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Old 08-12-2017, 06:15 PM   #1
DStarratt
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Default 82 240 turbo + Hot Engine = No Start

My 82 240 turbo, K Jet 100 k mikes sat for years. I'm getting her back on the road. It starts easily when the engine is cold. I can let it idol for a long time or take it on he road with no trouble. But when I turn the engine off I cannot start it again for hours. It will crank it won't start. As of this afternoon I could run it a while then turn it off. I could then turn it back on immediately a few times. But after waiting 30-60 min it won't start.

I replaced the coil with no change.

I think it may be loss of fuel pressure (maybe slowly) after turning it off. That may account for the recent ability to restart it immediately but not later. I'm thinking it could be leaking injectors.

Does anyone have any other ideas?
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Old 08-12-2017, 06:26 PM   #2
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Try unplugging the cold start injector after it warms up.
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Old 08-12-2017, 06:37 PM   #3
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240 turbos made after '82 were equipped with an impulse relay that activates the cold start valve when warm.



It's usually mounted to the ignition amplifier.



Do you have one?
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Old 08-12-2017, 10:18 PM   #4
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Yes, I have an impulse relay. You think I should unplug it?
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Old 08-12-2017, 10:37 PM   #5
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I'd check to see if it's working first.
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Old 08-13-2017, 12:11 AM   #6
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If the system won't hold rest pressure for one reason or another hot starts can be very difficult.
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Old 08-13-2017, 12:43 AM   #7
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Yes, but so will cold starts which he says isn't a problem.

I think the reasoning behind the impulse relay is that with such a low compression ratio, the air flow meter wasn't being lifted enough while cranking to allow fuel to flow. A squirt from the cold start injector gets the engine running fast enough to lift the metering plate and the engine runs.
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Old 08-13-2017, 05:36 AM   #8
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^Hot start is a LOT worse in warm weather though.

Cold start it might crank longer or can be overcome by the pumps running for a second before cranking. The hot start once the fuel boils is dreadful.
Doing much with k-jet without at least checking pressures is sort of a futile pursuit.

Impulse relay would make some sense if it's extremely hot out and the coolant won't cool quickly but just a little more fuel is needed to make the car start.
I've never seen a bad impulse relay yet, mostly just janky wiring in that circuit generally.
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Old 08-13-2017, 12:28 PM   #9
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car started fine this morning, as usual on a cold start. Drove her a few miles and parked her back in the garage. The car started back up immediately and started again after 5 min of sitting. After sitting 20 min it would not start. I unplugged the impulse relay with no change. I jumped fuses 5 and 7 with no luck. Oh, and I cleaned the fuel injectors last night. Still no change.
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Old 08-13-2017, 12:41 PM   #10
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I have this problem in hot Georgia weather. Hard hot starts. Pressures are normal. Pretty sure it's vapor lock. I am considering triggering the cold start with a simple relay and a push button.
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Old 08-13-2017, 11:56 PM   #11
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Thanks all. I'm in south Texas and it was 85 degrees out this morning when I ran the car. So maybe you're onto something. But does the immediate restart for up to 5 minutes even when the engine is hot and in 85 degree weather rule this out?

Any thoughts on whether it could be the accumulator that sits next to the fuel pump under the car? I don't see it leaking at the screw in the back but I suppose it could be bad. Or does the immediate restart and ability to start for up to 5 minutes rule that out?
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Old 08-14-2017, 12:13 AM   #12
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Fuel pump check valve.
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Old 08-14-2017, 06:55 AM   #13
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Quote:
Originally Posted by Kjets On a Plane View Post
^Hot start is a LOT worse in warm weather though.

Cold start it might crank longer or can be overcome by the pumps running for a second before cranking. The hot start once the fuel boils is dreadful.
Doing much with k-jet without at least checking pressures is sort of a futile pursuit.

