Fuel pressure on injector change
Thread Starter
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
Fuel pressure on injector change
I changed the injectors on my 89. I put in the Bosch III and I broke the rail down to change the o-rings. Before I took anything apart, with the key "on", my pressure would go to something like 40 and hold.
After changing the injectors and bolting down the rail and lines. I hooked up my pressure tester and primed the system a few times with the key "on". I noticed my pressure keeps dropping. Though after priming it several times over an hour or so, it seems to hold better as it was dropping fast.
Last I checked, the pressure at key "on" would go to 42. Then drop straight to 38 and start slowly dropping.
The injectors, send/return lines, and o-ring connections on the rail are all dry. So, I figured after several hours of priming and checking that I would have found something leaking by then. Or would this pressure drop be normal till after you run the car?
After changing the injectors and bolting down the rail and lines. I hooked up my pressure tester and primed the system a few times with the key "on". I noticed my pressure keeps dropping. Though after priming it several times over an hour or so, it seems to hold better as it was dropping fast.
Last I checked, the pressure at key "on" would go to 42. Then drop straight to 38 and start slowly dropping.
The injectors, send/return lines, and o-ring connections on the rail are all dry. So, I figured after several hours of priming and checking that I would have found something leaking by then. Or would this pressure drop be normal till after you run the car?
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
I removed the Schrader valve, screwed on my Accel fuel pressure gage then turned the key to ON. Pressure went to 46 psi and held steady for over an hour which is when I terminated the test.
Jake
Jake
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
I changed the injectors on my 89. I put in the Bosch III and I broke the rail down to change the o-rings. Before I took anything apart, with the key "on", my pressure would go to something like 40 and hold.
After changing the injectors and bolting down the rail and lines. I hooked up my pressure tester and primed the system a few times with the key "on". I noticed my pressure keeps dropping. Though after priming it several times over an hour or so, it seems to hold better as it was dropping fast.
Last I checked, the pressure at key "on" would go to 42. Then drop straight to 38 and start slowly dropping.
The injectors, send/return lines, and o-ring connections on the rail are all dry. So, I figured after several hours of priming and checking that I would have found something leaking by then. Or would this pressure drop be normal till after you run the car?
After changing the injectors and bolting down the rail and lines. I hooked up my pressure tester and primed the system a few times with the key "on". I noticed my pressure keeps dropping. Though after priming it several times over an hour or so, it seems to hold better as it was dropping fast.
Last I checked, the pressure at key "on" would go to 42. Then drop straight to 38 and start slowly dropping.
The injectors, send/return lines, and o-ring connections on the rail are all dry. So, I figured after several hours of priming and checking that I would have found something leaking by then. Or would this pressure drop be normal till after you run the car?
Thread Starter
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
Do you know if it is normal for the FPR to make a noise when you move it? I know it has a spring in it, but I noticed it sounded like the spring was loose when moving it around when I broke the rail down.
I may try pinching some lines at the tank and see what that does before I put it back together.
Drifting
Joined: Nov 2009
Posts: 1,341
Likes: 2
From: Perth Western Australia
St. Jude Donor '10
Burning Brakes
Joined: Aug 2004
Posts: 1,174
Likes: 125
From: Dunstable MA
St. Jude Donor '05
100%I had same effect after injector and FPR replacment on my 87. No matter how much I bled it through the gauge, the pressure dropped after a key actuation of the pump. After running the engine, no drop.
If you still get a drop after running the engine, there are other problems to solve.
