Car runs only with ignition switch in start

ignition
volvo
240
sensors

#1

Obviously this is a strain on the starter. I had the ignition switch changed - still same problem, just intermittent now - maybe was intermittent before - who knows. Question: does having the key in start bypass the mass air sensor or other sensor that kicks back in when key is released to run position? $550 in repairs - same problem - drat.


#2

Older ignition systems had a coil voltage dropping resistor that was bypassed when the key was in the “start” position to provide hotter spark while cranking…If that resistor burned out, the car would die when the key was released. The cure was to replace the “ballast resistor” or the “coil resistor wire”

If your Volvo has one coil and a distributor, this is likely the problem. Run a jumper wire from the + side of the coil to the positive post on the battery and see if it runs then. If so, you have found your problem. Don’t run it jumped like that for more than a few minutes or you will overheat the coil and the ignition electronics…

If there is no distributor, good luck…


#3

The problem might be with the ignition module. Ignition modules function in two modes. These are the start mode and the run mode. During the start mode the ignition module allows full battery voltage to the seconday ignition system to make sure there’s a hot enough spark to start a cold engine. In the run mode the ignition module steps the voltage down to the secondary ignition system. If this isn’t done the higher voltage will damage secondary ignition system components.

So it could be that the ignition module is functioning during the start mode, but failing in the run mode.

Tester


#4

Yes, the MAF turns on the fuel system when air flow is sensed and in the crank position the ignition switch triggers that function. A jumper can be installed at the MAF to over ride a faulty MAF.


#5

Your car’s ignition system is designed to run on something in the 9 volt range, instead of 12 volts. That’s because you want your ignition system to have all the input voltage it needs to operate when you’re trying to start your car on a weak battery (and your batter voltage drops to 10 volts during cranking).

That 9 volt range is obtained by inserting resistance in the older style ignitions, or through different paths in the ignition modules. Full battery voltage is applied to your ignition during cranking.


#6

Check paragraph 3. It may answer your question.

http://com2.runboard.com/bairheads.f16.t50


#7

When I found this quote last night I think my heartbeat doubled because this was the EXACT symptom I was experiencing: “Occasionally, this ballast resistor will fail and the classic symptom of this failure is that the engine runs while being cranked (while the resistor is bypassed) but stalls immediately when cranking ceases (and the resistor is re-connected in the circuit).” I immediately phoned the 24 hour Autozone and asked for a price. They said it is not available and cannot be ordered. GREAT. This morning I found a Volvo place that can order it from Volvo, but I looked for it under the hood to try to match the guy’s description (which agreed witht the image in the Haynes manual), I couldn’t find it. Then I read a little more and studied the ignition schematics and saw that starting in 1983 there was no more ballast resistor, which probably means the same function is being performed by the “Control unit”, which I think is the ignition module the next poster mentions. So this morning I drove it, having to grind the starter part of the way to keep it running, to the mechanic who replaced the ignition switch. He found the hose on the output side of the mass air sensor/air mass meter/MAF was loose. He tightened it back on and lo and behold the darn thing ran great again. I won’t know if that is just a result of an intermittent problem disappearing for a while or not until it either happens again or not. I am glad there is a way to diagnose it using the jumper wire on the coil method (I have one coil and an electronic distributor). A thousand thank yous for your info.


#8

Thank you. I think based on all these posts and which type of ignition system I appear to have (I wish I were an electrical engineer instead of a software engineer). I had read that bypassing the ballast resistor for short periods of time was not harmful and that over a longer period of time the rotor would need frequent replacement. I wonder if there is any work-around for the ignition module? Thanks again. I love this car, but then again I also loved my last 2 wives and got rid of them eventually, LOL.


#9

In an earlier post/reply I mentioned that the output hose on the air mass sensor (MAF the same thing?) was loose and when the mechanic tightened it the problem went away. Strange if that were causing the problem, but I won’t know until some time goes by. Thanks very much for the post.


#10

Thanks for the post. As I asked in an earlier reply, is there a way to defeat the system as a work-around or if it is the ignition module it’s replace only? I wouldn’t care if I had to get a new rotor every 2000 miles if I could just buy a little time. I only drive 400 miles/month.


#11

Hi and thanks,

Not sure about what you mean by paragraph 3. Is it the “fuel pump safety switch”?

Maybe I’m looking at wrong post there.


#12

Yes, the fuel pump safety switch is what turns on the fuel system when the engine starts. If it fails to power up the fuel pump the engine will stall as soon as the switch is released from the crank position.


#13

Car is still running great. I’m suspecting that the loose hose out of the MAF sensor was triggering the fuel pump safety switch or very similar issue. I am actually going to loosen that hose up again and see if I can replicate the problem - inquiring minds need to know. A by-product of the whole recent ordeal is that my mpg is back up to 20, having dropped from 21 to about 14.5 over a year’s period of time. I am getting the oxygen sensor replaced tomorrow morning and have getting the motor mounts replaced on the top of my to do next list. One funny thing about the O2 sensor is that in the owner’s pamplet maintenance schedule from the original owner, all that is shown for 7,500 miles, 15k, 22.5k, 30k miles etc., etc. up to 90,000 is “O/C & Filter” plus the mileage and date. It would appear that the O2 sensor on this beast may be the original, 23 years, 160,000 mile sensor. This brings up the other items in the routine maintenance schedule for EVERY 30-40k miles: a) change manual tranny fluit, b) change differential lubricant c) replace fuel filter d) replace timing belt, e) drain, flush, refill cooling system, f) tune-up related stuff. I know many of these items are never done and I have out of necessity replaced the fuel filter, ignition coil, timing belt and had tune-ups. I guess the universally accepted advice is that the oil changes are the most important and mandatory items, but I’m surprised that in the first 90k miles the dealer didn’t talk him into some of those other items. Anyway, I will be interested in what my mpg is after the O2 sensor gets replaced. Thanks again, just wanted to confirm the previous positive feedback. Any other comments would be welcome, but you really have helped enough already.