Sorry in advance about the long post. I need help with a not so straightforward no-start issue on my recently purchased 1990 240. I have spark at the coil and plugs and the fuel pump is working normally but the injectors don't appear to be triggering. When I try to use diagnostic test mode 2 - trouble codes or diagnostic test mode 3 - Injection System Component Activation Test, the LED lights up and stays lit as soon as I insert the test probe into socket 2, preventing me from getting any trouble codes or activating the fuel injection component tests. The ignition modes tests (socket 6) appear to work normally. I swapped out the ECU with a known good one, and the results were identical. The only weird thing I can find is that this car had an after-market alarm system installed. This is a one-owner car and the owner said that he had the alarm system "removed." However, there is a toggle switch installed next to the fuse box that only allows the car to crank in one of its positions. Also, if the passenger door is opened, this triggers flashing of all the turn signals and the dash module lighting. Obviously the alarm system was not 100% removed. I am beginning to suspect that this might be the root of my problem. Does this make any sense? I don't know how these alarm systems were wired into 240's. Any ideas as to how to determine if this is my no-start problem - or how I can 100% remove the alarm system, so I can return the car to its normal set-up?

 

we can't answer your last question since we have no idea what was modified to install that alarm.

sounds like the ECU is never getting powered. I think at this point, I'd be probing the ECU's connector with a volt meter to verify its getting power and so forth, with a 1990 240 greenbook schematic on my lap in front of me.

 

You may be on the right track! These alarms often use a "kill" switch preventing start if not disabled by the remote. They are usually pretty easy to remove even though about a mile of wiring will come out. Depending on how handy you are, you can do it yourself or go to one of those stereo/alarm outfits who specialize. Start with the main module, get it out, look at the wires, the aftermarket splices and addons are usually obvious. This likely is affecting the diagnostics. At any rate, don't do anything before getting rid of that alarm!

 

I had this happen on a friend's Subaru. The horn wasn't connected. It's a problem every time the battery is removed.

Read this and give it a try: How to Reset Aftermarket (Checkmate) Car Alarm: 10 Steps

Just try the toggle one way, and if it doesn't work, try it the other way. It's sounds like you are dead on. That system was not removed. That should get you going.

When it's warmer I'd yank that system. I'd look for a splice into an original wiring harness and cut out the alarm box (which is probaly hidden away under the toe box).

 

I think I'd I'd start at the 240 fuse panel, looking for stuff plugged into the connections to the right of the fuses thats not factory.

Also, right off the battery +, one of the medium gauge red wires goes to a blade fuse holder on the fender wall near the power steering reservoir, then to the fuel injection harness where its connected to 1) the ECU pin 4, 2) the fuel pump relay pin 3, and 3) the ICU pin 5, all with red medium gauge wires that are always powered.

Another candidate, red wire from the 'positive terminal' (which is near that blade fuse holder I mention above, but not connected to it) goes to the ignition switch in 30, putting a relay in that circuit would disable EVERything thats controlled by the switch. Pin 15 of the ignition switch is a blue wire that goes to the ECU pin 35, ICU pin 6, and diagnostic display box. interrupting that blue wire would also kill the engine.

if I was installing an alarm that wanted to disable the system, I'd likely stick a relay inline with these circuits.

and, I do believe I'd track down what that toggle switch you mention is connected to.

 

Thank you all for your valuable input. This has taken on a sort of spiritual quest. I drove by this car for five years seeing it sit in the driveway - and it took that long to talk the owner into parting with it. He finally admitted yesterday after I posted my question on this forum that he tried to disconnect the alarm himself and thought that he had done so - but he never got the car to start again, so there it sat. I will say it's a real beauty with a perfect paint job, pristine interior, etc. It certainly deserves to be resurrected.

As soon as the snow goes away (I am on Long Island) I will pursue these great suggestions. So far without removing anything, I've found this toggle switch which seems to stop the car from cranking in one position and an LED installed by the speedometer console that flashes. I did notice some non-Volvo looking wiring by the ECU. I was just amazed that someone would go to all that trouble - especially risking damaging the ECU.

Just for the record, I think the ECU must be receiving power. When I insert the diagnostic plug into socket 6 and turn the ign. switch to position II, the LED immediately flashes ten times, then goes out. This is repeatable. After that, I can conduct the ignition test, which reports 1-1-1. This is what I would expect after the battery was disconnected for so long, even though those 10 flashes are a mystery to me. But, as I said, the regular diagnostic mode and the fuel injection tests cannot be initialized. I will fix this, and report what I've found here in the hopes that it will help someone else.

 

So you never actually had the car running since you bought it?
Just get the alarm out, if you are very lucky may be that's the only thing that's wrong with it.

 

No I never got it started. However, I paid only $250.00 for the car with 140,000 miles showing on it and the body and interior in perfect condition, so I figured I couldn't lose on this deal. I could recoup my money on the parts by themselves. However, this is a Volvo that deserves a new lease in life no matter what it takes.

 

Well, finally the weather broke so I was able to get back to the car. I removed the alarm system. The big thing was a relay inserted between a thick red wire that terminated on the fuel pump relay. I couldn't fathom how the alarm system functioned exactly. it had two "black boxes" a toggle switch and a relay. But at least it was spliced into the wiring without cutting or re-routing any original wires, so it was no problem to identify and remove. The car still did not start - no fuel pump and no injection. The ECU diagnostics still behaved improperly as i described in the previous post. I replaced the Jetronic ECU and the diagnostic test module began to work. i put in some fresh gas and it started up and purred like a kitten after sitting dormant since 2006. I am just pleased that this beautiful Volvo will be back on the road rather than being crushed in some junk yard.

 

ah. that big red wire is the main power to both the fuel pumps and fuel injection (the fuel pump relay on a LH car is actually two relays in one).

and yeah, if the diag module is misbehaving there's a good chance the ECU is fried, as the diag module is connected directly to it via the jumper, its the ECU (or ICU in pin 6) thats reading the button and blinking the codes... the diag module itself is JUST an LED and button and the jumpers, there's no smarts in it at all. The ECU and ICU on a LH2.4 car are based on Intel 8051 type industrial microcontrollers.