Fuel problem

[Rml1708]

It appears that I have a fuel problem. Whit more that two people in the jeep climbing a hill it starts to sputter and runs out of Gas or at least appears to be running out of gas. First time this happened I thought I was out of gas. So I put the 4 gallons I carry in the Jerry can in the tank. tried to pour a little in the carb from the donkey dick and failed miserably and ended up with half a cup or so, dreadfully flooding the jeep. Battery died prior to getting it started. Towed it home. The last time we had symptoms like this one of the little values in the fuel pump had lost a spring. So I took apart the fuel pump and found nothing wrong. Diaphragm was good, both little values appeared OK (they both had their springs). I put it back together and used a Glass bowl this time. I pumped up the fuel pump with the lever and filled up the pump and had good stream of fuel when accelerator was pushed. She started right up and has run for a good week with usually only me in it. Yesterday I picked up my daughter from school and a couple of her friends (they all love the jeep) and headed to take them home. when heading up the long slight grade to leave the school it started to sputter. I just slowed down to a crawl and it never died. Once to the top of the hill it never had a problem going down the hill or any of the reasonably flat streets of the city. When I got home I left her run and popped the hood. I immediately noticed the air bubbles coming into the fuel bowl from the supply side. The fuel level was right at the level of the brass screen.


So far I have tried to tightened the fuel bowl screw. With much effort I tightened the adjuster maybe a quarter turn. I looked for any evidence of fuel leak or air leak from supply side of pump to filter on dash. Nothing seen to indicate the problem.I will tighten or at least check the fuel strainer on the firewall and chase back to the tank.

Any Ideas? I have had one suggestion to replace the condenser.

Thanks,

Robert

[Chuck Lutz]

Maybe 90% of the fuel problems are electrical, but I'll let others address that.

My old 1985 F-150 began to act up when I went up a nearby hill also....I needed to give it more gas on an incline anyway, but when I did she began to miss and buck a bit. I backed off on the gas and got in the slow lane and got over at about 20mph. Once over and on the downhill side she ran fine. This happened on the way back on the same hill, the only hill on my drive from home to/from San Rafael.

My mechaninc said it was probably one of two things.....a plugged up fuel filter.....or a plugged up catalytic converter. That time it was the cat and I replaced it and she ran like she did before. A couple years later she did the same thing in the same place....this time it was the gas filter.

Robert....clean the strainer on the firewall and check the dome on the little mushroom shaped filter screen inside the bowl on the fuel pump. When you can, you might want to check the tank for some rust or crud if you find the strainer is clogged up. I would suggest you blow air BACK from the strainer to the tank to clear the line and also remove/check the flexi line from strainer to pump for crud.

[Rml1708]

I opened up the fuel strainer and there is a small amount of junk at the bottom of the bowl. Cleaned it out real good. The brass strainer looks good, no indication of anything wrong. I replaced the gaskets since I was in there. Just for good measure I coated all fittings with shellac, now there are no air bubbles. The fuel level in the fuel pump is still not filling enough to put fuel in the output side of the fuel pump to pump up to the carb. The fuel level is just at the level of the brass screen in the fuel pump. Still not enough fuel going into pump to fill above the brass screen in fuel pump. Is it time to swap out the fuel pump spring? While doing all this tinkering I keep hearing Artificer in the back of my head saying don’t just swap parts diagnose and repair. I am now at the point I do not know what or how to diagnose further.

Robert

[Chuck Lutz]

Robert...the pump spring is not the problem...you found crud in the strainer so I'd follow that further.

By the way, you did check the oil pan to see if gas is leaking in from a crack in the diaphragm"?

1) Did you also blow out the line from strainer to fuel pump with pressure from the FP end? Did you capture any crud in a clean shop rag there?
2) Did you clean the screen on the mushroom filter in the FP?
3) Did you replace/tighten the gasket in the FP bowl?
4) Maybe you should remove the flexible line from strainer to pump and see if it is clogged up also?
5) With air having smaller molecules than gas, it will be sucked in from an airleak in the fuel system when the flow of gas is restricted if there is an airleak. so check all fittings in the system.

