Fuel pressure issues
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Joined: Dec 2002
Posts: 705
Likes: 2
From: Halifax, NS
Fuel pressure issues
I've tried to do my own research, as always.
Google, and of course, forum thread searches.
Still, curiosity remains:
My 1995 F150: 4.9L E4OD. No options. Has Air Pump.
Fuel Pressure at rail before starting (3 key cycles) 10 PSI, holds it.
Fuel Pressure at rail when running, including when vacuum removed from regulator: 20 psi steady.
Assuming this is far too low and that I should be looking for a new pump, or "FDM".
I have already changed the filter.
I've only owned this truck for a few weeks. 1 Hour of driving time, maybe 3 hours of time under the hood/under the truck.
Other things noted: Found major vacuum leak at rotten tee at intake. Replaced it, and it actually runs worse. Seems running lean helped it out.
It will idle, but when part of that air injection crap starts pulsing (receives vacuum signal?) the truck wants to die.
I have pulled an EGR code 332 using the ground STI method and counting flashes. This isn't long after battery was disconnected for an hour, so fresh code.
I have not tested the EGR yet with vacuum pump, nor checked all the plumbing.
Thinking I need to deal with fuel delivery first. Should this truck be about 45 PSI KOEO and slightly less on KOER with good vacuum ??
Thanks for reading
Google, and of course, forum thread searches.
Still, curiosity remains:
My 1995 F150: 4.9L E4OD. No options. Has Air Pump.
Fuel Pressure at rail before starting (3 key cycles) 10 PSI, holds it.
Fuel Pressure at rail when running, including when vacuum removed from regulator: 20 psi steady.
Assuming this is far too low and that I should be looking for a new pump, or "FDM".
I have already changed the filter.
I've only owned this truck for a few weeks. 1 Hour of driving time, maybe 3 hours of time under the hood/under the truck.
Other things noted: Found major vacuum leak at rotten tee at intake. Replaced it, and it actually runs worse. Seems running lean helped it out.
It will idle, but when part of that air injection crap starts pulsing (receives vacuum signal?) the truck wants to die.
I have pulled an EGR code 332 using the ground STI method and counting flashes. This isn't long after battery was disconnected for an hour, so fresh code.
I have not tested the EGR yet with vacuum pump, nor checked all the plumbing.
Thinking I need to deal with fuel delivery first. Should this truck be about 45 PSI KOEO and slightly less on KOER with good vacuum ??
Thanks for reading
Cargo Master
Joined: Jul 2009
Posts: 2,541
Likes: 54
From: Des Moines
I don't know what the particular specs are for the fuel pressure, but I am surprised that it even ran with such a low pressure!
If you've changed the filter, then 3 things come to mind (aside from a bad FDM):
1) There's a bunch of junk clogging up the strainer inside the fuel tank.
2) There's a blockage (or leak) in the line, either between the tank and filter, or the filter and fuel rail.
3) You have a bad fuel pressure regulator. I don't know about the 1995, but older models use a vacuum controlled regulator; and if there are definite vac leaks, that could be a large part of the cause.
Here's some info that may help you out:
Fuel Pressure Regulator: Fuel Injection Technical Library » Fuel Pressure Regulator (FPR)
EGR components: Fuel Injection Technical Library » EGR Valve Position sensor (EVP) Fuel Injection Technical Library » EGR Vacuum Regulator (EVR)
The bottom of this page talks about emission components: Fuel Injection Technical Library » Actuators
If you've changed the filter, then 3 things come to mind (aside from a bad FDM):
1) There's a bunch of junk clogging up the strainer inside the fuel tank.
2) There's a blockage (or leak) in the line, either between the tank and filter, or the filter and fuel rail.
3) You have a bad fuel pressure regulator. I don't know about the 1995, but older models use a vacuum controlled regulator; and if there are definite vac leaks, that could be a large part of the cause.
