Ford Fuel System :: 1988 - Fuel Pressure Drops Off Fairly Fast When Turned Off
Nov 7, 2009
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 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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cant figur this out have no signal to injectors and no power at fuel pump 88 f150 5-0
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I have an 88 E350 With a 460 EFI . Problem is there fuel is coming out of the ecs canister . It has the dual canister set up fuel comes out of the rear one after the engine starts. I have never seen this before. What would cause this ?
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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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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 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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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 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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I have an 03 Explorer that had a starting issue. Long story short, it had no fuel pressure. So after testing the relay, I switched out the pump with an Airtex unit . All seemed fine...for a while.
Became hard to start again, checked Schrader valve with the key on, and not running, no pressure. Strange though, it would run.
So got the fuel pressure gauge on it. Turn the key and pressure will go to about 5-10psi and then drop to zero. Turn key off and on again, up to 5-10psi, then drop to zero. Turn the key to start and pressure goes up to 10psi, then starts, then goes to 30 while running and you can drive it around. Shut off motor and pressure goes down to zero.how the sending unit is supposed to hold fuel pressure and not release it? Is there some kind of check valve in the sending unit assembly that can be cleaned or does it need a whole sending unit with another pump? I already spent the $100 for the pump, and it is working if you can drive it!
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Its an 88 F-250 4x4 with a 302 EFI 5-speed. Fair compression, runs smooth. When I press the gas pedal it takes about 5 seconds for the old girl to return to idle. I know nothing about EFI. My buddy,s out of town with the hand held mechanic. Is there anything I could check till he gets back.
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I have a '88 F250 with a couple of dual tank issues, first of all if I'm running on the rear tank the fuel returns in the front tank.... not an isssue if trhe front tank is empty, but if both tanks are full the front tank will overflow. If the front tank is empty I run on the back tank until I'm out of gas and switch to the front and I"ll have about a half a tank in the front tank.
Second issue, running the front tank the fuel gauge stays on full until I have about half a tank, then it works OK. If I'm running the back tank it stays on full, even after the tank runs out of gas??
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1988 F250 351 5.8
I've worked for months on this truck and I now have it in the shop. The truck shows a 41 code and has a lean miss at idle that get worse during acceleration and cruise. The injectors were refurbished 6 months ago and the ECM was replaced 3 months ago. All sensors are new and within specs. Fuel pressure is good and there are no vacuum leaks.
The mechanic has verified that the condition is not electrical related. The O2 sensor will react if carb cleaner is sprayed into the throttle but other wise shows constantly lean. He's now checking all pins at the computer for any off condition. He is suspicious of the refurbished injectors. I'm wondering if the computer somehow went out again. Which way to go or what/how next to test?
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This problem just cost me a new starter and flywheel, cuz after cranking my engine so many times the starter mess up the flywheel teths, anyways, i install a fuel gauge and i find out that my pressure drops in seconds, like i turn the key on (pos ii) and but the time i get out the car to the engine bay to look at the gauge, the pressure is almost ZERO
When I open the door the fuel pump primes and built pressure, when i turn the key i heard the pump primes too, but why does the pressure drops so fast?
I have an aeromotive fpr, and a bosch in line pump, turbo set up and 550 cc injectors( brand new )...
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1999 Savanna 1500 van. This has been a great Van, only has 70,000 miles and has never let me down until a few months ago in February when it was getting down to -20 degrees F. Seemed like it was cranking fast so I thought it was timing. Turned out there was no fuel pressure so first put the relay in, that didn't work so we dropped the tank and put a fuel pump in. This seemed like it cured the problem but I only drove it 200 miles until mid May when it did it again.
The security light wasn't staying on so we thought it must be the ignition switch. That didn't fix it either, we just got the ignition switch back together (not the actual switch but the wiring harness) and it's not starting again. It will start after some anguish and cursing at it. Seems like messing with the wires going to the fuel pump or hitting the cover over the fuel tank will cause it to start. I haven't checked it yet but I can guarantee it doesn't have any fuel pressure.
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Carburetor: Autolite 4100
Fast Idle Speed: 1250 RPM
Curb Idle Speed: 600 RPM (At normal operating temperature)
When I cold start my truck, the fast idle speed holds the throttle at 1500 RPM. I will let it idle about 30 seconds or so, and then I will tap the gas to bring the idle down.
When I do this, the idle will immediately drop all the way down, and too low for a cold engine. The engine won't stall, but it will hover just below 500 RPM, which is a bit too low to idle smoothly.
But when the engine is at operating temperature, the idle speed is 600 RPM and the engine will happily idle smoothly.
Shouldn't there be an "in between" speed? When I tap the gas pedal at 1500 RPM to bring the idle down some, shouldn't the speed drop down a little lower, like 1000 RPM since the engine is still a bit cold?
If so, what do I need to adjust? The Autolite 4100 works PERFECTLY otherwise.
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I have a 1994 f 150 5.8l 4x4 with 215000. Cold starting is fine runs well. After running it will not start after shut down. Wait till motor cools back down will start up and run fine ....
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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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2004 6.0. 160K miles.
I'm about to replace an injector and wanted baseline info on fuel pressure before doing the work. Using a gauge tapped into the top of an aluminum alloy fuel filter cap (from bulletproof diesel), I turned the switch key on but did not start the engine.
Static pressure jumped to 60psi, but as soon as the pump cut off the pressure dropped off to zero. Again, engine not started. I cycled the key off and back on and the pressure hit 60psi and held that until the pump cycled off, then dropped back to zero.
I'd like to get a few confirmations that fuel pressure should or should not fall off when the pump kicks off.
Side note, during the crank process the pressure jumps and holds at 60psi and stays at 60psi while idling. I have not conducted a dynamic road test yet. Didn't have the adapter to connect my long hose...
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I am wondering about how fast to accelerate for maximizing fuel economy. I understand with the P&G approach that you don't want to get up to speed too slowly. The question is whether it really is more efficient to go ahead and get up to speed or stay within the ECO guidelines? In particular, I find that getting up to highway speed especially that it can take quite a while to get up to 70 mph without having it going into the power range. It seems like it is better to get up to speed and then back off to go to the high efficiency mode.
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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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