# cold start good. warm start good. 30-90 minute restart, terrible



## epic designs (Feb 4, 2004)

Ok 1980 Scirocco 1.6 with CIS-basic. 

- Car starts amazing when its cold. first crank, 1200 RPM, good solid warmup. 
- Car will restart amazing when it's hot (within 20 minutes of shutdown).
- Car runs beautifully, solid 950 rpm idle all the time. A bit of popping from the exhaust on overrun.
- Really solid vacuum at the tank when I take the fuel cap off

If I restart between about 30-90 minutes, it cranks and cranks for a good 30 seconds, finally starts sputtering, then runs really rough, only firing a couple times per cycle. Runs rough for about 30 seconds, then its fine. Does this every time, and its really embarassing.

I assumed... residual fuel pressure issue!!

- Changed the F/P check valve.
- Changed the Accumulator with new.
- Changed all the rusty pipes and hoses between the tank, pump, accumulator, and fuel lines. ($$$)
- Pulled all the injectors and sprayed them into a cup. amount is equal, and no leaking at all with the pump running. 
- Pulled cold start injector. Works when it should, stops when it should, no leaking. Replaced gasket.
- Changed fuel injector seals.
- Changed fuel filter and all brass washers. 
- Cleaned Metering plate. Everything moves really smoothly and is nice and clean. Fuel sprays beautifully in very equal quantity out of each injector as the plate is moved up. 
- When it doesn't start, if I bypass the FP Relay with a switch and prime it, it should re-pressurize the system and it "should" fix the problem. But it doesn't help. 

I don't have a pressure gauge. Basically I don't mind throwing parts at it, because all the parts are 35 years old and need to go anyways. But I would like one of these efforts to fix the issue!

I am leaning towards the WUR. Any other hints?


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## 134hpvw (Sep 6, 2013)

I am more of a cis e motronic guy. Passat 16v. But I have a similar issue.

My engibe has 45000 miles on a rebuild. Chassis has 170.000 miles. I have had the car for 10 years now 

Never replaced the fuel filter or related to it. 

Fires ip at the first try every time. In minus 20 celsius or + 40 celsius. 

Idles at 800 + - 50 rpms.

If I shut it off after it warms up and try to restart within 20 minutes or so, it takes 3 or more attempts to start.


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## 134hpvw (Sep 6, 2013)

On a similar note.

I used to drive early toyota vans. 84 -89. E.f I. Prone to vapour lock in the fuel system. By 86 toyota fix this problem with a field service bulletin. They installed a fpr with higher operating system settings. Reworked the vaccum plumbing for the a/c idle up pressure switch.

I have called arpund a few older independent vw shops and dealers to inquiry if the vw cis equipped cars suffered from fuel vapour lock also.

Everyone said no.


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## CALLAWAY TURBO (Aug 27, 2005)

Warm up regulator? 
I have the same problem and does seem more pronounced in the summer.
Been meaning to replace my WUR as that seems like it could cause a problem.


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## Butcher (Jan 31, 2001)

Vapor lock from the fuel distributor to the injectors. If the injectors do not hold pressure [ie the opening pressures are too low, not leaking] then the fuel will vapor lock. The amount of fuel flowing thru the lines at idle [cranking speed] is very low. It takes some time for the liquid fuel to push out the fuel vapor out to the lines, hence the long cranking and sputtering. Once the liquid fluid gets to the injector tips, then it runs ok. 

Fuel vapor is hard to control so that is why you want liquid in the fuel lines. Liquid fuel does not burn, that is why you need vapor. Liquid fuel is sprayed into the port where it vaporizes. Liquid in the lines and vapor in the ports. Always remember that because it is that important.

So what can you do? Update the fuel injectors. The newer ones should have a higher opening pressure and therefore the extra pressure will assist in the vapor lock issue. You can also insulate the injector lines. That always looks like crap. You can try to insulate the lines first to see if the problem goes away. If it does, then you know you're on the right track. 

If you are using premium, try regular. The Reid vapor pressure can be higher with regular fuel and therefore would prevent this issue. Different gas companies have different formulas. Don't know what Reid vapor pressure is? Try this https://en.wikipedia.org/wiki/Reid_vapor_pressure. That is why there is winter fuel and summer fuel. That is why on hot winter days cars run like crap and cold summer days the same issue.


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## 134hpvw (Sep 6, 2013)

It makes sense on tbe last posting. I will insulate the lines on the engine bay and report back


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