Here's some info that may help you out:
Fuel Pressure Regulator: Fuel Injection Technical Library » Fuel Pressure Regulator (FPR)
EGR components: Fuel Injection Technical Library » EGR Valve Position sensor (EVP) Fuel Injection Technical Library » EGR Vacuum Regulator (EVR)
The bottom of this page talks about emission components: Fuel Injection Technical Library » Actuators
Thread Starter
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Joined: Dec 2002
Posts: 705
Likes: 2
From: Halifax, NS
DBGrif91
Thank you for the check list. I will take the time to go through the items you suggest, and read the links as well.
The regulator does have a vacuum line on it.
When I plugged a vacuum gauge into the tree today, there was 18" of vacuum at idle, although idle was about 1100.
I did try disconnecting (and plugging) vacuum at the FP regulator, there was no change on the fuel pressure gauge.
One bit of information I read through google suggested that I should see about 45 psi in these conditions, but I don't know how accurate that is.
Thank you for the check list. I will take the time to go through the items you suggest, and read the links as well.
The regulator does have a vacuum line on it.
When I plugged a vacuum gauge into the tree today, there was 18" of vacuum at idle, although idle was about 1100.
I did try disconnecting (and plugging) vacuum at the FP regulator, there was no change on the fuel pressure gauge.
One bit of information I read through google suggested that I should see about 45 psi in these conditions, but I don't know how accurate that is.
Cargo Master
Joined: Jul 2009
Posts: 2,541
Likes: 54
From: Des Moines
I forgot to mention it before, but an easy test for the FPR is to unhook the vac line and if you smell gas or see it dripping out of the line, then it's bad.
The fact that you unhooked it w/ no change in fuel pressure is interesting to me, but I don't know enough about fuel systems to say with certainty what that means.
The fact that you unhooked it w/ no change in fuel pressure is interesting to me, but I don't know enough about fuel systems to say with certainty what that means.
Thread Starter
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More Turbo
Joined: Dec 2002
Posts: 705
Likes: 2
From: Halifax, NS
No fuel dripped out, seemingly no change at all when removed line.
I think part of my mission is to check all vacuum lines and compare to a diagram. 18" of vacuum isn't bad, but I may have a small leak somewhere that could be affecting things. I still suspect the pump is weak, sometimes I have to cycle the pump a few times off the key before starting before it will pick up enough fuel to start.
I think part of my mission is to check all vacuum lines and compare to a diagram. 18" of vacuum isn't bad, but I may have a small leak somewhere that could be affecting things. I still suspect the pump is weak, sometimes I have to cycle the pump a few times off the key before starting before it will pick up enough fuel to start.
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
Bad pump or pumps...Do have dual tanks? Your best bet is to bite the bullet, drop tanks. As DBgrif pointed out, there could be trash blocking the strainer, many have blamed other things as electrical, etc. Start soaking the tank strap bolts, get some extensions, impact wrench, and those fuel line disconnect tools either from Sears, harbor freight, O'Reillys, wherever, and just got the 6 piece set with different colors. Get some PB blaster, start soaking the couplings for the fuel lines, good jack to support tank, and start.
I would drop tank, use compressed air to verify fuel lines are clear, be sure to disconnect the fuel lines at the injector rail to prevent any unwanted trash from plugging the injector screens up.
This is all I can think of to help you out, from being down this road several times. Maybe other wiser members can elaborate on some further troubleshooting.
I would drop tank, use compressed air to verify fuel lines are clear, be sure to disconnect the fuel lines at the injector rail to prevent any unwanted trash from plugging the injector screens up.
This is all I can think of to help you out, from being down this road several times. Maybe other wiser members can elaborate on some further troubleshooting.
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More Turbo
Joined: Dec 2002
Posts: 705
Likes: 2
From: Halifax, NS
Thank you Timbersteel,
Single tank truck.
I do have the removal tool, and will drop the tank. Previous owner "replaced the pump" at some point, so I am suspicious. At least the tank will come out ok.
