Ford Fuel System :: 1989 F250 Fuel Pressure Drop Quickly Under Heavy Load
Apr 4, 2010
I am a newbie as far as fuel injection. The original issue the truck had was no fuel. I tracked down the issues to a blown fuel pump relay and a melted inertia switch. I jumped the inertia wires with a new fuel pump relay installed and the truck ran at an idle and up to 3500 RPM when stationary. If the truck is going up a grade or needs more throttle it will start to lose fuel pressure and end up stalling. I had the fuel pressure gauge connected to the schrader valve on the fuel rail and had 30-35 PSI when idling. It runs good under light load on the throttle.
Under heavy load it starts to drop quickly and if you back off the throttle it will stay running some times. I changed the fuel filter and also replaced the high pressure pump on the main frame and it still has the same problems.The original pump was pumping about 13 ounces of fuel in the 20 second test that the repair manual suggested. I have even placed a jumper wire direct to the new fuel pump to bypass original wiring and possible problems. When it stalls under load (No Fuel pressure) at the schrader valve you can hear the fuel pump running but there is no fuel pressure.
If I turn off the ignition for a few minutes and then turn the key back to the on position it will start to pressurize and then start and run at an idle. I even replace the ignition switch as it was a little temperamental. I have not changed or checked the fuel pressure regulator as it is a pain to get to at the back of the engine. I do not want to spend a fortune tracking down this problem since the truck may not even pass its smog inspection and may be a parts truck only.
67 F-250 4x4
73 Crew 4x2 (4x4 Soon)
89 F-250 Super Cab 4x4
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for the past week we have been trying to figure out what is wrong with our truck. We recently bought it and it ran fine. Then got in a minor accident just a fender bender and it started acting up so I got towed to garage. First it would run when cold, but when hot fuel pressure would drop to 28 psi.
So I put new fuel pump, it started but still did the same thing hot 28 psi fuel pressure shuts off. So I put regulator on it, then had 0 fuel pressure won't even start. So got a another regulator thinking I got a bad one, still 0. Checked relay, there fine. I'm gonna check lines and see where fuel stops at but everything is new on it.
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I have a 1988 Ford F-250 Lariat, 7.5L 460, four-wheel drive. I have two fuel tanks on it, and I've been having a really annoying, obnoxious problem with it lately. After running it for a while, I noticed that I keep losing fuel pressure, and the truck stalls. When I try to start it, it does nothing but roll over. It just won't start. I've changed the fuel filter, I know both fuel pumps are working (I turn over the key, I can hear front, back, and high pressure pump attached to the left side frame rail kick in.) It's Fuel Injected, not EFI, hence that third pump. The problem happens a lot, and it's random. I could drive for 100 miles, stop to get something to eat, come out, and it won't start.
I thought maybe it was the fuel pressure regulator, but I don't think that's the case because it still runs. I would assume that if the regulator was bad, it wouldn't run at all. I also thought that maybe it was the relay, but according to some mechanics I spoke too, if I can hear the pumps kick in when I turn the key over, then the relay is fine. The only thing I could think of is that it might be the fuel selector switch. Maybe it's going bad, shorting out or something. When I flip the switch though, it switches between fuel tanks, and the gauge reads how much fuel is in it from the sending unit.
There's a schrader-type valve up by the fuel injectors. When I push it in, it barely squirts any fuel out, if at all, so I know the pressure is low. When I push it in on a good day, it sprays out like a water fountain. Just tried starting it again - no good. Pushed on the valve, it spurted out some fuel pretty well, but still won't start. Occasionally tries to, but ultimately won't. I know the spark is good, checked the plugs/distributor cap. Can't get the sucker to start.
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I just purchased a 1989 F250 with a 5.8 motor. Great truck for its age. Ive owned other Ford trucks in the past and my Dad had them as a kid. Love them.
When I bought the truck from the 2nd owner it had a problem so I bought this truck with the problem figuring with my past knowledge I could fix it. Not the case. When I got the truck it would start fine and run really great but when it got warm it seems it would die and I would have to wait till it was cooled down to start back up and again it would run fine. Well the problem got worse and worse and now it wont run at all.
It will run on starter fluid so that leads me immediately to the fuel pumps. I say that plural because none of them will run it seems. I did a fuel pressure test at the shrader valve at the top of the motor on the fuel rail and I get no pressure at all when I turn the key. The relay in the engine compartment seems to be working to as I can hear it. I put a new on of those on to to be sure. Leads me back to the pumps again. I replaced the external pump on the fuel rail and I know thats working. I replaced the fuel filter to while I was there.
Is it possible to have BOTH fuel pumps in the front and rear tanks go at once? Seems unusual. My other F150 with dual tanks worked great and when the back tank pump went I could just switch it over to the front tank.
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I have a '99 E-350 6.8L. Where is the check valve that maintains fuel pressure on the system?
