# 86 Jetta GLI/Carat Hot start issues



## westcoastjay (Jul 31, 2002)

Car starts and runs great when cold but if I stop the car once warm for 10-15 min and then start it up again it will bog/studder for about a minute and I have to rev it repeatedly and once it clears it drives perfect again.
Any thoughts?


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## Prairie (Aug 5, 2008)

Dia****m in the accumulator getting weak.


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## WaterWheels (Aug 14, 2005)

*Re: 86 Jetta GLI/Carat Hot start issues (westcoastjay)*

This can't be said enough; If you have and want to work on a CIS run engine, you need to break down and spend about $70 for a fuel pressure test kit. There are maybe a few different reasons for it to act this way, but without a lot to go on I would say it sounds like a rich stumble. Does it stumble and then recover if the throttle is held open, or stay flat until you let up on the throttle? Mixture setting, control pressure regulator, cold start valve, air sensor position, etc.
One reason would not be the accumulator though. It only holds pressure in the system when the engine is shut off. It also acts as a buffer for pressure pulses, but the pump would have to be shutting on and off or sticking or something real drastic for you to notice anything there. As long as the pump provides about 35spi or there abouts the spring in the accumulator is compressed and diaphram held open.


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## westcoastjay (Jul 31, 2002)

*Re: 86 Jetta GLI/Carat Hot start issues (WaterWheels)*


_Quote, originally posted by *WaterWheels* »_This can't be said enough; If you have and want to work on a CIS run engine, you need to break down and spend about $70 for a fuel pressure test kit. There are maybe a few different reasons for it to act this way, but without a lot to go on I would say it sounds like a rich stumble. Does it stumble and then recover if the throttle is held open, or stay flat until you let up on the throttle? Mixture setting, control pressure regulator, cold start valve, air sensor position, etc.
One reason would not be the accumulator though. It only holds pressure in the system when the engine is shut off. It also acts as a buffer for pressure pulses, but the pump would have to be shutting on and off or sticking or something real drastic for you to notice anything there. As long as the pump provides about 35spi or there abouts the spring in the accumulator is compressed and diaphram held open.

I have tested the fuel pressure and all looks good there, it basically will recover if I hold the throttle open for about a minute or pump the trottle for a minute. after it clears it runs great again. I have checked the CSV and the mixture


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## westcoastjay (Jul 31, 2002)

*Re: 86 Jetta GLI/Carat Hot start issues (westcoastjay)*

bump
still haven't found the issue, changed the CTS but no dice.


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## BSD (Jul 8, 2008)

My car does the same thing pretty much.


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## Fat Rabbit (Nov 18, 2001)

*Re: 86 Jetta GLI/Carat Hot start issues (westcoastjay)*

It sounds like you are having a hot soak problem. 
You mention checking fuel pressure. However there are several fuel pressures that need to be checked in diagnosing a CIS System. System pressure, control pressure and residual pressure. You need to be concerned about residual fuel pressure. It should stay around 43psi for at least 10 minutes. 
I can think if three items that could potentially cause your problem. (1.) One or more leaky injectors (including the cold start injector). (2.) A bad fuel accumulator. (3.) A bad fuel pump check valve.
I'd probably start by looking at the cold start injector and thermo time switch. When you pull the injectors to see if they leak under pressure it is a great time to renew the injector seals. 
The fuel accumulator holds fuel pressure on the fuel system for 1/2 hour or more -- it is nothing more than a can with a diaphram and spring inside. The fuel pressure helps the fuel from vaporizing in the fuel lines (vapor lock). They cost around $90 US new. It is located under the car next to the external fuel pump and fuel filter. There is a screw at the end of the accumulator away from the hoses. If that is taken out and the accumulator is full of gasoline it is bad. Also, most of them I have replaced over the years have shown outward signs of leakage. ie. they are visually damp with gas -- but not leaking so much as to drip on the ground. 
The fuel pump check valve also assists to hold pressure on the system after the engine is shut down. $15 US or so new. I guess you could attach a fuel pressure gauge to the valve and see if it leaks down but I usually just replace them. FR


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## westcoastjay (Jul 31, 2002)

*Re: 86 Jetta GLI/Carat Hot start issues (Fat Rabbit)*

changed the accumulator with no change to the issue. Found 3 corroded terminals at the ecu plug, changed those (they were for the idle switches) but still no luck
Check valve next


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## salz2135 (Sep 18, 2006)

what does the check valve look like?


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## Fat Rabbit (Nov 18, 2001)

*Re: (salz2135)*

The check valve doesn't look like much. Installed you really never see much of it. It sits at the outflow of the fuel pump. It is threaded at both ends and is maybe 1.5 inches long. It threads into the fuel pump and then the fuel line threads on to it with a banjo bolt. FR


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## salz2135 (Sep 18, 2006)

Do fuel pumps usually come with a new check valve? I replaced both my fuel pumps with brand new parts and I'm having warm start problems. I just can't recall if I swapped the old part over from the fried main pump or if my new one included it. 


_Modified by salz2135 at 7:54 PM 3-21-2009_


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## Fat Rabbit (Nov 18, 2001)

*Re: (salz2135)*

To install the fuel line you likely either changed the check valve over or it came with one. FR


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## woodrowstar (Jun 17, 2005)

why not replace the O2 sensor? a bad one will do the same thing the OP described.


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## westcoastjay (Jul 31, 2002)

*Re: (woodrowstar)*

Changed the Accumulator and the check valve and no dice. 
Changed a couple of pins at the ECU that were corroded
Possibly 02 sensor?


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## westcoastjay (Jul 31, 2002)

*Re: (westcoastjay)*

unplugged the O2 and same issue


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## westcoastjay (Jul 31, 2002)

*Re: (westcoastjay)*

resolved finally by accident
removed the front windshield and resealed it and voila no more issues. 
Looks like there was some water getting on the fuse box.


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## Scurvy Bandit (Sep 12, 2003)

*Re: (westcoastjay)*

that is insane...


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## Southcross (Jul 2, 2004)

*FV-QR*

haha... yep, that will do it


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