Wonder if a return line issue could be part of the problem if the last guy messed something up or something got pinched. I'll drop tank next week.
I have been trying to get as much information as possible before I begin, in order to avoid wasting time and money. Already swapped new filter on and bought the fuel pressure gauge. No waste there, but I'll be certain before I spend another dime on it.
What I'd really love to know, is exactly what pressures I should be seeing. Seems to be an elusive bit of information.
Single tank truck.
I do have the removal tool, and will drop the tank. Previous owner "replaced the pump" at some point, so I am suspicious. At least the tank will come out ok.
Wonder if a return line issue could be part of the problem if the last guy messed something up or something got pinched. I'll drop tank next week.
I have been trying to get as much information as possible before I begin, in order to avoid wasting time and money. Already swapped new filter on and bought the fuel pressure gauge. No waste there, but I'll be certain before I spend another dime on it.
What I'd really love to know, is exactly what pressures I should be seeing. Seems to be an elusive bit of information.
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Joined: Dec 2002
Posts: 705
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From: Halifax, NS
I think all the answers are in the links DBGrif91 posted in reply. Reading now. Thanks again. I will update with what I find.
I am definitely low on the pressure side as related to manifold vacuum. It didn't change at all when removing the vacuum line, where it should have risen to approximately 45psi.
I am definitely low on the pressure side as related to manifold vacuum. It didn't change at all when removing the vacuum line, where it should have risen to approximately 45psi.
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Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
I should mention this, check for a good 12 vlt. connection at pump. I actually remember the plug on mine came loose because I had not fully seated it and it the pump was performing intermittently. It would be terrible if this was just the case and you did all that work for something so easy a fix.
Keep us posted.
Keep us posted.
Senior User
Joined: May 2013
Posts: 102
Likes: 2
Cycle your key off to on a bunch of times then pull the oil dipstick out and smell it, does it smell like fuel? If so you have leaking injectors.
At the same time after you've smelled the dipstick, pull the vacuum line off at the FPR and smell it as well, if it also smells like fuel the diaphragm is broken and it isn't working, hence the no change in fuel pressure when the vacuum line is removed.
And one more question, in relation to these possibly leaking components, when you have the fuel pressure gauge hooked up, does the pressure bleed down noticeably when you sit and watch it for a minute or so?
At the same time after you've smelled the dipstick, pull the vacuum line off at the FPR and smell it as well, if it also smells like fuel the diaphragm is broken and it isn't working, hence the no change in fuel pressure when the vacuum line is removed.
And one more question, in relation to these possibly leaking components, when you have the fuel pressure gauge hooked up, does the pressure bleed down noticeably when you sit and watch it for a minute or so?
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
I think your fuel system is working OK. You do not have the gauge hook up very well.
The engine will not run at those fuel pressures.
I think your valve depressor is not pushing the valve down and opening up the valve on the fuel rail.
The engine will not run at those fuel pressures.
I think your valve depressor is not pushing the valve down and opening up the valve on the fuel rail.
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Joined: Dec 2002
Posts: 705
Likes: 2
From: Halifax, NS
The truck barely starts. I often have to cycle the pump a few times before it will start.
When I drive the truck, it begins starving for fuel on inclines.
It seems to build up a little pressure when going downhills, and I have good power for a minute .. Until it begins starving again once under load.
Something is definitely up. The last owner said he changed the pump, but either its a dud, it's the wrong one, or it was used and on its way out itself.
I'm certain I attached the tester to the Schrader valve correctly.
When I drive the truck, it begins starving for fuel on inclines.
It seems to build up a little pressure when going downhills, and I have good power for a minute .. Until it begins starving again once under load.
Something is definitely up. The last owner said he changed the pump, but either its a dud, it's the wrong one, or it was used and on its way out itself.
I'm certain I attached the tester to the Schrader valve correctly.