bad fuel pump?

[eric©]

bad fuel pump?FIXED, updated

Truck:1991 XLT, auto trans, 4WD, stock driveline.

Symptoms:been having hard starting the past few months or so, where it seems like I have to crank it longer than normal to get it to fire. The past couple of weeks it won't fire unless I give it a bit of gas pedal (if I don't, it seems to just want to crank forever without firing).

The other day I was running low on gas, and it stalled pulling into the back yard. I forgot about it, and went to the parts store the next day. Get about 3 blocks away, and it stalls, took forever to get it restarted. Just barely made it to the gas station 3 blocks further away. Wouldn't idle for crap, had zero mid range power, had to give it a lot of gas to keep it moving. Put about 1/4 tank of gas in (only had a few bucks on me). No change in symptoms. Get to parts store, get the stuff for the GF's truck, try to make it home. Truck still doesn't seem to want to idle (wanted to stall out), could barely muster 25mph with pedal floored. Seemed to run slightly better with pedal floored than with little pedal. Barely made it home, and the truck stalled pulling into back yard, wouldn't restart.

Let it sit for a day, turn the key on, I can hear the fuel pump running for a couple seconds. It fires right up, and dies a few seconds later. I can repeat this cycle now until the battery dies. Fires right up, and dies seconds later, seemingly like the key got shut off. If I give it gas, it dies faster. I haven't actually timed it, but it seems like it shuts off in the same amount of time everytime. After it shuts off, I can hear the pump running for a second or two, and it always fires right back up, only to die right away.


I've never had a pump go weak on me, they've always either worked or they didn't. Am I dealing with a weak pump here? I don't have a fuel pressure tester, can I fudge it with a tire pressure tester? I also haven't replaced any parts yet. I'm planning on picking up a new filter and pump later today, and replacing the filter first to see if that has any effect before replacing the (much more expensive, lol) pump.

 

[falls guy]

Sounds like your pump to me. I had the same symptoms, changed the filter and had a little better pressure but still wouldn't continue running. Before the filter change, when I pushed in on the valve on the fuel rail, with a rag there to catch any fuel, I had hardly any pressure. After the filter change I had more but still not enough. With the key on, when you push in on that valve it should squirt out really strong. Like if it were pointing up, it would spray the undernieth of the hood. I changed the pump and the truck fires up right away now. It has never skipped a beat since! Good luck!
Peace

 

[eric©]

yep, I just did the test port with a screwdriver thing, and got little more than a dribble. Went up the shaft of the screwdriver maybe 1/2", then quickly dropped back to a minor dribble. A couple other guys seem to think its the pressure regulator, but my understanding of the regulator is that it only prevents excessive pressure/flow from occuring. A bad regulator wouldn't cause too little fuel flow, right?

 

[eric©]

Got it going today, and god do I feel like a blind tool...turned out the problem was that the air intake tube fell off the throttle body. All the times I've been under the hood the past few days I don't know how I missed it, yet I did. Reattached the tube, tightended the clamp, and it runs again. Not well, as I've also got other gremlins to deal with (fairly positive I've got a bad coil as well), but it runs like it did before. Thanks for all the help regardless.