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Sputtering at sustained highway speeds

R

Rhinopkc

Bull in a China Shop
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Location
Lake Havasu City,AZ
I had a lift pump go out 2-3 weeks ago, replaced with new carter from NAPA (P74001), it's not the pump I wanted, but when you live in Havasu, you sometimes take what you can get when you don't have time to order it. This was the last pump in the whole town. I also replaced filter (no abnormal amount of junk on it or in the bowl) at the same time. Everything was fine for two weeks, now I'm having sputtering issues again, but only after a good hour of highway speed driving. The pump is delivering about 4-5 psi at idle, but only 2-3 at highway cruise, and vacuum condition when I get on it. When I back out of the throttle, the fuel pressure instantly comes back, so I don't think I have snotty sock, did I just get a crappy pump? Also pump gets almost too hot to touch after running a while, is that normal? I'm in Lakewood,Ca right now for work, so I was thinking about buying an Airtex E3158 from Autozone, but I don't want to buy another new pump if that's not my problem, I just can't see what else it could be.
 
Rhinopkc said:
I had a lift pump go out 2-3 weeks ago, replaced with new carter from NAPA (P74001), it's not the pump I wanted, but when you live in Havasu, you sometimes take what you can get when you don't have time to order it. This was the last pump in the whole town. I also replaced filter (no abnormal amount of junk on it or in the bowl) at the same time. Everything was fine for two weeks, now I'm having sputtering issues again, but only after a good hour of highway speed driving. The pump is delivering about 4-5 psi at idle, but only 2-3 at highway cruise, and vacuum condition when I get on it. When I back out of the throttle, the fuel pressure instantly comes back, so I don't think I have snotty sock, did I just get a crappy pump? Also pump gets almost too hot to touch after running a while, is that normal? I'm in Lakewood,Ca right now for work, so I was thinking about buying an Airtex E3158 from Autozone, but I don't want to buy another new pump if that's not my problem, I just can't see what else it could be.
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Try blowing air into tank via LP Inlet with fuel cap off just to verify its not a sock related. Takes 5 minutes.

It running warm may be starving for fresh fuel too, Try the air in the tank. See if it raises pressure up any, its free.

Are you reading 2-3 fuel pressure WHILE its stuttering? Or are you unhooked up at that point?
 
Vacuum at full load indicates insufficient supply volume, which could be the off-the-wall lp, or leaky fuel lines between the sock and the lp, or both - that lp is rated at 10-15psi @ 20gph, so seems like it should handle the load - oem is 4.5psi @ 15gph - 15gph @ 60mph is 4mpg
 
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Rhinopkc said:
2-3psi while cruising, sputtering or not. I'll try the air tomorrow.
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FWIW i had similar problem in wintertime clogged sock of some sort with a brand new tank/fsu installed 3 weeks prior. Turns out my new FSU had the gasser sock, not the diesel sock which has a flap or screen area to allow thickened cold diesel fuel to enter. I blew in there at about 90 psi a bunch of times, trying to blow my sock off was my plan. 6 months later i took the FSU out to verify problem, and sock was still attached.

I would hit it with 30psi or so, then check Fuel pressure. If it was a problem you should see immediate result. If not perhaps some of your other lines are caused by rust or something... perhaps this is why your old LP failed.

Burning Oil blew his lines out from Flt-mgr - Lift Pump and said a ton of crud came out. Resolved his problem.

Maybe its a bummed LP. Perhaps you should order up a Walbro FRB-5 as I plan to do. Under a bean and with the fittings from PMDCABLE.com you don't even need to cut factory fuel lines if you don't want, and you would always have your new low-pressure LP as a backup.
 
Tonight the truck started crapping out right out of the gate after work while everything was cold, the fuel pressure was 2-3 psi during the event, and I was at about 1/4 throttle.
 
New fuel filter seems to have fixed problem, the one I replaced has less than thousand miles on it, and doesn't look bad. No junk in bottom of fuel manager, must be a lot of real fine particles from a bad load of fuel. I bought 2 filters this time, I used to always carry a spare, but got lazy a while back. I think I'll order the Airtex E3158, it's 15gpm more than the pump I have now, hopefully that will feed this thing.
 
I thought I would give an update to this saga. New fuel filter fixed the prob for about 300 miles, then same problem. I put another new filter, blasted the sock with 120 psi air, and problem went away for a bit. Problem cam back over and over after repeated sock blastings and filter changings, plus new Airtex E3158, truck ran awesome for about 300 miles, then worse than ever. Dropped tank, sock was still attached, couldn't acquire new sock in a timely manner, so reassembled sans sock and ordered Racor from Ebay dude for $90. After checking all lines, reassembling, and firing up, still had problem!!! Blew out supply line from filter mgr to LP, now everything seems fine, but no junk came out, it was clean. Maybe a ghost turd was in there?
 
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