I have been experiencing a starting issue when the engine is hot. Cold starts are usually fine. I've replaced the in-tank fuel pump (pump only, not the assembly) to no avail. I was out of town and didn't have access to a fuel pressure gauge when the problem started so I couldn't say what I had prior to replacing the pump. But now, with a new pump, when I check pressure, I get about 40 psi when I first cycle the key on, but it drops right back to zero as soon as the pump shuts off. If I cycle the key on a few times, sometimes I can get it to hold pressure at about 32 psi, and it starts fine. When I shut if off, it goes back to zero psi, sometimes gradually, like a bleed down, and sometimes immediately.
My conclusion from this was that the check valve was bad. I was told it was part of the in tank fuel pump assembly. Since I didn't replace the entire assembly, this made sense. So I just dropped the tank back down, but I don't see anything as part of the pump assembly that serves as a check valve. There is a rubber nipple on the end of the return line, but I don't see how that can hold any significant pressure.
So, before I go out and spend another couple hundred bucks on the complete fuel pump assembly, which apparently can't be purchased without the actual pump, I thought I'd ask. Where is the check valve that holds the pressure in the fuel system?
BTW, I also have replaced the fuel rail pressure regulator, but it made no difference (I went there first since that was much easier than dropping the fuel tank a second time).
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Working on a 88 Ranger 2.9L 5-speed ext cab. The fuel pressure drops off fairly fast when turned off and I'm pretty sure that the check valve is bad. My question is, which pump has the check valve? It is a single mid tank set-up and has a pump in the tank and on the frame.
Pressure is fine while running. about 30psi @ idle and 40psi with no vacuum on the regulator. The pressure drops off within a couple of minutes which causes it to have to crank over for a bit to rebuild pressure and start.
It looks like the frame pump is readily available while the in take pump is special order. I just need to know which one has a check valve. I'm thinking the in tank pump, but I hate to waste money for the wrong pump.
Pressure drop rate
30 psi @ shut off
25 psi @ 1:05 min
20PSI @ 2:30 min
15psi @ 4:45 min
still dropping
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I just bought another 1991 Ford. This one is a 1/2 ton XLT Lariet with the 302 and for the first time I own a short bed. I also have a 1991 F-250 XLT with a 460 and a 8' bed.
Here is the problem, ( I think) it will not run or at least not for long. The fuel pump, which I am guessing is in the rear tank will not stop running. On the F-250 the pump stops running after a few seconds after I turn on the key.
Where should I start to find out my problem with the fuel system?
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My F250 heavy duty isnt getting voltage to the fuel pump relay.....
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I have a 94 F250 5.8 liter with 96K miles. Can I remove the fuel rail and clean or replace the filter that is placed at the top of the fuel injector?
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I have a 77 f-250 with a 460 engine and a 4bbl Motorcraft carb and its leaking a substantial amount of fuel out of the newly replaced filter that is attached to the carburetor. The fitting is tight and I even tried buying some small gaskets to seat it, but that didn't work either.
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My 88 F150 (300 six, 5 speed, dual tanks, 176,000 miles). The truck has the low pressure fuel pumps in the tanks and the high pressure pump on the frame rail setup. 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) or climbing steeper hills. 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, ignition coil, o2 sensor, cleaned throttle body, replaced IAC valve, numerous sensors). Timing is dead on at 10 deg. BTDC with SPOUT unplugged. My FPR was bad so I also replaced that. Condition exists regardless of which fuel tank I am using (no problems with tank selector).
Getting no KOEO codes, but getting KOER code 41 and plugs do seem to show a lean condition possibly. I'm still averaging around 16 MPG since this became a real problem about 3 months ago.
I removed the bowl from the reservoir 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
revving throttle with FPR connected - 46 psi maximum
Connector, where fuel pump relay plugs in, seems to be clean and not corroded at all.
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I have an ambient temp switch connected to the vac port on my throttle emissions control solenoid for my 2150 carburetor. It's a 78 F-150 with a 5.0L 302, automatic 2WD. Would a bad ambient temp switch screw up my idle? I've disconnected the vac hose and it won't idle at all, and it does the same thing when I disconnect the two wires from the ambient temp switch. If I leave everything alone, I can get the idle down to around 1800rpm, but any lower than that and it stalls.
Is it possible to swap out this throttle emissions control solenoid with another type? I've looked everywhere and can't find an exact replacement, and I have no instructions on how to tune it.
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I have a motocrap 2bbl on my 73 f-100 all stock 390 when I drop it into gear she wants to sputter and stall without warning at idle runs great but put a load on and forget it what is wrong with this thing?
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I have a 1989 GMC suburban V8 350 5.7l that will not start. I have replace the following fuel pump and sending unit, fuel pump relay, ECM computer brand new, new fuel filter. When I go to start it the fuel injectors dont spray fuel into the combustion chambers verified fuel injectors still work by bypassing them and they spray fuel. Fuse's are not blown. I have been told the oil pressure switch might be bad but I'm at my end of sanity on this.
Additional Details : Tried spraying fuel into the throttle body and still no fire, ignition module and ignition coil where replaced 15,000miles ago.
