I am working on a 90' 240 (non turbo) it idles fine, although upon quick throttle or above 1500 RPM the fuel injectors stop getting signal and cut out. When the RPM drops below the threshold, the injectors kick back in. Any ideas?

how consitent/accurateis it, and you are sure the sinal is cutting out, not the fuel supply? IE bad filter/regulator/pump(s)? Is it related to motor movement? IE bad wiring? If not, might be worst poosibl, EMU failure-prove everything else good first, then repalce it & retest, unless yours has a fault indicator LED at Left rear engine bay. See owners manual/other posts (search) for more info.

I used a noid light to check the signal, it is definatly cutting out. The In-tank pump was bad and the filter was clogged, I just replaced both of them and have the same symptoms.

The problem is constant.

The only code is 223.

The injectors are powered by the fuel pump relay and grounded by the ECU. The ECU is grounded by two wires attached to the fuel rail, just below it. I would clean both these connections.

You are loosing the 12V (pump relay), loosing the injector grounds (ECU) or the injectors are being turned on full time - engine flood (ECU, running rich)????

I have my doubts with using a noid light at high RPM's - it takes an o-scope which most people don't have access to, or maybe a good volt meter. A simple double check would be to hold something against the injector and your ear, listening to the clicking ....

:blush: I am not loosing power.
I am loosing ground.

I cleaned both of those grounds as instructed with no apperent change. The strange thing is when I unhook the grounds with the engine running, the black with the red tracer when unhooked kills the engine. Although the hefteir solid black wire when removed changes nothing.

Also, when I probe at the ignition coil with a test light the engine dies, the same thing happens when I probe at a fuel injector with the test light.

It does appear that I have a ground problem of sorts. Maybe a computer problem or a corroded ground. I am on the hunt to check all the grounds I can find now.

Any thoughts, Ideas?

O.K. I found a helpful pinout chart for the ECU in AllData. Everything is as it should be as far as power and grounds go. I am now sold out on the idea that the ECU is internally malfunctioning.

Next question:

Where do I get one?

You can try calling 603-887-2838 and ask for Bob if you can afford to wait a few days for the part to ship from nh. He runs a side business where he disassembles old 240s and sells the parts. His prices are very reasonable as he has no overhead.

Comment.

Electronics are strange things. In my experience, micro-computer design and maintenance, most things will work well enough for about 10 yrs, then the peripheral components such as resistors and capacitors start to ge too old, and become unreliable, and eventualy the circuit fails. The use of surface mount parts has improved the long term reliability greatly, and many circuits are now lasting 20 yrs or more with good reliability.

The problem is, that time alone will kill most older circuits, die to components ageing. Thus the use of a 20yo ECU become very much a gamble. It may work well for some years yet, or it may fail before you can install it, just because a part of it got old, and drifted out of its correct value. On the other hand, you you to the dealer, and buy a new EMU, which was made 15 yrs ago, and has been on the shelf ever since. Unless there's a date of manufacture on it, you wouldn't/couldn't know that it's already 15 yrs old, and you'll pay full price for it, and not get the 20+years you're entitled to froma recently manufactured part using newly made components. I can make this allegation because the microchips necessary to make the original unit are most probably out of production by now, and unless Bosch have updated the unit to run different chips, they will be NOS devices, and could be very old. IE I have little confidence that a dealer supplied new EMU has been made in anything like the last 2 yrs, and unless so, I will be reluctant to part with my hard-saved $$ at full retail for it. My opinion is in part formed by an understanding of the low turnover of the product, and the ongoing need to produce only small batches very occasionally. The cost of upgrading the chipset is not inconsiderable, and is an unlikely development, altho' I'd be very happy to be proven completely wrong.

To all those who were following the conversation:

After I pulled out all my hair, purchased Rogain, waited for my hair to grow back. . .

I purchase a used fuel control computer. The car now runs like a top.

Thanks