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Fuel Pressure Help Pls....Video attached.
- Thread starter BotakBeng
- Start date
- Location
- Minneapolis, MN
What do you think is wrong, and why ?
The needle bounces a little (might be just the gauge), but you have 50+ psi on average. Factory spec is 49 psi +/- 5 psi.
- Location
- on the beach in Ocean View, VA
I've never seen one stable on a "return-less" fuel system-- every time an injector opens the system loses a bit of pressure. If there were a return line and you checked at the rail (like the older design), you'd see a steady needle.
McQue
NAXJA Forum User
- Location
- Plainville, Connecticut
Fuel pressure test on my 01 Xj is very similar... needle on my gauge bounces a little less than yours... mine never seems to go over 52 psi...
- Location
- Minneapolis, MN
The 1997-01 are one way return-less fuel systems.
Sidewinder CC
NAXJA Forum User
- Location
- Canton, Michigan
BotakBeng,
I'm seeing [about] the same fuel pressure ocilliation, with a rough (intermittant muffled misfiring) running engine at idle. I see your pressure ocillation wanders between 48 - 55 psi; my baseline pressure is 48 psi, and with the engine running it ocillates pretty consistantly between 46 -50 psi. The odd thing I'm seeing however is the ocillation will occasionally slowly move to between 47 and 49 psi, with a noticeable change in the engine running rough, then returning to the 46 - 50 psi spread with the engine resuming the rough(er) running .
I did check injectors using a stethoscope and found that #1 and #2 injectors have a 'louder' click than the rest of the injectors. #5 and #6 seem to be the quiter ones. Also checked the damper and it clicks away and [seems] to be doing its job.
Can't figure out why the ocillation would move to 47 to 49, then back to the 46 to 50 psi. Unless during the 46 - 50 psi ocillation one or more injectors are not functioning properly, then decide to jump in and smooth out the ocillation, then go back to not functioning properly and causing the wider ocillation.
In my case, I'm not convinced injectors are causing the problem; however I will check the resistance of each injector. I don't think I need to use a noid light in this case. I changed my injectors, and rail, about two years ago and the engine ran fine up until about six months ago
As a note: I changed my spark plugs (looked good) and wires (cap and rotor changed a few months ago). This had no affect on the engine running rough.
Could there be any engine (mal)function that would cause the fuel pressure to ocillate outside a normal range, and in my case, periodically move to a tighter ocillation range? Valve timing? Exhaust back pressure?
~~~~~~~
BotakBeng,
How old are your injectors? Day one ('97)?
Have you listened to your injectors with a stethoscope?
Have your checked the resistance of your injector coils?
I'm seeing [about] the same fuel pressure ocilliation, with a rough (intermittant muffled misfiring) running engine at idle. I see your pressure ocillation wanders between 48 - 55 psi; my baseline pressure is 48 psi, and with the engine running it ocillates pretty consistantly between 46 -50 psi. The odd thing I'm seeing however is the ocillation will occasionally slowly move to between 47 and 49 psi, with a noticeable change in the engine running rough, then returning to the 46 - 50 psi spread with the engine resuming the rough(er) running .
I did check injectors using a stethoscope and found that #1 and #2 injectors have a 'louder' click than the rest of the injectors. #5 and #6 seem to be the quiter ones. Also checked the damper and it clicks away and [seems] to be doing its job.
Can't figure out why the ocillation would move to 47 to 49, then back to the 46 to 50 psi. Unless during the 46 - 50 psi ocillation one or more injectors are not functioning properly, then decide to jump in and smooth out the ocillation, then go back to not functioning properly and causing the wider ocillation.
In my case, I'm not convinced injectors are causing the problem; however I will check the resistance of each injector. I don't think I need to use a noid light in this case. I changed my injectors, and rail, about two years ago and the engine ran fine up until about six months ago
As a note: I changed my spark plugs (looked good) and wires (cap and rotor changed a few months ago). This had no affect on the engine running rough.
Could there be any engine (mal)function that would cause the fuel pressure to ocillate outside a normal range, and in my case, periodically move to a tighter ocillation range? Valve timing? Exhaust back pressure?
~~~~~~~
BotakBeng,
How old are your injectors? Day one ('97)?
Have you listened to your injectors with a stethoscope?
Have your checked the resistance of your injector coils?
Thx for the comment.
To be honest, i'm not really understanding you except the last few questions :laugh:.
Those are 784 injectors recently installed
I have to find out "how to check resistance of your injector coils".
Damn, that's alot of research for a weekend :hang:.
Are you saying is not normal for the bouncing?
To be honest, i'm not really understanding you except the last few questions :laugh:.
Those are 784 injectors recently installed
I have not but i'll do that over the weekend....what should i be listening for?
I have to find out "how to check resistance of your injector coils".
Damn, that's alot of research for a weekend :hang:.
Are you saying is not normal for the bouncing?
Sidewinder CC
NAXJA Forum User
- Location
- Canton, Michigan
1. What are "784" injectors. Do you have an internet link to them?
2. There's a youtube video showing checking the injectors with a stethoscope. Can't remember the key words for the vid but you might try 'testing fuel injectors'. Basically you will be placing the stethoscope probe on each injector (at the same place on each one) and listening for the coil in the injector to 'click' as it activates...at idle of course...listen for consistant clicking. Interrupted clicking or a very weak click may mean that injector is defective or weak. Also, make sure there is no corrosion on the injector connector pins and sockets.
I got my stethoscope at O'reilly auto parts - $10.00. It's a POS but works.
3. That much bounching may not be normal.
