I drive 2 Volvos. One is a 245, 84 and a 945,93. Live in Johnston, Iowa.
The 84 has 360,000 miles on it. It is getting in pretty rough shape but I
like to drive it because I put on so many miles going to work.
I am having a problem in deciding where my problem is located. I have a
mechanic working on it now and he is running in to a problem. Here is
what we have. Like I said it is a 1984 245 DL. Voltage at the injectors is
very low. It is less than 1 volt. When we shut return fuel line down the
car will idle but very rough. How do you test the ECM and how to boost
the voltage to the injectors? Is it only up to the ECM to supply voltage
to the injectors and is voltage dependent on any other component part?
The computer that is in the system is a Bosch Jetronic #0280-000-510
Voltage at the injectors is about 0.6V at the + side and 0.15 at the- side.
The spray from the injectors is very thin. Have tried a 12 Volt light
bulb and it just barly flickers at the injectors. Some of the places I
called the price is about $240. Need to find out or comfirm that it is
definately bad before buying another one. Like I said the car is in pretty
rough shape but it is still good transportation. I would appreciate and help
at all on this problem.
One other thing. A year or two ago I rewired the engine because the wiring
harness was getting in bad shape. I just replaced the wires inside the
engine compartent. The wires going to the computer all seem to be in good
shape.
Thanks
Roy Hockett

On your 1984 240, voltage to the fuel injectors comes from terminal 87/2 of the Fuel Injection Relay. You need to do the classic Fosterization of the relay. To the uninitiated, that is to re-solder the relay. Power comes to the Fuel Injection Relay at terminal 30, straight from the battery with no fusing. The relay has two coils, one to power the ECU, and the other to power the fuel injectors. The fuel injectors are grounded by terminal 13 of the ECU. Do you need a wiring diagram that is specific to this car?

Hi Roy,

Two of the five 240s I have are LH2.0 cars like yours. I've spent some time with the ECU used in these cars, inside and out.

The "+" side of the injector wiring is supplied from the battery through the 25A fuse and the contacts of the main relay-- meaning, if you have anything less than 12V engine running, you have a simple relay, wiring or fuse issue.

The "-" side of the injector is brought to ground by a transistor in the ECU, and depending on its duty cycle, will make a digital voltmeter read in the 3-9V range. But a small test lamp across the injector should flash brightly.

"When we shut return fuel line down the car will idle but very rough."

It does sound like you are somewhat overcoming a problem getting injectors to open by doubling the fuel pressure, verifying the lean condition. Mine would act like that when the air mass meter dies. Pretty simple test eliminates that, though, I'm assuming you know.

What is the symptom that led you to get the injection looked at?
--
Art Benstein near Baltimore