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78 CIS cold start issue

My engine always has a hard time starting when cold, regardless of outside temperature.
It takes sometime 10s of cranking, and generally does not fire all cylinders at once. Sometimes it will refuse to start, but will start right away if I lift the pressure plate to pump gas in the injectors. Once it has run, it will restart without issues.

I feel like there is not enough gas pressure to start cold. My question: is the fuel pump supposed to run when I turn the ignition on before cranking? I cannot hear mine and I wonder if that is normal. I imagine gas pressure has to be built before cranking occurs, is that correct? Car is 1978 SC with original CIS system.

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Old 10-19-2019, 04:45 AM
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Possible TTS (thermo time switch) or cold start injector. Or the wiring. If the car runs ok after you get it going the fuel pressure is most likely good. You should troubleshoot the TTS and the CS system. It's not that difficult. You can do it with a test light or a VOM. The fuel pump wont run until you engage the starter.
Old 10-19-2019, 05:06 AM
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Aurelien,

Mid years (like mine) and earlier CIS engines had the fuel pump come on with the key. On the later 3.0 liter SC engines, they included a switch. During slow cranking while trying to start, the small deflection of the air flow sensor plate toggles the fuel pump switch and the fuel pump runs - but only if the engine is turning over.
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Last edited by Walter_Middie; 10-19-2019 at 05:22 AM..
Old 10-19-2019, 05:11 AM
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OK, so the yellow wire on the starter must be for the cold start injector, correct? I have a feeling that one may be disconnected...
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2014 Cayenne platinum edition
2008 Benz C300 (wife’s)
2010 Honda Civic LX (daughter’s)
Old 10-19-2019, 05:24 AM
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Quote:
the yellow wire on the starter must be for the cold start injector, correct?
Yes - when cold, the yellow wire has +12V while the starter is engaged. This powers the cold start valve - or the injector on the engine conveniently located between the engine and the firewall where you can't see it or get to it.
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Old 10-19-2019, 10:29 AM
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Quote:
Originally Posted by Aurel View Post
OK, so the yellow wire on the starter must be for the cold start injector, correct? I have a feeling that one may be disconnected...
Should be the problem.
Old 10-19-2019, 11:12 AM
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Quote:
Originally Posted by gomezoneill View Post
Should be the problem.
Was hoping for it too, but I checked the wire, it is plugged normally. Maybe unplugged or broken on the other end...
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2014 Cayenne platinum edition
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2010 Honda Civic LX (daughter’s)
Old 10-20-2019, 04:40 AM
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Quote:
Originally Posted by Aurel View Post
Was hoping for it too, but I checked the wire, it is plugged normally. Maybe unplugged or broken on the other end...
Simply check it with a test light while engaging the starter.
Old 10-20-2019, 05:00 AM
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I have been having the same problem for three years.with my 1978 sc targa.. can someone please give me a photo tutorial
thanks
Old 11-17-2019, 06:32 PM
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Quote:
Originally Posted by stevebmd View Post
I have been having the same problem for three years.with my 1978 sc targa.. can someone please give me a photo tutorial
thanks
Buy a simple test light.

https://www.harborfreight.com/612v-circuit-tester-with-5-ft-lead-63603.html

Find the thermotime switch on the drivers side chain cover.



Ground the test light and touch the pointy end onto one of the thermotime switch terminals and have a friend crank the car when car is cold. Should light up. Turn off. Put the probe on the other terminal and start car again. If it lights the issue is not the switch.

If it lights on one side and not the other, its the switch. If no light on either side, problem is upstream of the TT switch.

Test the function of the test light on the battery just to make sure it works.
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Old 11-18-2019, 12:34 PM
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great thanks
Old 11-18-2019, 01:34 PM
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CIS troubleshooting........

Quote:
Originally Posted by Aurel View Post
My engine always has a hard time starting when cold, regardless of outside temperature.
It takes sometime 10s of cranking, and generally does not fire all cylinders at once. Sometimes it will refuse to start, but will start right away if I lift the pressure plate to pump gas in the injectors. Once it has run, it will restart without issues.

I feel like there is not enough gas pressure to start cold. My question: is the fuel pump supposed to run when I turn the ignition on before cranking? I cannot hear mine and I wonder if that is normal. I imagine gas pressure has to be built before cranking occurs, is that correct? Car is 1978 SC with original CIS system.


Aurel,

You need to test the CSV. At this point, you have no idea if the CSV is working or not. Since you are not able to start a cold motor by simply cranking the engine, a CSV could be the culprit. But we don’t know this as a fact. Maybe it is not getting power or not delivering fuel because of the TTS (thermotime switch). Maybe the TTS is not working?

You need to test and confirm to identify the culprit/s. If you don’t pull out the CSV, you are hoping it is good and working. Sometimes you are lucky and the CSV is good. But you can not rely on LUCK specially in a diagnostic test.

Tony

Old 11-18-2019, 08:58 PM
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