Gertrude86

Hey guys. I have a '86 CGT and would not start when the engine is hot. It starts just fine when cold and drives with no problems at all. If I turn of the engine and try to restart it wouldn't. I let it cool and it start right up. Changed coolant sensor, termo switch and I have the same problem.
Please help any advise would be helpful. Thx

Rogviler

Hot start problems are pretty common with CIS. Basically it comes down to the system losing pressure (most common) or something that causes the engine to flood, such as a bad cold-start valve system or leaking injectors.

If your fuel pump "primes" when you turn the key on, try priming it 5-10 times and see if it starts then. If so, it's likely going to be a pressure-loss problem.

Something the Porsche guys do is wire a switch that runs the fuel pump or cold-start valve manually so they can prime the system before starting. It's a cheap fix since many CIS parts can be very expensive to replace.

Another novel idea:

Quicker starts for CIS - hot or cold - Pelican Parts Technical BBS

The part causing the problem can be hard to track down, but common culprits include the accumulator:

VW Tech Tips @ Parts Place Inc.

Also the check valve after the fuel pump can get stuck. It should be installed right at the top of the pump, so easy to find.

It helps greatly if you get a fuel pressure tester. Then you can see if the pressure is dropping and where. Probably the cheapest one that's confirmed to work on CIS:

Master Fuel Injection Pressure Test Kit

Though you can spend a little more to get one with a better gauge.

If it's a flooding problem, see if unplugging the connector at the cold-start valve fixes it. You can also pull the injectors and see if any of them are dripping. Dripping injectors can also lead to a pressure loss in the system, so a double-whammy.

-Rog

Gertrude86

Thank you Rog for the quick response. I've read many of your post on the forum after I posted a thread a couple months back about my CGT smoking issues. Finally got it running decently but now new problems.
I will check the injectors and the cold start valve as the fuel accumulator is new( recently replaced). Unless you think that the new one just went bad prematurely 😁😁.
Also, I will try priming 5-10 times to see if the car would start that way.
Thanks again and I will report back with what I found, hopefully over the weekend.
Take care,
Otto

Gertrude86

Hey Rog. I've spent some time locking over a couple thing on my car. Followed young suggestion on unplugging the conectof for the cold start valve abc the car did not start. I'm assuming that the cold start valve is fine and the engine is not getting flooded.
The car started with no issues at all when the engine was cold. Run it for a whole than shut it off and tried priming 5-10 times and the car wouldn't start. When the car was running the fuel pump was making some noise, could that be an issue?
The fuel pump is the original one as the car has only 123k miles, all rusted and the black protective coat all oxidized and much of it gone.
Do you know the bosch part number for the fuel pump?
I will try to get a new one.
Thanks, Otto

AudiCoupeGT1986

You probably don't need the whole fuel pump. You may be able to just get the check valve and replace that. Also, would be worth checking the fuel accumulator. Could be either part is not able to keep pressure until the motor cools down.

Have you checked your O2 sensor? Take a multimeter to it to see it's actually working.

Gertrude86

Didn't check the O2 sensor but I've replaced the fuel accumulator recently. I am thinking of getting a new fuel pump because it looks like is still the original one and it is really noise and corroded.
Thx for the advise

Rogviler

I have two of the Bosch 69430 pumps, which are a good price (got mine on Amazon). It doesn't matter greatly which pump you get, as they mostly differ in the type of electrical connectors.

-Rog

Blewtoon

Check for vaccum leaks. With a minor one the fuel dist. diaphragm wont move & trigger the injectors unless the cold start valve sprays (when the engine is cold)

Gertrude86

I got the new fuel pump and installed it last night. It took a while for the car to start and now there is almost no noise. It works really nice.
Now for the bad part the car would not start when wormed up.
One thing I noticed as the engine was getting warner is if I tried to rev the engine up it would hesitate and spluter.
What would be the easiest way to check the O2 sensor to see if it work like it should?
Most likely that is the original one?
Thx guys

Blewtoon

It should run without the O2 sensor connected, just not as efficiently.