possibly fuel pump?
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possibly fuel pump?
Hey guys- I'm hoping someone can help me with my 88 F150 (300 six, 5 speed, dual tanks, 176,000 miles). Truck starts fine, but cuts out severely under acceleration for the first 30 seconds of driving. After that I only notice the problem when applying a lot of throttle (does not cut out under gradual acceleration). If I kill it for a few minutes and then take off again the problem is back for the first 30 seconds or so. I have replaced all the tune-up type stuff (all filters, plugs & wires, dist cap & rotor, ign coil, o2 sensor, cleaned throttle body, replaced IAC valve, numerous sensors). My FPR was bad so I also replaced that. I just bought a fuel pressure gauge and plan on testing the pressure. Can anyone tell me the procedure for this and am I possibly on the right track? Thanks alot.
Also I am getting no KOEO codes, but getting KOER code 41 and plugs do seem to show a lean condition possibly
Also I am getting no KOEO codes, but getting KOER code 41 and plugs do seem to show a lean condition possibly
Posting Guru
Joined: Sep 2004
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From: Yokosuka, Honshu, Japan
41 (KOER) System Indicates Lean
(KOEO) No HO2S Switching Detected
Usually indicates O2 sensor-related issues, but you installed a new one. Might want to check all of your electrical connections on the engine harness, especially the ground connections. If your fuel pressure is low, that might be contributing to the problem. Not sure if yours has the in-tank pump(s) or external, but the pump(s) might be an issue - check valve(s) could be going or the impeller is worn. What filters did you replace? Could be a problem in both tanks - the sock filters. I know some setups have multiple filters.
(KOEO) No HO2S Switching Detected
Usually indicates O2 sensor-related issues, but you installed a new one. Might want to check all of your electrical connections on the engine harness, especially the ground connections. If your fuel pressure is low, that might be contributing to the problem. Not sure if yours has the in-tank pump(s) or external, but the pump(s) might be an issue - check valve(s) could be going or the impeller is worn. What filters did you replace? Could be a problem in both tanks - the sock filters. I know some setups have multiple filters.
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I have the high pressure pump on the frame and low pressure pump in the tank set up. I replaced the inline fuel filter between the engine and the high pressure pump. I will check fuel pressure tomorrow and post my results. Thanks alot.
Posting Guru
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From: Yokosuka, Honshu, Japan
Check to see if you also have the low-pressure in-line canister between tank and hi-pressure pump. I've known some not to even have a filter in there, some to be all clogged to hell. Could be the in-tank pump(s) and/or sock filters or the main hi-pressure pump.
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Well, did some more investigating yesterday. I removed the bowl from the resevoir between the tanks and the high pressure pump on the frame. No filter in there, but it was clean with no gunk or sediment found. I removed the line from the inlet side of the high pressure pump and found that while cranking the engine I have fuel flowing freely (same amount of flow regardless of which tank I've switched to). The flow was steady, but not extremely strong. If I understand right the in-tank pumps are not designed to provide much pressure? Below is what I found at the schrader valve:
key on, engine off - high pressure pumps runs for about 1 second, brings gauge up to 48 psi
idle, FPR connected - 40 psi
idle FPR disconnected - 52 psi
reving throttle with FPR connected - 46 psi maximum
Connector where fuel pump relay plugs in seems to be clean and not corroded at all.
High pressure pump not doing it's job 100 percent?
Thanks for any input.
key on, engine off - high pressure pumps runs for about 1 second, brings gauge up to 48 psi
idle, FPR connected - 40 psi
idle FPR disconnected - 52 psi
reving throttle with FPR connected - 46 psi maximum
Connector where fuel pump relay plugs in seems to be clean and not corroded at all.
High pressure pump not doing it's job 100 percent?
Thanks for any input.
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Posting Guru
Joined: Sep 2004
Posts: 1,915
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From: Yokosuka, Honshu, Japan
Those numbers are all good. Your in-pump 'booster' low-pressure tanks pump around the same as the old carb mechanical pumps, not a lot of pressure, but good flow to the inlet of the hi-pressure pump. I would put a filter in that canister, though. Might be that the injectors are clogged or not firing at proper volume / duty cycle. Only way to tell that is by using a noid light on each injector to see if they are firing properly and checking flow from the injectors when you crank it - which involves removing the fuel rail and injectors. May want to try fuel system / injector cleaner in the tank for a few tankfuls to see if it clears it up as well as check all your wiring connections on the engine harness - especially all of your grounds, make sure they are clean and tight.
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I have never had the injectors cleaned by way of hooking pressurized cleaner to the schrader valve. Would that be a good idea? The only thing I've done is put a good quality cleaner in each tank about every 3000 miles.