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240 Runs on 3 cyls at startup.

Gabe244

Gabe244

New member
Joined
Jul 28, 2007
Location
Brisbane, Australia
Runs on 3 for around 20 seconds then the 4th kicks in. What gives? Intank pump is buggered, but the cpr has been cleaned out and injector cleaner used. The car has some vac leaks (oil catch can doesnt seal perfect and there is a slight "wooooooooooooowww" sound while driving which i think is either a bung diff, trans, or an intake mani gasket leak. The thermal timer might be bung, but surely the cold start injector wouldnt make that much of a difference in this heat :lol:. Any ideas?
 
Maybe a very slight head gasket leak that lets a little coolant into one cylinder which wets the plug. After a bit it will have cleared that out and then run fine.
Try letting the pressure off the coolant system (carefully) when you stop and leave the cap off until you next start it. Put the cap back on then
If there is no pressure in the coolant system when it is parked up less will get into the cylinder.
If it starts fine after that then it points to coolant getting past the head gasket.
I ran mine like that for ages until the gasket got so bad that I hydraulically locked the engine with coolant a couple of times and then decided I needed to change it.

Rob
 
Last edited:
HG is new. I'll check it out anyway. Thanks.

EDIT: Actually it might be the one way fuel pump valve. It only seems to happen on cold starts after a few days of not being used.
 
Do you know which cylinder it is?
Fire it up from cold and touch the exhaust manifold to find the cold one.
Then look at things related to that cylinder (leads / plug / injector etc)
 
Yeah, worth a try. Get the feeling its gonna be cyl 2 tho. It always goes funny when it starts getting under 1/2 tank and the main pump starts struggling.
 
Yeah its no.2. Plug looks black-ish as usual. Smelled like petrol. Mayby the injector isnt atomising properly causing an incomplete combustion. The problem gets worse as the tank drops in level, leading me to think that it is indeed to do with atomisation/pressure.
 
Most of the 240's with fuel injection use a, "Batch fire" system, wherein all the injectors pulse at the same time. If you are fouling #2 on a consistent basis, suspect that injector. You can use a noid light to see that the injector is receiving the signal, but I would suspect that your #2 injector is squirting a stream of fuel, instead of a correct spray pattern.
 
Also Consider Lift Or Main Pump Inpending Failure-Occulusion

What year and model? I missed that. My '78 242GT cold starts on 3; then goes to 4 after about 5 to 10 seconds. Seems worse with one quarter full tank or less. We found dirt in the works; ethenol fuel seems to reek havoc on the fuel tank liner. Filtures clogged up.

Cleaning the tank and replacing the lift pump and sock helped. Seems to be a recuring problem with my Volvo again based upon the tank lining dissolving over time with alcohol laced gasoline. 10% alcohol here in SW Oregon USA. You can conduct a fun experiment.

Stand on your gas pedal. Really rev out your engine. Burn rubber. If you get ANY bucking (fuel starvation) then most likely you have some occulsion in the fuel flow caused by ???? We eventually changed out both the lift and main pump. Check for vacumm leaks also. HB of CJ

cold start miss post
 
you probably have an injector that is leaking down when you shut the car off- the raw fuel drips into the affected cylinder,collects between the piston rings & cylinder wall causing a temporary loss of compression(and resulting misfire) untill the excess fuel burns off
 
I have the same thing going on, always have, got slightly better when I swapped my M cam for a B, but it still does it. I will be replacing both pumps and my injectors soon, hopefully thats it :)

Until then, I feel bad for my motor mounts during the cold-start dance...
 
Well i pulled that injector and sprayed it into a bottle whilst cranking/idling the car. Spray pattern looked like crap. I also noticed that when i stopped the car it did seem to get slightly wet at the tip. Im sure if it was left for long enough it would drip.

So thats likely to be the problem then. I'll see how it is after this tank of injector cleaner goes through it, but most likely i'll get them cleaned in the not too distant future.

Thanks for all the help everyone.
 
I had this start a few months ago, on cold starts only (car in sig). The plugs, wires, cap and rotor, inline fuel filter and B-cam had all been in the car for 5,000-15,000 miles.

I seafoamed via the intake vac and fuel tank, that fixed it for about a month, then it started coming back. For this engine it was the #1 cylinder. I checked, cleaned and regapped the plugs, no real change, also cleaned the rotor and cap pionts. I cleaned the IAC a while back aswell.

The latest thing was, I pulled injectors from a totalled '89 240 with 130,000 miles at the u-pull-it, had them tested and 'rebuilt'. It takes a second longer to start now, and after 2 weeks with the new injectors, the cold starts have started the 3 cylinder thing. I'm still happy the I have the 'new' injectors, the engine idles smoother (after the first few seconds of cold start rough idle) and seems MUCH happier revving and at highways speeds. The engine actually sounds better.

I'll keep my eye on this thread, a few good ideas to try.
If the HG was leaking would the exhaust smell like burning coolant and have white smoke as it burns off?
 
Damn, its gotten worse and is doing it on cyl 4 now. Weird. Need to get these carbs in. Its also making a slight *clack* noise at idle every few seconds so. Stops if you rev it. Hope its not a bearing or something :omg:. Other than that its running great. Pulls hard, pretty responsive and the missing stopped too.


EDIT: Think that noise may be piston slap.
 
Clack and misfire, I would be thinking sticking valve/ bucket. Time for a compression test. A vacuum gauge will also show a sticking valve really well.

Regards, Andrew.
 
I have the 3 cylinder problem too, It ides on 3 ALWAYS, and goes to die every time it comes down to idle, but I just tap the gas and its 4.

its 3 for the first 30 seconds of startup
 
i had that the other day. Flogged it round a bend, rear end came out to play, and it felt really weird after that. Turns out that my slight misfiring stopped and now its much smoother. Italian tuneup ftw indeed.

Thankfully its not a valve. Compression test shows normal results for rear two cyls. and the fronts are firing at startup. I think the clunking is the alternator bushings. The alternator can be rocked side to side at least 2cm, so that might be it.
 
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