Help diagnosing fuel issue (10 Viewers)

[JL2167]

78' FJ40 died suddenly while I was driving down the road at about 30 mph. Coasted to a stop and couldn't restart it. Acted like it was out of gas., but, my fuel gauge showed 3/4 full and I confirmed there was gas in the tank. But no fuel in carb float. Engine will turn over for a couple seconds when I put a little gas down the carb, otherwise nothing. I pulled the fuel hose off at the fuel pump intake and blew into it (took filler cap off first). Heard bubbles gurgling from the gas tank.

Strange because she was running great -- Solid acceleration, no sputtering or stalling, etc., -- right up until the moment she died. Fuel pump only has about 4,000 miles on it.

Any thoughts/suggestions on diagnosing the issue would be appreciated.

 

[Mark Jennings]

Vapor Lock is my first thought…..how how was it and are you running ethanol laced fuel (10%)????

Do you have an original mechanical pump or electric?

 

[Spike Strip]

Fuel Filter?

 

[JL2167]

Vapor Lock is my first thought…..how how was it and are you running ethanol laced fuel (10%)????

Do you have an original mechanical pump or electric?

Haven't noticed any signs of vapor lock. Running whatever the regular unleaded is at my corner Chevron station. It's a mechanical pump, engine and pump are off an '86 Fj60.

Vapor Lock is my first thought…..how how was it and are you running ethanol laced fuel (10%)????

Do you have an original mechanical pump or electric?

't notice

 

[JL2167]

Fuel Filter?

Ordered a new one, should be here on Tuesday. But if it was the fuel filter would I still be able to blow bubbles into the gas tank from the fuel pump intake hose? (Asking seriously -- I don't know).

 

[charliemeyer007]

Depends on what/how filter is plugged. Filters are cheap and easy to replace, you should carry a spare.
Fuel pump can develop a hair line crack and then not pump, later it can start pumping again for a while...
$10 diode electric fuel can be plumbed is a back up or in my case that is all I run. Primes the system and starts easily

 

[Spike Strip]

Ordered a new one, should be here on Tuesday. But if it was the fuel filter would I still be able to blow bubbles into the gas tank from the fuel pump intake hose? (Asking seriously -- I don't know).

It certainly can. Don't know if this is your issue, but a cheap filter will let you know. Had the same thing happen on my FJ60. Just driving and died. Tried everything and finally had to have my wife drive over a new filter (I was near home). Replaced the newish OE one (only 5K miles on it - that's why I couldn't believe it was the filter), and off I went!

I now keep one in the spares box. I suppose it only took one tank of dirty gas, cuz I cut open the old filter and silt/dirt was baked on the media.

Good luck!

 

[charliemeyer007]

Don't buy fuel if they are filling the underground tanks. The cheaper gas station has the fresher gas most of the time. Spring and fall, warm days cold nights will condense water out of the air into yours and theirs gas tank Yellow bottle gas drier every so often helps avoid issues.

Water will plug the paper element in the filter and not let gas pass. Leave filter in hot sun for a few days and it will dry out and be as good as new.

 

[CruiserInProgress]

Since you heard bubbles in the tank when blowing back from the fuel pump intake, that would suggest you have at least some amount of fuel in the tank and the fuel filter is not totally clogged.

Just curious though, how did you verify you have sufficient fuel in the tank?

If we can assume you have fuel and the filter is not clogged, you might try running a test of your fuel pump.

Pull the output line off your fuel pumpand crank the engine. If no output, pull the input line off and dip it into a container with gas in it. If still no output, you can assume a bad pump.

My 79 2F fuel pump died recently, but it dripped a bit out the weep hole as a symptom. I have also heard a failing pump can leak gas into your crankcase. So, you might check the oil level and see if you can detect the scent of gas on the dip stick.

 

[JL2167]

Thanks -- if new fuel filter doesn't fix it that's what Ill do.

 

[JL2167]

It certainly can. Don't know if this is your issue, but a cheap filter will let you know. Had the same thing happen on my FJ60. Just driving and died. Tried everything and finally had to have my wife drive over a new filter (I was near home). Replaced the newish OE one (only 5K miles on it - that's why I couldn't believe it was the filter), and off I went!

I now keep one in the spares box. I suppose it only took one tank of dirty gas, cuz I cut open the old filter and silt/dirt was baked on the media.

Good luck!

Thanks -- hopefully that's all it is!

 

[JL2167]

Since you heard bubbles in the tank when blowing back from the fuel pump intake, that would suggest you have at least some amount of fuel in the tank and the fuel filter is not totally clogged.

Just curious though, how did you verify you have sufficient fuel in the tank?

If we can assume you have fuel and the filter is not clogged, you might try running a test of your fuel pump.

