fuel pump as far back and a low as you can on the frame rail. For me I ran the pump as far as I could back on the frame rail by the rear frame wheel arch which moved the pump back almost a foot and a half. By keeping it low it helps to siphon fuel out of the tank with physics and your pump doesn't have to work as hard as if you mounted it above the fuel level and were pumping fuel upward fighting gravity. If your pump cant get fuel it will create heat which causes cavitation.

Dont run fuel pumps dry or low on fuel flow. It will greatly decrease the life of the pump and creates heat which causes cavitation.

Cavitation can also be caused by too small of an inlet or outlet and flow restrictions. Do not put a fine filtering fuel filter or check valve upstream of the fuel pump to the tank. The more fuel you are pushing at a higher flow rate the bigger the line size is needed. You are almost certainly trying to pull way too much fuel to feed 2 pumps than a 5/16 line can supply. Upgrade to a 3/8 hose and do not restrict the inlet size down if you are keeping both pumps.

Check that your exhaust is routed away from the tank. I have mine wrapped with turbocharger wrap because uninsulated it heats up my fuel tank. Its routed close enough to the tank to either boil the fuel or add enough residual temperature to the fuel which then reaches cavitation point in the fuel pump with very little additional pump heat. I must have it wrapped to stop fuel heat in the tank. Odds are you wont run into the issue with a full tank but when there is little fuel in the tank it heats up faster from the radiant exhaust heat.

Make sure your FPR and fuel lines are not right next to the foot heater lines. Mine got mild cavitation because the heat radiating off the foot heater lines heated up my aluminum FPR heating it up until it stopped fuel flow and gave me dry line symptoms.




I would reccomend ditching the second pumps and try plumbing everything as I have explained and run it on one pump.

Most external pumps are not suited for constant duty cycle either. That can be fixed by researching external fuel pump speed controllers that turns the pump on and off as it reaches required PSI in the lines. Less runtime, less heat, less cavitation risk. I do not have a pump speed controller on mine and it runs fine. Its not a racecar so its not pushing hundreds of gallons of fuel in a short period.

Ill find the thread I put photos of my setup on and link it.

 

[KWalkerM]

Look through this thread, its about V8s but the concepts are the same.

Fuel delivery issues fj60 with 6.0 vortec

The PO that did the vortec swap in my cruiser used a fuel pump mounted on the frame rail and braided lines with AN fittings. I’ve had issues with it since owning it now for almost 5 years to the point it gave up on me climbing mountain passes in co. I swapped the fuel pump in a parking lot and...

forum.ih8mud.com

Lastly I also have a long range tank so other than the motor and flow rate I had essentially the same problem as you