? for who has tested CIS injectors

1980SC · 04-13-2002, 09:11 AM

Should my injectors drip with the fuel pump running, but the sensor plate at rest?

I purchased one new injector to compare the spray patterns of the rest of mine. The new one has a slightly better spray, but I noticed they all drip slowly without lifting the sensor plate. Is this so the car will idle, or could my sensor plate be adjusted slightly too high? Anyone know? I doubt it's because of the injectors leaking, since they all do it, even the new one.

Thanks,
Rob
1980SC

wckrause · wckrause's Garage

Without jumpering the fuel pump relay, your fuel pump should not be running with the sensor plate at rest (unless the starter is engaged).

It is possible to have the at rest position adjusted high enough that the fuel distributor is metering fuel out to the injectors.

Check to see that the sensor plate moves freely, and nothing is causing it from resting on the small metal leaf spring.

At the end of this thread is a diagram of the sensor plate assy. that may help.

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=64761&highlight=leaf

1980SC · 04-13-2002, 12:15 PM

My fuel pump was jumpered to do this test. My air flow switch is hooked up and working correctly. Sensor plate moves very freely and rests on it's stop. My question is, should the injectors drip with the pump running and the sensor plate at rest? Or should they not drip, and I need to fix something?

-Thanks
Rob

wckrause · wckrause's Garage

I don't think they should drip. If they drip with the pump on, then they probably would leak after the pump turns off and your
system wouldn't hold residual pressure.

Do you ever have a problem with hot starts?

You might try pulling down on the sensor plate, against the leaf spring and see if they stop dripping.

emcon5 · emcon5's Garage

I can't find my Bosch FI book, but I looked in the Bentley manual, and it didn't say. That is not how it said to test the injectors though. It said you should, with the ignition on, lift the sensor plate briefly to check the spray pattern. It also said with the sensor plate at rest, they should not drip, which makes sense as if it is at rest, the pump won't be running. It did not say to jump the fuel pump relay for this test.

If you think about it, having the fuel pump running, but the sensor plate at rest is not a condition the car would ever be at during normal running. If it is at idle, wouldn't the sensor plate will be lifted slightly due to the airflow needed for idle?

Tom

sammyg2 · 04-13-2002, 06:37 PM

What was your system pressure?
You really can't troubleshoot a CIS system to the level you want unless you can measure pressures.
To answer yuor question, no. They should not drip. Either they are faulty, or your pressure is too high and is causing them to open. If I remember right, they open at around 45 psi. if your system pressure is lower than that and they leak, time to buy new injectors. I paid around $21 a piece for mine last year.

Superman · 04-13-2002, 10:33 PM

I know this one. The short answer is not they should not drip, bu tyes, many injectors do drip. When you shut the car off, the pressure in the system is "system" pressure until and unless it bleeds down. At this time the injectors will be under the same pressure as if the FP is running. So it doesn't matter whether the FP would ever be running while the car is not.

Most of the injectors I have ever tested drip somewhat. They don't drip drip drip, but they get wet on the end and occasionally let fuel fall. This can be a source of fuel pressure bleed down, but after the system pressure has fallen enough, the injectors will quit leaking.

No, they're not supposed to do it but yes, its kinda normal. More important is a balanced spray pattern and volume.

wckrause · wckrause's Garage

If the sensor plate is at rest, shouldn't the fuel distributor be completely closed so that the injectors don't get any fuel?

In other words, I don't think this is an issue with faulty injectors. Even his brand new injector drips. I think this is either a problem with the at-rest position of his sensor plate, or a problem with the fuel distributor.

The only bad side that I see with this condition is that the system won't hold residual pressure and my have hot start problems.

1980SC · 04-19-2002, 04:48 PM

Thank you all for the responses. I've been too busy with work to play with my "toy".

I believe everything is fine. I pulled the injectors again tonight, and pulled down on the sensor plate. The dripping stops. So my injectors don't leak. I could see this being a problem if my fuel pump ran when the ignition was turned on, because I'd be dripping fuel into my non-running engine. But I'm not.

Rob
1980SC