While you do find an air pocket in the glass bowl, if there is not enough gas being pumped to satisfy the motor, then you should also check the pump output.
Here is where a vacuum gauge will come in handy....but the analog test is to remove the gas line at the carb and run it into a measuring cup. I believe the test is to hit the starter (ignition off) for 30 seconds and I believe you should have half a cup of gas in there. Someone will confirm that test for you.

If this gets you nowhere, then you'll have to address possible issues in the carburetor.

[Rml1708]

By the way, you did check the oil pan to see if gas is leaking in from a crack in the diaphragm"? Checked oil, no rise in level and does not smell of gas.

1) Did you also blow out the line from strainer to fuel pump with pressure from the FP end? Did you capture any crud in a clean shop rag there? I blew out the line from strainer to tank, but not FP to strainer.
2) Did you clean the screen on the mushroom filter in the FP? Inspected and nothing to clean there
3) Did you replace/tighten the gasket in the FP bowl? Yes, and tightened the nut or tried to each time I have opened the hood. There was nothing wrong with the old gaskets as well.
4) Maybe you should remove the flexible line from strainer to pump and see if it is clogged up also? I replaced the flex line and have confirmed that there are no leaks in either old of new flex line
5) With air having smaller molecules than gas, it will be sucked in from an airleak in the fuel system when the flow of gas is restricted if there is an airleak. so check all fittings in the system. Checked all fittings and then sealed tehm with shellac.

While you do find an air pocket in the glass bowl, if there is not enough gas being pumped to satisfy the motor, then you should also check the pump output.
Here is where a vacuum gauge will come in handy....but the analog test is to remove the gas line at the carb and run it into a measuring cup. I believe the test is to hit the starter (ignition off) for 30 seconds and I believe you should have half a cup of gas in there. Someone will confirm that test for you. its kinda tough to check output when there isn't enough gas in the FP to be pumped out.

If this gets you nowhere, then you'll have to address possible issues in the carburetor.[/quote]

I will go blow air from FP to strainer into clean rag to see what if anything comes out.

Robert

[artificer]

You heard right....Guessing going on.

I read about 1/4 of what has been written & wondered why FUEL & why the fuel pump was pulled apart before, & still has not been tested with a $15 HF vacuum/pressure gauge & PROPERLY eliminated.
If a vehicle runs fine & fuel is OK, on the flat, in all gears @ all RPM then fuel is definitely not suspect @ this stage.

Ignition issues commonly associated with this type problem that need to be eliminated:
1. Failing spark plugs or bad leads. Very common problem missing [kangaroo-ing] under load on slight or any incline. Sound familiar?
This is why cleaned spark plugs are tested under air pressure to simulate combustion pressures.
2. Points closed up from not greasing the rubbing block with a dab of high speed grease. Check gap 0,020" or more simply hook up dwell meter 41-42*.
3. The spring loaded carbon contact missing from the centre of the distributor cap to rotor
4. Carbon tracking distributor cap or coil top

[Joe Gopan]

And remember, when all else fails, there is no shame in going to your neighborhood small town garage.

[artificer]

Robert FYI fuel connections should not need any sealants & shellac is definitely something I would not be using. But that is not your issue.

And remember, when all else fails, there is no shame in going to your neighborhood small town garage.

Given up on possibilities?
Why should all things fail?
Eliminating possible faults one @ a time should take about 15 minutes total, before pin pointing the issue @ hand.
From my exposure to US & modern mechanics, the garage would do less than most are offering on G503 before probably turning Robert away [or emptying his pockets replacing everything] as their mechanics [SIC] would not know where to hook the OBD scanner.

[Chuck Lutz]

Hi Robert:
1) runs outta gas going uphill/under a load
2) no gas in bowl

I would STILL remove the line from the carb and let the FP crank for 30 secs and see how much fuel (if any) is collected.

1) little or no fuel collected would tend to eliminate electrical gremlins or place them in second place
2) it would also isolate the problem between the strainer and the carb (you got a full tank and no gas to the carb? Gee, that isolates it pretty well.
3) you blew out the tank/strainer line and cleaned crud outta the brass strainer (hint, hint....crud is in the tank and where else....???)

