Testing for Injector signal

[ausgezeichnet]

The Bently manual says to backprobe the injector connector while the engine is running to test for a pulsed injector signal. Why wouldn't I be able to just disconnect the connector and do the test? Thanks.

-Mike

[jyl]

I don't see why either, but want to point out a related problem - how will you tell if the signal is pulsed without special equipment?

I recently had to investigate an injector, and realized that my digital multimeter couldn't change its display fast enough to keep up with the signal anyway (1000 rpm = one signal every 1/20 second or so, right?)

Anyway, I just pulled off the plug and checked that there was 12v showing at the leads. It showed as a constant 12v. After replacing the injector, the problem was fixed.

[rattlsnak]

You can buy a "noid" light to check this easily. ($16.00) You unplug the injector, plug this in, and crank or start the car, and it will pulse a light accordingly.

http://buy1.snapon.com/catalog/item.asp?P65=&tool=diagnostics&item_ID=11235&group_ID=1452&store=snapon-store&dir=catalog

Thta isnt the exact one, but it is a better picture.

[ausgezeichnet]

Thanks for the feedback. I just bought a Multimeter with a Duty Cycle function. Could I use that to measure the signal pulse?

If I went the noid route, would i need a noid for Bosch PFI or Bosch 2 injectors on my 84 3.2L?

Thanks

[Early_S_Man]

Mike,

The reason for not just pulling the connector off the injector to do the test is that you would be interrupting the current flow and signal, as the injector is getting a switched, staurated transistor to ground from the DME ... classic case of the observer interfering with the phenomenon [from college physics class] ...

But, your pulses/duty cycle function on the multimeter should read the signal just fine if you backprobe, or use a small 'extension cord' with two male and two female 0.110" Faston connectors ... to monitor the signal. A CMOS logic probe with pulses monitor can also be used on the injector signal!

[ausgezeichnet]

Early-S_Man,

Thank you. Good idea regarding the faston connectors. Do you know where I get a few Faston connector?

[Early_S_Man]

Mike,

Almost any dealer/most brands ... because of the widespread use of Bosch F.I. components! Well, the female connector, anyway.

Radio Shack has some male Fastons, but maybe only in 0.187" ... which could be trimmed with diagonal cutters to fit the 0.110" injector plug.

[ausgezeichnet]

Great. Thanks. I'll let you know how I make out.

[ausgezeichnet]

I found a pack of .187 fastons at Radio Shack and cut them down to approximately .11. Made 2 small "extensions" and wired them between the connector and the injector. I set my Multimeter to ms%, started the motor and then tested both wires. One wire gave no reading and the other gave a reading of .93 m s

If I read the manual right this reading is supposed to represent the percent of low (-) (ON) time in a duty cycle. In a calculation for dwell the manual shows the reading as % duty cycle. This means that the injector is on .93% of the time. Did I interpret that correct.? If so, that seems bad. What would be a good duty cycle % for the injector to be on?