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240 What's the best way to temporarily disable EFI

N

Notn4

New member
Joined
Oct 6, 2016
Location
Finland
As the title says, I want to temporarily disable fuel injection.

This is a sketchy workaround fix for a problem I don't want to deal with properly yet since it's way too cold outside currently.

My 240 seems to flood occasionally, causing the car to start but only on 2-3 cylinders. The cylinders that failed to fire during starting remain dead because the fuel injection is constantly dumping more fuel onto an already soaked sparkplug. I usually just start driving with the engine still running like crap, get up to speed and shift it into a really low gear, pop the clutch and let the engine rev up to 4-5krpm. This flushes all cylinders and lets the soaked plugs start firing.

Now with ice and snow on the road, engine braking is somewhat sketchy, I thought it might be possible to install a switch inside the car that would kill the fuel delivery entirely while still keeping spark. This way, if the car floods again, I could flip the switch and just crank the engine for a bit to clear the cylinders, flip the switch again and start with fresh non-flooded cylinders.

What I'm asking is, what wire should I interrupt with a switch? Would the main fuse that's under the hood be fine? I still want to have spark.
 
Notn4 said:
As the title says, I want to temporarily disable fuel injection.

This is a sketchy workaround fix for a problem I don't want to deal with properly yet since it's way too cold outside currently.

My 240 seems to flood occasionally, causing the car to start but only on 2-3 cylinders. The cylinders that failed to fire during starting remain dead because the fuel injection is constantly dumping more fuel onto an already soaked sparkplug. I usually just start driving with the engine still running like crap, get up to speed and shift it into a really low gear, pop the clutch and let the engine rev up to 4-5krpm. This flushes all cylinders and lets the soaked plugs start firing.

Now with ice and snow on the road, engine braking is somewhat sketchy, I thought it might be possible to install a switch inside the car that would kill the fuel delivery entirely while still keeping spark. This way, if the car floods again, I could flip the switch and just crank the engine for a bit to clear the cylinders, flip the switch again and start with fresh non-flooded cylinders.

What I'm asking is, what wire should I interrupt with a switch? Would the main fuse that's under the hood be fine? I still want to have spark.
Click to expand...

Seriously? You are going to hack the wiring harness to install a kill switch for the efi when the problem could actually be the injector wiring itself?.......Or an ignition wiring issue?
Air Fuel Spark.
Get troubleshooting, son.
 
It's a b230f
New plugs
New ignition wires
New distributor cap and rotor

I'm not hacking up the wiring harness, if the main fuse under the hood is supplying the EFI then I'll just put the switch there. That fuse holder need to be relocated anyway.

The issue with the flooding WILL be troubleshot and fixed as soon as it either gets warm enough that I don't need a bonfire next to my spanners so they don't shatter from the cold or I get an opportunity to wrench in a garage. As stated in my OP, this is only a workaround to buy me more time, I use this car as my DD to work so it needs to run.

Before more people chime in with their panties in a bunch about how I'm hacking up the car, it's a 200$ junkyard rescue that is so beat up that hacking a wiring harness is improving it. I'm not ruining a mint 240 here.
 
Broke4speed said:
This is probably an easy fix, you'll spend more time ghetto-rigging a switch than solving the problem. I bet it's the coolant temp sensor, as mentioned above.
Click to expand...
This exactly. Plus by the end of the winter, with it running like poop, it may have cost you more in wasted fuel than the repair would have. Btw, I completely know Where you are coming from. I once replaced the starter in a parking lot on a jetta at night. It was -42c and 45km/h wind.....Btw, on that jetta one of the starter bolts holds up the engine. When i removed it the engine dropped over an inch. That was fun to line up again. Had to do what i had to to go to work. I grew up where it regularly goes below -20c........
My panties are down filled felted wool. They don't bunch up easy.
 
