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Fuel pressure spec?
- Thread starter jandaraw
- Start date
Matthew Currie
NAXJA Member #760
- Location
- Vermont, land of big clay
I don't know whether it changed, but for the 95, it's 31 psi at idle, 39 with the regulator vacuum line disconnected.
corbinafly
"Mmmm. More please."
- Location
- lakewood,ca
I think for '96 on up it's 49psi. Changed when they went to OBDII.
K
K
Re: Fuel pressure problem
My situation is this: My 97 XJ is at 40 psi when idling...that would seem to indicate a pump problem if the spec is 49. When I shut it off, the pressure at the rail drops completely off to 0 in less than a second. That would seem to indicate the pressure regulator.?
Any advice as to which of these might be causing my problem??
My situation is this: My 97 XJ is at 40 psi when idling...that would seem to indicate a pump problem if the spec is 49. When I shut it off, the pressure at the rail drops completely off to 0 in less than a second. That would seem to indicate the pressure regulator.?
Any advice as to which of these might be causing my problem??
langer1
NAXJA Forum User
- Location
- Mineral City,Ohio
Re: Fuel pressure problem
Yes among other things, what's the problem your trouble shooting?jandaraw said:
It is starting hard as it cranks several times before firing. Once running it does fine. When I cycle the key 5 or 6 times to prime the pump it will usually fire right up. It is obviously not holding pressure in the rail (as the pressure gauge confirmed). I just don't know if it is the pump check valve or the pressure regulator causing this. I guess it could also be an injector but not sure how to test this. I also get a cylinder misfire code.
Any advice is appreciated.
Any advice is appreciated.
corbinafly
"Mmmm. More please."
- Location
- lakewood,ca
I would think that it's either the pump check valve or, since you mentioned the cylinder misfire code, an injector that's stuck open.jandaraw said:
Since you only read 40 psi when running, you could also have a plugged filter/regulator.
K
I have seen several people refer to a check valve in the pump. Is this valve actually in the pump or in the regulator on top of the pump?
Can someone explain what the regulator actually does? It would seem the regulator would hold the pressure in the rail instead of the pump check valve.?
Can someone explain what the regulator actually does? It would seem the regulator would hold the pressure in the rail instead of the pump check valve.?
langer1
NAXJA Forum User
- Location
- Mineral City,Ohio
Generaly the regulator is on the end of the fuel rail, It keeps the same pressure on the injectors, the check valve is part of the pump. The block on top of your pump is the filter I think.jandaraw said:
So the regulator holds pressure on one end of the rail and the pump check holds pressure on the other end. In between the two are your injectors and they must also shut off 100% to hold rail pressure.
langer1
NAXJA Forum User
- Location
- Mineral City,Ohio
Regardless of where it's located it's connected the way it said.jandaraw said:
corbinafly
"Mmmm. More please."
- Location
- lakewood,ca
On his '97, there is no return line like the pre OBDII vehicles have. The regulator and filter are the same unit. It's a filter/regulator combined into one. That said, I believe the check valve is actually in the pump assembly. But I could be wrong on this.langer1 said:
K
