Could it be the Cold Start Valve? - Page 3

Ringmaster · 30-07-23, 03:48 PM

Just a quick update folks,

The car seems to be following a definite pattern....

Yesterday it started up well from cold. Ticked over happily for about 1 minute and stalled. After some difficulty it started again but I had to keep my foot on the throttle to prevent stalling. I did this for four minutes and switched off. Started up again and all was fine!!

Drove around for 2 hours without incident although the idling was a tad rough at times. Parked for an hour, started well and drove for another half hour without a hitch.

Have topped up the tank and added a fuel cleaner. Must get myself a voltmeter. Never used one before (I'm ashamed to say). I think it will be worth checking if the thermostat is getting current among all else that's been suggested.

Ringmaster · 31-07-23, 06:16 PM

Got a multimeter and tested the cable to the Thermotime switch.

Result - 0.02 volts with ignition on....

Tested resistance on Thermotime swich. Result - 0.07 ohms.

K Simmonds · 18-08-23, 05:00 AM

I think at 36 years old and probably at least 100K miles? The old fuel pump could easily be struggling. I have spares from C4's that all work very well but a new one isn't too expensive if you shop around, be sure to get a European manufacured unit NOT one from the east!

All the other suggestions from everyone else make sense, the tanks are metal and if you drive around with less than half a tank the whole time some minor suface rust can develop and fall into the strainer on the the bottom of the pumps basket, some can make it though the pump and into the filter and strainers.

However if that was the case I'd expect it start porely all the time from cold and the pump could also be noisy.

I like K-Jet car's and own one myself and it's a great system when everything is working and can give MPG figures nealy as good a multipoint injection, which is amazing when you consider how they actually work...

Have responded to your PM regarding a warm reg rebuild as I said not a big job, I've done a coupe but a vice and compressed air are esscencial.

Ringmaster · 19-08-23, 03:18 PM

Folks,

Is there a Non Return Valve on the K-jet fuel system? Where is it? Would it be in the fuel tank with the pump?

84CoupeGT · 19-08-23, 10:39 PM

Quote:

Originally Posted by Ringmaster

Folks,

Is there a Non Return Valve on the K-jet fuel system? Where is it? Would it be in the fuel tank with the pump?

On my B2 Coupe it's just after the fuel pump, before the line that goes to the accumulator. Mine doesn't have an in-tank pump though so might be different.

Ringmaster · 20-08-23, 11:47 AM

Quote:

Originally Posted by 84CoupeGT

On my B2 Coupe it's just after the fuel pump, before the line that goes to the accumulator. Mine doesn't have an in-tank pump though so might be different.

Thanks mate. Sounds like it won't be far from my pump either.... Will have to look more closely at my Haynes manual..

84CoupeGT · 20-08-23, 04:37 PM

No probs. Just had a quick look at ETKA for 1987 KU, the non-return valve is indeed attached to the pump outlet

urquattr085 · 20-08-23, 04:40 PM

According to the notes, it's item 30 but only for a Bosch pump.

Hope this helps

Ringmaster · 20-08-23, 08:33 PM

Many thanks.

I tried 7zap earlier today but the image was completely garbled for some reason..

BTW.. I have discovered another trick... If I just turn the ignition on and off (without starting the engine) twice and then turn the engine on, the car starts up and drives well. Sometimes the engine surges from 800 to 1100 rpm when idling, but otherwise OK..

It's definitely pointing to a problem pump or return valve...

ovalking · 23-08-23, 05:36 PM

Quote:

Originally Posted by Ringmaster

Tested resistance on Thermotime swich. Result - 0.07 ohms.

I got 60ohms (ambient temp).

I don't think it's your problem, but you need to monitor the cold start valve supply voltage to check its operation. It only comes on for 3 or 4 secs at most. This is detailed in the Haynes.

Edit: because forum can't display ohms symbol!

18-08-23, 05:00 AM	#23
K Simmonds Senior Member Classic Audi Club Member Join Date: Dec 2009 Location: Mid Wales Posts: 1,060	I think at 36 years old and probably at least 100K miles? The old fuel pump could easily be struggling. I have spares from C4's that all work very well but a new one isn't too expensive if you shop around, be sure to get a European manufacured unit NOT one from the east! All the other suggestions from everyone else make sense, the tanks are metal and if you drive around with less than half a tank the whole time some minor suface rust can develop and fall into the strainer on the the bottom of the pumps basket, some can make it though the pump and into the filter and strainers. However if that was the case I'd expect it start porely all the time from cold and the pump could also be noisy. I like K-Jet car's and own one myself and it's a great system when everything is working and can give MPG figures nealy as good a multipoint injection, which is amazing when you consider how they actually work... Have responded to your PM regarding a warm reg rebuild as I said not a big job, I've done a coupe but a vice and compressed air are esscencial. __________________ Still have my RS2 tuck up safe, also a 1992 C4 2.8 Avant quattro and a B3 quattro Saloon G60 conversion in progress.

20-08-23, 04:40 PM	#28
urquattr085 Senior Member Classic Audi Club Member Join Date: May 2016 Location: Displaced Northerner in Essex Posts: 1,528	According to the notes, it's item 30 but only for a Bosch pump. Hope this helps __________________ 1985 WR quattro 2010 A6 3.0Tdi Allroad 2010 A3 1.4 tfsi Sport - Sold but still in the family 1984 80 Quattro - Sold many moons ago 1981 Coupe GT - Sold to buy above

30-07-23, 03:48 PM	#21
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,333	Just a quick update folks, The car seems to be following a definite pattern.... Yesterday it started up well from cold. Ticked over happily for about 1 minute and stalled. After some difficulty it started again but I had to keep my foot on the throttle to prevent stalling. I did this for four minutes and switched off. Started up again and all was fine!! Drove around for 2 hours without incident although the idling was a tad rough at times. Parked for an hour, started well and drove for another half hour without a hitch. Have topped up the tank and added a fuel cleaner. Must get myself a voltmeter. Never used one before (I'm ashamed to say). I think it will be worth checking if the thermostat is getting current among all else that's been suggested.

31-07-23, 06:16 PM	#22
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,333	Got a multimeter and tested the cable to the Thermotime switch. Result - 0.02 volts with ignition on.... Tested resistance on Thermotime swich. Result - 0.07 ohms.

19-08-23, 03:18 PM	#24
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,333	Folks, Is there a Non Return Valve on the K-jet fuel system? Where is it? Would it be in the fuel tank with the pump?

20-08-23, 04:37 PM	#27
84CoupeGT Grown up member Join Date: Nov 2020 Posts: 309	No probs. Just had a quick look at ETKA for 1987 KU, the non-return valve is indeed attached to the pump outlet

20-08-23, 08:33 PM	#29
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,333	Many thanks. I tried 7zap earlier today but the image was completely garbled for some reason.. BTW.. I have discovered another trick... If I just turn the ignition on and off (without starting the engine) twice and then turn the engine on, the car starts up and drives well. Sometimes the engine surges from 800 to 1100 rpm when idling, but otherwise OK.. It's definitely pointing to a problem pump or return valve...