Fuel delivery issue?

[effjay55]

1974 55 series
F.5 engine
3 speed manual

So Ive got a problem Im trying to pinpoint.
The truck starts great, and idles fine. After letting it idle a bit, I’ll go for a drive and initially runs great and pulls strong through all three gears. But then it seems as if when everything starts to warm up it will start popping loudly and bogging and hesitating, almost stalling.

I pull over and checked the sight glass but it seemed ok? Maybe a bit low.

When i give it wot in neutral she purrs along just fine and strong, I can rev it for days, but when moving along it starts giving issues…again this is after everything is sort of warmed up.

The weirdest thing is Ive been driving this thing around trying to troubleshoot so I know Ive used quite a bit of gas, but I opened the fuel cap and saw that the fuel is almost to the top!

I pulled and blew into the charcoal canister house that goes towards the tank, everything is ok. (Orange)

The other top hose goes to the vsv but that one is completely blocked, not sure if its solenoid activated.(Red)

The bottom hose i havent checked yet…(Green)

Anyone know if those two issues are related? (The bogging/popping and the gas tank which seems to have some sort of back pressure)..

 

[fjc-man]

Your avatar implies 55, are you talking about a 40? What model year? Was there pressure in the tank when you released the gas cap?

 

[effjay55]

Shoot sorry forgot to add all the details

1974 55 series
F.5 engine
3 speed manual

There was no pressure when opening up the tank.

 

[effjay55]

<duplicate reply>

 

[fjc-man]

Hopefully the 55 crew will chime in with some ideas.

 

[trainbufftony]

I say slap a fresh fuel filter on it.
A carburetor uses vacuum to pull fuel into its various circuits. Vacuum is much higher under load and so is fuel demand so it works. Fj55s commonly develop particulate matter in the tank and that junk will pack up in the filter and lines, starving you of fuel.
As a test, pull the filter, blow on the outlet, does flakey crap come out the inlet?
Either way, put a fuel filter on it, it can't hurt anything.
Do not adjust your carb, do not retime your ignition, and leave your valves alone for now.
If the filter solves it, it's a $20 fix

 

[effjay55]

I say slap a fresh fuel filter on it.
A carburetor uses vacuum to pull fuel into its various circuits. Vacuum is much higher under load and so is fuel demand so it works. Fj55s commonly develop particulate matter in the tank and that junk will pack up in the filter and lines, starving you of fuel.
As a test, pull the filter, blow on the outlet, does flakey crap come out the inlet?
Either way, put a fuel filter on it, it can't hurt anything.
Do not adjust your carb, do not retime your ignition, and leave your valves alone for now.
If the filter solves it, it's a $20 fix

Thanks ill try this test and see if i see any muck , but either way I have one on order!

 

[effjay55]

So I went for a drive, got out to check the sight glass when the issue started happening and it was pretty low.

Supposedly the pump has been recently changed, so Im really hoping its just a plugged up filter.

 

[igotta40]

The symptoms you describe sound like burnt ignition points.

 

[bikersmurf]

So I went for a drive, got out to check the sight glass when the issue started happening and it was pretty low.

Supposedly the pump has been recently changed, so Im really hoping its just a plugged up filter.

Many moons ago my roommate had an ‘82 Toyota mini truck… same-same.

It had similar fuel delivery issues. The fuel filter would get plugged, we’d blow it out backwards with compressed air, but that didn’t always solve it. We also had to loosen the fuel cap and blow air from the carb end into the tank. It would behave for a while until more sediment clogged the line and we’d have to do it again. After repeatedly doing this, the lines stayed clear.

Lean fuel can cause a pop/miss. Bog can also be caused by running lean.

A mechanic would get drain it all, flush it all and put Fresh gas in and go for a drive… but we didn’t want to drain $20 of gas and refill it so we changed and cleaned filters till it behaved itself.

Recently my 40 did something similar to yours. The idle circuit in the carb was gummed up from sitting for a year. Pulled the top off the carb, cleaned out the jelly, and blew air through the jets and we were back in business.

 

[JohnnyC]

55’s not really my thing … however if I had the gas that high in my tank it will have gas throughout the evap

and the gas tank which seems to have some sort of back pressure

There was no pressure when opening up the tank.

Which is it? It’s hard to diagnose issues when you give conflicting comments

Could be plugged fuel filter (rust in tank and or lines)

Vapor locking (try driving with the gas cap off my first thought as your gas is full as much as it is)

Points as mentioned above (usually happens throughout drive imo …. File points and regap)

Collapsing rubber fuel line … does it have any long stretches of rubber fuel line? It could be kinked or collapsing when driving it … replace with steel line if it is

 

[effjay55]

55’s not really my thing … however if I had the gas that high in my tank it will have gas throughout the evap




Which is it? It’s hard to diagnose issues when you give conflicting comments

Could be plugged fuel filter (rust in tank and or lines)

Vapor locking (try driving with the gas cap off my first thought as your gas is full as much as it is)

Points as mentioned above (usually happens throughout drive imo …. File points and regap)

Collapsing rubber fuel line … does it have any long stretches of rubber fuel line? It could be kinked or collapsing when driving it … replace with steel line if it is

I realized the conflicting statements later on, back pressure was definitely the wrong word. It just seems like the fuel in the tank somehow was being not being vented (that is probably the correct term).

There is absolutely no pressure when I open the fuel cap. No air comes out, and its not hard to remove.

Ill have to check the fuel lines to see if there are any kinks.

This is my first carbureted engine with distributor, so Ill have to look into the distributor points to try and understand how that could cause the symptoms I am having.

The plot thickens, but Ill start off with the cheapest fix first.

