fuel pump, dumb question

sleeperjeeper · Sep 14, 2011

I was having a weird fuel problem where my engine would die on steep inclines going up, but not down.

A friend suggested that I might have my supply and return lines switched on my fuel pump.

looking in the hanes manual, the picture of the fuel pump has the 'outlet' line as the longer top tube, but the picture of the fuel tank shows the lower shorter line as the feed line and the upper line as the return line.

So I'm confused. does anyone know which is which? should I just disconnect both, turn the key and see which one squirts gas?

thanks in advance

sleeperjeeper · Sep 14, 2011

FYI, It's an 89 XJ with a 4.0 fuel injected

I turned the key and fuel came out of the larger upper line, which is the one I originally had connected to the fuel filter. So I went ahead and put it back together the way it was.

any ideas on what could be causing my issue?

Symptoms:

stalled out on steep uphill climb, but not on steep downhill incline. I had half a tank of gas at the time. afterwards, fuel pump made loud humming noise all the way home, but hasn't made a sound since.

engine sputters and has low power on long semi-steep uphill drives.

ParadiseXJ · Sep 14, 2011

sleeperjeeper said:
FYI, It's an 89 XJ with a 4.0 fuel injected

I turned the key and fuel came out of the larger upper line, which is the one I originally had connected to the fuel filter. So I went ahead and put it back together the way it was.

any ideas on what could be causing my issue?

Symptoms:

stalled out on steep uphill climb, but not on steep downhill incline. I had half a tank of gas at the time. afterwards, fuel pump made loud humming noise all the way home, but hasn't made a sound since.

engine sputters and has low power on long semi-steep uphill drives.

I know it sounds kinda weird but my GAUGE can go from 1/2 to almost E (as in my fuel light will come on) when I'm hitting a steep uphill climb...turning left. Downhill, up and right, level...not a problem.
Never having to deal with an errant fuel pump I do not know which hose belongs where, but it looks like I've just poked a hole in my tank turning left, uphill.
Weak point?? Methinks, yes.

Flyfisher · Sep 14, 2011

ditto the above. Fuel pump and pick-up are located at the front of the tank. Steep up-hill climbs might leave the pump intake dry, whereas steep down-hill decents won't. My advice..keep the tank full

sleeperjeeper · Sep 14, 2011

still, I never had the problem in the past, and I shouldn't have it on mountain highway grades.

The only thing that changed was me putting my fuel tank skid on which pressed the fuel tank up against the under body of my jeep. Its possible that one of the two vent lines is slightly pinched. Could that cause problems?

PDXGraham · Sep 14, 2011

how full was the tank? the fuel pump is in the front of the tank and maybe on steeper inclines when wheeling all the fueld sloshes and settle to the rear and the pump simply isnt sucking in any fuel. highway grade arent steep enough for this to happen as far as i know.

O-Gauge Steamer · Sep 14, 2011

Fuel Pumps can exhibit some very strange problems. How about... The engine, on a 97, momentarily shuts down on a hard left corner? Turned out that the lousy little "filter" on the bottom of the pump had come loose and during aggresive LEFT cornering, obscured the pump intake shutting off the fuel.

So, I would recommend adding a fuel pressure gauge and monitor what is going on. Then, once you have some meaningful data, you can make an informed decision.

Scorpion8 · Sep 14, 2011

Flyfisher said:
My advice..keep the tank full

That's only addressing the symptom, not the problem and is a patch-it fix that may not always be available.

sleeperjeeper said:
still, I never had the problem in the past, and I shouldn't have it on mountain highway grades.

The only thing that changed was me putting my fuel tank skid on which pressed the fuel tank up against the under body of my jeep. Its possible that one of the two vent lines is slightly pinched. Could that cause problems?

o-gauge-steamer said:
So, I would recommend adding a fuel pressure gauge and monitor what is going on. Then, once you have some meaningful data, you can make an informed decision.

Overkill, I think. If the problem started right after adding the skid plate, then obviously I'd remove the skid plate and see if the problem went away, and then troubleshoot how the skid plate affects the fuel tank set-up. Do the easy thing first, rather than adding gauges that were never needed before.

fuel pump, dumb question

sleeperjeeper

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sleeperjeeper

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ParadiseXJ

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Flyfisher

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sleeperjeeper

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PDXGraham

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O-Gauge Steamer

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Scorpion8

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