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914World.com _ 914World Garage _ High fuel pressure
Posted by: mtndawg Jan 3 2010, 04:42 PM
I picked up a fuel pressure gauge today at the local harbor freight and connected to the fuel rail. Wow! over 60 psi. Luckily, I haven't driven much since I have recently put the engine back in after replacing fuel lines, seals etc. This is a 1.7L d-jet system. I loosened the adjustment screw and nut, which took quite a bit of force. I made some adjustment and tightened the lock nut. Then turned the key to run the fuel pump and the adjustment screw now leaks. I haven't actually started the car because of the obvious problem. Now I've taken the regulator out to have a closer look. It looks like the cone end of the screw seats against a diaphragm inside the unit. Is that right? Why would it now be leaking?
Posted by: McMark Jan 3 2010, 05:14 PM
I bet you've got your fuel lines backwards. It should go like this:
From Tank -> Fuel Pump -> PS Fuel Rail -> DS Fuel Rail -> Regulator -> Back to Tank
Posted by: mtndawg Jan 3 2010, 05:42 PM
Thanks McMark, that's how it's connected.
Posted by: McMark Jan 3 2010, 05:46 PM
Sumthin's plugged or the regulator failed. Let me know if you need a spare. I've got a few.
Posted by: davesprinkle Jan 3 2010, 06:24 PM
If you have fuel coming out of the adjuster screw, then your diaphragm is ruptured. Throw the reg away.
The inlet fitting is located on the side of the reg. The outlet fitting is on the end of the reg. Make sure you've got it plumbed correctly.
Posted by: mtndawg Jan 4 2010, 09:35 AM
McMark, I sent you a PM.
This may partly explain why my car is running so rich. Maybe there has been a higher volume of fuel pushing through the injectors (and cold start injector) because of the extra high fuel pressure.
Posted by: pbanders Jan 4 2010, 11:09 AM
I picked up a fuel pressure gauge today at the local harbor freight and connected to the fuel rail. Wow! over 60 psi. Luckily, I haven't driven much since I have recently put the engine back in after replacing fuel lines, seals etc. This is a 1.7L d-jet system. I loosened the adjustment screw and nut, which took quite a bit of force. I made some adjustment and tightened the lock nut. Then turned the key to run the fuel pump and the adjustment screw now leaks. I haven't actually started the car because of the obvious problem. Now I've taken the regulator out to have a closer look. It looks like the cone end of the screw seats against a diaphragm inside the unit. Is that right? Why would it now be leaking?
Another thing to check is if your return line is kinked or blocked, which will also cause sky-high fuel pressure. If you find it's blocked, and the lines seem to be OK, check the return port on the fuel tank. Ask me how I know
Posted by: ClayPerrine Jan 4 2010, 12:37 PM
I picked up a fuel pressure gauge today at the local harbor freight and connected to the fuel rail. Wow! over 60 psi. Luckily, I haven't driven much since I have recently put the engine back in after replacing fuel lines, seals etc. This is a 1.7L d-jet system. I loosened the adjustment screw and nut, which took quite a bit of force. I made some adjustment and tightened the lock nut. Then turned the key to run the fuel pump and the adjustment screw now leaks. I haven't actually started the car because of the obvious problem. Now I've taken the regulator out to have a closer look. It looks like the cone end of the screw seats against a diaphragm inside the unit. Is that right? Why would it now be leaking?
Another thing to check is if your return line is kinked or blocked, which will also cause sky-high fuel pressure. If you find it's blocked, and the lines seem to be OK, check the return port on the fuel tank. Ask me how I know
I found the same thing on the Rennlist 914 that we gave to Mike Cooley. I had to clean out the return line on the tank before I could get the fuel pressure down to a reasonable level.
Posted by: kwales Jan 4 2010, 12:46 PM
Another thought is....
How accurate is yer fine low cost chinese fuel pressure gauge.....
In engineering, if you have known components hooked together and you get a really high reading from a brand new gauge, you would check the hookup, the gauge, and the components......
Posted by: ClayPerrine Jan 4 2010, 12:51 PM
Another thought is....
How accurate is yer fine low cost chinese fuel pressure gauge.....
In engineering, if you have known components hooked together and you get a really high reading from a brand new gauge, you would check the hookup, the gauge, and the components......
good thought. Always verify your test equipment.
Posted by: kg6dxn Jan 4 2010, 06:40 PM
Grianger has some cheap $20 gauges with 1/4npt threads. We use them all the time for Diesel Generator fuel lines. I'm a little worried about the HF quality...
Posted by: toon1 Jan 4 2010, 09:20 PM
something is definetly wrong, I don't recall the press. regulator being able to get 60 psi.
Posted by: mtndawg Jan 4 2010, 10:02 PM
Yes! something is definitely not right.
Gauge: possibly bad
Regulator: definitely bad
Fuel lines at the bottom of the tank: this is what I'll check along with the regulator
Sock at the bottom of the tank: need to replace, but I haven't seen it yet
Fuel lines in the engine bay: new (yes, the right size)
Fuel lines at the pump: new (yes, the right size here too)
Fuel filter: new
Here's what seems like an obvious question to me while looking at the Grainger site. When I search for liquid pressure, I get a list of fluid filled gauges, not gauges that measure fluid pressure. Here's the obvious question to a "non-pro" mechanic like myself. How do I know which gauges measure fluid pressure because, that's not indicated in the description of the guage????
Posted by: kg6dxn Jan 4 2010, 10:12 PM
Yes! something is definitely not right.
Gauge: possibly bad
Regulator: definitely bad
Fuel lines at the bottom of the tank: this is what I'll check along with the regulator
Sock at the bottom of the tank: need to replace, but I haven't seen it yet
Fuel lines in the engine bay: new (yes, the right size)
Fuel lines at the pump: new (yes, the right size here too)
Fuel filter: new
Here's what seems like an obvious question to me look at the Grainger site. When I search for liquid pressure, I get a list of fluid filled gauges, not gauges that measure fluid pressure. Here's the obvious question to a "non-pro" mechanic like myself. How do I know which gauges measure fluid pressure because, that's not indicated in the description of the guage????
If this is only a test rig and not for perminant installation, use any gauge they sell. We usually get the combo gauge vac/pressure. $18 or so. Many have been left in sites for years without any leaking. Just don't bang on them. Diesel is a great solvent and will eat through most types of rubber. If you can find one with a "Viton" diaphram, that would be best. The only advantage to a liquid filled gauge would be a pulsing pressure signal, the liquid stabilizes the needle. I you want a gauge for a perminant install but a Holley 1/8npt and plumb it into the system. Jegs or Summit Racing will both have good prices on the Holley $30 or so.
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