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Fuel Pressure Damper vs Fuel Pressure Regulator

BigPip

Active Member
Joined
September 10, 2011
Messages
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City, State
Central Florida
Year, Model & Trim Level
98 Explorer
I am fighting a fuel pressure problem and now I find myself in an odd spot... My truck is a 98 SOHC with a 99 OHV engine (truck is running on SOHC ecm). I finally have it running surprisingly well. I am ALMOST positive I need a new fuel pump which I will replace when I come back from my trip this weekend.

However, I noticed this regulator / damper that is on my fuel rail. What's the difference in them and if I wanted to replace it, which one would I use? I have a hard start problem which I know is fuel, I sprayed some brake clean in the pcv port and it started immediately! Compared to my 4-6 seconds (even more at times) of just cranking over.

I know the 99 engine did not have a return fuel like but my 98 does and it is hooked up and working on my truck. I tried to get a pressure reading on 2 pieces of equipment but the first one was leaking from both ends so I didn't start the truck, I knew it would not be accurate and the 2 one, a machine that was hooked up to the truck just sucked the gas out of my line and only read 6psi.
 



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:dunno: n-e-body
 






fuel pressure regulator

Your 1998 chassis is set up for a fuel return system with a fuel pressure regulator (FPR) mounted on the SOHC V6 fuel rail. The 1999 OHV V6 is set up for the returnless fuel system with the fuel pressure regulator mounted in the fuel tank and a fuel pressure damper mounted on the engine fuel rail. Normally the return fuel system is lower pressure than the returnless system. The FPR varies the fuel pressure according the vacuum. High vacuum (engine idle) is low fuel pressure and low vacuum (WOT) is high fuel pressure. Your 1998 SOHC PCM assumes a return fuel system. You need to make your OHV compatible with a return system by utilizing a FPR. Once you have done that you can test the fuel pressure to determine if your fuel pump is defective. I don't know if you can just replace the damper with a FPR. They may not have the same physical configuration. You may have to obtain a 1998 or earlier OHV fuel rail that has the FPR. Fuel pressure test procedure
 






both pieces look identical, I guess it could be a learning trip to the bone yard.
My system does NOT hold pressure at all when I turn the engine off. Is there a check valve in the fuel pump that is supposed to keep pressure in the line? I hooked up a pressure gauge and I only got to 58, as soon as I turned it off it went straight to 10 psi and continued to slowly drop.
 






I am fairly confident that I have a damper on my fuel rail after looking at it today-
One question, where is the fuel supply on our motors?
 






so, did the damper get moved from the sohc to the ohv?

My 2000 X has a regulator/returnless system and my fuel pressure stays high at the rail for quite a while after my key is pulled.

By fuel supply, do you mean fuel pump? In the fuel tank
If you mean supply to the motor, its on the front left of the fuel rail on the ohv.
 






damper stayed on the motor when it was moved over from the 99 model truck into my 98.

I hooked up a fuel pressure gauge at the fuel rail, the pressure drops immediately after turning the truck off. I can cycle the ignition a few times (FAST) to build pressure to the fuel rail and it will start a lot faster!

Does anyone know where I can find a diagram/schematic of the fuel system? My haynes manual don't show me anything useful.
 






both pieces look identical, I guess it could be a learning trip to the bone yard.
My system does NOT hold pressure at all when I turn the engine off. Is there a check valve in the fuel pump that is supposed to keep pressure in the line? I hooked up a pressure gauge and I only got to 58, as soon as I turned it off it went straight to 10 psi and continued to slowly drop.

The fuel pressure regualtor and the fuel damper are completely different in function and form...The FPR has a larger body and a vacuum line to regulate the fuel system pressure by vacuum load... The fuel damper is much smaller and only dampens the fuel pulses to the injectors...

The next important difference is the fuel system with the fpr has 2 lines; one supply line and one return...The fuel system with the fuel damper only has the one supply line to the fuel rail... There is no return line back to the tank...

The specs on the Ford fuel systems are...Return type 30-45 psi, vacuum dependent...

Returnless type 55-72 psi, constant pressure...

On any Ford fuel system in these trucks, at least to 2001 model year, there is a check valve in the outlet side of the fuel pump to maintain pressure in the supply lines to help prevent vapor lock...If your fuel system drops as soon as the pump is off, either the system has a leak, the check valve is not working, or one or more of the injectors is staying open and bleeding down into the cylinder(s)...

Frankly I would install a fuel rail and injector system from a 98 OHV engine with the fpr and return lines as the sohc engine was setup and see how the engine runs...

And if you need a diagram of the fuel systems check out www.fordpartsgiant.com for exploded views of Ford vehicle systems...
 






one or more of the injectors is staying open and bleeding down into the cylinder(s)...

How could I check the fuel injectors? Also, if i am getting 2 codes (171 & 174) lean on both banks, wouldn't a leaking injector make it rich?
 






How could I check the fuel injectors? Also, if i am getting 2 codes (171 & 174) lean on both banks, wouldn't a leaking injector make it rich?

Yup, your right.
Back to a fuel delivery issue.

What does the round canister look like on the fuel rail that the fuel line goes in to? Can you take a picture and post it?
On my 'Canister' on my fuel rail, I have the fuel line going in to it, and that's it.
You need your 'Canister' to match the rest of your fuel system.

That means taking it off the old motor.
 






It has a steel braided line that goes to the fuel rail and looks to go back to the tank.
It is silver and looks like this: http://www.rockauto.com/catalog/moreinfo.php?pk=930042


The charcoal canister has, IIRC, two hoses on it and one of them goes to the front of the Throttle Body. I don't know if that is right or not but that is where it goes, the other one I didn't pay much attention you but I will check it later.
 






It looks like your fuel system matches ok, but it sure sounds like you have a fuel delivery issue.

Here is what my damper looks like.
http://www.rockauto.com/catalog/moreinfo.php?pk=942057
Notice it only has 2 holes. Fuel line screws in to one, and the other to the fuel rail
 






On second look. what I see on rock auto's site is not what I have.
I have another input on mine that is not connected. Its on the bottom, and looks like a vacuum line could connect to it, although there is nothing connected.

Now I don't know what to say.

EDIT:Looking closely at the picture I posted, it is the right one. In the pic you just can't see where the fuel line screws on, thats all
 






I know the 99 engine did not have a return fuel like but my 98 does and it is hooked up and working on my truck.

I stand corrected- I just found the return line lying around in the engine compartment tucked away. I will be at the bone yard this weekend pickup up a new fuel rail with the return line.
 






I bought the fuel rail but did not buy injectors yet, it looks like the injectors are the same. What would the difference be between them? Logically I could see where the 99 non return system would require a stronger psi injector...

I need to do more research I guess to figure out if the injectors are different
 






Maybe a rockauto search could help by checking both years?
 






Maybe a rockauto search could help by checking both years?

I tried that method but came up with mixed results. There were about 3 or so that followed both years. I tried AutoZone and they show different. I guess I will be ordering some of those now.
 






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