NotSoFresh said:
This exactly. Plus by the end of the winter, with it running like poop, it may have cost you more in wasted fuel than the repair would have. Btw, I completely know Where you are coming from. I once replaced the starter in a parking lot on a jetta at night. It was -42c and 45km/h wind.....Btw, on that jetta one of the starter bolts holds up the engine. When i removed it the engine dropped over an inch. That was fun to line up again. Had to do what i had to to go to work. I grew up where it regularly goes below -20c........
My panties are down filled felted wool. They don't bunch up easy.
Click to expand...

pictures
 
1) It can't really be a wiring issue - since the LH injector wiring features a single 'batch' fire - all 4 injectors get 12V+ switched on one side, and they all ground through a common wire leading to the ECU. The separate grounds from the injectors are all spliced together a few inches into the wiring harness. That means if a single injector is sticking on, shutting off all of them won't really help.

2) FWIW, cars still sometimes get flooded, even with modern EFI. So they have the WOT switch set to do a 'flood clear' - where the engine cranks but the injectors don't fire. So try that next time? Floor the pedal, crank it some.

You could pull a fuse in the fuse panel to disable the fuel pump - don't even need to open the hood. Or get into the passenger side kick panel and unplug the fuel pump relay.
 
Notn4 said:
Now with ice and snow on the road, engine braking is somewhat sketchy, I thought it might be possible to install a switch inside the car that would kill the fuel delivery entirely while still keeping spark.
Click to expand...


WOT and cranking will do what you want.
 
These cars don't have a clear flood feature. Flooring the gas works on some modern cars, but not these.
 
Was it the coolant temp sensor that was such a PITA to get at? I happen to have a week off from work soon so can go without the car for a few days then. Was thinking about just getting an electric heater and see if that would make wrenching in the snow a bit more bearable. While I have the opportunity to leave the car sitting for a few days, do you guys think it would be a good idea to send the injectors to be flushed?

Could it also be the cold start valve or whatever it's called?

In the meantime I just resorted to having a fresh or atleast "fresher" set of plugs with me at all times, so I can swap out the wet ones if needed.
 
Quick update, the flooding has gotten worse, today it started and immediately died, no amount of cranking, WOT or not made it fire up again. Threw in my spare set of plugs, which were Bosch as my parts store didn't have genuine Volvo ones. This made it start again without issues.

The plugs I removed were completely soaked, I tried pulling the fuel pump relay and cranking the engine to clear the plugs but it didn't help. This is also something I'll never do again since the connector for the relay broke, one of the wires came out of it, it's back in there again but I'd rather not go poke at it again.

The weather is easing up a bit here so might go throwing tools at it this weekend. What's the first thing I should start swearing at? My current plan is to get a new engine coolant sensor as they were pretty cheap, then after that maybe remove the injectors and dump them into the ultrasonic cleaner at work. The ultrasonic cleaner we have at work is made to handle flammable solvents as cleaning agents so might go with carb cleaner.

Anyone have better ideas?
 
Get out the manual and get troubleshooting. Replacing parts and hoping is usually more expensive and takes longer.
The reason I suggested this before is problems like you have will never get better on their own, only worse.
You are going to be stranded by the car, and have to pay for a tow out of the money you didn't make missing work....Its happened to me..
Yes it is cold. Yes it will suck. Its also gonna be cold on the side of the road waiting for a tow....
Fuel, air spark. You have air and fuel and spark at least sometimes. The flooding is either too much fuel or not enough spark. How are you sure your ignition is not weak?
You may have serviced it but getting dead parts brand new is not uncommon these days. Perhaps there is a short in the ignition start circuit? Perhaps the coil is not getting enough/intermittent power during starting. A plug wire with a bad end, with an intermittent connection..
How are the engine grounds? Coil grounds?
How is the o2 sensor? is it there and plugged in? If the o2 reading is off, the engine may dump fuel.
There are procedures for testing sensors. Coolant temp sensor can be removed, taken inside, wired into a multimeter and placed in heating water with a thermometer. You may not be able to see if it is accurate, but you can see if it is reacting to temp change.
Taking out a temp sensor takes roughly 1/4 the time it takes to take out a spark plug......

Is it the same cylinder/s that get flooded and don't fire or does it move around? If its the same one, switch the injectors with another hole. Does the problem follow the injector? If it does=injector bad. If it doesn't move, its something else on that hole like the wiring for injector/plug.
If it moves around from hole to hole, it wont be injectors,plugs or wires. It will be something that is common to all the cylinders like the coil, or the coolant sensor.
 
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