Impulse relay would make some sense if it's extremely hot out and the coolant won't cool quickly but just a little more fuel is needed to make the car start.
I've never seen a bad impulse relay yet, mostly just janky wiring in that circuit generally.
I have experienced this and the symptom came from poor rest pressure. If your rest pressure is not within spec what was described above will happen in hot weather. Check the rest pressure. From there it could be leaks, fuel pump check valve, accumulator.

Fuel leaks you can see or smell if they are large enough.
Check valve is pretty cheap, but mucking with it may require you replace / rebuilt the cross over fuel line between the fuel pump and accumulator.
If it is the accumulator at least the prices of these have dropped dramatically since I replaced mine.

I would also check that there is a copper crush washer on the fuel pressure regulator which is located on the fuel dizzy. The problem I had with mine is the PO removed the crush washer which resulted in a misalignment inside the fuel dizzy which allowed fuel past the pressure regulator.

Best of luck!
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Old 08-15-2017, 01:09 AM   #14
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That is all great info. I don't have any fuel leaks. I'm going to pick up an accumulator. They definitely have come down in price. I have a new fuel pump on the shelf so I think I'll put that on at the same time. Hopefully that will fix the problem and prevent others for a while. The biggest problem will be that hose between the fuel pump and accumulator.

Tonight I started the car with no trouble and let it idle for 30 minutes in 97 degree heat. I shut it off and restarted it immediately three times. I noticed the fuel pump buzzed each time when I turned the ignition "on."

The car started again at 20 min, 35 min and 50 min but at these times the fuel pump didn't buzz when I turned the ignition on before I turned it to start. I also noticed the first start each time was a little slow. I let it sit for another 2.5 hours then it would not start.

I'm chalking this all up to loss of residual fuel pressure as has been recommended. I'm thinking there was enough residual pressure at 5, 20, 35 and 50 minutes. Maybe each start restored some pressure too. But it lost too much pressure after 3 hrs.

Does anyone think I am missing anything?
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Old 08-15-2017, 01:16 AM   #15
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Other than a gauge to verify your hypothesis before firing the parts cannon?

Did you ever verify that the impulse relay is activating the cold start valve?
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Old 08-15-2017, 06:26 AM   #16
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Quote:
Originally Posted by hiperfauto View Post
Other than a gauge to verify your hypothesis before firing the parts cannon?
Agreed!

If you plan on keeping the car get a fuel pressure test gauge.
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Old 08-15-2017, 06:29 PM   #17
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Quote:
Originally Posted by hiperfauto View Post
Other than a gauge to verify your hypothesis before firing the parts cannon?

Did you ever verify that the impulse relay is activating the cold start valve?
I unplugged the impulse relay while the engine was warm and it didn't make a difference. I'm not sure that verified it was working or not.
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Old 08-15-2017, 07:13 PM   #18
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Use a test light or noid light at the CS injector to check the operation of the relay.

If the relay isn't working, unplugging it won't tell you anything.
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Old 08-18-2017, 10:00 PM   #19
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Thanks, that's a good idea.

I put a new fuel pump and check valve in last night. I had one on the shelf. It's still doing the exact same thing. Cold start is no problem. I heat it up then shut it off. The car starts immediately and starts again but slowly after 20 minutes. Then when I let it sit a couple hours it wont start. I still need to check the cold start injector and maybe change the fuel accumulator.
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Old 08-19-2017, 12:15 AM   #20
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If the accumulator were bad, it would be hard to start when cold. It should also be leaking fuel from the back of the accumulator. If its an early style with the hose connected to the fuel sender, you may not see it leaking until you remove the hose.

A fuel pressure gauge would reveal whether or not the system is holding rest pressure.
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Old 08-19-2017, 06:00 PM   #21
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I hooked up the noid light to the electrical connector for the csi. I'm getting power for about a second as I turn the ignition to start. Then no power. That sounds normal to me. Two issues though: the noid light does the same whether the car is hot or cold and whether the impulse relay is connected or not.

Any thoughts based on that new info?
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