Today I am planning to try and drive about 60 miles, don’t think Ill make it the whole way to he honest. About a 3000 ft elevation change (so going up hill the entire time).

Once I get it to my garage though Ill finally be able to dig into it. Can’t do really much of anything other than look at it where it’s currently parked.

 

[effjay55]

Many moons ago my roommate had an ‘82 Toyota mini truck… same-same.

It had similar fuel delivery issues. The fuel filter would get plugged, we’d blow it out backwards with compressed air, but that didn’t always solve it. We also had to loosen the fuel cap and blow air from the carb end into the tank. It would behave for a while until more sediment clogged the line and we’d have to do it again. After repeatedly doing this, the lines stayed clear.

Lean fuel can cause a pop/miss. Bog can also be caused by running lean.

A mechanic would get drain it all, flush it all and put Fresh gas in and go for a drive… but we didn’t want to drain $20 of gas and refill it so we changed and cleaned filters till it behaved itself.

Recently my 40 did something similar to yours. The idle circuit in the carb was gummed up from sitting for a year. Pulled the top off the carb, cleaned out the jelly, and blew air through the jets and we were back in business.

Appreciate the response!
I want to check the fuel filter, but currently don't really have much room to work with, but I plan on trying to move it today to my garage with proper tools.
I will probably start with checking the fuel filter, but I wasn't sure where to go from there.
Thank you.

 

[effjay55]

The symptoms you describe sound like burnt ignition points.

Need to look into this, thanks for the suggestion.

 

[trainbufftony]

One thing at a time.
Sure buy some points, put them in, follow the service manual. Do you have a timing light?
Consider borrowing one before you take the distributor apart. Also, I'd go straight to toyota for the points. Retail auto parts stores sell points, but they're usually trash, made for old hot rod guys who trailer to car shows and replace the points every year for nostalgia sake. When I did mine a month or so back the toyota condenser I bought, didn't fit, and once I rigged it up, it didn't work.
I had a condenser for an old Ford tractor which my dad hoarded years ago, brand new in the box so I put that on and have had zero ignition problems since.

Another good solution for ignition problems is to swap the points out entirely, in exchange for a pertronix style electronic pickup. Won't be original, and won't do anything to help anyone's electromagnetic pulse conspiracy, but your truck will start and (provided you can get fuel to the combustion chamber)& it will run like a scared rabbit.
I run points, just so I can tell people I don't have a single solid state transistor in the vehicle, a personal point of pride.
Do one thing at a time.
Disconnect the fuel line from the pump, put it in a bucket, and give the fuel tank a bit of pressure from a compressor.
The hose should run like a dang ol garden hose. If it does anything less pull off the filter and same test. As you continue towards the fuel tank you'll find a point where you remove something and get the garden hose style flow that you're after.
Use the tools at hand to verify this before going further. If you don't have steady fuel flow, nothing else is going to make a bit of difference.
Process of elimination.
Deductive reasoning.
Pliers and a screw driver.
These are your tools. Now put down the smart phone and check that the fuel can actually flow out of the tank.

 

[bikersmurf]

There’s a very good chance that there are a number of different problems adding up to the end result you’re seeing. As you peel back the layers it’ll slowly improve until all the layers exposed.

I’d expect that by the time you’re finished you’ll have replaced the fuel filter, cap & rotor, points, plugs, ignition wires, and cleaned your grounds & battery terminals.

 

[effjay55]

Well I made the 60 mile drive up the hill, and finally shes at home base where Ill be tearing into her for the time being.

Learned a bunch of things! Like for one: this thing has a tiny aftermarket re-usable glass fuel filter. For some reason I thought someone fit this inline glass filter before the OEM fuel filter, but turns nope… this is it. I’m a dummy who was confusing the fuel pump for the fuel filter lol… don’t ask

So after driving about 10 minutes the problem reared it’s ugly head and had to pull over. I looked at the inline filter and noticed a huge amount of sediment and gunk, took it off to see if fuel would come out of the lines and thats when I discovered I could take the filter apart and clean it. I quickly cleaned it out and popped it back in, started it up, and we were back in business! I drove like this for about 45 minutes before it started to give me trouble again. So I figured the same treatment was in order, and quickly went through the paces and I was good for another 30-40 minutes.

I ended up stopping to fiddle with the fuel filter about 4 times after that… but I ended up noticing whats actually happening is that a giant bubble is forming in the fuel filter, so I started just to drain the fuel filter instead of cleaning it out each time which resulted in significant time savings…

So I think this aftermarket reusable filter isn’t providing enough flow or something…and even worse it forms a bubble that causes the fuel delivery issue.

Also found out the dizzy is electronic and not point ignition .

One step at a time I guess…anyways I think I am on the right track and cant wait to clean everything out and slap a new filter on there to see how it runs.

 

[bikersmurf]

Sounds like you are making some progress and are on the right path.

The fuel filter in itself should be able to handle the flow.
That said… the filter element could be clogged up with shmag limiting flow, the seals could be dried out allowing air to be sucked in, and/or there’s too much shmag in the fuel pickup line and it’s limiting flow.

Can you have the fuel filter vertical while it’s running to bleed the air out of it? If you successfully get the air out. Does it come back?

If you blow air into the tank does it go through freely? Do you hear bubbles in the tank?

 

[trainbufftony]

I'd say use the rebuildable unit until the sediment stops or at least stops being a problem, then put on a factory filter which won't leak air. Congratulations on the electronic pickup. I think you're on the tight track!

 

[pb4ugo]

I agree, It sounds like it's sucking air at the hose, clamps or filter housing. Glass filters are dangerous. I ran one of those for yrs, till a friend saw it. He almost lost a car when his broke. You can find clear plastic filters if you want to see.