But...I would NEVER reuse a strainer gasket or bowl gasket! In fact, check the strainer for more than one gasket....When I found my "F" marked strainer assembly and restored it, there were TWO gaskets on it....probably a recipe for air leaks.

Finish ONE area of possible problems before jumping to the other suggestions. One of the rules of diagnostics is to eliminate those associated with ONE problem before jumping to a different area (electrical in this case). Until you get fuel out of the gas line to the carb when turning over the motor....you need to fix/find the cause....

[artificer]

I don't disagree with one thing @ a time. If the fuel pump has been tested & doesn't pull a vacuum or create pressure, there is a fuel related problem.
But nowhere do I see other than

the jeep climbing a hill it starts to sputter and assumed runs out of Gas or at least appears to be running out of gas.

then jumping from pillar to post looking for something related to gas.
FI....Fuel pump bowls are often not full, have a bowl pulsation air cushion & do create fuel pressure. Robert needs to check this & let us know.

This vehicle runs fine unless under load on an upslope, is all I read into this thread that makes 'mechanic' sense & should be diagnosed logically.
The assuming, guessing, wild goose chase is never a winner

Hi Robert:
1) runs outta gas going uphill/under a load I think it is just an assumption on someone's part
2) no gas in bowl Where was this mentioned, as the case?
....With air having smaller molecules than gas, it will be sucked in from an airleak in the fuel system when the flow of gas is restricted if there is an airleak. It is no wonder people have trouble diagnosing fuel flow issues....
Air pressure on top of fuel in the tank causes flow to the lower pressure created by the fuel pump. That pressure differential causes fuel to be lifted out of the tank then that fuel can flow along the fuel line....any air leak between the tank & fuel pump equalizes/negates the air pressure on the tank fuel, so fuel can't be lifted BY THE AIR PRESSURE out of the tank to be able to flow @ all. The lower pressure created by the fuel pump will be fed by the air leak [compressible] not the non compressible fuel so NO FLOW ....nothing to do with molecules.

Until you get fuel out of the gas line to the carb when turning over the motor....you need to fix/find the cause....
if this is the case, I agree but the pressure/vac gauge would have told us this yesterday & all the fooling around could possibly have introduced something other than the original, still there, issue

As far as the condenser suggestion they fail other than going up hills & if the spark is good crisp blue when the problem occurs that is not the issue.

[Scoutpilot]

Please pardon a silly question. It is not my intention to insult you. How much fuel was in the tank at the time of the first bad experience? Just how steep is the hill it died on? Is the tank free of floating objects?

[pkozak1]

While in the military I had a grader that would run for a while and then die, let sit while you bleed the air out of the system (diesel) and it ran strong again, then die out. Well after this went on for a bit I decided to look in the fuel tank and found a coffee cup floating in the. It would starve out the engine after getting vacuumed to the suction tube then the engine would die and the cup would come free until the next time it got vacuumed to the pick up tube.

[dinof]

RM-1708 Just to be clear, you can go up the hill with just you in the jeep but when you have more weight/passengers it does this problem?

Dino

[Chuck Lutz]

Robert....by any chance are you using a NON-VENTING gas cap? If you do, the fuel pump will not be able to overcome that sealed tank! Do the same test again with the cap slightly loose to prove/disprove that theory!

When the diaphragm in the pump moves AWAY from the source of fuel with the valve open, it creates a VACUUM and pulls fuel into the pump. When the diaphragm starts to close, the valves switch and the PRESSURE of the diaphragm forces fuel towards the carburetor. ....it is the vacuum created by the pump in the fuel system that PULLS fuel into the pump and the pressure created by the closing action of the diaphragm that moves it towards the carb.In the case of a non-vented cap, a greater vacuum than the pump can overcome will eventually starve the carb.

Air molecules are less dense than gas/water molecules and will flow to the vacuum created by the pump before those liquids will be pulled from the tank/source. This is why an air leak in the system eventually causes a lack of fuel to the carb.

Gas cap?
Air leak?
Sticky pump valve? (you checked this)

PS...the valves in replacement kits seem to fail occasionally....unless there is a reason to replace original ones you should probably avoid doing that.
(if it works, don't "fix" it!)

[Joe Gopan]

How about dirt or water in the fuel tank. Dry as is always a good idea.