Pull the output line off your fuel pumpand crank the engine. If no output, pull the input line off and dip it into a container with gas in it. If still no output, you can assume a bad pump.

My 79 2F fuel pump died recently, but it dripped a bit out the weep hole as a symptom. I have also heard a failing pump can leak gas into your crankcase. So, you might check the oil level and see if you can detect the scent of gas on the dip stick.

CIP:

Following up on my attempt to diagnosis my fuel problem. I first changed the fuel filter and the flexible fuel lines in the engine bay, no fuel came out of them in the process. So I worked my way back toward the gas tank. I pulled the flexible fuel line off the hard line where it starts to run along the frame (beneath the gas tank) and no fuel came out there. I blew into the line back towards the gas tank, and suddenly fuel started flowing. Strange, yes?

After changing my fuel-soaked shirt I pulled the flexible fuel line off at the fuel pump, where it intakes from the fuel filter. Once I had the line low enough in the engine bay ('cause gravity) fuel started flowing there too. So, at that point I was confident the fuel line was clear from the gas tank to the fuel pump.

Next, I detached the hard fuel line where it intakes to the carburator, and cranked the engine. Of course engine would not start, but it cranked. However, no fuel came out the line. So I sucked on it and after a couple tries got a small mouthful. That seems to indicate that my fuel line is clear from the pump to the carburator.

Checked the oil, looks good but smells off. Might be a fuel smell.

Anything else you'd try before replacing the (fairly new) fuel pump?

Thanks, I appreciate your help.

 

[CruiserInProgress]

Good troubleshooting. And that smell of fuel is a definite clue pointing to the fuel pump at this point.

It also sounds like you had a clog of some sort in your fuel intake line from the tank. Mine had the same issue, clogged with sediment and a decade of varnish. I ended up flushing my tank and lines several times to fix that from recurring. This may be needed here as well.

But, in your case, you seem to have at least temporarily have fuel passing through your lines, filter and pump.

Do you have any leaks in the lines , filter or pump? Do you see air bubbles forming in your filter while cranking?
The reason I ask, is your pump creates positive pressure post-pump, but creates negative pressure pre-pump. If you have some sort of air leak pre-pump, your pump may not deliver fuel properly. Mine had lots of bubbles in the filter with my old pump. Not sure why exactly.

With your ignition disabled (to avoid a fire) and your line to the carb disconnected as before, I'd try cranking some more. Verify again you have no output from the line, and watch the filter for flow or bubbles.

Failing all that, your fuel pump seems the logical culprit, that is assuming that line from the tank hasn't plugged again.

 

[charliemeyer007]

Vacuum/pressure gauge that can handle fuel - needs to be able to measure like 10 psi accurately for carb
I built the fuel transfer unit for like $50 several years ago from parts on Amoron/ebay - gave away like ten to family and friends.
Water proof switch, fused, filtered 5' draft 20' delivery hose, can be plugged into cig lighter or clamped to the battery 12' away. Not really fast maybe 0.5 gal per minute.

Very handy to add gas to your rig from 5 gal cans - you don't have to hold them up and the system doesn't spill.
Can be used to drain tanks by reversing the hoses. While help clear the fuel of water and crud - have spare filters - you can dry water wet ones in the sun for a few days and they will be good again. Will work for diesel as a transfer. For my LC or F150 I have scabbed the unit in bypassing the mechanical fuel pump and crappy old gas in the tank to be able to drive around.

 

[MDH33]

CIP:

Following up on my attempt to diagnosis my fuel problem. I first changed the fuel filter and the flexible fuel lines in the engine bay, no fuel came out of them in the process. So I worked my way back toward the gas tank. I pulled the flexible fuel line off the hard line where it starts to run along the frame (beneath the gas tank) and no fuel came out there. I blew into the line back towards the gas tank, and suddenly fuel started flowing. Strange, yes?

After changing my fuel-soaked shirt I pulled the flexible fuel line off at the fuel pump, where it intakes from the fuel filter. Once I had the line low enough in the engine bay ('cause gravity) fuel started flowing there too. So, at that point I was confident the fuel line was clear from the gas tank to the fuel pump.

Next, I detached the hard fuel line where it intakes to the carburator, and cranked the engine. Of course engine would not start, but it cranked. However, no fuel came out the line. So I sucked on it and after a couple tries got a small mouthful. That seems to indicate that my fuel line is clear from the pump to the carburator.

Checked the oil, looks good but smells off. Might be a fuel smell.

Anything else you'd try before replacing the (fairly new) fuel pump?

Thanks, I appreciate your help.

After you primed the line by sucking gas through, did you try cranking it over to see if the pump continued to deliver? If it does, reconnect to carb and see if it gets past the float needle, it may just be stuck.