Injector leaking test

[jayknockout]

Can u test the injecters ion a 2l FI in a bay if they are leaking by getting pressure in the lines (starting fuel pump in afm) and look if they are leaking,

knew that u could do this on the late T25´s to have pressure in the lines and look if the injector is dripping.

[VWLover77]

Yes.
_________________
Don

1978 Westy
1971 Super Beetle Convertible


"If more of us valued food and cheer and song above hoarded gold, it would be a merrier world." - J.R.R. Tolkien

[Randy in Maine]

I would install my fuel pressure gauge, fire it up, shut if off and watch for the residual pressure.

[RZAR]

[Randy in Maine]

There are 2 check valves, one if the pump and one in the regulator that can also cause a drop in the residual fuel pressure.

But look at it this way.....if the pressure holds for a day without dropping much, everything is likely to be good.

[Tcash]

To link to this post copy and paste

[furgo]

Awesome, thanks Tcash! Just what I needed to test my fuel rail

I've got a few questions, though. Taking step 5 for instance:

[Tcash]

I can't picture the correlation between the side of the rail behind the pinch point holding pressure and a leaky fuel pump check valve.
I have the gauge in the wrong place on #5
[fuel tank]__________[fuel pump]___________[0 gauge]_______[clamp]

And in the case it all works as expected (i.e. does not hold pressure), where/how is the pressure being relieved?
The check valve in the fuel pump is allowing pressure to return to the fuel tank.
[fuel tank]__________[fuel pump]___________[0 gauge]_______[clamp]

Does the pinch introduce extra pressure that is being then relieved by the FPR opening its valve and returning fuel to the tank?
The pressure is captured between the pinch and the Fuel pump. The FPR is not involved in test #5.

Finally, should "holds pressure" be determined after a given period of time (e.g. 20 minutes) or instantly?
Good question. The pressure should not drop below 14 psi in a 10 minute period of time.

[furgo]

Ok, that step makes sense now, thanks.

Moving on to #6, which is the one I'm mostly interested in atm (still unsure if my FPR is working correctly), should the gauge not be placed between the FPR and the clamp?

Then if pressure does not hold (again for a given amount of time, I guess) we can determine that the FPR is leaky.

Otherwise, in the way diagram #6 is right now, the gauge is measuring pressure in a closed circuit between the two clamps, where the FPR is not involved. In this scenario, it should hold pressure. If it didn't, pressure would have been relieved through a leaky injector, correct?

Also, what's the purpose of the clamp between the fuel pump and the 3/4 rail in this step? Is it to rule out pressure escaping via the pump's check valve?
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[Tcash]

Moving on to #6, should the gauge not be placed between the FPR and the clamp?
This is an exercise in the process of elimination. Taking one component out of the picture, one at a time to isolate the faulty component. As long as the fuel gauge is in the section that is being tested. It does not matter where it is installed.

Then if pressure does not hold (again for a given amount of time, I guess) we can determine that the FPR is leaky.
If pressure does not hold, one of the 5 injectors is the problem. Not the FPR. If pressure holds, it is the FPR.
Not a timed event. The initial Residual pressure test that you performed and failed and #5 are the only timed events.

Otherwise, in the way diagram #6 is right now, the gauge is measuring pressure in a closed circuit between the two clamps, where the FPR is not involved. In this scenario, it should hold pressure. If it didn't, pressure would have been relieved through a leaky injector, correct?
That is correct.

Also, what's the purpose of the clamp between the fuel pump and the 3/4 rail in this step? Is it to rule out pressure escaping via the pump's check valve?
Yes it is. It takes the fuel pump check valve out of the test. Eliminating the chance of the check valve hanging open resulting in inaccurate test results.

[furgo]

[Clatter]

What an awesome post.

Someone is an L-Jet ninja for sure..
_________________
Bus Motor Build

I have excellent news for the world...
There is no such thing as patina.
It does not exist!

[Tcash]

[furgo]

[raygreenwood]

[Tcash]

On a healthy system, "holds pressure" on step #6 would not necessarily mean the FPR is at fault.
That is correct. On a system that is initially holding pressure and not leaking.


But if pressure is held at that point, then there is probably no need to follow the rest of the steps, as if there isn't a leak,
That is correct. There is no need to follow the rest of the steps, if the gauge holds pressure. This would indicate that none of the 5 injectors are leaking.
Test done.

In my particular case, I don't yet have a reason to believe there is a leak, as overall pressure holds even after a few hours I've turned the engine off. So unless I'm mistaken (not unheard of Wink ) I assume the check valves on pump and FPR are ok, as are the injectors.
In your case (hard start, dies on idle) could be a leaky injector. You would want to jump to step #6, to test just the 5 injectors.
Gauge holds pressure, none of the 5 injectors are leaking.
Pressure drops move onto next step.