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I need to check the fuel pressure to verify if my fuel pump is functioning. What is the procedure and PSI?
Assume that I open the valve on fuel rail with engine off, then connect pressure tester kit, put key in ignition to "on" position, then pump up to specified PSI???
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2 wks ago I was running down I95 at about 95-100 mph (basically floored) in a rush to get somewhere on time. Since then my truck has been running for crap. It threw the p0171 code when I checked it. When driving under normal conditions it pings a lot and my mpg is down about 3 mpg and has this hesitation when you get on it. Even when you accelerate at a normal rate it surges a little, it pings a lot and has a loss of power, about 30-40%. It feels really sluggish and doesnt want to pull and then you will feel it starting to pull a little harder then it starts to surge/hesitate a little again.
Truck has 147k on it. I was having a similar situation until I had the plugs replaced at 125k, so I figured the plugs shouldn't be the problem. So I replaced the fuel and air filters, cleaned the maf w/maf cleaner and Throttle body w/tb cleaner and replaced the pcv with a new one from ford. Still pings bad under load and still has the hesitation/surging and crappy fuel economy. Its running smoother but no fix yet. This is crazy trying to pinpoint this issue. The detonating isnt crappy gas because I used super and it still detonates quite a bit.
Its a 06' F250 5.4 3V XLT Lariat SC FX4....
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I've got a 2003 F250, SD, 5.4L Triton that I've owned since new. It has 205,000 kms on it and has run flawlessly since owning it.
Yesterday I went to use the truck after it sitting for about 2 weeks, which isn't uncommon for this time of year as I'm in the landscaping business. It never sits long, though as I make a point of using all the trucks, periodically, just to "blow the stink off" as my Dad would say.
Anyway, when I fired it up the gauge was drop-dead below "E" so I go to fill it up and it takes in fuel and it won't take a drop more. I got under the truck and knocked on the tank in various spots and the tank seems almost plum full.
When I power the truck off and back on, all the gauges come to life and settle on their appropriate readings, except for the fuel gauge. It powers up to full and then drops to below "E" as though I had turned the truck off again.
My question is, am I reasonably safe to assume my sending unit has bitten the dust? I figured that since the gauge comes to life upon startup and then drops to "E" after the rest of the gauges initialize, the fuel gauge itself probably isn't the problem?
Is there a chance that as I drive it over the next few days, and the tank empties, maybe the "sloshing" of fuel might dislodge a stuck part?
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I have a 2008 prius. Usually it gets me around 52-55mpg, I've had it since January. Since a couple of days ago its not giving me anything above 49. I know thats a normal number, but considering the fact that its usually quite a bit higher I'm wondering what the cause of the drop is. Also around the same time, when I pull out of my driveway I notice what appears to be a bit of water leakage. Its under the vehicle in the front center, and it only happens when I start the car for the day and pull out of my driveway (its on an incline).
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Today, my 1995 E150 suddenly started acting like it was running out of fuel Lucky for me, this happened close to both a parts store and my usual mechanic's shop. Unluckily for me, it happened on Saturday, and my shop can't get to it until Thursday. So here I am, hoping to do a fix in the meantime.
At first, it seemed that it must have been the fuel pump, because I couldn't hear it come on when I turned on the ignition. Then, a guy who said he was a mechanic told me he could hear the pump cycling, and that my problem was the fuel pressure regulator. So he managed to start the vehicle after a few tries, then it crapped out again. He did this twice. Then he went away.
I called every parts store in town, and none of them had a fuel pressure regulator for my vehicle, and the earliest any of them could get one was Monday. But I knew I was due for a fuel filter, and I'd changed filters on this vehicle before, so I got one of those and put it in. To my delight, the van started right up and idled beautifully. In fact, it ran beautifully for about 15 minutes, until I came to a slight rise, then it crapped out again. It still started up and idled smoothly, and even revved up smoothly, until it reached a high idle speed, at which point it crapped out. I did manage to limp into the parking lot of my shop - which, again, can't get to it until Thursday.
So my question is: does this sound like a fuel pressure regulator to you? If so, is that a job which somebody with a reasonable mechanical aptitude (i.e., at least good enough to change the fuel filter) should be able to feel safe doing? If the answer to those two is "yes" (or even if it's "no")....
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I have a 1990 Ranger with a 4.0L that I just changer the intake gasket on. I broke the fuel line at the Fuel Pressure Regulator. Cant seem to find one anywhere. It is a nylon inside/rubber outside with a cloth mesh and quick connect fitting line. Where to get one? Can I hose clamp it the FPR by cutting off the connector that broke?
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I have a 1988 f-250 with a 460 motor. I have fuel and I have fire. And the truck starts with I prime it. I tried looking for the crank sensor but can't find it. I looked behind the balancer and I didn't feel any wires or anything. I checked on the sides of the motor nothing. It has a new coil pack and ignition mod. Fuel pump and starter. What else can it be?
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